docs/master: discussion.roff annotate

docs/master

annotate discussion.roff @ 208:fead1fc981f0

Added note about the `a' message sequence.

author	markus schnalke <meillo@marmaro.de>
date	Thu, 12 Jul 2012 12:27:18 +0200
parents	5cd9bacdfcd3
children	9317d789cef9

rev	line source
meillo@58	1 .H0 "Discussion
meillo@0	2 .P
meillo@169	3 This main chapter discusses the practical work accomplished in the
meillo@169	4 mmh project.
meillo@169	5 It is structured along the goals set for the project.
meillo@169	6 The concrete work undertaken
meillo@58	7 is described in the examples of how the general goals were achieved.
meillo@87	8 The discussion compares the current version of mmh with the state of
meillo@171	9 nmh just before the mmh project started, i.e. fall 2011.
meillo@87	10 Current changes of nmh will be mentioned only as side notes.
meillo@87	11 .\" XXX where do I discuss the parallel development of nmh?
meillo@187	12 .P
meillo@187	13 For the reader's convenience, the structure of modern email systems
meillo@187	14 is depicted in the figure.
meillo@187	15 It illustrates the path a message takes from sender to recipient.
meillo@187	16 .sp
meillo@187	17 .KS
meillo@187	18 .in 2c
meillo@187	19 .so input/mail-agents.pic
meillo@187	20 .KE
meillo@187	21 .sp
meillo@187	22 .LP
meillo@187	23 The ellipses denote mail agents, i.e. different jobs in email processing:
meillo@187	24 .IP "Mail User Agent (MUA)
meillo@187	25 The only program the user interacts directly with.
meillo@187	26 It includes functions to compose new mail, display received mail,
meillo@187	27 and to manage the mail storage.
meillo@187	28 Also called \fImail client\fP.
meillo@187	29 .IP "Mail Submission Agent (MSA)
meillo@187	30 A special kind of Mail Transfer Agent, used to submit mail into the
meillo@187	31 mail transport system.
meillo@187	32 .IP "Mail Transfer Agent (MTA)
meillo@187	33 A node in the mail transport system.
meillo@187	34 Transfers incoming mail to a transport node nearer to the final destination.
meillo@187	35 It may be the final destination itself.
meillo@187	36 .IP "Mail Delivery Agent (MDA)
meillo@187	37 Delivers mail by storing it onto disk, usually according to a set of rules.
meillo@187	38 .IP "Mail Retrieval Agent (MRA)
meillo@187	39 Initiates the transfer of mail from a remote server to the local machine.
meillo@187	40 (The dashed arrow represents the pull request.)
meillo@187	41 .P
meillo@187	42 The dashed boxes represent groups that usually reside on single machines.
meillo@187	43 The box on the lower left represents the sender's local system.
meillo@187	44 The box on the upper left represents the first mail transfer node.
meillo@187	45 The box on the upper right represents the transfer node responsible for the
meillo@187	46 destination address.
meillo@187	47 The box on the lower right represents the recipient's local system.
meillo@187	48 Often, the boxes above the dotted line are servers on the Internet.
meillo@187	49 Many mail clients, including nmh, have all of the components below
meillo@187	50 the dotted line implemented.
meillo@187	51 Not so in mmh, which is an MUA only.
meillo@187	52
meillo@187	53
meillo@187	54
meillo@58	55
meillo@58	56
meillo@58	57
meillo@133	58 .\" --------------------------------------------------------------
meillo@125	59 .H1 "Streamlining
meillo@58	60
meillo@0	61 .P
meillo@169	62 MH once provided anything necessary for email handling.
meillo@169	63 The community around nmh has the similar understanding that nmh should
meillo@169	64 provide a complete email system.
meillo@178	65 In fundamental contrast, mmh shall be an MUA only.
meillo@87	66 I believe that the development of all-in-one mail systems is obsolete.
meillo@173	67 Today, email is too complex to be fully covered by a single project.
meillo@173	68 Such a project will not be able to excel in all aspects.
meillo@159	69 Instead, the aspects of email should be covered by multiple projects,
meillo@87	70 which then can be combined to form a complete system.
meillo@169	71 Excellent implementations for the various aspects of email already exist.
meillo@87	72 Just to name three examples: Postfix is a specialized MTA,
meillo@159	73 .\" XXX homepages verlinken
meillo@87	74 Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89	75 I believe that it is best to use such specialized tools instead of
meillo@87	76 providing the same function again as a side-component in the project.
meillo@164	77 .\" XXX mail agent picture here
meillo@58	78 .P
meillo@169	79 Doing something well requires focusing on a small set of specific aspects.
meillo@169	80 Under the assumption that development focussed on a particular area
meillo@169	81 produces better results there, specialized projects will be superior
meillo@87	82 in their field of focus.
meillo@87	83 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87	84 or modular \(en will never be the best choice in any of the fields.
meillo@169	85 Even in providing the best consistent all-in-one system, they are likely
meillo@87	86 to be beaten by projects that focus only on integrating existing mail
meillo@169	87 components to create a homogeneous system.
meillo@87	88 .P
meillo@173	89 The limiting resource in the community development of free software
meillo@87	90 is usually man power.
meillo@171	91 .\" XXX FIXME ref!
meillo@87	92 If the development power is spread over a large development area,
meillo@87	93 it becomes even more difficult to compete with the specialists in the
meillo@87	94 various fields.
meillo@87	95 The concrete situation for MH-based mail systems is even tougher,
meillo@169	96 given their small and aged community, concerning both developers and users.
meillo@87	97 .P
meillo@87	98 In consequence, I believe that the available development resources
meillo@100	99 should focus on the point where MH is most unique.
meillo@87	100 This is clearly the user interface \(en the MUA.
meillo@125	101 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60	102
meillo@60	103
meillo@100	104 .H2 "Mail Transfer Facilities
meillo@154	105 .Id mail-transfer-facilities
meillo@60	106 .P
meillo@60	107 In contrast to nmh, which also provides mail submission and mail retrieval
meillo@178	108 agents, mmh is an MUA only.
meillo@100	109 This general difference initiated the development of mmh.
meillo@169	110 The removal of the mail transfer facilities was the first work task
meillo@76	111 in the mmh project.
meillo@60	112 .P
meillo@169	113 Focusing on one mail agent role only, is motivated by Eric Allman's
meillo@105	114 experience with Sendmail.
meillo@159	115 He identified the limitation of Sendmail to the MTA task as one reason for
meillo@105	116 its success:
meillo@105	117 .[ [
meillo@105	118 costales sendmail
meillo@105	119 .], p. xviii]
meillo@105	120 .QS
meillo@105	121 Second, I limited myself to the routing function \(en
meillo@110	122 I wouldn't write user agents or delivery back-ends.
meillo@105	123 This was a departure of the dominant through of the time,
meillo@105	124 in which routing logic, local delivery, and often the network code
meillo@105	125 were incorporated directly into the user agents.
meillo@105	126 .QE
meillo@105	127 .P
meillo@187	128 In nmh, the MSA is called \fIMessage Transfer Service\fP (MTS).
meillo@105	129 This facility, implemented by the
meillo@105	130 .Pn post
meillo@105	131 command, established network connections and spoke SMTP to submit
meillo@159	132 messages to be relayed to the outside world.
meillo@169	133 The changes in email demanded changes in this part of nmh as well.
meillo@89	134 Encryption and authentication for network connections
meillo@87	135 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87	136 This added complexity to nmh without improving it in its core functions.
meillo@87	137 Also, keeping up with recent developments in the field of
meillo@87	138 mail transfer requires development power and specialists.
meillo@169	139 In mmh, this whole facility was simply cut off.
meillo@76	140 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76	141 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76	142 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87	143 Instead, mmh depends on an external MSA.
meillo@60	144 The only outgoing interface available to mmh is the
meillo@60	145 .Pn sendmail
meillo@87	146 command, which almost any MSA provides.
meillo@87	147 If not, a wrapper program can be written.
meillo@87	148 It must read the message from the standard input, extract the
meillo@87	149 recipient addresses from the message header, and hand the message
meillo@87	150 over to the MSA.
meillo@87	151 For example, a wrapper script for qmail would be:
meillo@87	152 .VS
meillo@87	153 #!/bin/sh
meillo@138	154 exec qmail-inject # ignore command line arguments
meillo@87	155 VE
meillo@87	156 The requirement to parse the recipient addresses out of the message header
meillo@87	157 is likely to be removed in the future.
meillo@169	158 Then mmh would pass the recipient addresses as command line arguments.
meillo@100	159 This appears to be the better interface.
meillo@87	160 .\" XXX implement it
meillo@60	161 .P
meillo@60	162 To retrieve mail, the
meillo@60	163 .Pn inc
meillo@187	164 command acted as an MRA.
meillo@100	165 It established network connections
meillo@76	166 and spoke POP3 to retrieve mail from remote servers.
meillo@76	167 As with mail submission, the network connections required encryption and
meillo@87	168 authentication, thus TLS and SASL were added.
meillo@169	169 Support for message retrieval through IMAP will soon become necessary
meillo@169	170 additions, too, and likewise for any other changes in mail transfer.
meillo@100	171 Not so for mmh because it has dropped the support for retrieving mail
meillo@100	172 from remote locations.
meillo@76	173 .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76	174 Instead, it depends on an external tool to cover this task.
meillo@169	175 Mmh has two paths for messages to enter mmh's mail storage:
meillo@100	176 (1) Mail can be incorporated with
meillo@60	177 .Pn inc
meillo@87	178 from the system maildrop, or (2) with
meillo@60	179 .Pn rcvstore
meillo@87	180 by reading them, one at a time, from the standard input.
meillo@60	181 .P
meillo@60	182 With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@178	183 mail system to being an MUA only.
meillo@60	184 Now, of course, mmh depends on third-party software.
meillo@87	185 An external MSA is required to transfer mail to the outside world;
meillo@60	186 an external MRA is required to retrieve mail from remote machines.
meillo@169	187 Excellent implementations of such software exist,
meillo@159	188 which likely are superior than the internal version.
meillo@159	189 Additionally, the best suiting programs can be freely chosen.
meillo@60	190 .P
meillo@60	191 As it had already been possible to use an external MSA or MRA,
meillo@60	192 why not keep the internal version for convenience?
meillo@159	193 .\" XXX ueberleitung
meillo@76	194 The question whether there is sense in having a fall-back pager in all
meillo@76	195 the command line tools, for the cases when
meillo@60	196 .Pn more
meillo@60	197 or
meillo@60	198 .Pn less
meillo@173	199 are not available, appears to be ridiculous.
meillo@100	200 Of course, MSAs and MRAs are more complex than text pagers
meillo@87	201 and not necessarily available but still the concept of orthogonal
meillo@87	202 design holds: ``Write programs that do one thing and do it well.''
meillo@87	203 .[
meillo@87	204 mcilroy unix phil
meillo@87	205 p. 53
meillo@87	206 .]
meillo@87	207 .[
meillo@87	208 mcilroy bstj foreword
meillo@87	209 .]
meillo@87	210 Here, this part of the Unix philosophy was applied not only
meillo@87	211 to the programs but to the project itself.
meillo@87	212 In other words:
meillo@164	213 Develop projects that focus on one thing and do it well.
meillo@169	214 Projects which have grown complex should be split, for the same
meillo@169	215 reasons that programs which have grown complex should be split.
meillo@100	216 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87	217 separate projects then they should be separated.
meillo@169	218 In my opinion, this is the case here.
meillo@87	219 The RFCs propose this separation by clearly distinguishing the different
meillo@199	220 mail handling tasks [RFC\\|821].
meillo@87	221 The small interfaces between the mail agents support the separation.
meillo@76	222 .P
meillo@169	223 Email once had been small and simple.
meillo@100	224 At that time,
meillo@60	225 .Pn /bin/mail
meillo@169	226 had covered everything there was to email and still was small and simple.
meillo@100	227 Later, the essential complexity of email increased.
meillo@87	228 (Essential complexity is the complexity defined by the problem itself.\0
meillo@87	229 .[[
meillo@87	230 brooks no silver bullet
meillo@87	231 .]])
meillo@171	232 Email systems reacted to this change: they grew.
meillo@100	233 RFCs started to introduce the concept of mail agents to separate the
meillo@100	234 various tasks because they became more extensive and new tasks appeared.
meillo@100	235 As the mail systems grew even more, parts were split off.
meillo@169	236 For instance, a POP server was included in the original MH;
meillo@169	237 it was removed in nmh.
meillo@164	238 Now is the time to go one step further and split off the MSA and MRA, too.
meillo@87	239 Not only does this decrease the code size of the project,
meillo@169	240 more importantly, it unburdens mmh of the whole field of
meillo@87	241 message transfer with all its implications for the project.
meillo@169	242 There is no more need for concern with changes in network transfer.
meillo@169	243 This independence is gained by depending on an external program
meillo@76	244 that covers the field.
meillo@76	245 Today, this is a reasonable exchange.
meillo@60	246 .P
meillo@159	247 .\" XXX ueberleitung ???
meillo@100	248 Functionality can be added in three different ways:
meillo@171	249 .LI 1
meillo@169	250 Implementing the function in the project itself.
meillo@171	251 .LI 2
meillo@87	252 Depending on a library that provides the function.
meillo@171	253 .LI 3
meillo@87	254 Depending on a program that provides the function.
meillo@171	255 .LP
meillo@159	256 .\" XXX Rework sentence
meillo@169	257 While implementing the function in the project itself leads to the
meillo@169	258 largest increase in code size and requires the most maintenance
meillo@169	259 and development work,
meillo@169	260 it increases the project's independence of other software the most.
meillo@169	261 Using libraries or external programs requires less maintenance work
meillo@87	262 but introduces dependencies on external software.
meillo@169	263 Programs have the smallest interfaces and provide the best separation,
meillo@87	264 but possibly limit the information exchange.
meillo@169	265 External libraries are more strongly connected than external programs,
meillo@169	266 thus information can be exchanged in a more flexible manner.
meillo@87	267 Adding code to a project increases maintenance work.
meillo@87	268 .\" XXX ref
meillo@159	269 Implementing complex functions in the project itself adds
meillo@87	270 a lot of code.
meillo@87	271 This should be avoided if possible.
meillo@169	272 Hence, the dependencies only change in their character,
meillo@169	273 not in their existence.
meillo@66	274 In mmh, library dependencies on
meillo@66	275 .Pn libsasl2
meillo@66	276 and
meillo@66	277 .Pn libcrypto /\c
meillo@66	278 .Pn libssl
meillo@159	279 were traded against program dependencies on an MSA and an MRA.
meillo@159	280 This also meant trading build-time dependencies against run-time
meillo@87	281 dependencies.
meillo@169	282 Besides providing stronger separation and greater flexibility,
meillo@169	283 program dependencies also allowed
meillo@66	284 over 6\\|000 lines of code to be removed from mmh.
meillo@66	285 This made mmh's code base about 12\\|% smaller.
meillo@87	286 Reducing the project's code size by such an amount without actually
meillo@87	287 losing functionality is a convincing argument.
meillo@87	288 Actually, as external MSAs and MRAs are likely superior to the
meillo@87	289 project's internal versions, the common user even gains functionality.
meillo@66	290 .P
meillo@169	291 Users of MH should not have problems setting up an external MSA and MRA.
meillo@60	292 Also, the popular MSAs and MRAs have large communities and a lot
meillo@169	293 of available documentation.
meillo@169	294 Choices for MSAs range from full-featured MTAs such as
meillo@159	295 .\" XXX refs
meillo@169	296 .I Postfix ,
meillo@169	297 over mid-size MTAs such as
meillo@60	298 .I masqmail
meillo@60	299 and
meillo@169	300 .I dma ,
meillo@169	301 to small forwarders such as
meillo@60	302 .I ssmtp
meillo@60	303 and
meillo@60	304 .I nullmailer .
meillo@60	305 Choices for MRAs include
meillo@60	306 .I fetchmail ,
meillo@60	307 .I getmail ,
meillo@60	308 .I mpop
meillo@60	309 and
meillo@60	310 .I fdm .
meillo@60	311
meillo@60	312
meillo@100	313 .H2 "Non-MUA Tools
meillo@60	314 .P
meillo@87	315 One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@181	316 Furthermore, any tools that do not significantly improve the MUA's job
meillo@87	317 should be removed.
meillo@87	318 Loosely related and rarely used tools distract from the lean appearance.
meillo@87	319 They require maintenance work without adding much to the core task.
meillo@125	320 By removing these tools, the project shall become more streamlined
meillo@87	321 and focused.
meillo@169	322 In mmh, the following tools are not available anymore:
meillo@62	323 .BU
meillo@58	324 .Pn conflict
meillo@87	325 was removed
meillo@76	326 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87	327 because it is a mail system maintenance tool that is not MUA-related.
meillo@87	328 It even checked
meillo@58	329 .Fn /etc/passwd
meillo@58	330 and
meillo@58	331 .Fn /etc/group
meillo@87	332 for consistency, which is completely unrelated to email.
meillo@87	333 A tool like
meillo@87	334 .Pn conflict
meillo@87	335 is surely useful, but it should not be shipped with mmh.
meillo@76	336 .\" XXX historic reasons?
meillo@62	337 .BU
meillo@58	338 .Pn rcvtty
meillo@87	339 was removed
meillo@87	340 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89	341 because its use case of writing to the user's terminal
meillo@200	342 on reception of mail is obsolete.
meillo@87	343 If users like to be informed of new mail, the shell's
meillo@58	344 .Ev MAILPATH
meillo@87	345 variable or graphical notifications are technically more appealing.
meillo@169	346 Writing directly to terminals is hardly ever desired today.
meillo@169	347 If, though, one prefers this approach, the standard tool
meillo@58	348 .Pn write
meillo@58	349 can be used in a way similar to:
meillo@82	350 .VS
meillo@58	351 scan -file - \| write `id -un`
meillo@82	352 VE
meillo@62	353 .BU
meillo@58	354 .Pn viamail
meillo@159	355 .\" XXX was macht viamail
meillo@87	356 was removed
meillo@87	357 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87	358 when the new attachment system was activated, because
meillo@58	359 .Pn forw
meillo@76	360 could then cover the task itself.
meillo@62	361 The program
meillo@58	362 .Pn sendfiles
meillo@62	363 was rewritten as a shell script wrapper around
meillo@58	364 .Pn forw .
meillo@76	365 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62	366 .BU
meillo@58	367 .Pn msgchk
meillo@159	368 .\" XXX was macht msgchk
meillo@87	369 was removed
meillo@87	370 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87	371 because it lost its use case when POP support was removed.
meillo@76	372 A call to
meillo@58	373 .Pn msgchk
meillo@87	374 provided hardly more information than:
meillo@82	375 .VS
meillo@58	376 ls -l /var/mail/meillo
meillo@82	377 VE
meillo@100	378 It did distinguish between old and new mail, but
meillo@169	379 these details can be retrieved with
meillo@76	380 .Pn stat (1),
meillo@62	381 too.
meillo@100	382 A small shell script could be written to print the information
meillo@76	383 in a similar way, if truly necessary.
meillo@76	384 As mmh's
meillo@76	385 .Pn inc
meillo@87	386 only incorporates mail from the user's local maildrop,
meillo@62	387 and thus no data transfers over slow networks are involved,
meillo@169	388 there is hardly any need to check for new mail before incorporating it.
meillo@62	389 .BU
meillo@58	390 .Pn msh
meillo@87	391 was removed
meillo@76	392 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87	393 because the tool was in conflict with the philosophy of MH.
meillo@76	394 It provided an interactive shell to access the features of MH,
meillo@173	395 but it was not just a shell tailored to the needs of mail handling.
meillo@169	396 Instead, it was one large program that had several MH tools built in.
meillo@76	397 This conflicts with the major feature of MH of being a tool chest.
meillo@76	398 .Pn msh 's
meillo@159	399 main use case had been accessing Bulletin Boards, which have ceased to
meillo@62	400 be popular.
meillo@62	401 .P
meillo@62	402 Removing
meillo@169	403 .Pn msh
meillo@76	404 together with the truly archaic code relicts
meillo@58	405 .Pn vmh
meillo@58	406 and
meillo@169	407 .Pn wmh
meillo@62	408 saved more than 7\\|000 lines of C code \(en
meillo@66	409 about 15\\|% of the project's original source code amount.
meillo@100	410 Having less code \(en with equal readability, of course \(en
meillo@76	411 for the same functionality is an advantage.
meillo@63	412 Less code means less bugs and less maintenance work.
meillo@76	413 As
meillo@63	414 .Pn rcvtty
meillo@63	415 and
meillo@63	416 .Pn msgchk
meillo@87	417 are assumed to be rarely used and can be implemented in different ways,
meillo@87	418 why should one keep them?
meillo@125	419 Removing them streamlines mmh.
meillo@63	420 .Pn viamail 's
meillo@63	421 use case is now partly obsolete and partly covered by
meillo@63	422 .Pn forw ,
meillo@76	423 hence there's no reason to still maintain it.
meillo@63	424 .Pn conflict
meillo@76	425 is not related to the mail client, and
meillo@63	426 .Pn msh
meillo@63	427 conflicts with the basic concept of MH.
meillo@169	428 These two tools might still be useful, but they should not be part of mmh.
meillo@63	429 .P
meillo@169	430 Finally, there is
meillo@76	431 .Pn slocal .
meillo@76	432 .Pn slocal
meillo@76	433 is an MDA and thus not directly MUA-related.
meillo@100	434 It should be removed from mmh, because including it conflicts with
meillo@178	435 the idea that mmh is an MUA only.
meillo@100	436 .Pn slocal
meillo@100	437 should rather become a separate project.
meillo@87	438 However,
meillo@76	439 .Pn slocal
meillo@76	440 provides rule-based processing of messages, like filing them into
meillo@76	441 different folders, which is otherwise not available in mmh.
meillo@87	442 Although
meillo@76	443 .Pn slocal
meillo@169	444 neither pulls in dependencies, nor does it include a separate
meillo@154	445 technical area (cf. Sec.
meillo@154	446 .Cf mail-transfer-facilities ),
meillo@169	447 it still accounts for about 1\\|000 lines of code that need to be maintained.
meillo@76	448 As
meillo@76	449 .Pn slocal
meillo@76	450 is almost self-standing, it should be split off into a separate project.
meillo@76	451 This would cut the strong connection between the MUA mmh and the MDA
meillo@76	452 .Pn slocal .
meillo@87	453 For anyone not using MH,
meillo@87	454 .Pn slocal
meillo@87	455 would become yet another independent MDA, like
meillo@87	456 .I procmail .
meillo@100	457 Then
meillo@87	458 .Pn slocal
meillo@100	459 could be installed without the complete MH system.
meillo@76	460 Likewise, mmh users could decide to use
meillo@76	461 .I procmail
meillo@87	462 without having a second, unused MDA,
meillo@87	463 .Pn slocal ,
meillo@76	464 installed.
meillo@100	465 That appears to be conceptionally the best solution.
meillo@76	466 Yet,
meillo@76	467 .Pn slocal
meillo@87	468 is not split off.
meillo@100	469 I defer the decision over
meillo@78	470 .Pn slocal
meillo@169	471 out of a need for deeper investigation.
meillo@100	472 In the meanwhile, it remains part of mmh.
meillo@159	473 However, its continued existence is not significant because
meillo@100	474 .Pn slocal
meillo@100	475 is unrelated to the rest of the project.
meillo@0	476
meillo@58	477
meillo@133	478
meillo@134	479 .H2 "Displaying Messages
meillo@155	480 .Id mhshow
meillo@131	481 .P
meillo@133	482 Since the very beginning, already in the first concept paper,
meillo@159	483 .\" XXX ref!!!
meillo@58	484 .Pn show
meillo@62	485 had been MH's message display program.
meillo@58	486 .Pn show
meillo@76	487 mapped message numbers and sequences to files and invoked
meillo@58	488 .Pn mhl
meillo@89	489 to have the files formatted.
meillo@173	490 With MIME, this approach was not sufficient anymore.
meillo@100	491 MIME messages can consist of multiple parts. Some parts are not
meillo@100	492 directly displayable and text content might be encoded in
meillo@58	493 foreign charsets.
meillo@58	494 .Pn show 's
meillo@76	495 understanding of messages and
meillo@58	496 .Pn mhl 's
meillo@173	497 display capabilities could not cope with the task any longer.
meillo@62	498 .P
meillo@88	499 Instead of extending these tools, additional tools were written from
meillo@88	500 scratch and added to the MH tool chest.
meillo@88	501 Doing so is encouraged by the tool chest approach.
meillo@88	502 Modular design is a great advantage for extending a system,
meillo@88	503 as new tools can be added without interfering with existing ones.
meillo@62	504 First, the new MIME features were added in form of the single program
meillo@58	505 .Pn mhn .
meillo@58	506 The command
meillo@82	507 .Cl "mhn -show 42
meillo@58	508 would show the MIME message numbered 42.
meillo@58	509 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58	510 the split of
meillo@58	511 .Pn mhn
meillo@88	512 into a set of specialized tools, which together covered the
meillo@88	513 multiple aspects of MIME.
meillo@88	514 One of them was
meillo@69	515 .Pn mhshow ,
meillo@88	516 which replaced
meillo@88	517 .Cl "mhn -show" .
meillo@88	518 It was capable of displaying MIME messages appropriately.
meillo@62	519 .P
meillo@88	520 From then on, two message display tools were part of nmh,
meillo@76	521 .Pn show
meillo@76	522 and
meillo@76	523 .Pn mhshow .
meillo@88	524 To ease the life of users,
meillo@69	525 .Pn show
meillo@69	526 was extended to automatically hand the job over to
meillo@69	527 .Pn mhshow
meillo@69	528 if displaying the message would be beyond
meillo@69	529 .Pn show 's
meillo@69	530 abilities.
meillo@88	531 In consequence, the user would simply invoke
meillo@69	532 .Pn show
meillo@69	533 (possibly through
meillo@69	534 .Pn next
meillo@69	535 or
meillo@69	536 .Pn prev )
meillo@69	537 and get the message printed with either
meillo@69	538 .Pn show
meillo@69	539 or
meillo@69	540 .Pn mhshow ,
meillo@69	541 whatever was more appropriate.
meillo@69	542 .P
meillo@69	543 Having two similar tools for essentially the same task is redundant.
meillo@173	544 Usually, users would not distinguish between
meillo@88	545 .Pn show
meillo@88	546 and
meillo@88	547 .Pn mhshow
meillo@88	548 in their daily mail reading.
meillo@88	549 Having two separate display programs was therefore mainly unnecessary
meillo@88	550 from a user's point of view.
meillo@88	551 Besides, the development of both programs needed to be in sync,
meillo@76	552 to ensure that the programs behaved in a similar way,
meillo@76	553 because they were used like a single tool.
meillo@76	554 Different behavior would have surprised the user.
meillo@69	555 .P
meillo@69	556 Today, non-MIME messages are rather seen to be a special case of
meillo@100	557 MIME messages, although it is the other way round.
meillo@69	558 As
meillo@69	559 .Pn mhshow
meillo@159	560 had already been able to display non-MIME messages, it appeared natural
meillo@69	561 to drop
meillo@69	562 .Pn show
meillo@69	563 in favor of using
meillo@69	564 .Pn mhshow
meillo@69	565 exclusively.
meillo@88	566 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88	567 Removing
meillo@88	568 .Pn show
meillo@88	569 is no loss in function, because functionally
meillo@88	570 .Pn mhshow
meillo@88	571 covers it completely.
meillo@88	572 The old behavior of
meillo@88	573 .Pn show
meillo@88	574 can still be emulated with the simple command line:
meillo@88	575 .VS
meillo@88	576 mhl `mhpath c`
meillo@88	577 VE
meillo@88	578 .P
meillo@76	579 For convenience,
meillo@76	580 .Pn mhshow
meillo@88	581 was renamed to
meillo@88	582 .Pn show
meillo@88	583 after
meillo@88	584 .Pn show
meillo@88	585 was gone.
meillo@88	586 It is clear that such a rename may confuse future developers when
meillo@88	587 trying to understand the history.
meillo@88	588 Nevertheless, I consider the convenience on the user's side,
meillo@88	589 to call
meillo@88	590 .Pn show
meillo@88	591 when they want a message to be displayed, to outweigh the inconvenience
meillo@88	592 on the developer's side when understanding the project history.
meillo@69	593 .P
meillo@88	594 To prepare for the transition,
meillo@69	595 .Pn mhshow
meillo@69	596 was reworked to behave more like
meillo@69	597 .Pn show
meillo@69	598 first.
meillo@154	599 (cf. Sec.
meillo@154	600 .Cf mhshow )
meillo@164	601 .\" XXX code commits?
meillo@88	602 Once the tools behaved more alike, the replacing appeared to be
meillo@88	603 even more natural.
meillo@88	604 Today, mmh's new
meillo@69	605 .Pn show
meillo@159	606 has become the one single message display program once more,
meillo@159	607 with the difference
meillo@88	608 that today it handles MIME messages as well as non-MIME messages.
meillo@88	609 The outcome of the transition is one program less to maintain,
meillo@88	610 no second display program for users to deal with,
meillo@88	611 and less system complexity.
meillo@69	612 .P
meillo@88	613 Still, removing the old
meillo@69	614 .Pn show
meillo@88	615 hurts in one regard: It had been such a simple program.
meillo@159	616 Its lean elegance is missing from the new
meillo@159	617 .Pn show ,
meillo@159	618 .\" XXX
meillo@159	619 however there is no alternative;
meillo@159	620 supporting MIME demands higher essential complexity.
meillo@58	621
meillo@134	622 .ig
meillo@134	623 XXX
meillo@134	624 Consider including text on scan listings here
meillo@58	625
meillo@134	626 Scan listings shall not contain body content. Hence, removed this feature.
meillo@134	627 Scan listings shall operator on message headers and non-message information
meillo@134	628 only. Displaying the beginning of the body complicates everything too much.
meillo@134	629 That's no surprise, because it's something completely different. If you
meillo@134	630 want to examine the body, then use show(1)/mhshow(1).
meillo@134	631 Changed the default scan formats accordingly.
meillo@134	632 .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134	633 ..
meillo@131	634
meillo@131	635
meillo@131	636
meillo@133	637
meillo@100	638 .H2 "Configure Options
meillo@58	639 .P
meillo@76	640 Customization is a double-edged sword.
meillo@76	641 It allows better suiting setups, but not for free.
meillo@76	642 There is the cost of code complexity to be able to customize.
meillo@76	643 There is the cost of less tested setups, because there are
meillo@171	644 more possible setups and especially corner cases.
meillo@159	645 Additionally, there is the cost of choice itself.
meillo@76	646 The code complexity directly affects the developers.
meillo@173	647 Less tested code affects both users and developers.
meillo@159	648 The problem of choice affects the users, for once by having to choose,
meillo@159	649 but also by more complex interfaces that require more documentation.
meillo@159	650 Whenever options add few advantages but increase the complexity of the
meillo@159	651 system, they should be considered for removal.
meillo@72	652 I have reduced the number of project-specific configure options from
meillo@72	653 fifteen to three.
meillo@74	654
meillo@76	655 .U3 "Mail Transfer Facilities
meillo@74	656 .P
meillo@85	657 With the removal of the mail transfer facilities five configure
meillo@85	658 options vanished:
meillo@85	659 .P
meillo@85	660 The switches
meillo@85	661 .Sw --with-tls
meillo@85	662 and
meillo@85	663 .Sw --with-cyrus-sasl
meillo@89	664 had activated the support for transfer encryption and authentication.
meillo@159	665 .\" XXX cf
meillo@159	666 .\" XXX gruende kurz wiederholen
meillo@85	667 This is not needed anymore.
meillo@85	668 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85	669 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85	670 .P
meillo@159	671 .\" XXX cf
meillo@159	672 .\" XXX ``For the same reason ...''
meillo@85	673 The configure switch
meillo@85	674 .Sw --enable-pop
meillo@85	675 activated the message retrieval facility.
meillo@85	676 The code area that would be conditionally compiled in for TLS and SASL
meillo@85	677 support had been small.
meillo@85	678 The conditionally compiled code area for POP support had been much larger.
meillo@85	679 Whereas the code base changes would only slightly change on toggling
meillo@85	680 TLS or SASL support, it changed much on toggling POP support.
meillo@85	681 The changes in the code base could hardly be overviewed.
meillo@159	682 By having POP support togglable, a second code base had been created,
meillo@85	683 one that needed to be tested.
meillo@85	684 This situation is basically similar for the conditional TLS and SASL
meillo@85	685 code, but there the changes are minor and can yet be overviewed.
meillo@85	686 Still, conditional compilation of a code base creates variations
meillo@85	687 of the original program.
meillo@85	688 More variations require more testing and maintenance work.
meillo@85	689 .P
meillo@85	690 Two other options only specified default configuration values:
meillo@100	691 .Sw --with-mts
meillo@164	692 defined the default transport service.
meillo@85	693 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85	694 With
meillo@100	695 .Sw --with-smtpservers
meillo@164	696 default SMTP servers could be specified.
meillo@72	697 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@164	698 Both of them became irrelevant when the SMTP transport service was removed.
meillo@164	699 .\" XXX code ref
meillo@164	700 In mmh, all messages are handed over to
meillo@164	701 .Pn sendmail
meillo@164	702 for transportation.
meillo@164	703
meillo@72	704
meillo@74	705 .U3 "Backup Prefix
meillo@74	706 .P
meillo@76	707 The backup prefix is the string that was prepended to message
meillo@76	708 filenames to tag them as deleted.
meillo@173	709 By default it had been the comma character (`\fL,\fP').
meillo@159	710 .\" XXX Zeitlich ordnen
meillo@78	711 In July 2000, Kimmo Suominen introduced
meillo@78	712 the configure option
meillo@78	713 .Sw --with-hash-backup
meillo@173	714 to change the default to the hash character `\f(CW#\fP'.
meillo@78	715 The choice was probably personal preference, because first, the
meillo@78	716 option was named
meillo@78	717 .Sw --with-backup-prefix.
meillo@173	718 and had the prefix character as argument.
meillo@173	719 But giving the hash character as argument caused too many problems
meillo@100	720 for Autoconf,
meillo@173	721 thus the option was limited to use the hash character as the default prefix.
meillo@100	722 This supports the assumption, that the choice for the hash was
meillo@100	723 personal preference only.
meillo@173	724 Being related or not, words that start with the hash character
meillo@78	725 introduce a comment in the Unix shell.
meillo@72	726 Thus, the command line
meillo@72	727 .Cl "rm #13 #15
meillo@72	728 calls
meillo@72	729 .Pn rm
meillo@173	730 without arguments because the first hash character starts the comment
meillo@72	731 that reaches until the end of the line.
meillo@72	732 To delete the backup files,
meillo@72	733 .Cl "rm ./#13 ./#15"
meillo@72	734 needs to be used.
meillo@100	735 Using the hash as backup prefix can be seen as a precaution against
meillo@78	736 data loss.
meillo@78	737 .P
meillo@159	738 First, I removed the configure option but added the profile entry
meillo@72	739 .Pe backup-prefix ,
meillo@72	740 which allows to specify an arbitrary string as backup prefix.
meillo@72	741 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76	742 Profile entries are the common method to change mmh's behavior.
meillo@76	743 This change did not remove the choice but moved it to a location where
meillo@72	744 it suited better.
meillo@76	745 .P
meillo@78	746 Eventually, however, the new trash folder concept
meillo@154	747 (cf. Sec.
meillo@154	748 .Cf trash-folder )
meillo@164	749 removed the need for the backup prefix completely.
meillo@78	750 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133	751 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133	752
meillo@76	753
meillo@76	754 .U3 "Editor and Pager
meillo@74	755 .P
meillo@74	756 The two configure options
meillo@74	757 .CW --with-editor=EDITOR
meillo@74	758 .CW --with-pager=PAGER
meillo@74	759 were used to specify the default editor and pager at configure time.
meillo@109	760 Doing so at configure time made sense in the eighties,
meillo@76	761 when the set of available editors and pagers varied much across
meillo@76	762 different systems.
meillo@89	763 Today, the situation is more homogeneous.
meillo@74	764 The programs
meillo@74	765 .Pn vi
meillo@74	766 and
meillo@74	767 .Pn more
meillo@76	768 can be expected to be available on every Unix system,
meillo@74	769 as they are specified by POSIX since two decades.
meillo@74	770 (The specifications for
meillo@74	771 .Pn vi
meillo@74	772 and
meillo@74	773 .Pn more
meillo@74	774 appeared in
meillo@74	775 .[
meillo@74	776 posix 1987
meillo@74	777 .]
meillo@74	778 and,
meillo@74	779 .[
meillo@74	780 posix 1992
meillo@74	781 .]
meillo@74	782 respectively.)
meillo@74	783 As a first step, these two tools were hard-coded as defaults.
meillo@74	784 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74	785 Not changed were the
meillo@74	786 .Pe editor
meillo@74	787 and
meillo@74	788 .Pe moreproc
meillo@76	789 profile entries, which allowed the user to override the system defaults.
meillo@74	790 Later, the concept was reworked to respect the standard environment
meillo@74	791 variables
meillo@74	792 .Ev VISUAL
meillo@74	793 and
meillo@74	794 .Ev PAGER
meillo@76	795 if they are set.
meillo@74	796 Today, mmh determines the editor to use in the following order,
meillo@74	797 taking the first available and non-empty item:
meillo@171	798 .LI 1
meillo@74	799 Environment variable
meillo@74	800 .Ev MMHEDITOR
meillo@171	801 .LI 2
meillo@74	802 Profile entry
meillo@74	803 .Pe Editor
meillo@171	804 .LI 3
meillo@74	805 Environment variable
meillo@74	806 .Ev VISUAL
meillo@171	807 .LI 4
meillo@74	808 Environment variable
meillo@74	809 .Ev EDITOR
meillo@171	810 .LI 5
meillo@74	811 Command
meillo@74	812 .Pn vi .
meillo@171	813 .LP
meillo@76	814 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76	815 .P
meillo@89	816 The pager to use is determined in a similar order,
meillo@74	817 also taking the first available and non-empty item:
meillo@171	818 .LI 1
meillo@74	819 Environment variable
meillo@74	820 .Ev MMHPAGER
meillo@171	821 .LI 2
meillo@74	822 Profile entry
meillo@74	823 .Pe Pager
meillo@74	824 (replaces
meillo@74	825 .Pe moreproc )
meillo@171	826 .LI 3
meillo@74	827 Environment variable
meillo@74	828 .Ev PAGER
meillo@171	829 .LI 4
meillo@74	830 Command
meillo@74	831 .Pn more .
meillo@171	832 .LP
meillo@74	833 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74	834 .P
meillo@76	835 By respecting the
meillo@74	836 .Ev VISUAL /\c
meillo@74	837 .Ev EDITOR
meillo@74	838 and
meillo@74	839 .Ev PAGER
meillo@76	840 environment variables,
meillo@76	841 the new behavior confirms better to the common style on Unix systems.
meillo@76	842 Additionally, the new approach is more uniform and clearer to users.
meillo@72	843
meillo@72	844
meillo@76	845 .U3 "ndbm
meillo@72	846 .P
meillo@74	847 .Pn slocal
meillo@78	848 used to depend on
meillo@74	849 .I ndbm ,
meillo@74	850 a database library.
meillo@76	851 The database is used to store the `\fLMessage-ID\fP's of all
meillo@76	852 messages delivered.
meillo@74	853 This enables
meillo@74	854 .Pn slocal
meillo@74	855 to suppress delivering the same message to the same user twice.
meillo@74	856 (This features was enabled by the
meillo@74	857 .Sw -suppressdup
meillo@74	858 switch.)
meillo@74	859 .P
meillo@100	860 A variety of versions of the database library exist.
meillo@78	861 .[
meillo@78	862 wolter unix incompat notes dbm
meillo@78	863 .]
meillo@74	864 Complicated autoconf code was needed to detect them correctly.
meillo@181	865 Furthermore, the configure switches
meillo@74	866 .Sw --with-ndbm=ARG
meillo@74	867 and
meillo@74	868 .Sw --with-ndbmheader=ARG
meillo@74	869 were added to help with difficult setups that would
meillo@78	870 not be detected automatically or correctly.
meillo@74	871 .P
meillo@74	872 By removing the suppress duplicates feature of
meillo@74	873 .Pn slocal ,
meillo@74	874 the dependency on
meillo@74	875 .I ndbm
meillo@78	876 vanished and 120 lines of complex autoconf code could be saved.
meillo@74	877 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@89	878 The change removed functionality too, but that is minor to the
meillo@78	879 improvement by dropping the dependency and the complex autoconf code.
meillo@159	880 .\" XXX argument: slocal ist sowieso nicht teil vom mmh kern
meillo@72	881
meillo@74	882 .U3 "mh-e Support
meillo@72	883 .P
meillo@74	884 The configure option
meillo@74	885 .Sw --disable-mhe
meillo@74	886 was removed when the mh-e support was reworked.
meillo@74	887 Mh-e is the Emacs front-end to MH.
meillo@76	888 It requires MH to provide minor additional functions.
meillo@76	889 The
meillo@76	890 .Sw --disable-mhe
meillo@76	891 configure option could switch these extensions off.
meillo@76	892 After removing the support for old versions of mh-e,
meillo@74	893 only the
meillo@74	894 .Sw -build
meillo@76	895 switches of
meillo@74	896 .Pn forw
meillo@74	897 and
meillo@74	898 .Pn repl
meillo@76	899 are left to be mh-e extensions.
meillo@76	900 They are now always built in because they add little code and complexity.
meillo@76	901 In consequence, the
meillo@74	902 .Sw --disable-mhe
meillo@76	903 configure option was removed
meillo@72	904 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74	905 Removing the option removed a second code setup that would have
meillo@74	906 needed to be tested.
meillo@159	907 .\" XXX datum?
meillo@169	908 This change was first accomplished in nmh and thereafter merged into mmh.
meillo@76	909 .P
meillo@76	910 The interface changes in mmh require mh-e to be adjusted in order
meillo@76	911 to be able to use mmh as back-end.
meillo@76	912 This will require minor changes to mh-e, but removing the
meillo@76	913 .Sw -build
meillo@76	914 switches would require more rework.
meillo@72	915
meillo@74	916 .U3 "Masquerading
meillo@72	917 .P
meillo@74	918 The configure option
meillo@74	919 .Sw --enable-masquerade
meillo@76	920 could take up to three arguments:
meillo@76	921 `draft_from', `mmailid', and `username_extension'.
meillo@74	922 They activated different types of address masquerading.
meillo@74	923 All of them were implemented in the SMTP-speaking
meillo@74	924 .Pn post
meillo@76	925 command, which provided an MSA.
meillo@76	926 Address masquerading is an MTA's task and mmh does not cover
meillo@76	927 this field anymore.
meillo@76	928 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74	929 .P
meillo@74	930 The
meillo@74	931 .I mmailid
meillo@74	932 masquerading type is the oldest one of the three and the only one
meillo@74	933 available in the original MH.
meillo@74	934 It provided a
meillo@74	935 .I username
meillo@74	936 to
meillo@74	937 .I fakeusername
meillo@76	938 mapping, based on the password file's GECOS field.
meillo@74	939 The man page
meillo@181	940 .Mp mh-tailor (5)
meillo@74	941 described the use case as being the following:
meillo@98	942 .QS
meillo@74	943 This is useful if you want the messages you send to always
meillo@74	944 appear to come from the name of an MTA alias rather than your
meillo@74	945 actual account name. For instance, many organizations set up
meillo@74	946 `First.Last' sendmail aliases for all users. If this is
meillo@74	947 the case, the GECOS field for each user should look like:
meillo@74	948 ``First [Middle] Last <First.Last>''
meillo@98	949 .QE
meillo@74	950 .P
meillo@74	951 As mmh sends outgoing mail via the local MTA only,
meillo@76	952 the best location to do such global rewrites is there.
meillo@74	953 Besides, the MTA is conceptionally the right location because it
meillo@74	954 does the reverse mapping for incoming mail (aliasing), too.
meillo@181	955 Furthermore, masquerading set up there is readily available for all
meillo@74	956 mail software on the system.
meillo@76	957 Hence, mmailid masquerading was removed.
meillo@74	958 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74	959 .P
meillo@74	960 The
meillo@74	961 .I username_extension
meillo@76	962 masquerading type did not replace the username but would append a suffix,
meillo@76	963 specified by the
meillo@74	964 .Ev USERNAME_EXTENSION
meillo@76	965 environment variable, to it.
meillo@76	966 This provided support for the
meillo@74	967 .I user-extension
meillo@74	968 feature of qmail and the similar
meillo@74	969 .I "plussed user
meillo@74	970 processing of sendmail.
meillo@74	971 The decision to remove this username_extension masquerading was
meillo@74	972 motivated by the fact that
meillo@74	973 .Pn spost
meillo@173	974 had not supported it already.
meillo@76	975 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76	976 Username extensions are possible in mmh, but less convenient to use.
meillo@159	977 .\" XXX covered by next paragraph
meillo@76	978 .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74	979 .P
meillo@74	980 The
meillo@74	981 .I draft_from
meillo@74	982 masquerading type instructed
meillo@74	983 .Pn post
meillo@84	984 to use the value of the
meillo@84	985 .Hd From
meillo@84	986 header field as SMTP envelope sender.
meillo@76	987 Sender addresses could be replaced completely.
meillo@74	988 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76	989 Mmh offers a kind of masquerading similar in effect, but
meillo@74	990 with technical differences.
meillo@76	991 As mmh does not transfer messages itself, the local MTA has final control
meillo@76	992 over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76	993 by the MTA.
meillo@76	994 In times of pedantic spam checking, an MTA will take care to use
meillo@76	995 sensible envelope sender addresses to keep its own reputation up.
meillo@84	996 Nonetheless, the MUA can set the
meillo@84	997 .Hd From
meillo@84	998 header field and thereby propose
meillo@76	999 a sender address to the MTA.
meillo@74	1000 The MTA may then decide to take that one or generate the canonical sender
meillo@74	1001 address for use as envelope sender address.
meillo@74	1002 .P
meillo@74	1003 In mmh, the MTA will always extract the recipient and sender from the
meillo@84	1004 message header (\c
meillo@74	1005 .Pn sendmail 's
meillo@74	1006 .Sw -t
meillo@74	1007 switch).
meillo@84	1008 The
meillo@84	1009 .Hd From
meillo@84	1010 header field of the draft may be set arbitrary by the user.
meillo@74	1011 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74	1012
meillo@74	1013 .U3 "Remaining Options
meillo@74	1014 .P
meillo@74	1015 Two configure options remain in mmh.
meillo@74	1016 One is the locking method to use:
meillo@74	1017 .Sw --with-locking=[dot\|fcntl\|flock\|lockf] .
meillo@76	1018 The idea of removing all methods except the portable dot locking
meillo@76	1019 and having that one as the default is appealing, but this change
meillo@76	1020 requires deeper technical investigation into the topic.
meillo@76	1021 The other option,
meillo@74	1022 .Sw --enable-debug ,
meillo@74	1023 compiles the programs with debugging symbols and does not strip them.
meillo@74	1024 This option is likely to stay.
meillo@72	1025
meillo@72	1026
meillo@58	1027
meillo@63	1028
meillo@100	1029 .H2 "Command Line Switches
meillo@58	1030 .P
meillo@171	1031 The command line switches of MH tools is similar to the X Window style.
meillo@171	1032 .\" XXX ref
meillo@93	1033 They are words, introduced by a single dash.
meillo@93	1034 For example:
meillo@93	1035 .Cl "-truncate" .
meillo@93	1036 Every program in mmh has two generic switches:
meillo@93	1037 .Sw -help ,
meillo@93	1038 to print a short message on how to use the program, and
meillo@159	1039 .Sw -Version
meillo@164	1040 (with capital `V'), to tell what version of mmh the program belongs to.
meillo@93	1041 .P
meillo@93	1042 Switches change the behavior of programs.
meillo@93	1043 Programs that do one thing in one way require no switches.
meillo@93	1044 In most cases, doing something in exactly one way is too limiting.
meillo@97	1045 If there is basically one task to accomplish, but it should be done
meillo@93	1046 in various ways, switches are a good approach to alter the behavior
meillo@93	1047 of a program.
meillo@93	1048 Changing the behavior of programs provides flexibility and customization
meillo@97	1049 to users, but at the same time it complicates the code, documentation and
meillo@93	1050 usage of the program.
meillo@97	1051 .\" XXX: Ref
meillo@93	1052 Therefore, the number of switches should be kept small.
meillo@93	1053 A small set of well-chosen switches does no harm.
meillo@93	1054 But usually, the number of switches increases over time.
meillo@93	1055 Already in 1985, Rose and Romine have identified this as a major
meillo@93	1056 problem of MH:
meillo@93	1057 .[ [
meillo@93	1058 rose romine real work
meillo@93	1059 .], p. 12]
meillo@98	1060 .QS
meillo@93	1061 A complaint often heard about systems which undergo substantial development
meillo@93	1062 by many people over a number of years, is that more and more options are
meillo@93	1063 introduced which add little to the functionality but greatly increase the
meillo@93	1064 amount of information a user needs to know in order to get useful work done.
meillo@93	1065 This is usually referred to as creeping featurism.
meillo@93	1066 .QP
meillo@93	1067 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93	1068 ten or so well-meaning programmers (the present authors included),
meillo@93	1069 suffers mightily from this.
meillo@98	1070 .QE
meillo@93	1071 .P
meillo@97	1072 Being reluctant to adding new switches \(en or `options',
meillo@97	1073 as Rose and Romine call them \(en is one part of a counter-action,
meillo@97	1074 the other part is removing hardly used switches.
meillo@97	1075 Nmh's tools had lots of switches already implemented,
meillo@97	1076 hence, cleaning up by removing some of them was the more important part
meillo@97	1077 of the counter-action.
meillo@93	1078 Removing existing functionality is always difficult because it
meillo@93	1079 breaks programs that use these functions.
meillo@93	1080 Also, for every obsolete feature, there'll always be someone who still
meillo@93	1081 uses it and thus opposes its removal.
meillo@93	1082 This puts the developer into the position,
meillo@93	1083 where sensible improvements to style are regarded as destructive acts.
meillo@97	1084 Yet, living with the featurism is far worse, in my eyes, because
meillo@97	1085 future needs will demand adding further features,
meillo@93	1086 worsening the situation more and more.
meillo@93	1087 Rose and Romine added in a footnote,
meillo@93	1088 ``[...]
meillo@93	1089 .Pn send
meillo@93	1090 will no doubt acquire an endless number of switches in the years to come.''
meillo@97	1091 Although clearly humorous, the comment points to the nature of the problem.
meillo@97	1092 Refusing to add any new switches would encounter the problem at its root,
meillo@97	1093 but this is not practical.
meillo@97	1094 New needs will require new switches and it would be unwise to block
meillo@97	1095 them strictly.
meillo@97	1096 Nevertheless, removing obsolete switches still is an effective approach
meillo@97	1097 to deal with the problem.
meillo@97	1098 Working on an experimental branch without an established user base,
meillo@97	1099 eased my work because I did not offend users when I removed existing
meillo@110	1100 functions.
meillo@93	1101 .P
meillo@93	1102 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93	1103 .Pn send .
meillo@97	1104 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@182	1105 At the time of writing, no more than 4 visible switches and 1 hidden switch
meillo@97	1106 have remained in mmh's
meillo@97	1107 .Pn send .
meillo@183	1108 These numbers include two generic switches,
meillo@182	1109 .Sw -help
meillo@182	1110 and
meillo@183	1111 .Sw -Version .
meillo@183	1112 Hidden switches are ones not documented.
meillo@183	1113 In mmh, 12 tools have hidden switches.
meillo@183	1114 9 of them are
meillo@183	1115 .Sw -debug
meillo@183	1116 switches, the other 6 provide special interfaces for internal use.
meillo@93	1117 .P
meillo@154	1118 The figure displays the number of switches for each of the tools
meillo@159	1119 that is available in both nmh and mmh.
meillo@100	1120 The tools are sorted by the number of switches they had in nmh.
meillo@100	1121 Visible and hidden switches were counted,
meillo@97	1122 but not the generic help and version switches.
meillo@93	1123 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93	1124 now it has no more than 5 \(en only half as many.
meillo@93	1125 If the `no' switches and similar inverse variant are folded onto
meillo@100	1126 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100	1127 has 4 now.
meillo@93	1128 The total number of functional switches in mmh dropped from 465
meillo@182	1129 to 233.
meillo@58	1130
meillo@93	1131 .KS
meillo@93	1132 .in 1c
meillo@93	1133 .so input/switches.grap
meillo@93	1134 .KE
meillo@58	1135
meillo@93	1136 .P
meillo@93	1137 A part of the switches vanished after functions were removed.
meillo@93	1138 This was the case for network mail transfer, for instance.
meillo@97	1139 Sometimes, however, the work flow was the other way:
meillo@97	1140 I looked through the
meillo@97	1141 .Mp mh-chart (7)
meillo@97	1142 man page to identify the tools with apparently too many switches.
meillo@97	1143 Then considering the value of each of the switches by examining
meillo@97	1144 the tool's man page and source code, aided by recherche and testing.
meillo@97	1145 This way, the removal of functions was suggested by the aim to reduce
meillo@97	1146 the number of switches per command.
meillo@97	1147
meillo@58	1148
meillo@93	1149 .U3 "Draft Folder Facility
meillo@93	1150 .P
meillo@100	1151 A change early in the project was the complete transition from
meillo@93	1152 the single draft message to the draft folder facility.
meillo@97	1153 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@164	1154 .\" XXX ref to section ...
meillo@109	1155 The draft folder facility was introduced in the mid-eighties, when
meillo@100	1156 Rose and Romine called it a ``relatively new feature''.
meillo@93	1157 .[
meillo@93	1158 rose romine real work
meillo@93	1159 .]
meillo@110	1160 Since then, the facility had existed but was inactive by default.
meillo@93	1161 The default activation and the related rework of the tools made it
meillo@93	1162 possible to remove the
meillo@93	1163 .Sw -[no]draftfolder ,
meillo@93	1164 and
meillo@93	1165 .Sw -draftmessage
meillo@93	1166 switches from
meillo@93	1167 .Pn comp ,
meillo@93	1168 .Pn repl ,
meillo@93	1169 .Pn forw ,
meillo@93	1170 .Pn dist ,
meillo@93	1171 .Pn whatnow ,
meillo@93	1172 and
meillo@93	1173 .Pn send .
meillo@97	1174 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@97	1175 The only flexibility removed with this change is having multiple
meillo@97	1176 draft folders within one profile.
meillo@97	1177 I consider this a theoretical problem only.
meillo@159	1178 At the same time, the
meillo@93	1179 .Sw -draft
meillo@93	1180 switch of
meillo@93	1181 .Pn anno ,
meillo@93	1182 .Pn refile ,
meillo@93	1183 and
meillo@93	1184 .Pn send
meillo@93	1185 was removed.
meillo@159	1186 The special treatment of \fIthe\fP draft message became irrelevant after
meillo@93	1187 the rework of the draft system.
meillo@159	1188 (cf. Sec.
meillo@154	1189 .Cf draft-folder )
meillo@164	1190 Furthermore,
meillo@95	1191 .Pn comp
meillo@164	1192 no longer needs a
meillo@95	1193 .Sw -file
meillo@164	1194 switch as the draft folder facility together with the
meillo@95	1195 .Sw -form
meillo@164	1196 switch are sufficient.
meillo@93	1197
meillo@95	1198
meillo@102	1199 .U3 "In Place Editing
meillo@93	1200 .P
meillo@93	1201 .Pn anno
meillo@93	1202 had the switches
meillo@93	1203 .Sw -[no]inplace
meillo@100	1204 to either annotate the message in place and thus preserve hard links,
meillo@93	1205 or annotate a copy to replace the original message, breaking hard links.
meillo@97	1206 Following the assumption that linked messages should truly be the
meillo@97	1207 same message, and annotating it should not break the link, the
meillo@93	1208 .Sw -[no]inplace
meillo@93	1209 switches were removed and the previous default
meillo@93	1210 .Sw -inplace
meillo@93	1211 was made the only behavior.
meillo@97	1212 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0
meillo@93	1213 The
meillo@93	1214 .Sw -[no]inplace
meillo@93	1215 switches of
meillo@93	1216 .Pn repl ,
meillo@93	1217 .Pn forw ,
meillo@93	1218 and
meillo@93	1219 .Pn dist
meillo@93	1220 could be removed, too, as they were simply passed through to
meillo@93	1221 .Pn anno .
meillo@93	1222 .P
meillo@93	1223 .Pn burst
meillo@93	1224 also had
meillo@93	1225 .Sw -[no]inplace
meillo@95	1226 switches, but with different meaning.
meillo@95	1227 With
meillo@95	1228 .Sw -inplace ,
meillo@95	1229 the digest had been replaced by the table of contents (i.e. the
meillo@110	1230 introduction text) and the burst messages were placed right
meillo@95	1231 after this message, renumbering all following messages.
meillo@95	1232 Also, any trailing text of the digest was lost, though,
meillo@95	1233 in practice, it usually consists of an end-of-digest marker only.
meillo@95	1234 Nontheless, this behavior appeared less elegant than the
meillo@95	1235 .Sw -noinplace
meillo@95	1236 behavior, which already had been the default.
meillo@95	1237 Nmh's
meillo@95	1238 .Mp burst (1)
meillo@95	1239 man page reads:
meillo@98	1240 .QS
meillo@164	1241 If
meillo@164	1242 .Sw -noinplace
meillo@164	1243 is given, each digest is preserved, no table
meillo@93	1244 of contents is produced, and the messages contained within
meillo@93	1245 the digest are placed at the end of the folder. Other messages
meillo@93	1246 are not tampered with in any way.
meillo@98	1247 .QE
meillo@95	1248 .LP
meillo@93	1249 The decision to drop the
meillo@93	1250 .Sw -inplace
meillo@95	1251 behavior was supported by the code complexity and the possible data loss
meillo@95	1252 it caused.
meillo@93	1253 .Sw -noinplace
meillo@95	1254 was chosen to be the definitive behavior.
meillo@97	1255 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93	1256
meillo@95	1257
meillo@95	1258 .U3 "Forms and Format Strings
meillo@93	1259 .P
meillo@95	1260 Historically, the tools that had
meillo@95	1261 .Sw -form
meillo@95	1262 switches to supply a form file had
meillo@95	1263 .Sw -format
meillo@95	1264 switches as well to supply the contents of a form file as a string
meillo@95	1265 on the command line directly.
meillo@95	1266 In consequence, the following two lines equaled:
meillo@95	1267 .VS
meillo@95	1268 scan -form scan.mailx
meillo@95	1269 scan -format "`cat .../scan.mailx`"
meillo@95	1270 VE
meillo@95	1271 The
meillo@95	1272 .Sw -format
meillo@95	1273 switches were dropped in favor for extending the
meillo@95	1274 .Sw -form
meillo@95	1275 switches.
meillo@97	1276 .Ci f51956be123db66b00138f80464d06f030dbb88d
meillo@95	1277 If their argument starts with an equal sign (`='),
meillo@95	1278 then the rest of the argument is taken as a format string,
meillo@95	1279 otherwise the arguments is treated as the name of a format file.
meillo@95	1280 Thus, now the following two lines equal:
meillo@95	1281 .VS
meillo@95	1282 scan -form scan.mailx
meillo@95	1283 scan -form "=`cat .../scan.mailx`"
meillo@95	1284 VE
meillo@95	1285 This rework removed the prefix collision between
meillo@95	1286 .Sw -form
meillo@95	1287 and
meillo@95	1288 .Sw -format .
meillo@95	1289 Now, typing
meillo@95	1290 .Sw -fo
meillo@95	1291 suffices to specify form or format string.
meillo@95	1292 .P
meillo@95	1293 The different meaning of
meillo@95	1294 .Sw -format
meillo@95	1295 for
meillo@95	1296 .Pn repl
meillo@95	1297 and
meillo@95	1298 .Pn forw
meillo@95	1299 was removed in mmh.
meillo@95	1300 .Pn forw
meillo@95	1301 was completely switched to MIME-type forwarding, thus removing the
meillo@95	1302 .Sw -[no]format .
meillo@97	1303 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@95	1304 For
meillo@95	1305 .Pn repl ,
meillo@95	1306 the
meillo@95	1307 .Sw -[no]format
meillo@95	1308 switches were reworked to
meillo@95	1309 .Sw -[no]filter
meillo@95	1310 switches.
meillo@97	1311 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@95	1312 The
meillo@95	1313 .Sw -format
meillo@95	1314 switches of
meillo@95	1315 .Pn send
meillo@95	1316 and
meillo@95	1317 .Pn post ,
meillo@95	1318 which had a third meaning,
meillo@95	1319 were removed likewise.
meillo@97	1320 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9
meillo@95	1321 Eventually, the ambiguity of the
meillo@95	1322 .Sw -format
meillo@95	1323 switches was resolved by not anymore having any such switch in mmh.
meillo@95	1324
meillo@95	1325
meillo@95	1326 .U3 "MIME Tools
meillo@95	1327 .P
meillo@95	1328 The MIME tools, which were once part of
meillo@100	1329 .Pn mhn
meillo@164	1330 .\" XXX
meillo@164	1331 (whatever that stood for),
meillo@95	1332 had several switches that added little practical value to the programs.
meillo@95	1333 The
meillo@95	1334 .Sw -[no]realsize
meillo@95	1335 switches of
meillo@95	1336 .Pn mhbuild
meillo@95	1337 and
meillo@95	1338 .Pn mhlist
meillo@97	1339 were removed, doing real size calculations always now
meillo@97	1340 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c ,
meillo@159	1341 as nmh's
meillo@159	1342 .Mp mhbuild (1)
meillo@159	1343 man page states
meillo@95	1344 ``This provides an accurate count at the expense of a small delay.''
meillo@95	1345 This small delay is not noticable on modern systems.
meillo@95	1346 .P
meillo@95	1347 The
meillo@95	1348 .Sw -[no]check
meillo@95	1349 switches were removed together with the support for
meillo@95	1350 .Hd Content-MD5
meillo@199	1351 header fields [RFC\\|1864].
meillo@97	1352 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@154	1353 (cf. Sec.
meillo@154	1354 .Cf content-md5 )
meillo@95	1355 .P
meillo@95	1356 The
meillo@95	1357 .Sw -[no]ebcdicsafe
meillo@95	1358 and
meillo@95	1359 .Sw -[no]rfc934mode
meillo@95	1360 switches of
meillo@95	1361 .Pn mhbuild
meillo@95	1362 were removed because they are considered obsolete.
meillo@97	1363 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@97	1364 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88
meillo@95	1365 .P
meillo@95	1366 Content caching of external MIME parts, activated with the
meillo@95	1367 .Sw -rcache
meillo@95	1368 and
meillo@95	1369 .Sw -wcache
meillo@95	1370 switches was completely removed.
meillo@97	1371 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269
meillo@97	1372 External MIME parts are rare today, having a caching facility
meillo@159	1373 for them appears to be unnecessary.
meillo@95	1374 .P
meillo@95	1375 In pre-MIME times,
meillo@95	1376 .Pn mhl
meillo@95	1377 had covered many tasks that are part of MIME handling today.
meillo@95	1378 Therefore,
meillo@95	1379 .Pn mhl
meillo@95	1380 could be simplified to a large extend, reducing the number of its
meillo@95	1381 switches from 21 to 6.
meillo@97	1382 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@97	1383 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@95	1384
meillo@95	1385
meillo@95	1386
meillo@95	1387
meillo@95	1388 .U3 "Header Printing
meillo@95	1389 .P
meillo@95	1390 .Pn folder 's
meillo@95	1391 data output is self-explaining enough that
meillo@159	1392 displaying the header line makes little sense.
meillo@95	1393 Hence, the
meillo@95	1394 .Sw -[no]header
meillo@95	1395 switch was removed and headers are never printed.
meillo@97	1396 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7
meillo@95	1397 .P
meillo@95	1398 In
meillo@95	1399 .Pn mhlist ,
meillo@95	1400 the
meillo@95	1401 .Sw -[no]header
meillo@95	1402 switches were removed, too.
meillo@97	1403 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f
meillo@95	1404 But in this case headers are always printed,
meillo@95	1405 because the output is not self-explaining.
meillo@95	1406 .P
meillo@95	1407 .Pn scan
meillo@95	1408 also had
meillo@95	1409 .Sw -[no]header
meillo@95	1410 switches.
meillo@95	1411 Printing the header had been sensible until the introduction of
meillo@95	1412 format strings made it impossible to display the column headings.
meillo@95	1413 Only the folder name and the current date remained to be printed.
meillo@95	1414 As this information can be perfectly retrieved by
meillo@95	1415 .Pn folder
meillo@95	1416 and
meillo@95	1417 .Pn date ,
meillo@95	1418 consequently, the switches were removed.
meillo@97	1419 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e
meillo@95	1420 .P
meillo@95	1421 By removing all
meillo@95	1422 .Sw -header
meillo@95	1423 switches, the collision with
meillo@95	1424 .Sw -help
meillo@95	1425 on the first two letters was resolved.
meillo@95	1426 Currently,
meillo@95	1427 .Sw -h
meillo@95	1428 evaluates to
meillo@95	1429 .Sw -help
meillo@95	1430 for all tools of mmh.
meillo@95	1431
meillo@95	1432
meillo@139	1433 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95	1434 .P
meillo@95	1435 The
meillo@95	1436 .Sw -noedit
meillo@100	1437 switch of
meillo@95	1438 .Pn comp ,
meillo@95	1439 .Pn repl ,
meillo@95	1440 .Pn forw ,
meillo@95	1441 .Pn dist ,
meillo@95	1442 and
meillo@95	1443 .Pn whatnow
meillo@95	1444 was removed, but it can now be replaced by specifying
meillo@95	1445 .Sw -editor
meillo@95	1446 with an empty argument.
meillo@97	1447 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9
meillo@95	1448 (Specifying
meillo@159	1449 .Cl "-editor /bin/true
meillo@95	1450 is nearly the same, only differing by the previous editor being set.)
meillo@95	1451 .P
meillo@95	1452 The more important change is the removal of the
meillo@95	1453 .Sw -nowhatnowproc
meillo@95	1454 switch.
meillo@97	1455 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622
meillo@95	1456 This switch had introduced an awkward behavior, as explained in nmh's
meillo@95	1457 man page for
meillo@95	1458 .Mp comp (1):
meillo@98	1459 .QS
meillo@164	1460 The
meillo@164	1461 .Sw -editor
meillo@164	1462 .Ar editor
meillo@164	1463 switch indicates the editor to use for
meillo@164	1464 the initial edit. Upon exiting from the editor,
meillo@164	1465 .Pn comp
meillo@164	1466 will invoke the
meillo@164	1467 .Pn whatnow
meillo@164	1468 program. See
meillo@164	1469 .Mp whatnow (1)
meillo@164	1470 for a discussion of available options.
meillo@164	1471 The invocation of this program can be
meillo@164	1472 inhibited by using the
meillo@164	1473 .Sw -nowhatnowproc
meillo@164	1474 switch. (In truth of fact, it is the
meillo@164	1475 .Pn whatnow
meillo@164	1476 program which starts the initial edit.
meillo@164	1477 Hence,
meillo@164	1478 .Sw -nowhatnowproc
meillo@164	1479 will prevent any edit from occurring.)
meillo@98	1480 .QE
meillo@95	1481 .P
meillo@95	1482 Effectively, the
meillo@95	1483 .Sw -nowhatnowproc
meillo@100	1484 switch creates only a draft message.
meillo@95	1485 As
meillo@159	1486 .Cl "-whatnowproc /bin/true
meillo@95	1487 causes the same behavior, the
meillo@95	1488 .Sw -nowhatnowproc
meillo@95	1489 switch was removed for being redundant.
meillo@100	1490 Likely, the
meillo@95	1491 .Sw -nowhatnowproc
meillo@100	1492 switch was intended to be used by front-ends.
meillo@95	1493
meillo@95	1494
meillo@95	1495
meillo@95	1496 .U3 "Various
meillo@95	1497 .BU
meillo@139	1498 With the removal of MMDF maildrop format support,
meillo@139	1499 .Pn packf
meillo@139	1500 and
meillo@139	1501 .Pn rcvpack
meillo@139	1502 no longer needed their
meillo@139	1503 .Sw -mbox
meillo@139	1504 and
meillo@139	1505 .Sw -mmdf
meillo@139	1506 switches.
meillo@139	1507 .Sw -mbox
meillo@154	1508 is the sole behavior now.
meillo@139	1509 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@171	1510 Further rework in both tools made the
meillo@139	1511 .Sw -file
meillo@171	1512 switch unnecessary.
meillo@139	1513 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e
meillo@139	1514
meillo@139	1515 .BU
meillo@139	1516 Mmh's tools will no longer clear the screen (\c
meillo@139	1517 .Pn scan 's
meillo@139	1518 and
meillo@139	1519 .Pn mhl 's
meillo@139	1520 .Sw -[no]clear
meillo@139	1521 switches
meillo@139	1522 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139	1523 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@139	1524 Neither will
meillo@139	1525 .Pn mhl
meillo@139	1526 ring the bell (\c
meillo@139	1527 .Sw -[no]bell
meillo@139	1528 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@139	1529 nor page the output itself (\c
meillo@139	1530 .Sw -length
meillo@139	1531 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@159	1532 .\" XXX Ref
meillo@139	1533 Generally, the pager to use is no longer specified with the
meillo@139	1534 .Sw -[no]moreproc
meillo@139	1535 command line switches for
meillo@139	1536 .Pn mhl
meillo@139	1537 and
meillo@139	1538 .Pn show /\c
meillo@139	1539 .Pn mhshow .
meillo@139	1540 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a
meillo@139	1541
meillo@139	1542 .BU
meillo@96	1543 In order to avoid prefix collisions among switch names, the
meillo@95	1544 .Sw -version
meillo@95	1545 switch was renamed to
meillo@95	1546 .Sw -Version
meillo@95	1547 (with capital `V').
meillo@97	1548 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a
meillo@95	1549 Every program has the
meillo@95	1550 .Sw -version
meillo@95	1551 switch but its first three letters collided with the
meillo@95	1552 .Sw -verbose
meillo@95	1553 switch, present in many programs.
meillo@95	1554 The rename solved this problem once for all.
meillo@95	1555 Although this rename breaks a basic interface, having the
meillo@95	1556 .Sw -V
meillo@95	1557 abbreviation to display the version information, isn't all too bad.
meillo@139	1558
meillo@95	1559 .BU
meillo@95	1560 .Sw -[no]preserve
meillo@95	1561 of
meillo@95	1562 .Pn refile
meillo@168	1563 was removed
meillo@168	1564 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168	1565 because what use was it anyway?
meillo@168	1566 Quoting nmh's man page
meillo@165	1567 .Mp refile (1):
meillo@98	1568 .QS
meillo@95	1569 Normally when a message is refiled, for each destination
meillo@95	1570 folder it is assigned the number which is one above the current
meillo@95	1571 highest message number in that folder. Use of the
meillo@164	1572 .Sw -preserv
meillo@164	1573 [sic!] switch will override this message renaming, and try
meillo@95	1574 to preserve the number of the message. If a conflict for a
meillo@164	1575 particular folder occurs when using the
meillo@164	1576 .Sw -preserve
meillo@164	1577 switch, then
meillo@164	1578 .Pn refile
meillo@164	1579 will use the next available message number which
meillo@95	1580 is above the message number you wish to preserve.
meillo@98	1581 .QE
meillo@139	1582
meillo@95	1583 .BU
meillo@95	1584 The removal of the
meillo@95	1585 .Sw -[no]reverse
meillo@95	1586 switches of
meillo@95	1587 .Pn scan
meillo@97	1588 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@95	1589 is a bug fix, supported by the comments
meillo@95	1590 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95	1591 by Rose and
meillo@95	1592 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@95	1593 This should be considered a bug.'' by Romine in the documentation.
meillo@159	1594 .\" XXX Ref: welche datei genau.
meillo@97	1595 The question remains why neither Rose and Romine had fixed this
meillo@109	1596 bug in the eighties when they wrote these comments nor has anyone
meillo@95	1597 thereafter.
meillo@93	1598
meillo@93	1599
meillo@93	1600 .ig
meillo@93	1601
meillo@95	1602 forw: [no]dashstuffing(mhl)
meillo@93	1603
meillo@95	1604 mhshow: [no]pause [no]serialonly
meillo@93	1605
meillo@93	1606 mhmail: resent queued
meillo@93	1607 inc: snoop, (pop)
meillo@93	1608
meillo@95	1609 mhl: [no]faceproc folder sleep
meillo@95	1610 [no]dashstuffing(forw) digest list volume number issue number
meillo@93	1611
meillo@95	1612 prompter: [no]doteof
meillo@93	1613
meillo@93	1614 refile: [no]preserve [no]unlink [no]rmmproc
meillo@93	1615
meillo@95	1616 send: [no]forward [no]mime [no]msgid
meillo@93	1617 [no]push split [no]unique (sasl) width snoop [no]dashstuffing
meillo@93	1618 attach attachformat
meillo@93	1619 whatnow: (noedit) attach
meillo@93	1620
meillo@93	1621 slocal: [no]suppressdups
meillo@93	1622
meillo@95	1623 spost: [no]filter [no]backup width [no]push idanno
meillo@93	1624 [no]check(whom) whom(whom)
meillo@93	1625
meillo@93	1626 whom: ???
meillo@93	1627
meillo@95	1628 ..
meillo@93	1629
meillo@93	1630
meillo@93	1631 .ig
meillo@93	1632
meillo@93	1633 .P
meillo@93	1634 In the best case, all switches are unambiguous on the first character,
meillo@93	1635 or on the three-letter prefix for the `no' variants.
meillo@96	1636 Reducing switch prefix collisions, shortens the necessary prefix length
meillo@93	1637 the user must type.
meillo@93	1638 Having less switches helps best.
meillo@93	1639
meillo@93	1640 ..
meillo@58	1641
meillo@95	1642
meillo@102	1643 .\" XXX: whatnow prompt commands
meillo@102	1644
meillo@102	1645
meillo@95	1646
meillo@95	1647
meillo@133	1648 .\" --------------------------------------------------------------
meillo@74	1649 .H1 "Modernizing
meillo@102	1650 .P
meillo@164	1651 In the more than thirty years of MH's existence, its code base was
meillo@159	1652 increasingly extended.
meillo@118	1653 New features entered the project and became alternatives to the
meillo@118	1654 existing behavior.
meillo@118	1655 Relicts from several decades have gathered in the code base,
meillo@118	1656 but seldom obsolete features were dropped.
meillo@118	1657 This section describes the removing of old code
meillo@118	1658 and the modernizing of the default setup.
meillo@118	1659 It focuses on the functional aspect only;
meillo@154	1660 the non-functional aspects of code style are discussed in Sec.
meillo@154	1661 .Cf code-style .
meillo@58	1662
meillo@58	1663
meillo@100	1664 .H2 "Code Relicts
meillo@0	1665 .P
meillo@159	1666 My position regarding the removal of obsolete functions of mmh,
meillo@159	1667 .\" XXX ``in order to remove old code,''
meillo@159	1668 is much more revolutional than the nmh community appreciates.
meillo@159	1669 Working on an experimental version, I was quickly able to drop
meillo@104	1670 functionality I considered ancient.
meillo@104	1671 The need for consensus with peers would have slowed this process down.
meillo@104	1672 Without the need to justify my decisions, I was able to rush forward.
meillo@110	1673 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@159	1674 .\" XXX ugs
meillo@104	1675 do the work:
meillo@104	1676 .[
meillo@104	1677 paul vixie edginess nmh-workers
meillo@104	1678 .]
meillo@104	1679 .QS
meillo@104	1680 let's stop walking on egg shells with this code base. there's no need to
meillo@104	1681 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104	1682 we don't need a separate branch for removing vmh
meillo@104	1683 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@164	1684 or depending on pure ansi/posix ``libc''.
meillo@104	1685 .QP
meillo@164	1686 these things should each be a day or two of work and the ``main branch''
meillo@104	1687 should just be modern. [...]
meillo@104	1688 let's push forward, aggressively.
meillo@104	1689 .QE
meillo@104	1690 .LP
meillo@104	1691 I did so already in the months before.
meillo@104	1692 I pushed forward.
meillo@159	1693 .\" XXX semicolon ?
meillo@104	1694 I simply dropped the cruft.
meillo@104	1695 .P
meillo@104	1696 The decision to drop a feature was based on literature research and
meillo@159	1697 careful thinking, but whether having had contact with this particular
meillo@104	1698 feature within my own computer life served as a rule of thumb.
meillo@159	1699 I explained my reasons in the commit messages
meillo@109	1700 in the version control system.
meillo@104	1701 Hence, others can comprehend my view and argue for undoing the change
meillo@104	1702 if I have missed an important aspect.
meillo@109	1703 I was quick in dropping parts.
meillo@179	1704 I rather include falsely dropped parts again, than going at a slower pace.
meillo@179	1705 Mmh is experimental work; it requires tough decisions.
meillo@159	1706 .\" XXX ``exp. work'' schon oft gesagt
meillo@12	1707
meillo@102	1708
meillo@104	1709 .U3 "Forking
meillo@12	1710 .P
meillo@109	1711 Being a tool chest, MH creates many processes.
meillo@104	1712 In earlier times
meillo@104	1713 .Fu fork()
meillo@104	1714 had been an expensive system call, because the process's image needed
meillo@159	1715 to be completely duplicated at once.
meillo@200	1716 This expensive work was especially unnecessary in the commonly occurring
meillo@159	1717 case wherein the image is replaced by a call to
meillo@104	1718 .Fu exec()
meillo@104	1719 right after having forked the child process.
meillo@104	1720 The
meillo@104	1721 .Fu vfork()
meillo@104	1722 system call was invented to speed up this particular case.
meillo@104	1723 It completely omits the duplication of the image.
meillo@104	1724 On old systems this resulted in significant speed ups.
meillo@104	1725 Therefore MH used
meillo@104	1726 .Fu vfork()
meillo@104	1727 whenever possible.
meillo@12	1728 .P
meillo@104	1729 Modern memory management units support copy-on-write semantics, which make
meillo@104	1730 .Fu fork()
meillo@104	1731 almost as fast as
meillo@104	1732 .Fu vfork() .
meillo@104	1733 The man page of
meillo@104	1734 .Mp vfork (2)
meillo@104	1735 in FreeBSD 8.0 states:
meillo@104	1736 .QS
meillo@104	1737 This system call will be eliminated when proper system sharing mechanisms
meillo@104	1738 are implemented. Users should not depend on the memory sharing semantics
meillo@104	1739 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104	1740 .QE
meillo@104	1741 .LP
meillo@104	1742 Vixie supports the removal with the note that ``the last
meillo@104	1743 system on which fork was so slow that an mh user would notice it, was
meillo@104	1744 Eunice. that was 1987''.
meillo@104	1745 .[
meillo@104	1746 nmh-workers vixie edginess
meillo@104	1747 .]
meillo@104	1748 I replaced all calls to
meillo@104	1749 .Fu vfork()
meillo@104	1750 with calls to
meillo@104	1751 .Fu fork() .
meillo@109	1752 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104	1753 .P
meillo@104	1754 Related to the costs of
meillo@104	1755 .Fu fork()
meillo@104	1756 is the probability of its success.
meillo@109	1757 In the eighties, on heavy loaded systems, calls to
meillo@104	1758 .Fu fork()
meillo@104	1759 were prone to failure.
meillo@104	1760 Hence, many of the
meillo@104	1761 .Fu fork()
meillo@104	1762 calls in the code were wrapped into loops to retry the
meillo@104	1763 .Fu fork()
meillo@159	1764 several times, to increase the chances to succeed, eventually.
meillo@109	1765 On modern systems, a failing
meillo@104	1766 .Fu fork()
meillo@109	1767 call is unusual.
meillo@104	1768 Hence, in the rare case when
meillo@104	1769 .Fu fork()
meillo@104	1770 fails, mmh programs simply abort.
meillo@109	1771 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12	1772
meillo@12	1773
meillo@109	1774 .U3 "Header Fields
meillo@104	1775 .BU
meillo@84	1776 The
meillo@84	1777 .Hd Encrypted
meillo@104	1778 header field was introduced by RFC\\|822,
meillo@109	1779 but already marked as legacy in RFC\\|2822.
meillo@109	1780 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104	1781 messages [RFC\\|4880, RFC\\|3156].
meillo@109	1782 Hence, the support for
meillo@104	1783 .Hd Encrypted
meillo@104	1784 header fields is removed in mmh.
meillo@109	1785 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104	1786 .BU
meillo@159	1787 The native support for
meillo@84	1788 .Hd Face
meillo@104	1789 header fields has been removed, as well.
meillo@109	1790 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104	1791 This feature is similar to the
meillo@84	1792 .Hd X-Face
meillo@84	1793 header field in its intent,
meillo@21	1794 but takes a different approach to store the image.
meillo@84	1795 Instead of encoding the image data directly into the header field,
meillo@109	1796 it contains the hostname and UDP port where the image
meillo@109	1797 date can be retrieved.
meillo@159	1798 There is even a third Face system,
meillo@109	1799 which is the successor of
meillo@109	1800 .Hd X-Face ,
meillo@109	1801 although it re-uses the
meillo@104	1802 .Hd Face
meillo@109	1803 header field.
meillo@109	1804 It was invented in 2005 and supports colored PNG images.
meillo@104	1805 None of the Face systems described here is popular today.
meillo@104	1806 Hence, mmh has no direct support for them.
meillo@104	1807 .BU
meillo@154	1808 .Id content-md5
meillo@104	1809 The
meillo@104	1810 .Hd Content-MD5
meillo@104	1811 header field was introduced by RFC\\|1864.
meillo@104	1812 It provides detection of data corruption during the transfer.
meillo@104	1813 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104	1814 [RFC\\|1864].
meillo@104	1815 The proper approach to verify content integrity in an
meillo@166	1816 end-to-end relationship is the use of digital signatures.
meillo@104	1817 .\" XXX (RFCs FIXME).
meillo@104	1818 On the other hand, transfer protocols should detect corruption during
meillo@109	1819 the transmission.
meillo@109	1820 The TCP includes a checksum field therefore.
meillo@104	1821 These two approaches in combinations render the
meillo@104	1822 .Hd Content-MD5
meillo@104	1823 header field superfluous.
meillo@109	1824 Not a single one out of 4\\|200 messages from two decades
meillo@109	1825 in an nmh-workers mailing list archive contains a
meillo@104	1826 .Hd Content-MD5
meillo@104	1827 header field.
meillo@104	1828 Neither did any of the 60\\|000 messages in my personal mail storage.
meillo@104	1829 Removing the support for this header field,
meillo@104	1830 removed the last place where MD5 computation was needed.
meillo@109	1831 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104	1832 Hence, the MD5 code could be removed as well.
meillo@104	1833 Over 500 lines of code vanished by this one change.
meillo@104	1834
meillo@104	1835
meillo@104	1836 .U3 "MMDF maildrop support
meillo@21	1837 .P
meillo@104	1838 This type of format is conceptionally similar to the mbox format,
meillo@139	1839 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139	1840 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104	1841 Mbox is the de-facto standard maildrop format on Unix,
meillo@159	1842 whereas the MMDF maildrop format is now forgotten.
meillo@159	1843 By dropping the MMDF maildrop format support,
meillo@159	1844 mbox became the only packed mailbox format supported in mmh.
meillo@104	1845 .P
meillo@109	1846 The simplifications within the code were moderate.
meillo@109	1847 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109	1848 But also, switches of
meillo@109	1849 .Pn packf
meillo@104	1850 and
meillo@109	1851 .Pn rcvpack
meillo@109	1852 could be removed.
meillo@109	1853 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109	1854 In the message parsing function
meillo@109	1855 .Fn sbr/m_getfld.c ,
meillo@109	1856 knowledge of MMDF packed mail boxes was removed.
meillo@109	1857 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109	1858 Further code structure simplifications may be possible there,
meillo@109	1859 because only one single packed mailbox format is left to be supported.
meillo@104	1860 I have not worked on them yet because
meillo@104	1861 .Fu m_getfld()
meillo@104	1862 is heavily optimized and thus dangerous to touch.
meillo@104	1863 The risk of damaging the intricate workings of the optimized code is
meillo@104	1864 too high.
meillo@104	1865
meillo@12	1866
meillo@101	1867 .U3 "Prompter's Control Keys
meillo@20	1868 .P
meillo@20	1869 The program
meillo@20	1870 .Pn prompter
meillo@104	1871 queries the user to fill in a message form.
meillo@104	1872 When used by
meillo@20	1873 .Pn comp
meillo@104	1874 as
meillo@104	1875 .Cl "comp -editor prompter" ,
meillo@20	1876 the resulting behavior is similar to
meillo@20	1877 .Pn mailx .
meillo@51	1878 Apparently,
meillo@20	1879 .Pn prompter
meillo@173	1880 had not been touched lately.
meillo@104	1881 Otherwise it's hardly explainable why it
meillo@20	1882 still offered the switches
meillo@84	1883 .Sw -erase
meillo@84	1884 .Ar chr
meillo@20	1885 and
meillo@84	1886 .Sw -kill
meillo@84	1887 .Ar chr
meillo@20	1888 to name the characters for command line editing.
meillo@21	1889 The times when this had been necessary are long time gone.
meillo@20	1890 Today these things work out-of-the-box, and if not, are configured
meillo@20	1891 with the standard tool
meillo@20	1892 .Pn stty .
meillo@104	1893 The switches are removed now
meillo@104	1894 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20	1895
meillo@104	1896
meillo@109	1897 .U3 "Hardcopy Terminal Support
meillo@21	1898 .P
meillo@109	1899 More of a funny anecdote is a check for being connected to a
meillo@109	1900 hardcopy terminal.
meillo@159	1901 It remained in the code until spring 2012, when I finally removed it
meillo@104	1902 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@21	1903 .P
meillo@109	1904 The check only prevented a pager to be placed between the printing
meillo@104	1905 program (\c
meillo@104	1906 .Pn mhl )
meillo@104	1907 and the terminal.
meillo@109	1908 In nmh, this could have been ensured statically with the
meillo@104	1909 .Sw -nomoreproc
meillo@109	1910 at the command line, too.
meillo@121	1911 In mmh, setting the profile entry
meillo@104	1912 .Pe Pager
meillo@104	1913 or the environment variable
meillo@104	1914 .Ev PAGER
meillo@104	1915 to
meillo@109	1916 .Pn cat
meillo@159	1917 is sufficient.
meillo@104	1918
meillo@104	1919
meillo@21	1920
meillo@12	1921
meillo@58	1922 .H2 "Attachments
meillo@22	1923 .P
meillo@101	1924 The mind model of email attachments is unrelated to MIME.
meillo@199	1925 Although the MIME RFCs [RFC\\|2045\(enRFC\\|2049] define the technical
meillo@109	1926 requirements for having attachments, they do not mention the word
meillo@181	1927 attachment.
meillo@101	1928 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101	1929 [RFC\\|2045], a more general concept.
meillo@101	1930 Multi-part messages are messages
meillo@101	1931 ``in which one or more different
meillo@101	1932 sets of data are combined in a single body''
meillo@101	1933 [RFC\\|2046].
meillo@101	1934 MIME keeps its descriptions generic;
meillo@101	1935 it does not imply specific usage models.
meillo@109	1936 One usage model became prevalent: attachments.
meillo@101	1937 The idea is having a main text document with files of arbitrary kind
meillo@101	1938 attached to it.
meillo@101	1939 In MIME terms, this is a multi-part message having a text part first
meillo@110	1940 and parts of arbitrary type following.
meillo@101	1941 .P
meillo@101	1942 MH's MIME support is a direct implementation of the RFCs.
meillo@101	1943 The perception of the topic described in the RFCs is clearly visible
meillo@101	1944 in MH's implementation.
meillo@159	1945 .\" XXX rewrite ``no idea''.
meillo@159	1946 As a result,
meillo@159	1947 MH had all the MIME features but no idea of attachments.
meillo@173	1948 But users do not need all the MIME features,
meillo@109	1949 they want convenient attachment handling.
meillo@109	1950
meillo@102	1951
meillo@102	1952 .U3 "Composing MIME Messages
meillo@102	1953 .P
meillo@102	1954 In order to improve the situation on the message composing side,
meillo@102	1955 Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101	1956 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102	1957 In the file
meillo@102	1958 .Fn docs/README-ATTACHMENTS ,
meillo@102	1959 he described his motivation to do so as such:
meillo@101	1960 .QS
meillo@159	1961 Although nmh contains the necessary functionality for MIME message
meillo@159	1962 handing [sic!], the interface to this functionality is pretty obtuse.
meillo@101	1963 There's no way that I'm ever going to convince my partner to write
meillo@101	1964 .Pn mhbuild
meillo@101	1965 composition files!
meillo@101	1966 .QE
meillo@102	1967 .LP
meillo@102	1968 With this change, the mind model of attachments entered nmh.
meillo@102	1969 In the same document:
meillo@101	1970 .QS
meillo@101	1971 These changes simplify the task of managing attachments on draft files.
meillo@101	1972 They allow attachments to be added, listed, and deleted.
meillo@101	1973 MIME messages are automatically created when drafts with attachments
meillo@101	1974 are sent.
meillo@101	1975 .QE
meillo@102	1976 .LP
meillo@102	1977 Unfortunately, the attachment system,
meillo@102	1978 like any new facilities in nmh,
meillo@110	1979 was inactive by default.
meillo@101	1980 .P
meillo@101	1981 During my work in Argentina, I tried to improve the attachment system.
meillo@102	1982 But, because of great opposition in the nmh community,
meillo@102	1983 my patch died as a proposal on the mailing list, after long discussions.
meillo@101	1984 .[
meillo@101	1985 nmh-workers attachment proposal
meillo@101	1986 .]
meillo@110	1987 In January 2012, I extended the patch and applied it to mmh.
meillo@101	1988 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102	1989 In mmh, the attachment system is active by default.
meillo@102	1990 Instead of command line switches, the
meillo@102	1991 .Pe Attachment-Header
meillo@102	1992 profile entry is used to specify
meillo@102	1993 the name of the attachment header field.
meillo@102	1994 It is pre-defined to
meillo@102	1995 .Hd Attach .
meillo@101	1996 .P
meillo@159	1997 To add an attachment to a draft, a header line needs to be added:
meillo@101	1998 .VS
meillo@101	1999 To: bob
meillo@101	2000 Subject: The file you wanted
meillo@101	2001 Attach: /path/to/the/file-bob-wanted
meillo@101	2002 --------
meillo@101	2003 Here it is.
meillo@101	2004 VE
meillo@101	2005 The header field can be added to the draft manually in the editor,
meillo@102	2006 or by using the `attach' command at the WhatNow prompt, or
meillo@102	2007 non-interactively with
meillo@101	2008 .Pn anno :
meillo@101	2009 .VS
meillo@102	2010 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101	2011 VE
meillo@102	2012 Drafts with attachment headers are converted to MIME automatically by
meillo@102	2013 .Pn send .
meillo@102	2014 The conversion to MIME is invisible to the user.
meillo@159	2015 The draft stored in the draft folder is always in source form with
meillo@101	2016 attachment headers.
meillo@179	2017 If the MIMEification fails (e.g. because the file to attach
meillo@179	2018 is not accessible) the original draft is not changed.
meillo@101	2019 .P
meillo@102	2020 The attachment system handles the forwarding of messages, too.
meillo@173	2021 If the attachment header value starts with a plus character (`\fL+\fP'),
meillo@101	2022 like in
meillo@101	2023 .Cl "Attach: +bob 30 42" ,
meillo@159	2024 the given messages in the specified folder will be attached.
meillo@101	2025 This allowed to simplify
meillo@101	2026 .Pn forw .
meillo@101	2027 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101	2028 .P
meillo@101	2029 Closely related to attachments is non-ASCII text content,
meillo@101	2030 because it requires MIME too.
meillo@102	2031 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101	2032 to have the draft converted to MIME.
meillo@102	2033 This was necessary whenever the draft contained non-ASCII characters.
meillo@101	2034 If the user did not call `mime', a broken message would be sent.
meillo@101	2035 Therefore, the
meillo@101	2036 .Pe automimeproc
meillo@101	2037 profile entry could be specified to have the `mime' command invoked
meillo@102	2038 automatically each time.
meillo@179	2039 Unfortunately, this approach conflicted with the attachment system
meillo@101	2040 because the draft would already be in MIME format at the time
meillo@101	2041 when the attachment system wanted to MIMEify it.
meillo@102	2042 To use nmh's attachment system, `mime' must not be called at the
meillo@102	2043 WhatNow prompt and
meillo@101	2044 .Pe automimeproc
meillo@102	2045 must not be set in the profile.
meillo@101	2046 But then the case of non-ASCII text without attachment headers was
meillo@101	2047 not caught.
meillo@102	2048 All in all, the solution was complex and irritating.
meillo@168	2049 My patch from December 2010
meillo@168	2050 .[
meillo@168	2051 nmh-workers attachment proposal
meillo@168	2052 .]
meillo@168	2053 would have simplified the situation.
meillo@102	2054 .P
meillo@101	2055 Mmh's current solution is even more elaborate.
meillo@101	2056 Any necessary MIMEification is done automatically.
meillo@101	2057 There is no `mime' command at the WhatNow prompt anymore.
meillo@102	2058 The draft will be converted automatically to MIME when either an
meillo@102	2059 attachment header or non-ASCII text is present.
meillo@173	2060 Furthermore, the hash character (`\fL#\fP') is not special any more
meillo@159	2061 at line beginnings in the draft message.
meillo@159	2062 .\" XXX REF ?
meillo@159	2063 Users need not concern themselves with the whole topic at all.
meillo@101	2064 .P
meillo@102	2065 Although the new approach does not anymore support arbitrary MIME
meillo@102	2066 compositions directly, the full power of
meillo@101	2067 .Pn mhbuild
meillo@101	2068 can still be accessed.
meillo@102	2069 Given no attachment headers are included, the user can create
meillo@101	2070 .Pn mhbuild
meillo@102	2071 composition drafts like in nmh.
meillo@101	2072 Then, at the WhatNow prompt, he needs to invoke
meillo@101	2073 .Cl "edit mhbuild
meillo@101	2074 to convert it to MIME.
meillo@110	2075 Because the resulting draft does neither contain non-ASCII characters
meillo@102	2076 nor has it attachment headers, the attachment system will not touch it.
meillo@101	2077 .P
meillo@159	2078 The approach taken in mmh is tailored towards today's most common case:
meillo@159	2079 a text part, possibly with attachments.
meillo@159	2080 This case was simplified.
meillo@102	2081
meillo@112	2082
meillo@102	2083 .U3 "MIME Type Guessing
meillo@102	2084 .P
meillo@159	2085 From the programmer's point of view, the use of
meillo@101	2086 .Pn mhbuild
meillo@159	2087 composition drafts had one notable advantage over attachment headers:
meillo@159	2088 The user provides the appropriate MIME types for files to include.
meillo@102	2089 The attachment system needs to find out the correct MIME type itself.
meillo@102	2090 This is a difficult task, yet it spares the user irritating work.
meillo@102	2091 Determining the correct MIME type of content is partly mechanical,
meillo@102	2092 partly intelligent work.
meillo@102	2093 Forcing the user to find out the correct MIME type,
meillo@102	2094 forces him to do partly mechanical work.
meillo@179	2095 Letting the computer do the work can lead to bad choices for difficult
meillo@102	2096 content.
meillo@102	2097 For mmh, the latter option was chosen.
meillo@102	2098 .P
meillo@102	2099 Determining the MIME type by the suffix of the file name is a dumb
meillo@102	2100 approach, yet it is simple to implement and provides good results
meillo@102	2101 for the common cases.
meillo@102	2102 Mmh implements this approach in the
meillo@102	2103 .Pn print-mimetype
meillo@102	2104 script.
meillo@112	2105 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44
meillo@102	2106 Using it is the default choice.
meillo@102	2107 .P
meillo@112	2108 A far better, though less portable, approach is the use of
meillo@102	2109 .Pn file .
meillo@102	2110 This standard tool tries to determine the type of files.
meillo@102	2111 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102	2112 Additionally, its output was only intended for human beings,
meillo@102	2113 but not to be used by programs.
meillo@102	2114 It varies much.
meillo@102	2115 Nevertheless, modern versions of GNU
meillo@102	2116 .Pn file ,
meillo@102	2117 which is prevalent on the popular GNU/Linux systems,
meillo@159	2118 provide MIME type output in machine-readable form.
meillo@102	2119 Although this solution is highly system-dependent,
meillo@102	2120 it solves the difficult problem well.
meillo@102	2121 On systems where GNU
meillo@102	2122 .Pn file ,
meillo@102	2123 version 5.04 or higher, is available it should be used.
meillo@102	2124 One needs to specify the following profile entry to do so:
meillo@112	2125 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6
meillo@102	2126 .VS
meillo@102	2127 Mime-Type-Query: file -b --mime
meillo@102	2128 VE
meillo@102	2129 .LP
meillo@102	2130 Other versions of
meillo@102	2131 .Pn file
meillo@102	2132 might possibly be usable with wrapper scripts to reformat the output.
meillo@102	2133 The diversity among
meillo@102	2134 .Pn file
meillo@102	2135 implementations is great; one needs to check the local variant.
meillo@102	2136 .P
meillo@102	2137 If no MIME type can be determined, text content gets sent as
meillo@102	2138 `text/plain' and anything else under the generic fall-back type
meillo@102	2139 `application/octet-stream'.
meillo@102	2140 It is not possible in mmh to override the automatic MIME type guessing
meillo@102	2141 for a specific file.
meillo@159	2142 To do so, either the user would need to know in advance for which file
meillo@159	2143 the automatic guessing fails, or the system would require interaction.
meillo@102	2144 I consider both cases impractical.
meillo@102	2145 The existing solution should be sufficient.
meillo@102	2146 If not, the user may always fall back to
meillo@102	2147 .Pn mhbuild
meillo@102	2148 composition drafts and ignore the attachment system.
meillo@101	2149
meillo@102	2150
meillo@102	2151 .U3 "Storing Attachments
meillo@102	2152 .P
meillo@169	2153 Extracting MIME parts of a message and storing them to disk is performed by
meillo@108	2154 .Pn mhstore .
meillo@108	2155 The program has two operation modes,
meillo@108	2156 .Sw -auto
meillo@108	2157 and
meillo@108	2158 .Sw -noauto .
meillo@108	2159 With the former one, each part is stored under the filename given in the
meillo@108	2160 MIME part's meta information, if available.
meillo@108	2161 This naming information is usually available for modern attachments.
meillo@108	2162 If no filename is available, this MIME part is stored as if
meillo@108	2163 .Sw -noauto
meillo@108	2164 would have been specified.
meillo@108	2165 In the
meillo@108	2166 .Sw -noauto
meillo@108	2167 mode, the parts are processed according to rules, defined by
meillo@108	2168 .Pe mhstore-store-*
meillo@108	2169 profile entries.
meillo@108	2170 These rules define generic filename templates for storing
meillo@108	2171 or commands to post-process the contents in arbitrary ways.
meillo@108	2172 If no matching rule is available the part is stored under a generic
meillo@108	2173 filename, built from message number, MIME part number, and MIME type.
meillo@108	2174 .P
meillo@108	2175 The
meillo@108	2176 .Sw -noauto
meillo@108	2177 mode had been the default in nmh because it was considered safe,
meillo@108	2178 in contrast to the
meillo@108	2179 .Sw -auto
meillo@108	2180 mode.
meillo@108	2181 In mmh,
meillo@108	2182 .Sw -auto
meillo@108	2183 is not dangerous anymore.
meillo@108	2184 Two changes were necessary:
meillo@171	2185 .LI 1
meillo@108	2186 Any directory path is removed from the proposed filename.
meillo@108	2187 Thus, the files are always stored in the expected directory.
meillo@108	2188 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@171	2189 .LI 2
meillo@108	2190 Tar files are not extracted automatically any more.
meillo@108	2191 Thus, the rest of the file system will not be touched.
meillo@108	2192 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2193 .LP
meillo@108	2194 Now, the outcome of mmh's
meillo@108	2195 .Cl "mhstore -auto
meillo@110	2196 can be foreseen from the output of
meillo@108	2197 .Cl "mhlist -verbose" .
meillo@108	2198 .P
meillo@108	2199 The
meillo@108	2200 .Sw -noauto
meillo@108	2201 mode is seen to be more powerful but less convenient.
meillo@108	2202 On the other hand,
meillo@108	2203 .Sw -auto
meillo@108	2204 is safe now and
meillo@108	2205 storing attachments under their original name is intuitive.
meillo@108	2206 Hence,
meillo@108	2207 .Sw -auto
meillo@108	2208 serves better as the default option.
meillo@108	2209 .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108	2210 .P
meillo@108	2211 Files are stored into the directory given by the
meillo@108	2212 .Pe Nmh-Storage
meillo@108	2213 profile entry, if set, or
meillo@108	2214 into the current working directory, otherwise.
meillo@108	2215 Storing to different directories is only possible with
meillo@108	2216 .Pe mhstore-store-*
meillo@108	2217 profile entries.
meillo@108	2218 .P
meillo@108	2219 Still, in both modes, existing files get overwritten silently.
meillo@108	2220 This can be considered a bug.
meillo@108	2221 Yet, each other behavior has its draw-backs, too.
meillo@108	2222 Refusing to replace files requires adding a
meillo@108	2223 .Sw -force
meillo@108	2224 option.
meillo@108	2225 Users will likely need to invoke
meillo@108	2226 .Pn mhstore
meillo@108	2227 a second time with
meillo@159	2228 .Sw -force .
meillo@159	2229 Eventually, only the user can decide in the specific case.
meillo@108	2230 This requires interaction, which I like to avoid if possible.
meillo@108	2231 Appending a unique suffix to the filename is another bad option.
meillo@108	2232 For now, the behavior remains as it is.
meillo@108	2233 .P
meillo@108	2234 In mmh, only MIME parts of type message are special in
meillo@108	2235 .Pn mhstore 's
meillo@108	2236 .Sw -auto
meillo@108	2237 mode.
meillo@108	2238 Instead of storing message/rfc822 parts as files to disk,
meillo@108	2239 they are stored as messages into the current mail folder.
meillo@159	2240 The same applies to message/partial, although the parts are
meillo@159	2241 automatically reassembled beforehand.
meillo@159	2242 MIME parts of type message/external-body are not automatically retrieved
meillo@159	2243 anymore.
meillo@159	2244 Instead, information on how to retrieve them is output.
meillo@108	2245 Not supporting this rare case saved nearly one thousand lines of code.
meillo@108	2246 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108	2247 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108	2248 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@159	2249 `application/octet-stream; type=tar' is not special anymore.
meillo@108	2250 Automatically extracting such MIME parts had been the dangerous part
meillo@108	2251 of the
meillo@108	2252 .Sw -auto
meillo@108	2253 mode.
meillo@108	2254 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2255
meillo@102	2256
meillo@102	2257
meillo@102	2258 .U3 "Showing MIME Messages
meillo@102	2259 .P
meillo@114	2260 The program
meillo@114	2261 .Pn mhshow
meillo@114	2262 had been written to display MIME messages.
meillo@114	2263 It implemented the conceptional view of the MIME RFCs.
meillo@114	2264 Nmh's
meillo@114	2265 .Pn mhshow
meillo@114	2266 handled each MIME part independently, presenting them separately
meillo@114	2267 to the user.
meillo@114	2268 This does not match today's understanding of email attachments,
meillo@114	2269 where displaying a message is seen to be a single, integrated operation.
meillo@114	2270 Today, email messages are expected to consist of a main text part
meillo@114	2271 plus possibly attachments.
meillo@114	2272 They are not any more seen to be arbitrary MIME hierarchies with
meillo@114	2273 information on how to display the individual parts.
meillo@114	2274 I adjusted
meillo@114	2275 .Pn mhshow 's
meillo@114	2276 behavior to the modern view on the topic.
meillo@114	2277 .P
meillo@159	2278 One should note that this section completely ignores the original
meillo@114	2279 .Pn show
meillo@114	2280 program, because it was not capable to display MIME messages
meillo@114	2281 and is no longer part of mmh.
meillo@179	2282 .\" XXX ref to other section
meillo@114	2283 Although
meillo@114	2284 .Pn mhshow
meillo@114	2285 was renamed to
meillo@114	2286 .Pn show
meillo@114	2287 in mmh, this section uses the name
meillo@114	2288 .Pn mhshow ,
meillo@114	2289 in order to avoid confusion.
meillo@114	2290 .P
meillo@114	2291 In mmh, the basic idea is that
meillo@114	2292 .Pn mhshow
meillo@114	2293 should display a message in one single pager session.
meillo@114	2294 Therefore,
meillo@114	2295 .Pn mhshow
meillo@114	2296 invokes a pager session for all its output,
meillo@114	2297 whenever it prints to a terminal.
meillo@114	2298 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e
meillo@114	2299 In consequence,
meillo@114	2300 .Pn mhl
meillo@114	2301 does no more invoke a pager.
meillo@114	2302 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@114	2303 With
meillo@114	2304 .Pn mhshow
meillo@114	2305 replacing the original
meillo@114	2306 .Pn show ,
meillo@114	2307 output from
meillo@114	2308 .Pn mhl
meillo@114	2309 does not go to the terminal directly, but through
meillo@114	2310 .Pn mhshow .
meillo@114	2311 Hence,
meillo@114	2312 .Pn mhl
meillo@114	2313 does not need to invoke a pager.
meillo@114	2314 The one and only job of
meillo@114	2315 .Pn mhl
meillo@114	2316 is to format messages or parts of them.
meillo@114	2317 The only place in mmh, where a pager is invoked is
meillo@114	2318 .Pn mhshow .
meillo@114	2319 .P
meillo@114	2320 .Pe mhshow-show-*
meillo@114	2321 profile entries can be used to display MIME parts in a specific way.
meillo@114	2322 For instance, PDF and Postscript files could be converted to plain text
meillo@114	2323 to display them in the terminal.
meillo@169	2324 In mmh, MIME parts will always be displayed serially.
meillo@114	2325 The request to display the MIME type `multipart/parallel' in parallel
meillo@114	2326 is ignored.
meillo@114	2327 It is simply treated as `multipart/mixed'.
meillo@114	2328 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6
meillo@114	2329 This could already be requested with the, now removed,
meillo@114	2330 .Sw -serialonly
meillo@114	2331 switch of
meillo@114	2332 .Pn mhshow .
meillo@179	2333 As MIME parts are always processed exclusively, i.e. serially,
meillo@114	2334 the `%e' escape in
meillo@114	2335 .Pe mhshow-show-*
meillo@114	2336 profile entries became useless and was thus removed.
meillo@114	2337 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae
meillo@114	2338 .P
meillo@114	2339 In the intended setup, only text content would be displayed.
meillo@114	2340 Non-text content would be converted to text by appropriate
meillo@114	2341 .Pe mhshow-show-*
meillo@114	2342 profile entries before, if possible and wanted.
meillo@114	2343 All output would be displayed in a single pager session.
meillo@114	2344 Other kinds of attachments are ignored.
meillo@114	2345 With
meillo@114	2346 .Pe mhshow-show-*
meillo@114	2347 profile entries for them, they can be displayed serially along
meillo@114	2348 the message.
meillo@114	2349 For parallel display, the attachments need to be stored to disk first.
meillo@114	2350 .P
meillo@114	2351 To display text content in foreign charsets, they need to be converted
meillo@114	2352 to the native charset.
meillo@114	2353 Therefore,
meillo@114	2354 .Pe mhshow-charset-*
meillo@114	2355 profile entries used to be needed.
meillo@169	2356 In mmh, the conversion is performed automatically by piping the
meillo@169	2357 text through the
meillo@114	2358 .Pn iconv
meillo@114	2359 command, if necessary.
meillo@114	2360 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60
meillo@114	2361 Custom
meillo@114	2362 .Pe mhshow-show-*
meillo@114	2363 rules for textual content might need a
meillo@114	2364 .Cl "iconv -f %c %f \|
meillo@114	2365 prefix to have the text converted to the native charset.
meillo@114	2366 .P
meillo@121	2367 Although the conversion of foreign charsets to the native one
meillo@114	2368 has improved, it is not consistent enough.
meillo@114	2369 Further work needs to be done and
meillo@114	2370 the basic concepts in this field need to be re-thought.
meillo@114	2371 Though, the default setup of mmh displays message in foreign charsets
meillo@114	2372 correctly without the need to configure anything.
meillo@114	2373
meillo@114	2374
meillo@114	2375 .ig
meillo@114	2376
meillo@114	2377 .P
meillo@114	2378 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@173	2379 These tools will not download the contents automatically anymore. Instead,
meillo@114	2380 they print the information needed to get the contents. If someone should
meillo@114	2381 really receive one of those rare message/external-body messages, he can
meillo@114	2382 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114	2383 it!
meillo@114	2384 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114	2385 ~/.netrc are gone now.)
meillo@114	2386 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114	2387
meillo@114	2388 ..
meillo@102	2389
meillo@58	2390
meillo@58	2391
meillo@166	2392 .H2 "Signing and Encrypting
meillo@22	2393 .P
meillo@166	2394 Nmh offers no direct support for digital signatures and message encryption.
meillo@157	2395 This functionality needed to be added through third-party software.
meillo@166	2396 In mmh, the functionality should be included because it
meillo@166	2397 is a part of modern email and likely wanted by users of mmh.
meillo@157	2398 A fresh mmh installation should support signing and encrypting
meillo@157	2399 out-of-the-box.
meillo@157	2400 Therefore, Neil Rickert's
meillo@157	2401 .Pn mhsign
meillo@157	2402 and
meillo@157	2403 .Pn mhpgp
meillo@157	2404 scripts
meillo@157	2405 .[
meillo@157	2406 neil rickert mhsign mhpgp
meillo@157	2407 .]
meillo@177	2408 were included into mmh
meillo@177	2409 .Ci f45cdc98117a84f071759462c7ae212f4bc5ab2e
meillo@177	2410 .Ci 58cf09aa36e9f7f352a127158bbf1c5678bc6ed8 .
meillo@177	2411 The scripts fit well because they are lightweight and
meillo@177	2412 similar of style to the existing tools.
meillo@157	2413 Additionally, no licensing difficulties appeared,
meillo@157	2414 as they are part of the public domain.
meillo@112	2415 .P
meillo@157	2416 .Pn mhsign
meillo@157	2417 handles the signing and encrypting part.
meillo@157	2418 It comprises about 250 lines of shell code and interfaces between
meillo@157	2419 .Pn gnupg
meillo@157	2420 and
meillo@157	2421 the MH system.
meillo@177	2422 It was meant to be invoked manually at the WhatNow prompt, but in mmh,
meillo@157	2423 .Pn send
meillo@177	2424 invokes
meillo@177	2425 .pn mhsign
meillo@177	2426 automatically
meillo@177	2427 .Ci c7b5e1df086bcc37ff40163ee67571f076cf6683 .
meillo@177	2428 Special header fields were introduced to request this action.
meillo@157	2429 If a draft contains the
meillo@157	2430 .Hd Sign
meillo@157	2431 header field,
meillo@157	2432 .Pn send
meillo@177	2433 will initiate the signing.
meillo@177	2434 The signing key is either chosen automatically or specified by the
meillo@157	2435 .Pe Pgpkey
meillo@157	2436 profile entry.
meillo@157	2437 .Pn send
meillo@177	2438 always create signatures using the PGP/MIME standard, \" REF XXX
meillo@157	2439 but by manually invoking
meillo@157	2440 .Pn mhsign ,
meillo@157	2441 old-style non-MIME signatures can be created as well.
meillo@177	2442 To encrypt an outgoing message, the draft needs to contain an
meillo@157	2443 .Hd Enc
meillo@157	2444 header field.
meillo@177	2445 Public keys of all recipients are searched for in the gnupg keyring and
meillo@177	2446 in a file called
meillo@177	2447 .Fn pgpkeys ,
meillo@177	2448 which contains exceptions and overrides.
meillo@157	2449 Unless public keys are found for all recipients,
meillo@177	2450 .Pn mhsign
meillo@177	2451 will refuse to encrypt it.
meillo@157	2452 Currently, messages with hidden (BCC) recipients can not be encrypted.
meillo@171	2453 This work is pending because it requires a structurally more complex
meillo@171	2454 approach.
meillo@157	2455 .P
meillo@177	2456 .Pn mhpgp
meillo@177	2457 is the companion to
meillo@177	2458 .Pn mhsign .
meillo@177	2459 It verifies signatures and decrypts messages.
meillo@177	2460 Encrypted messages can either be temporarily decrypted for display
meillo@177	2461 or permanently decrypted and stored into the current folder.
meillo@177	2462 Currently,
meillo@177	2463 .Pn mhpgp
meillo@177	2464 needs to be invoked manually.
meillo@177	2465 The integration into
meillo@177	2466 .Pn show
meillo@177	2467 and
meillo@177	2468 .Pn mhstore
meillo@177	2469 to verify signatures and decrypt messages as needs
meillo@177	2470 is planned but not realized yet.
meillo@177	2471 .P
meillo@177	2472 Both scripts were written for nmh, hence they needed to be adjust
meillo@177	2473 according to the differences between nmh and mmh.
meillo@177	2474 For instance, they use the backup prefix no longer.
meillo@181	2475 Furthermore, compatibility support for old PGP features was dropped.
meillo@177	2476 .P
meillo@157	2477 The integrated message signing and encrypting support is one of the
meillo@157	2478 most recent features in mmh.
meillo@177	2479 It has not yet had the time to mature.
meillo@177	2480 User feedback and personal experience need to be accumulated to
meillo@177	2481 direct the further development of the facility.
meillo@177	2482 Although the feedback and experience is still missing,
meillo@177	2483 it seems to be worthwhile to consider adding
meillo@157	2484 .Sw -[no]sign
meillo@157	2485 and
meillo@157	2486 .Sw -[no]enc
meillo@157	2487 switches to
meillo@157	2488 .Pn send ,
meillo@177	2489 to be able to override the corresponding header fields.
meillo@177	2490 A profile entry:
meillo@157	2491 .VS
meillo@157	2492 send: -sign
meillo@157	2493 VE
meillo@177	2494 would then activate signing for all outgoing messages.
meillo@177	2495 With the present approach, a
meillo@177	2496 .Hd Send
meillo@177	2497 header component needs to be added to each draft template
meillo@177	2498 to achieve the same result.
meillo@177	2499 Adding the switches would ease the work greatly and keep the
meillo@177	2500 template files clean.
meillo@157	2501
meillo@58	2502
meillo@58	2503
meillo@102	2504
meillo@133	2505 .H2 "Draft and Trash Folder
meillo@131	2506 .P
meillo@58	2507
meillo@131	2508 .U3 "Draft Folder
meillo@154	2509 .Id draft-folder
meillo@131	2510 .P
meillo@131	2511 In the beginning, MH had the concept of a draft message.
meillo@131	2512 This is the file
meillo@131	2513 .Fn draft
meillo@131	2514 in the MH directory, which is treated special.
meillo@131	2515 On composing a message, this draft file was used.
meillo@131	2516 When starting to compose another message before the former one was sent,
meillo@131	2517 the user had to decide among:
meillo@171	2518 .LI 1
meillo@168	2519 Using the old draft to finish and send it before starting with a new one.
meillo@171	2520 .LI 2
meillo@168	2521 Discarding the old draft and replacing it with a new one.
meillo@171	2522 .LI 3
meillo@168	2523 Preserving the old draft by refiling it to a folder.
meillo@171	2524 .LP
meillo@168	2525 It was only possible to work in alternation on multiple drafts.
meillo@131	2526 Therefore, the current draft needed to be refiled to a folder and
meillo@168	2527 another one re-used for editing.
meillo@131	2528 Working on multiple drafts at the same time was impossible.
meillo@131	2529 The usual approach of switching to a different MH context did not
meillo@168	2530 help anything.
meillo@131	2531 .P
meillo@131	2532 The draft folder facility exists to
meillo@131	2533 allow true parallel editing of drafts, in a straight forward way.
meillo@131	2534 It was introduced by Marshall T. Rose, already in 1984.
meillo@131	2535 Similar to other new features, the draft folder was inactive by default.
meillo@131	2536 Even in nmh, the highly useful draft folder was not available
meillo@131	2537 out-of-the-box.
meillo@131	2538 At least, Richard Coleman added the man page
meillo@131	2539 .Mp mh-draft (5)
meillo@131	2540 to better document the feature.
meillo@131	2541 .P
meillo@131	2542 Not using the draft folder facility has the single advantage of having
meillo@131	2543 the draft file at a static location.
meillo@131	2544 This is simple in simple cases but the concept does not scale for more
meillo@131	2545 complex cases.
meillo@131	2546 The concept of the draft message is too limited for the problem.
meillo@131	2547 Therefore the draft folder was introduced.
meillo@131	2548 It is the more powerful and more natural concept.
meillo@131	2549 The draft folder is a folder like any other folder in MH.
meillo@131	2550 Its messages can be listed like any other messages.
meillo@131	2551 A draft message is no longer a special case.
meillo@131	2552 Tools do not need special switches to work on the draft message.
meillo@171	2553 Hence corner cases were removed.
meillo@131	2554 .P
meillo@131	2555 The trivial part of the work was activating the draft folder with a
meillo@131	2556 default name.
meillo@131	2557 I chose the name
meillo@131	2558 .Fn +drafts
meillo@131	2559 for obvious reasons.
meillo@131	2560 In consequence, the command line switches
meillo@131	2561 .Sw -draftfolder
meillo@131	2562 and
meillo@131	2563 .Sw -draftmessage
meillo@131	2564 could be removed.
meillo@131	2565 More difficult but also more improving was updating the tools to the
meillo@131	2566 new concept.
meillo@131	2567 For nearly three decades, the tools needed to support two draft handling
meillo@131	2568 approaches.
meillo@131	2569 By fully switching to the draft folder, the tools could be simplified
meillo@131	2570 by dropping the awkward draft message handling code.
meillo@131	2571 .Sw -draft
meillo@131	2572 switches were removed because operating on a draft message is no longer
meillo@131	2573 special.
meillo@131	2574 It became indistinguishable to operating on any other message.
meillo@168	2575 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@168	2576 .P
meillo@168	2577 There is no more need to query the user for draft handling
meillo@168	2578 .Ci 2d48b455c303a807041c35e4248955f8bec59eeb .
meillo@131	2579 It is always possible to add another new draft.
meillo@131	2580 Refiling drafts is without difference to refiling other messages.
meillo@168	2581 All of these special cases are gone.
meillo@131	2582 Yet, one draft-related switch remained.
meillo@131	2583 .Pn comp
meillo@131	2584 still has
meillo@131	2585 .Sw -[no]use
meillo@131	2586 for switching between two modes:
meillo@171	2587 .LI 1
meillo@168	2588 .Sw -use
meillo@168	2589 to modify an existing draft.
meillo@171	2590 .LI 2
meillo@168	2591 .Sw -nouse
meillo@168	2592 to compose a new draft, possibly taking some existing message as template.
meillo@171	2593 .LP
meillo@131	2594 In either case, the behavior of
meillo@131	2595 .Pn comp
meillo@131	2596 is deterministic.
meillo@131	2597 .P
meillo@131	2598 .Pn send
meillo@131	2599 now operates on the current message in the draft folder by default.
meillo@131	2600 As message and folder can both be overridden by specifying them on
meillo@131	2601 the command line, it is possible to send any message in the mail storage
meillo@131	2602 by simply specifying its number and folder.
meillo@131	2603 In contrast to the other tools,
meillo@131	2604 .Pn send
meillo@131	2605 takes the draft folder as its default folder.
meillo@131	2606 .P
meillo@131	2607 Dropping the draft message concept in favor for the draft folder concept,
meillo@131	2608 removed special cases with regular cases.
meillo@131	2609 This simplified the source code of the tools, as well as the concepts.
meillo@131	2610 In mmh, draft management does not break with the MH concepts
meillo@131	2611 but applies them.
meillo@133	2612 .Cl "scan +drafts" ,
meillo@133	2613 for instance, is a truly natural request.
meillo@169	2614 Most of the work was already performed by Rose in the eighties.
meillo@133	2615 The original improvement of mmh is dropping the old draft message approach
meillo@133	2616 and thus simplifying the tools, the documentation and the system as a whole.
meillo@131	2617 Although my part in the draft handling improvement was small,
meillo@133	2618 it was an important one.
meillo@131	2619
meillo@131	2620
meillo@131	2621 .U3 "Trash Folder
meillo@154	2622 .Id trash-folder
meillo@131	2623 .P
meillo@131	2624 Similar to the situation for drafts is the situation for removed messages.
meillo@131	2625 Historically, a message was ``deleted'' by prepending a specific
meillo@173	2626 \fIbackup prefix\fP, usually the comma character,
meillo@173	2627 to the file name.
meillo@164	2628 The specific file would then be ignored by MH because only files with
meillo@164	2629 names consisting of digits only are treated as messages.
meillo@131	2630 Although files remained in the file system,
meillo@168	2631 the messages were no longer visible in MH.
meillo@168	2632 To truly delete them, a maintenance job was needed.
meillo@168	2633 Usually a cron job was installed to delete them after a grace time.
meillo@131	2634 For instance:
meillo@131	2635 .VS
meillo@131	2636 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131	2637 VE
meillo@168	2638 In such a setup, the original message could be restored
meillo@131	2639 within the grace time interval by stripping the
meillo@164	2640 backup prefix from the file name.
meillo@168	2641 But the user could not rely on this statement.
meillo@168	2642 If the last message of a folder with six messages (\fL1-6\fP) was removed,
meillo@131	2643 message
meillo@131	2644 .Fn 6 ,
meillo@168	2645 became file
meillo@131	2646 .Fn ,6 .
meillo@168	2647 If then a new message entered the same folder, it would be named with
meillo@168	2648 the number one above the highest existing message number.
meillo@168	2649 In this case the message would be named
meillo@131	2650 .Fn 6
meillo@131	2651 then.
meillo@168	2652 If this new message would be removed as well,
meillo@168	2653 then the backup of the former message is overwritten.
meillo@168	2654 Hence, the ability to restore removed messages did not only depend on
meillo@181	2655 the sweeping cron job but also on the removing of further messages.
meillo@131	2656 It is undesirable to have such obscure and complex mechanisms.
meillo@168	2657 The user should be given a small set of clear assertions, such as
meillo@131	2658 ``Removed files are restorable within a seven-day grace time.''
meillo@131	2659 With the addition ``... unless a message with the same name in the
meillo@131	2660 same folder is removed before.'' the statement becomes complex.
meillo@131	2661 A user will hardly be able to keep track of any removal to know
meillo@131	2662 if the assertion still holds true for a specific file.
meillo@164	2663 In practice, the real mechanism is unclear to the user.
meillo@131	2664 The consequences of further removals are not obvious.
meillo@131	2665 .P
meillo@181	2666 Furthermore, the backup files are scattered within the whole mail storage.
meillo@131	2667 This complicates managing them.
meillo@164	2668 It is possible with the help of
meillo@131	2669 .Pn find ,
meillo@131	2670 but everything would be more convenient
meillo@131	2671 if the deleted messages would be collected in one place.
meillo@131	2672 .P
meillo@131	2673 The profile entry
meillo@131	2674 .Pe rmmproc
meillo@131	2675 (previously named
meillo@131	2676 .Pe Delete-Prog )
meillo@131	2677 was introduced very early to improve the situation.
meillo@164	2678 It could be set to any command, which would be executed to remove
meillo@131	2679 the specified messages.
meillo@168	2680 This would override the default action described above.
meillo@168	2681 Refiling the to-be-removed files to a trash folder is the usual example.
meillo@131	2682 Nmh's man page
meillo@131	2683 .Mp rmm (1)
meillo@131	2684 proposes to set the
meillo@131	2685 .Pe rmmproc
meillo@131	2686 to
meillo@131	2687 .Cl "refile +d
meillo@168	2688 to move messages to the trash folder,
meillo@131	2689 .Fn +d ,
meillo@131	2690 instead of renaming them with the backup prefix.
meillo@131	2691 The man page proposes additionally the expunge command
meillo@131	2692 .Cl "rm `mhpath +d all`
meillo@168	2693 to empty the trash folder.
meillo@131	2694 .P
meillo@131	2695 Removing messages in such a way has advantages.
meillo@131	2696 The mail storage is prevented from being cluttered with removed messages
meillo@131	2697 because they are all collected in one place.
meillo@131	2698 Existing and removed messages are thus separated more strictly.
meillo@131	2699 No backup files are silently overwritten.
meillo@164	2700 But most important is the ability to keep removed messages in the MH domain.
meillo@131	2701 Messages in the trash folder can be listed like those in any other folder.
meillo@131	2702 Deleted messages can be displayed like any other messages.
meillo@169	2703 .Pn refile
meillo@169	2704 can restore deleted messages.
meillo@131	2705 All operations on deleted files are still covered by the MH tools.
meillo@131	2706 The trash folder is just like any other folder in the mail storage.
meillo@131	2707 .P
meillo@131	2708 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131	2709 in favor for replacing it by the better suiting trash folder system.
meillo@131	2710 Hence,
meillo@131	2711 .Pn rmm
meillo@131	2712 calls
meillo@131	2713 .Pn refile
meillo@131	2714 to move the to-be-removed message to the trash folder,
meillo@131	2715 .Fn +trash
meillo@131	2716 by default.
meillo@164	2717 To sweep it clean, the user can use
meillo@131	2718 .Cl "rmm -unlink +trash a" ,
meillo@131	2719 where the
meillo@131	2720 .Sw -unlink
meillo@131	2721 switch causes the files to be unlinked.
meillo@168	2722 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168	2723 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@131	2724 .P
meillo@168	2725 Dropping the legacy approach and converting to the new approach completely
meillo@131	2726 simplified the code base.
meillo@131	2727 The relationship between
meillo@131	2728 .Pn rmm
meillo@131	2729 and
meillo@131	2730 .Pn refile
meillo@131	2731 was inverted.
meillo@131	2732 In mmh,
meillo@131	2733 .Pn rmm
meillo@131	2734 invokes
meillo@131	2735 .Pn refile ,
meillo@131	2736 which used to be the other way round.
meillo@131	2737 Yet, the relationship is simpler now.
meillo@164	2738 Loops, like described in nmh's man page for
meillo@131	2739 .Mp refile (1),
meillo@164	2740 can no longer occur:
meillo@131	2741 .QS
meillo@131	2742 Since
meillo@131	2743 .Pn refile
meillo@131	2744 uses your
meillo@131	2745 .Pe rmmproc
meillo@131	2746 to delete the message, the
meillo@131	2747 .Pe rmmproc
meillo@131	2748 must NOT call
meillo@131	2749 .Pn refile
meillo@131	2750 without specifying
meillo@131	2751 .Sw -normmproc
meillo@131	2752 or you will create an infinite loop.
meillo@131	2753 .QE
meillo@131	2754 .LP
meillo@131	2755 .Pn rmm
meillo@131	2756 either unlinks a message with
meillo@131	2757 .Fu unlink()
meillo@131	2758 or invokes
meillo@131	2759 .Pn refile
meillo@131	2760 to move it to the trash folder.
meillo@131	2761 .Pn refile
meillo@131	2762 does not invoke any tools.
meillo@131	2763 .P
meillo@136	2764 By generalizing the message removal in the way that it became covered
meillo@136	2765 by the MH concepts made the whole system more powerful.
meillo@131	2766
meillo@131	2767
meillo@131	2768
meillo@131	2769
meillo@131	2770
meillo@133	2771 .H2 "Modern Defaults
meillo@133	2772 .P
meillo@133	2773 Nmh has a bunch of convenience-improving features inactive by default,
meillo@133	2774 although one can expect every new user wanting to have them active.
meillo@133	2775 The reason they are inactive by default is the wish to stay compatible
meillo@133	2776 with old versions.
meillo@136	2777 But what is the definition for old versions?
meillo@136	2778 Still, the highly useful draft folder facility has not been activated
meillo@136	2779 by default although it was introduced over twenty-five years ago.
meillo@133	2780 .[
meillo@133	2781 rose romine real work
meillo@133	2782 .]
meillo@136	2783 The community seems not to care.
meillo@136	2784 This is one of several examples that require new users to first build up
meillo@136	2785 a profile before they can access the modern features of nmh.
meillo@136	2786 Without an extensive profile, the setup is hardly usable
meillo@133	2787 for modern emailing.
meillo@133	2788 The point is not the customization of the setup,
meillo@136	2789 but the need to activate generally useful facilities.
meillo@133	2790 .P
meillo@133	2791 Yet, the real problem lies less in enabling the features, as this is
meillo@133	2792 straight forward as soon as one knows what he wants.
meillo@168	2793 The real problem is that new users need deep insight into the project
meillo@168	2794 to find out about inactive features nmh already provides.
meillo@133	2795 To give an example, I needed one year of using nmh
meillo@133	2796 before I became aware of the existence of the attachment system.
meillo@133	2797 One could argue that this fact disqualifies my reading of the
meillo@133	2798 documentation.
meillo@133	2799 If I would have installed nmh from source back then, I could agree.
meillo@133	2800 Yet, I had used a prepackaged version and had expected that it would
meillo@133	2801 just work.
meillo@133	2802 Nevertheless, I had been convinced by the concepts of MH already
meillo@133	2803 and I am a software developer,
meillo@133	2804 still I required a lot of time to discover the cool features.
meillo@133	2805 How can we expect users to be even more advanced than me,
meillo@133	2806 just to allow them use MH in a convenient and modern way?
meillo@133	2807 Unless they are strongly convinced of the concepts, they will fail.
meillo@133	2808 I have seen friends of me giving up disappointed
meillo@133	2809 before they truly used the system,
meillo@133	2810 although they had been motivated in the beginning.
meillo@173	2811 They suffer hard enough to get used to the tool chest approach,
meillo@179	2812 we developers should spare them further inconveniences.
meillo@133	2813 .P
meillo@136	2814 Maintaining compatibility for its own sake is bad,
meillo@136	2815 because the code base collects more and more compatibility code.
meillo@200	2816 Sticking to the compatibility code means remaining limited;
meillo@168	2817 whereas adjusting to the changes renders the compatibility unnecessary.
meillo@168	2818 Keeping unused alternatives in the code is a bad choice as they likely
meillo@136	2819 gather bugs, by not being well tested.
meillo@136	2820 Also, the increased code size and the greater number of conditions
meillo@136	2821 increase the maintenance costs.
meillo@133	2822 If any MH implementation would be the back-end of widespread
meillo@133	2823 email clients with large user bases, compatibility would be more
meillo@133	2824 important.
meillo@133	2825 Yet, it appears as if this is not the case.
meillo@133	2826 Hence, compatibility is hardly important for technical reasons.
meillo@133	2827 Its importance originates rather from personal reasons.
meillo@133	2828 Nmh's user base is small and old.
meillo@133	2829 Changing the interfaces would cause inconvenience to long-term users of MH.
meillo@133	2830 It would force them to change their many years old MH configurations.
meillo@168	2831 I do understand this aspect, but by sticking to the old users,
meillo@168	2832 new users are kept away.
meillo@133	2833 Yet, the future lies in new users.
meillo@168	2834 In consequence, mmh invites new users by providing a convenient
meillo@168	2835 and modern setup, readily usable out-of-the-box.
meillo@133	2836 .P
meillo@136	2837 In mmh, all modern features are active by default and many previous
meillo@136	2838 approaches are removed or only accessible in manual ways.
meillo@136	2839 New default features include:
meillo@133	2840 .BU
meillo@133	2841 The attachment system (\c
meillo@133	2842 .Hd Attach ).
meillo@133	2843 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@133	2844 .BU
meillo@133	2845 The draft folder facility (\c
meillo@133	2846 .Fn +drafts ).
meillo@133	2847 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@133	2848 .BU
meillo@133	2849 The unseen sequence (`u')
meillo@133	2850 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@133	2851 and the sequence negation prefix (`!').
meillo@133	2852 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc
meillo@133	2853 .BU
meillo@133	2854 Quoting the original message in the reply.
meillo@133	2855 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@133	2856 .BU
meillo@133	2857 Forwarding messages using MIME.
meillo@133	2858 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@171	2859 .LP
meillo@136	2860 In consequence, a setup with a profile that defines only the path to the
meillo@136	2861 mail storage, is already convenient to use.
meillo@168	2862 Again, Paul Vixie's ``edginess'' call supports the direction I took:
meillo@136	2863 ``the `main branch' should just be modern''.
meillo@136	2864 .[
meillo@136	2865 paul vixie edginess nmh-workers
meillo@136	2866 .]
meillo@131	2867
meillo@133	2868
meillo@133	2869
meillo@133	2870
meillo@133	2871
meillo@133	2872 .\" --------------------------------------------------------------
meillo@131	2873 .H1 "Styling
meillo@22	2874 .P
meillo@118	2875 Kernighan and Pike have emphasized the importance of style in the
meillo@118	2876 preface of their book:
meillo@118	2877 .[ [
meillo@118	2878 kernighan pike practice of programming
meillo@118	2879 .], p. x]
meillo@118	2880 .QS
meillo@118	2881 Chapter 1 discusses programming style.
meillo@118	2882 Good style is so important to good programming that we have chose
meillo@118	2883 to cover it first.
meillo@118	2884 .QE
meillo@168	2885 This section covers changes in mmh that were guided by the desire
meillo@118	2886 to improve on style.
meillo@118	2887 Many of them follow the rules given in the quoted book.
meillo@118	2888 .[
meillo@118	2889 kernighan pike practice of programming
meillo@118	2890 .]
meillo@118	2891
meillo@118	2892
meillo@127	2893
meillo@127	2894
meillo@127	2895 .H2 "Code Style
meillo@154	2896 .Id code-style
meillo@118	2897 .P
meillo@118	2898 .U3 "Indentation Style
meillo@118	2899 .P
meillo@118	2900 Indentation styles are the holy cow of programmers.
meillo@168	2901 Kernighan and Pike
meillo@118	2902 .[ [
meillo@118	2903 kernighan pike practice of programming
meillo@118	2904 .], p. 10]
meillo@168	2905 wrote:
meillo@118	2906 .QS
meillo@118	2907 Programmers have always argued about the layout of programs,
meillo@118	2908 but the specific style is much less important than its consistent
meillo@118	2909 application.
meillo@121	2910 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118	2911 time arguing.
meillo@118	2912 .QE
meillo@118	2913 .P
meillo@118	2914 I agree that the constant application is most important,
meillo@118	2915 but I believe that some styles have advantages over others.
meillo@118	2916 For instance the indentation with tab characters only.
meillo@118	2917 Tab characters directly map to the nesting level \(en
meillo@118	2918 one tab, one level.
meillo@118	2919 Tab characters are flexible because developers can adjust them to
meillo@118	2920 whatever width they like to have.
meillo@118	2921 There is no more need to run
meillo@118	2922 .Pn unexpand
meillo@118	2923 or
meillo@118	2924 .Pn entab
meillo@118	2925 programs to ensure the correct mixture of leading tabs and spaces.
meillo@118	2926 The simple rules are: (1) Leading whitespace must consist of tabs only.
meillo@118	2927 (2) Any other whitespace should consist of spaces.
meillo@121	2928 These two rules ensure the integrity of the visual appearance.
meillo@121	2929 Although reformatting existing code should be avoided, I did it.
meillo@200	2930 I did not waste time arguing; I just reformatted the code.
meillo@118	2931 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118	2932
meillo@118	2933 .U3 "Comments
meillo@118	2934 .P
meillo@118	2935 Section 1.6 of
meillo@118	2936 .[ [
meillo@118	2937 kernighan pike practice of programming
meillo@118	2938 .], p. 23]
meillo@118	2939 demands: ``Don't belabor the obvious.''
meillo@122	2940 Hence, I simply removed all the comments in the following code excerpt:
meillo@118	2941 .VS
meillo@120	2942 context_replace(curfolder, folder); /* update current folder */
meillo@120	2943 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120	2944 seq_save(mp); /* synchronize message sequences */
meillo@120	2945 folder_free(mp); /* free folder/message structure */
meillo@120	2946 context_save(); /* save the context file */
meillo@120	2947
meillo@120	2948 [...]
meillo@120	2949
meillo@120	2950 int c; /* current character */
meillo@120	2951 char cp; / miscellaneous character pointer */
meillo@120	2952
meillo@120	2953 [...]
meillo@120	2954
meillo@120	2955 /* NUL-terminate the field */
meillo@120	2956 *cp = '\0';
meillo@118	2957 VE
meillo@120	2958 .Ci 426543622b377fc5d091455cba685e114b6df674
meillo@118	2959 .P
meillo@136	2960 The program code explains enough itself, already.
meillo@136	2961
meillo@118	2962
meillo@118	2963 .U3 "Names
meillo@118	2964 .P
meillo@118	2965 Kernighan and Pike suggest:
meillo@118	2966 ``Use active names for functions''.
meillo@118	2967 .[ [
meillo@118	2968 kernighan pike practice of programming
meillo@118	2969 .], p. 4]
meillo@118	2970 One application of this rule was the rename of
meillo@118	2971 .Fu check_charset()
meillo@118	2972 to
meillo@118	2973 .Fu is_native_charset() .
meillo@118	2974 .Ci 8d77b48284c58c135a6b2787e721597346ab056d
meillo@181	2975 The same change fixed a violation of ``Be accurate''
meillo@181	2976 .[ [
meillo@181	2977 kernighan pike practice of programming
meillo@181	2978 .], p. 4]
meillo@181	2979 as well.
meillo@118	2980 The code did not match the expectation the function suggested,
meillo@118	2981 as it, for whatever reason, only compared the first ten characters
meillo@118	2982 of the charset name.
meillo@118	2983 .P
meillo@118	2984 More important than using active names is using descriptive names.
meillo@145	2985 .VS
meillo@145	2986 m_unknown(in); /* the MAGIC invocation... */
meillo@145	2987 VE
meillo@145	2988 Renaming the obscure
meillo@118	2989 .Fu m_unknown()
meillo@145	2990 function was a delightful event, although it made the code less funny.
meillo@118	2991 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846
meillo@118	2992 .P
meillo@118	2993 Magic numbers are generally considered bad style.
meillo@118	2994 Obviously, Kernighan and Pike agree:
meillo@118	2995 ``Give names to magic numbers''.
meillo@118	2996 .[ [
meillo@118	2997 kernighan pike practice of programming
meillo@118	2998 .], p. 19]
meillo@118	2999 One such change was naming the type of input \(en mbox or mail folder \(en
meillo@118	3000 to be scanned:
meillo@118	3001 .VS
meillo@118	3002 #define SCN_MBOX (-1)
meillo@118	3003 #define SCN_FOLD 0
meillo@118	3004 VE
meillo@118	3005 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@118	3006 .P
meillo@118	3007 The argument
meillo@118	3008 .Ar outnum
meillo@118	3009 of the function
meillo@118	3010 .Fu scan()
meillo@118	3011 in
meillo@118	3012 .Fn uip/scansbr.c
meillo@118	3013 defines the number of the message to be created.
meillo@118	3014 If no message is to be created, the argument is misused to transport
meillo@118	3015 program logic.
meillo@118	3016 This lead to obscure code.
meillo@118	3017 I improved the clarity of the code by introducing two variables:
meillo@118	3018 .VS
meillo@118	3019 int incing = (outnum > 0);
meillo@118	3020 int ismbox = (outnum != 0);
meillo@118	3021 VE
meillo@118	3022 They cover the magic values and are used for conditions.
meillo@118	3023 The variable
meillo@118	3024 .Ar outnum
meillo@118	3025 is only used when it holds an ordinary message number.
meillo@118	3026 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f
meillo@118	3027 The clarity improvement of the change showed detours in the program logic
meillo@118	3028 of related code parts.
meillo@118	3029 Having the new variables with descriptive names, a more
meillo@121	3030 straight forward implementation became apparent.
meillo@169	3031 Before the code was clarified, the possibility to improve had not be seen.
meillo@118	3032 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723
meillo@118	3033
meillo@133	3034
meillo@133	3035
meillo@133	3036 .H2 "Structural Rework
meillo@133	3037 .P
meillo@136	3038 Although the stylistic changes described up to here improve the
meillo@136	3039 readability of the source code, all of them are changes ``in the small''.
meillo@136	3040 Structural changes affect a much larger area.
meillo@136	3041 They are more difficult to do but lead to larger improvements,
meillo@136	3042 especially as they influence the outer shape of the tools as well.
meillo@118	3043 .P
meillo@118	3044 At the end of their chapter on style,
meillo@118	3045 Kernighan and Pike ask: ``But why worry about style?''
meillo@181	3046 .[ [
meillo@181	3047 kernighan pike practice of programming
meillo@181	3048 .], p. 28]
meillo@136	3049 Following are two examples of structural rework that show
meillo@136	3050 why style is important in the first place.
meillo@136	3051
meillo@136	3052
meillo@136	3053 .U3 "Rework of \f(CWanno\fP
meillo@118	3054 .P
meillo@120	3055 Until 2002,
meillo@120	3056 .Pn anno
meillo@120	3057 had six functional command line switches,
meillo@120	3058 .Sw -component
meillo@120	3059 and
meillo@120	3060 .Sw -text ,
meillo@168	3061 which have an argument each,
meillo@120	3062 and the two pairs of flags,
meillo@120	3063 .Sw -[no]date
meillo@120	3064 and
meillo@120	3065 .Sw -[no]inplace .
meillo@120	3066 Then Jon Steinhart introduced his attachment system.
meillo@120	3067 In need for more advanced annotation handling, he extended
meillo@120	3068 .Pn anno .
meillo@120	3069 He added five more switches:
meillo@120	3070 .Sw -draft ,
meillo@120	3071 .Sw -list ,
meillo@120	3072 .Sw -delete ,
meillo@120	3073 .Sw -append ,
meillo@120	3074 and
meillo@120	3075 .Sw -number ,
meillo@120	3076 the last one taking an argument.
meillo@121	3077 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@120	3078 Later,
meillo@120	3079 .Sw -[no]preserve
meillo@120	3080 was added.
meillo@121	3081 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@120	3082 Then, the Synopsis section of the man page
meillo@120	3083 .Mp anno (1)
meillo@120	3084 read:
meillo@120	3085 .VS
meillo@120	3086 anno [+folder] [msgs] [-component field] [-inplace \| -noinplace]
meillo@120	3087 [-date \| -nodate] [-draft] [-append] [-list] [-delete]
meillo@120	3088 [-number [num\|all]] [-preserve \| -nopreserve] [-version]
meillo@120	3089 [-help] [-text body]
meillo@120	3090 VE
meillo@120	3091 .LP
meillo@120	3092 The implementation followed the same structure.
meillo@120	3093 Problems became visible when
meillo@120	3094 .Cl "anno -list -number 42
meillo@120	3095 worked on the current message instead on message number 42,
meillo@120	3096 and
meillo@120	3097 .Cl "anno -list -number l:5
meillo@124	3098 did not work on the last five messages but failed with the mysterious
meillo@120	3099 error message: ``anno: missing argument to -list''.
meillo@121	3100 Yet, the invocation matched the specification in the man page.
meillo@120	3101 There, the correct use of
meillo@120	3102 .Sw -number
meillo@120	3103 was defined as being
meillo@120	3104 .Cl "[-number [num\|all]]
meillo@120	3105 and the textual description for the combination with
meillo@120	3106 .Sw -list
meillo@120	3107 read:
meillo@120	3108 .QS
meillo@164	3109 The
meillo@164	3110 .Sw -list
meillo@164	3111 option produces a listing of the field bodies for
meillo@120	3112 header fields with names matching the specified component,
meillo@164	3113 one per line. The listing is numbered, starting at 1, if the
meillo@164	3114 .Sw -number
meillo@164	3115 option is also used.
meillo@120	3116 .QE
meillo@120	3117 .LP
meillo@120	3118 The problem was manifold.
meillo@120	3119 The code required a numeric argument to the
meillo@120	3120 .Sw -number
meillo@120	3121 switch.
meillo@120	3122 If it was missing or non-numeric,
meillo@120	3123 .Pn anno
meillo@120	3124 aborted with an error message that had an off-by-one error,
meillo@120	3125 printing the switch one before the failing one.
meillo@120	3126 Semantically, the argument to the
meillo@120	3127 .Sw -number
meillo@120	3128 switch is only necessary in combination with
meillo@120	3129 .Sw -delete ,
meillo@120	3130 but not with
meillo@120	3131 .Sw -list .
meillo@120	3132 .P
meillo@171	3133 Trying to fix these problems on the surface would not have solved
meillo@180	3134 them truly, as they originate from a discrepance between the
meillo@120	3135 structure of the problem and the structure implemented in the program.
meillo@120	3136 Such structural differences can not be cured on the surface.
meillo@120	3137 They need to be solved by adjusting the structure of the implementation
meillo@120	3138 to the structure of the problem.
meillo@120	3139 .P
meillo@120	3140 In 2002, the new switches
meillo@120	3141 .Sw -list
meillo@120	3142 and
meillo@120	3143 .Sw -delete
meillo@120	3144 were added in the same way, the
meillo@120	3145 .Sw -number
meillo@120	3146 switch for instance had been added.
meillo@120	3147 Yet, they are of structural different type.
meillo@120	3148 Semantically,
meillo@120	3149 .Sw -list
meillo@120	3150 and
meillo@120	3151 .Sw -delete
meillo@120	3152 introduce modes of operation.
meillo@120	3153 Historically,
meillo@120	3154 .Pn anno
meillo@120	3155 had only one operation mode: adding header fields.
meillo@180	3156 With the extension it got two more modes:
meillo@180	3157 .\" XXX got
meillo@120	3158 listing and deleting header fields.
meillo@120	3159 The structure of the code changes did not pay respect to this
meillo@120	3160 fundamental change to
meillo@120	3161 .Pn anno 's
meillo@120	3162 behavior.
meillo@120	3163 Neither the implementation nor the documentation did clearly
meillo@120	3164 define them as being exclusive modes of operation.
meillo@120	3165 Having identified the problem, I solved it by putting structure into
meillo@120	3166 .Pn anno
meillo@120	3167 and its documentation.
meillo@120	3168 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11
meillo@120	3169 .P
meillo@173	3170 The difference is visible in both the code and the documentation.
meillo@121	3171 The following code excerpt:
meillo@120	3172 .VS
meillo@120	3173 int delete = -2; /* delete header element if set */
meillo@120	3174 int list = 0; /* list header elements if set */
meillo@120	3175 [...]
meillo@121	3176 case DELETESW: /* delete annotations */
meillo@121	3177 delete = 0;
meillo@121	3178 continue;
meillo@121	3179 case LISTSW: /* produce a listing */
meillo@121	3180 list = 1;
meillo@121	3181 continue;
meillo@120	3182 VE
meillo@121	3183 .LP
meillo@121	3184 was replaced by:
meillo@120	3185 .VS
meillo@120	3186 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120	3187 [...]
meillo@121	3188 case DELETESW: /* delete annotations */
meillo@121	3189 mode = MODE_DEL;
meillo@121	3190 continue;
meillo@121	3191 case LISTSW: /* produce a listing */
meillo@121	3192 mode = MODE_LIST;
meillo@121	3193 continue;
meillo@120	3194 VE
meillo@120	3195 .LP
meillo@121	3196 The replacement code does not only reflect the problem's structure better,
meillo@121	3197 it is easier to understand as well.
meillo@121	3198 The same applies to the documentation.
meillo@120	3199 The man page was completely reorganized to propagate the same structure.
meillo@121	3200 This is visible in the Synopsis section:
meillo@120	3201 .VS
meillo@120	3202 anno [+folder] [msgs] [-component field] [-text body]
meillo@120	3203 [-append] [-date \| -nodate] [-preserve \| -nopreserve]
meillo@120	3204 [-Version] [-help]
meillo@120	3205
meillo@120	3206 anno -delete [+folder] [msgs] [-component field] [-text
meillo@120	3207 body] [-number num \| all ] [-preserve \| -nopreserve]
meillo@120	3208 [-Version] [-help]
meillo@120	3209
meillo@120	3210 anno -list [+folder] [msgs] [-component field] [-number]
meillo@120	3211 [-Version] [-help]
meillo@120	3212 VE
meillo@121	3213 .\" XXX think about explaining the -preserve rework?
meillo@118	3214
meillo@58	3215
meillo@58	3216
meillo@133	3217 .U3 "Path Conversion
meillo@133	3218 .P
meillo@134	3219 Four kinds of path names can appear in MH:
meillo@171	3220 .LI 1
meillo@134	3221 Absolute Unix directory paths, like
meillo@134	3222 .Fn /etc/passwd .
meillo@171	3223 .LI 2
meillo@134	3224 Relative Unix directory paths, like
meillo@134	3225 .Fn ./foo/bar .
meillo@171	3226 .LI 3
meillo@134	3227 Absolute MH folder paths, like
meillo@134	3228 .Fn +friends/phil .
meillo@171	3229 .LI 4
meillo@134	3230 Relative MH folder paths, like
meillo@134	3231 .Fn @subfolder .
meillo@171	3232 .LP
meillo@134	3233 The last type, relative MH folder paths, are hardly documented.
meillo@134	3234 Nonetheless, they are useful for large mail storages.
meillo@134	3235 The current mail folder is specified as `\c
meillo@134	3236 .Fn @ ',
meillo@134	3237 just like the current directory is specified as `\c
meillo@134	3238 .Fn . '.
meillo@134	3239 .P
meillo@134	3240 To allow MH tools to understand all four notations,
meillo@134	3241 they need to convert between them.
meillo@180	3242 .\" XXX between?
meillo@134	3243 In nmh, these path name conversion functions were located in the files
meillo@134	3244 .Fn sbr/path.c
meillo@134	3245 (``return a pathname'') and
meillo@134	3246 .Fn sbr/m_maildir.c
meillo@134	3247 (``get the path for the mail directory'').
meillo@134	3248 The seven functions in the two files were documented with no more
meillo@134	3249 than two comments, which described obvious information.
meillo@134	3250 The function signatures were neither explaining:
meillo@134	3251 .VS
meillo@134	3252 char path(char , int);
meillo@134	3253 char pluspath(char );
meillo@134	3254 char m_mailpath(char );
meillo@134	3255 char m_maildir(char );
meillo@134	3256 VE
meillo@134	3257 .P
meillo@134	3258 My investigation provides the following description:
meillo@171	3259 .LI 1
meillo@134	3260 The second parameter of
meillo@134	3261 .Fu path()
meillo@134	3262 defines the type of path given as first parameter.
meillo@134	3263 Directory paths are converted to absolute directory paths.
meillo@134	3264 Folder paths are converted to absolute folder paths.
meillo@173	3265 Folder paths must not include a leading `\fL@\fP' character.
meillo@134	3266 Leading plus characters are preserved.
meillo@134	3267 The result is a pointer to newly allocated memory.
meillo@171	3268 .LI 2
meillo@134	3269 .Fu pluspath()
meillo@134	3270 is a convenience-wrapper to
meillo@134	3271 .Fu path() ,
meillo@134	3272 to convert folder paths only.
meillo@134	3273 This function can not be used for directory paths.
meillo@134	3274 An empty string parameter causes a buffer overflow.
meillo@171	3275 .LI 3
meillo@134	3276 .Fu m_mailpath()
meillo@134	3277 converts directory paths to absolute directory paths.
meillo@173	3278 The characters `\fL+\fP' or `\fL@\fP' at the beginning of the path name are
meillo@134	3279 treated literal, i.e. as the first character of a relative directory path.
meillo@134	3280 Hence, this function can not be used for folder paths.
meillo@134	3281 In any case, the result is an absolute directory path.
meillo@134	3282 The result is a pointer to newly allocated memory.
meillo@171	3283 .LI 4
meillo@134	3284 .Fu m_maildir()
meillo@134	3285 returns the parameter unchanged if it is an absolute directory path
meillo@173	3286 or begins with the entry `\fL.\fP' or `\fL..\fP'.
meillo@134	3287 All other strings are prepended with the current working directory.
meillo@134	3288 Hence, this functions can not be used for folder paths.
meillo@134	3289 The result is either an absolute directory path or a relative
meillo@134	3290 directory path, starting with a dot.
meillo@134	3291 In contrast to the other functions, the result is a pointer to
meillo@134	3292 static memory.
meillo@134	3293 .P
meillo@134	3294 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@134	3295 No clear terminology was used to name the different kinds of path names.
meillo@134	3296 The first argument of
meillo@134	3297 .Fu m_mailpath() ,
meillo@134	3298 for instance, was named
meillo@134	3299 .Ar folder ,
meillo@134	3300 though
meillo@134	3301 .Fu m_mailpath()
meillo@134	3302 can not be used for MH folders.
meillo@134	3303 .P
meillo@134	3304 I reworked the path name conversion completely, introducing clarity.
meillo@134	3305 First of all, the terminology needed to be defined.
meillo@134	3306 A path name is either in the Unix domain, then it is called
meillo@134	3307 \fIdirectory path\fP, `dirpath' for short, or it is in the MH domain,
meillo@134	3308 then it is called \fIfolder path\fP, `folpath' for short.
meillo@134	3309 The two terms need to be used with strict distinction.
meillo@134	3310 Having a clear terminology is often an indicator of having understood
meillo@134	3311 the problem itself.
meillo@134	3312 Second, I exploited the concept of path type indicators.
meillo@134	3313 By requesting every path name to start with a clear type identifier,
meillo@134	3314 conversion between the types can be fully automated.
meillo@134	3315 Thus the tools can accept paths of any type from the user.
meillo@134	3316 Therefore, it was necessary to require relative directory paths to be
meillo@134	3317 prefixed with a dot character.
meillo@134	3318 In consequence, the dot character could no longer be an alias for the
meillo@134	3319 current message.
meillo@134	3320 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134	3321 Third, I created three new functions to replace the previous mess:
meillo@171	3322 .LI 1
meillo@134	3323 .Fu expandfol()
meillo@134	3324 converts folder paths to absolute folder paths,
meillo@134	3325 without the leading plus character.
meillo@134	3326 Directory paths are simply passed through.
meillo@134	3327 This function is to be used for folder paths only, thus the name.
meillo@134	3328 The result is a pointer to static memory.
meillo@171	3329 .LI 2
meillo@134	3330 .Fu expanddir()
meillo@134	3331 converts directory paths to absolute directory paths.
meillo@134	3332 Folder paths are treated as relative directory paths.
meillo@134	3333 This function is to be used for directory paths only, thus the name.
meillo@134	3334 The result is a pointer to static memory.
meillo@171	3335 .LI 3
meillo@134	3336 .Fu toabsdir()
meillo@134	3337 converts any type of path to an absolute directory path.
meillo@134	3338 This is the function of choice for path conversion.
meillo@134	3339 Absolute directory paths are the most general representation of a
meillo@134	3340 path name.
meillo@134	3341 The result is a pointer to static memory.
meillo@134	3342 .P
meillo@180	3343 .\" XXX ueberfluessig?
meillo@134	3344 The new functions have names that indicate their use.
meillo@134	3345 Two of the functions convert relative to absolute path names of the
meillo@134	3346 same type.
meillo@134	3347 The third function converts any path name type to the most general one,
meillo@134	3348 the absolute directory path.
meillo@134	3349 All of the functions return pointers to static memory.
meillo@134	3350 All three functions are implemented in
meillo@134	3351 .Fn sbr/path.c .
meillo@134	3352 .Fn sbr/m_maildir.c
meillo@134	3353 is removed.
meillo@168	3354 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134	3355 .P
meillo@134	3356 Along with the path conversion rework, I also replaced
meillo@134	3357 .Fu getfolder(FDEF)
meillo@134	3358 with
meillo@134	3359 .Fu getdeffol()
meillo@134	3360 and
meillo@134	3361 .Fu getfolder(FCUR)
meillo@134	3362 with
meillo@134	3363 .Fu getcurfol() ,
meillo@134	3364 which is only a convenience wrapper for
meillo@134	3365 .Fu expandfol("@") .
meillo@134	3366 This code was moved from
meillo@134	3367 .Fn sbr/getfolder.c
meillo@134	3368 to
meillo@134	3369 .Fn sbr/path.c .
meillo@168	3370 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134	3371 .P
meillo@134	3372 The related function
meillo@134	3373 .Fu etcpath()
meillo@134	3374 was moved to
meillo@134	3375 .Fn sbr/path.c ,
meillo@168	3376 too
meillo@168	3377 .Ci b4c29794c12099556151d93a860ee51badae2e35 .
meillo@134	3378 Previously, it had been located in
meillo@134	3379 .Fn config/config.c ,
meillo@134	3380 for whatever reasons.
meillo@134	3381 .P
meillo@134	3382 .Fn sbr/path.c
meillo@134	3383 now contains all path handling code.
meillo@180	3384 .\" XXX naechste zeile weg?
meillo@134	3385 Only 173 lines of code were needed to replace the previous 252 lines.
meillo@134	3386 The readability of the code is highly improved.
meillo@134	3387 Additionally, each of the six exported and one static functions
meillo@134	3388 is introduced by an explaining comment.
meillo@133	3389
meillo@133	3390
meillo@133	3391
meillo@133	3392
meillo@133	3393 .H2 "Profile Reading
meillo@133	3394 .P
meillo@138	3395 The MH profile contains the configuration for the user-specific MH setup.
meillo@138	3396 MH tools read the profile right after starting up,
meillo@138	3397 as it contains the location of the user's mail storage
meillo@138	3398 and similar settings that influence the whole setup.
meillo@181	3399 Furthermore, the profile contains the default switches for the tools,
meillo@138	3400 hence, it must be read before the command line switches are processed.
meillo@138	3401 .P
meillo@138	3402 For historic reasons, some MH tools did not read the profile and context.
meillo@138	3403 Among them were
meillo@138	3404 .Pn post /\c
meillo@138	3405 .Pn spost ,
meillo@138	3406 .Pn mhmail ,
meillo@138	3407 and
meillo@138	3408 .Pn slocal .
meillo@138	3409 The reason why these tools ignored the profile were not clearly stated.
meillo@138	3410 During the discussion on the nmh-workers mailing list,
meillo@181	3411 David Levine posted an explanation, quoting John Romine:
meillo@138	3412 .[
meillo@138	3413 nmh-workers levine post profile
meillo@138	3414 .]
meillo@138	3415 .QS
meillo@138	3416 I asked John Romine and here's what he had to say, which
meillo@138	3417 agrees and provides an example that convinces me:
meillo@138	3418 .QS
meillo@164	3419 My take on this is that
meillo@164	3420 .Pn post
meillo@164	3421 should not be called by users directly, and it doesn't read the
meillo@164	3422 .Fn .mh_profile
meillo@138	3423 (only front-end UI programs read the profile).
meillo@138	3424 .QP
meillo@164	3425 For example, there can be contexts where
meillo@164	3426 .Pn post
meillo@164	3427 is called by a helper program (like `\c
meillo@164	3428 .Pn mhmail ')
meillo@164	3429 which may be run by a non-MH user.
meillo@164	3430 We don't want this to prompt the user to create an MH profile, etc.
meillo@138	3431 .QP
meillo@164	3432 My suggestion would be to have
meillo@164	3433 .Pn send
meillo@164	3434 pass a (hidden) `\c
meillo@164	3435 .Sw -fileproc
meillo@164	3436 .Ar proc '
meillo@164	3437 option to
meillo@164	3438 .Pn post
meillo@164	3439 if needed.
meillo@164	3440 You could also
meillo@164	3441 use an environment variable (I think
meillo@164	3442 .Pn send /\c
meillo@164	3443 .Pn whatnow
meillo@164	3444 do this).
meillo@138	3445 .QE
meillo@164	3446 I think that's the way to go.
meillo@164	3447 My personal preference is to use a command line option,
meillo@164	3448 not an environment variable.
meillo@138	3449 .QE
meillo@138	3450 .P
meillo@138	3451 To solve the problem of
meillo@138	3452 .Pn post
meillo@138	3453 not honoring the
meillo@138	3454 .Pe fileproc
meillo@138	3455 profile entry,
meillo@138	3456 the community roughly agreed that a switch
meillo@138	3457 .Sw -fileproc
meillo@138	3458 should be added to
meillo@138	3459 .Pn post
meillo@138	3460 to be able to pass a different fileproc.
meillo@138	3461 I strongly disagree with this approach because it does not solve
meillo@138	3462 the problem; it only removes a single symptom.
meillo@138	3463 The problem is that
meillo@138	3464 .Pn post
meillo@138	3465 does not behave as expected.
meillo@138	3466 But all programs should behave as expected.
meillo@138	3467 Clear and simple concepts are a precondition for this.
meillo@138	3468 Hence, the real solution is having all MH tools read the profile.
meillo@138	3469 .P
meillo@180	3470 The problem has a further aspect.
meillo@138	3471 It mainly originates in
meillo@138	3472 .Pn mhmail .
meillo@138	3473 .Pn mhmail
meillo@138	3474 was intended to be a replacement for
meillo@138	3475 .Pn mailx
meillo@138	3476 on systems with MH installations.
meillo@138	3477 .Pn mhmail
meillo@138	3478 should have been able to use just like
meillo@138	3479 .Pn mailx ,
meillo@138	3480 but sending the message via MH's
meillo@138	3481 .Pn post
meillo@138	3482 instead of
meillo@138	3483 .Pn sendmail .
meillo@138	3484 Using
meillo@138	3485 .Pn mhmail
meillo@138	3486 should not be influenced by the question whether the user had
meillo@138	3487 MH set up for himself or not.
meillo@138	3488 .Pn mhmail
meillo@138	3489 did not read the profile as this requests the user to set up MH
meillo@138	3490 if not done yet.
meillo@138	3491 As
meillo@138	3492 .Pn mhmail
meillo@138	3493 used
meillo@138	3494 .Pn post ,
meillo@138	3495 .Pn post
meillo@138	3496 could not read the profile neither.
meillo@138	3497 This is the reason why
meillo@138	3498 .Pn post
meillo@138	3499 does not read the profile.
meillo@138	3500 This is the reason for the actual problem.
meillo@138	3501 It was not much of a problem because
meillo@138	3502 .Pn post
meillo@138	3503 was not intended to be used by users directly.
meillo@138	3504 .Pn send
meillo@138	3505 is the interactive front-end to
meillo@138	3506 .Pn post .
meillo@138	3507 .Pn send
meillo@138	3508 read the profile and passed all relevant values on the command line to
meillo@138	3509 .Pn post
meillo@138	3510 \(en an awkward solution.
meillo@138	3511 .P
meillo@138	3512 The important insight is that
meillo@138	3513 .Pn mhmail
meillo@138	3514 is no true MH tool.
meillo@138	3515 The concepts broke because this outlandish tool was treated as any other
meillo@138	3516 MH tool.
meillo@138	3517 Instead it should have been treated accordingly to its foreign style.
meillo@138	3518 The solution is not to prevent the tools reading the profile but
meillo@138	3519 to instruct them reading a different profile.
meillo@138	3520 .Pn mhmail
meillo@138	3521 could have set up a well-defined profile and caused all MH tools
meillo@180	3522 in the session to use it by exporting an environment variable.
meillo@138	3523 With this approach, no special cases would have been introduced,
meillo@138	3524 no surprises would have been caused.
meillo@138	3525 By writing a clean-profile-wrapper, the concept could have been
meillo@173	3526 generalized orthogonally to the whole MH tool chest.
meillo@138	3527 Then Rose's motivation behind the decision that
meillo@138	3528 .Pn post
meillo@138	3529 ignores the profile, as quoted by Jeffrey Honig,
meillo@181	3530 would have become possible:
meillo@138	3531 .[
meillo@197	3532 nmh-workers honig post profile
meillo@138	3533 .]
meillo@138	3534 .QS
meillo@138	3535 when you run mh commands in a script, you want all the defaults to be
meillo@138	3536 what the man page says.
meillo@138	3537 when you run a command by hand, then you want your own defaults...
meillo@138	3538 .QE
meillo@138	3539 .LP
meillo@171	3540 Yet, I consider this explanation shortsighted.
meillo@138	3541 We should rather regard theses two cases as just two different MH setups,
meillo@138	3542 based on two different profiles.
meillo@138	3543 Mapping such problems on the concepts of switching between different
meillo@138	3544 profiles, solves them once for all.
meillo@138	3545 .P
meillo@138	3546 In mmh, the wish to have
meillo@138	3547 .Pn mhmail
meillo@173	3548 as a replacement for
meillo@138	3549 .Pn mailx
meillo@138	3550 is considered obsolete.
meillo@138	3551 Mmh's
meillo@138	3552 .Pn mhmail
meillo@138	3553 does no longer cover this use-case.
meillo@138	3554 Currently,
meillo@138	3555 .Pn mhmail
meillo@138	3556 is in a transition state.
meillo@138	3557 .Ci 32d4f9daaa70519be3072479232ff7be0500d009
meillo@138	3558 It may become a front-end to
meillo@138	3559 .Pn comp ,
meillo@138	3560 which provides an interface more convenient in some cases.
meillo@138	3561 In this case,
meillo@138	3562 .Pn mhmail
meillo@138	3563 will become an ordinary MH tool, reading the profile.
meillo@138	3564 If, however, this idea will not convince, then
meillo@138	3565 .Pn mhmail
meillo@138	3566 will be removed.
meillo@138	3567 .P
meillo@173	3568 Every program in the mmh tool chest reads the profile.
meillo@138	3569 The only exception is
meillo@138	3570 .Pn slocal ,
meillo@173	3571 which is not considered part of the mmh tool chest.
meillo@138	3572 This MDA is only distributed with mmh, currently.
meillo@138	3573 Mmh has no
meillo@138	3574 .Pn post
meillo@138	3575 program, but
meillo@138	3576 .Pn spost ,
meillo@138	3577 which now reads the profile.
meillo@138	3578 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8
meillo@138	3579 With this change,
meillo@138	3580 .Pn send
meillo@138	3581 and
meillo@138	3582 .Pn spost
meillo@138	3583 can be considered to be merged.
meillo@138	3584 .Pn spost
meillo@169	3585 is only invoked directly by the to-be-changed
meillo@138	3586 .Pn mhmail
meillo@138	3587 implementation and by
meillo@138	3588 .Pn rcvdist ,
meillo@138	3589 which will require rework.
meillo@138	3590 .P
meillo@138	3591 The
meillo@138	3592 .Fu context_foil()
meillo@138	3593 function to pretend to have read an empty profile was removed.
meillo@138	3594 .Ci 68af8da96bea87a5541988870130b6209ce396f6
meillo@138	3595 All mmh tools read the profile.
meillo@133	3596
meillo@133	3597
meillo@127	3598
meillo@121	3599 .H2 "Standard Libraries
meillo@22	3600 .P
meillo@121	3601 MH is one decade older than the POSIX and ANSI C standards.
meillo@121	3602 Hence, MH included own implementations of functions
meillo@121	3603 that are standardized and thus widely available today,
meillo@121	3604 but were not back then.
meillo@121	3605 Today, twenty years after the POSIX and ANSI C were published,
meillo@180	3606 developers can expect systems to comply with these standards.
meillo@121	3607 In consequence, MH-specific replacements for standard functions
meillo@121	3608 can and should be dropped.
meillo@121	3609 Kernighan and Pike advise: ``Use standard libraries.''
meillo@121	3610 .[ [
meillo@121	3611 kernighan pike practice of programming
meillo@121	3612 .], p. 196]
meillo@121	3613 Actually, MH had followed this advice in history,
meillo@121	3614 but it had not adjusted to the changes in this field.
meillo@121	3615 The
meillo@121	3616 .Fu snprintf()
meillo@121	3617 function, for instance, was standardized with C99 and is available
meillo@121	3618 almost everywhere because of its high usefulness.
meillo@180	3619 The project's own implementation of
meillo@121	3620 .Fu snprintf()
meillo@123	3621 was dropped in March 2012 in favor for using the one of the
meillo@123	3622 standard library.
meillo@123	3623 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32
meillo@123	3624 Such decisions limit the portability of mmh
meillo@173	3625 if systems do not support these standardized and widespread functions.
meillo@123	3626 This compromise is made because mmh focuses on the future.
meillo@121	3627 .P
meillo@180	3628 .\" XXX kuerzen und mit dem naechsten Absatz vereinen
meillo@180	3629 I am still in my twenties and my C and Unix experience comprises
meillo@123	3630 only half a dozen years.
meillo@121	3631 Hence, I need to learn about the history in retrospective.
meillo@121	3632 I have not used those ancient constructs myself.
meillo@121	3633 I have not suffered from their incompatibilities.
meillo@121	3634 I have not longed for standardization.
meillo@121	3635 All my programming experience is from a time when ANSI C and POSIX
meillo@121	3636 were well established already.
meillo@121	3637 I have only read a lot of books about the (good) old times.
meillo@180	3638 This puts me in a difficult position when working with old code.
meillo@123	3639 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123	3640 programming styles, whereas older programmers know these things by
meillo@123	3641 heart from their own experience.
meillo@121	3642 .P
meillo@123	3643 Being aware of the situation, I rather let people with more historic
meillo@123	3644 experience replace ancient code constructs with standardized ones.
meillo@121	3645 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121	3646 He converted project-specific functions to POSIX replacements,
meillo@121	3647 also removing the conditionals compilation of now standardized features.
meillo@123	3648 Ken Hornstein and David Levine had their part in the work, too.
meillo@121	3649 Often, I only needed to pull over changes from nmh into mmh.
meillo@121	3650 These changes include many commits; these are among them:
meillo@121	3651 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121	3652 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102	3653 .P
meillo@123	3654 During my own work, I tidied up the \fIMH standard library\fP,
meillo@123	3655 .Fn libmh.a ,
meillo@123	3656 which is located in the
meillo@123	3657 .Fn sbr
meillo@123	3658 (``subroutines'') directory in the source tree.
meillo@123	3659 The MH library includes functions that mmh tools usually need.
meillo@123	3660 Among them are MH-specific functions for profile, context, sequence,
meillo@123	3661 and folder handling, but as well
meillo@123	3662 MH-independent functions, such as auxiliary string functions,
meillo@123	3663 portability interfaces and error-checking wrappers for critical
meillo@123	3664 functions of the standard library.
meillo@123	3665 .P
meillo@123	3666 I have replaced the
meillo@121	3667 .Fu atooi()
meillo@121	3668 function with calls to
meillo@123	3669 .Fu strtoul()
meillo@139	3670 with the third parameter, the base, set to eight.
meillo@121	3671 .Fu strtoul()
meillo@123	3672 is part of C89 and thus considered safe to use.
meillo@121	3673 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74
meillo@102	3674 .P
meillo@121	3675 I did remove project-included fallback implementations of
meillo@121	3676 .Fu memmove()
meillo@121	3677 and
meillo@121	3678 .Fu strerror() ,
meillo@121	3679 although Peter Maydell had re-included them into nmh in 2008
meillo@121	3680 to support SunOS 4.
meillo@121	3681 Nevertheless, these functions are part of ANSI C.
meillo@121	3682 Systems that do not even provide full ANSI C support should not
meillo@121	3683 put a load on mmh.
meillo@121	3684 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215
meillo@121	3685 .P
meillo@121	3686 The
meillo@121	3687 .Fu copy()
meillo@180	3688 function copies the string in parameter one to the location in
meillo@180	3689 parameter two.
meillo@121	3690 In contrast to
meillo@121	3691 .Fu strcpy() ,
meillo@121	3692 it returns a pointer to the terminating null-byte in the destination area.
meillo@123	3693 The code was adjusted to replace
meillo@121	3694 .Fu copy()
meillo@123	3695 with
meillo@121	3696 .Fu strcpy() ,
meillo@121	3697 except within
meillo@121	3698 .Fu concat() ,
meillo@121	3699 where
meillo@121	3700 .Fu copy()
meillo@123	3701 was more convenient.
meillo@123	3702 Therefore, the definition of
meillo@121	3703 .Fu copy()
meillo@123	3704 was moved into the source file of
meillo@121	3705 .Fu concat()
meillo@123	3706 and its visibility is now limited to it.
meillo@121	3707 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb
meillo@121	3708 .P
meillo@121	3709 The function
meillo@121	3710 .Fu r1bindex()
meillo@121	3711 had been a generalized version of
meillo@121	3712 .Fu basename()
meillo@121	3713 with minor differences.
meillo@121	3714 As all calls to
meillo@121	3715 .Fu r1bindex()
meillo@121	3716 had the slash (`/') as delimiter anyway,
meillo@121	3717 replacing
meillo@121	3718 .Fu r1bindex()
meillo@121	3719 with the more specific and better-named function
meillo@121	3720 .Fu basename()
meillo@121	3721 became desirable.
meillo@121	3722 Unfortunately, many of the 54 calls to
meillo@121	3723 .Fu r1bindex()
meillo@123	3724 depended on a special behavior,
meillo@121	3725 which differed from the POSIX specification for
meillo@121	3726 .Fu basename() .
meillo@121	3727 Hence,
meillo@121	3728 .Fu r1bindex()
meillo@121	3729 was kept but renamed to
meillo@123	3730 .Fu mhbasename() ,
meillo@123	3731 fixing the delimiter to the slash.
meillo@121	3732 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60
meillo@121	3733 For possible uses of
meillo@121	3734 .Fu r1bindex()
meillo@121	3735 with a different delimiter,
meillo@121	3736 the ANSI C function
meillo@121	3737 .Fu strrchr()
meillo@121	3738 provides the core functionality.
meillo@121	3739 .P
meillo@121	3740 The
meillo@121	3741 .Fu ssequal()
meillo@121	3742 function \(en apparently for ``substring equal'' \(en
meillo@121	3743 was renamed to
meillo@121	3744 .Fu isprefix() ,
meillo@121	3745 because this is what it actually checks.
meillo@121	3746 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711
meillo@121	3747 Its source file had included the following comments, no joke.
meillo@121	3748 .VS
meillo@121	3749 /*
meillo@121	3750 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121	3751 * It is actually checking if s1 is a PREFIX of s2.
meillo@121	3752 * All calls to this function need to be checked to see
meillo@121	3753 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121	3754 * should be kept if it's sufficient.
meillo@121	3755 */
meillo@121	3756
meillo@121	3757 /*
meillo@121	3758 * Check if s1 is a substring of s2.
meillo@121	3759 * If yes, then return 1, else return 0.
meillo@121	3760 */
meillo@121	3761 VE
meillo@123	3762 Two months later, it was completely removed by replacing it with
meillo@123	3763 .Fu strncmp() .
meillo@123	3764 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb
meillo@121	3765
meillo@102	3766
meillo@102	3767
meillo@102	3768
meillo@133	3769
meillo@133	3770 .H2 "User Data Locations
meillo@133	3771 .P
meillo@133	3772 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133	3773 The profile is a file named
meillo@133	3774 .Fn \&.mh_profile
meillo@133	3775 in the user's home directory.
meillo@133	3776 It contains the static configuration.
meillo@133	3777 It also contains the location of the MH directory in the profile entry
meillo@133	3778 .Pe Path .
meillo@133	3779 The MH directory contains the mail storage and is the first
meillo@133	3780 place to search for personal forms, scan formats, and similar
meillo@133	3781 configuration files.
meillo@133	3782 The location of the MH directory can be chosen freely by the user.
meillo@133	3783 The default and usual name is a directory named
meillo@133	3784 .Fn Mail
meillo@133	3785 in the home directory.
meillo@133	3786 .P
meillo@200	3787 The way MH data is split between profile and MH directory is a legacy.
meillo@133	3788 It is only sensible in a situation where the profile is the only
meillo@133	3789 configuration file.
meillo@133	3790 Why else should the mail storage and the configuration files be intermixed?
meillo@133	3791 They are different kinds of data:
meillo@133	3792 The data to be operated on and the configuration to change how
meillo@133	3793 tools operate.
meillo@180	3794 .\" XXX bad ... inapropriate?
meillo@133	3795 Splitting the configuration between the profile and the MH directory
meillo@133	3796 is bad.
meillo@133	3797 Merging the mail storage and the configuration in one directory is bad
meillo@133	3798 as well.
meillo@133	3799 As the mail storage and the configuration were not separated sensibly
meillo@133	3800 in the first place, I did it now.
meillo@133	3801 .P
meillo@133	3802 Personal mmh data is grouped by type, resulting in two distinct parts:
meillo@171	3803 the mail storage and the configuration.
meillo@133	3804 In mmh, the mail storage directory still contains all the messages,
meillo@133	3805 but, in exception of public sequences files, nothing else.
meillo@133	3806 In difference to nmh, the auxiliary configuration files are no longer
meillo@133	3807 located there.
meillo@133	3808 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@133	3809 but his \fImail storage\fP.
meillo@133	3810 Its location is still user-chosen, with the default name
meillo@133	3811 .Fn Mail ,
meillo@133	3812 in the user's home directory.
meillo@133	3813 In mmh, the configuration is grouped together in
meillo@133	3814 the hidden directory
meillo@133	3815 .Fn \&.mmh
meillo@133	3816 in the user's home directory.
meillo@133	3817 This \fImmh directory\fP contains the context file, personal forms,
meillo@133	3818 scan formats, and the like, but also the user's profile, now named
meillo@133	3819 .Fn profile .
meillo@133	3820 The location of the profile is no longer fixed to
meillo@133	3821 .Fn $HOME/.mh_profile
meillo@133	3822 but to
meillo@133	3823 .Fn $HOME/.mmh/profile .
meillo@173	3824 Having both the file
meillo@133	3825 .Fn $HOME/.mh_profile
meillo@133	3826 and the configuration directory
meillo@133	3827 .Fn $HOME/.mmh
meillo@133	3828 appeared to be inconsistent.
meillo@133	3829 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133	3830 Unix users.
meillo@168	3831 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133	3832 .P
meillo@168	3833 MH allows users to have multiple MH setups.
meillo@133	3834 Therefore, it is necessary to select a different profile.
meillo@133	3835 The profile is the single entry point to access the rest of a
meillo@133	3836 personal MH setup.
meillo@133	3837 In nmh, the environment variable
meillo@133	3838 .Ev MH
meillo@200	3839 could be used to specify a different profile.
meillo@133	3840 To operate in the same MH setup with a separate context,
meillo@133	3841 the
meillo@133	3842 .Ev MHCONTEXT
meillo@133	3843 environment variable could be used.
meillo@133	3844 This allows having own current folders and current messages in
meillo@133	3845 each terminal, for instance.
meillo@133	3846 In mmh, three environment variables are used.
meillo@133	3847 .Ev MMH
meillo@133	3848 overrides the default location of the mmh directory (\c
meillo@133	3849 .Fn .mmh ).
meillo@133	3850 .Ev MMHP
meillo@133	3851 and
meillo@133	3852 .Ev MMHC
meillo@133	3853 override the paths to the profile and context files, respectively.
meillo@133	3854 This approach allows the set of personal configuration files to be chosen
meillo@133	3855 independently from the profile, context, and mail storage.
meillo@168	3856 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133	3857 .P
meillo@133	3858 The separation of the files by type is sensible and convenient.
meillo@133	3859 The new approach has no functional disadvantages,
meillo@133	3860 as every setup I can imagine can be implemented with both approaches,
meillo@133	3861 possibly even easier with the new approach.
meillo@133	3862 The main achievement of the change is the clear and sensible split
meillo@133	3863 between mail storage and configuration.
meillo@133	3864
meillo@133	3865
meillo@133	3866
meillo@133	3867
meillo@133	3868
meillo@118	3869 .H2 "Modularization
meillo@118	3870 .P
meillo@123	3871 The source code of the mmh tools is located in the
meillo@122	3872 .Fn uip
meillo@123	3873 (``user interface programs'') directory.
meillo@180	3874 Each tool has a source file with the name of the command.
meillo@122	3875 For example,
meillo@122	3876 .Pn rmm
meillo@122	3877 is built from
meillo@122	3878 .Fn uip/rmm.c .
meillo@123	3879 Some source files are used for multiple programs.
meillo@122	3880 For example
meillo@122	3881 .Fn uip/scansbr.c
meillo@173	3882 is used for both
meillo@122	3883 .Pn scan
meillo@122	3884 and
meillo@122	3885 .Pn inc .
meillo@122	3886 In nmh, 49 tools were built from 76 source files.
meillo@123	3887 This is a ratio of 1.6 source files per program.
meillo@123	3888 32 programs depended on multiple source files;
meillo@123	3889 17 programs depended on one source file only.
meillo@122	3890 In mmh, 39 tools are built from 51 source files.
meillo@123	3891 This is a ratio of 1.3 source files per program.
meillo@123	3892 18 programs depend on multiple source files;
meillo@123	3893 21 programs depend on one source file only.
meillo@123	3894 (These numbers and the ones in the following text ignore the MH library
meillo@123	3895 as well as shell scripts and multiple names for the same program.)
meillo@180	3896 .\" XXX graph
meillo@122	3897 .P
meillo@123	3898 Splitting the source code of a large program into multiple files can
meillo@122	3899 increase the readability of its source code.
meillo@180	3900 .\" XXX however?
meillo@180	3901 Most of the mmh tools are simple and straight-forward programs.
meillo@122	3902 With the exception of the MIME handling tools,
meillo@122	3903 .Pn pick
meillo@179	3904 is the largest tool.
meillo@180	3905 It contains 1\\|037 lines of source code, excluding the MH library.
meillo@122	3906 Only the MIME handling tools (\c
meillo@122	3907 .Pn mhbuild ,
meillo@122	3908 .Pn mhstore ,
meillo@122	3909 .Pn show ,
meillo@122	3910 etc.)
meillo@122	3911 are larger.
meillo@122	3912 Splitting programs with less than 1\\|000 lines of code into multiple
meillo@123	3913 source files seldom leads to better readability.
meillo@123	3914 For such tools, splitting makes sense
meillo@122	3915 when parts of the code are reused in other programs,
meillo@179	3916 and the reused code fragment is (1) not general enough
meillo@179	3917 for including it in the MH library
meillo@179	3918 or (2) has dependencies on a library that only few programs need.
meillo@122	3919 .Fn uip/packsbr.c ,
meillo@122	3920 for instance, provides the core program logic for the
meillo@122	3921 .Pn packf
meillo@122	3922 and
meillo@122	3923 .Pn rcvpack
meillo@122	3924 programs.
meillo@122	3925 .Fn uip/packf.c
meillo@122	3926 and
meillo@122	3927 .Fn uip/rcvpack.c
meillo@122	3928 mainly wrap the core function appropriately.
meillo@122	3929 No other tools use the folder packing functions.
meillo@123	3930 As another example,
meillo@123	3931 .Fn uip/termsbr.c
meillo@123	3932 provides termcap support, which requires linking with a termcap or
meillo@123	3933 curses library.
meillo@123	3934 Including
meillo@123	3935 .Fn uip/termsbr.c
meillo@123	3936 into the MH library would require every program to be linked with
meillo@123	3937 termcap or curses, although only few of the programs require it.
meillo@122	3938 .P
meillo@122	3939 The task of MIME handling is complex enough that splitting its code
meillo@122	3940 into multiple source files improves the readability.
meillo@122	3941 The program
meillo@122	3942 .Pn mhstore ,
meillo@122	3943 for instance, is compiled out of seven source files with 2\\|500
meillo@122	3944 lines of code in summary.
meillo@122	3945 The main code file
meillo@122	3946 .Fn uip/mhstore.c
meillo@123	3947 consists of 800 lines; the other 1\\|700 lines of code are reused in
meillo@123	3948 other MIME handling tools.
meillo@123	3949 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123	3950 a MH-MIME library, as a companion to the MH standard library.
meillo@122	3951 This is left open for the future.
meillo@122	3952 .P
meillo@169	3953 The work already accomplished focussed on the non-MIME tools.
meillo@122	3954 The amount of code compiled into each program was reduced.
meillo@123	3955 This eases the understanding of the code base.
meillo@122	3956 In nmh,
meillo@122	3957 .Pn comp
meillo@122	3958 was built from six source files:
meillo@122	3959 .Fn comp.c ,
meillo@122	3960 .Fn whatnowproc.c ,
meillo@122	3961 .Fn whatnowsbr.c ,
meillo@122	3962 .Fn sendsbr.c ,
meillo@122	3963 .Fn annosbr.c ,
meillo@122	3964 and
meillo@122	3965 .Fn distsbr.c .
meillo@122	3966 In mmh, it builds from only two:
meillo@122	3967 .Fn comp.c
meillo@122	3968 and
meillo@122	3969 .Fn whatnowproc.c .
meillo@123	3970 In nmh's
meillo@123	3971 .Pn comp ,
meillo@123	3972 the core function of
meillo@122	3973 .Pn whatnow ,
meillo@122	3974 .Pn send ,
meillo@122	3975 and
meillo@122	3976 .Pn anno
meillo@123	3977 were compiled into
meillo@122	3978 .Pn comp .
meillo@123	3979 This saved the need to execute these programs with
meillo@122	3980 .Fu fork()
meillo@122	3981 and
meillo@122	3982 .Fu exec() ,
meillo@122	3983 two expensive system calls.
meillo@171	3984 Whereas this approach improved the time performance,
meillo@171	3985 it interwove the source code.
meillo@122	3986 Core functionalities were not encapsulated into programs but into
meillo@122	3987 function, which were then wrapped by programs.
meillo@122	3988 For example,
meillo@122	3989 .Fn uip/annosbr.c
meillo@122	3990 included the function
meillo@122	3991 .Fu annotate() .
meillo@122	3992 Each program that wanted to annotate messages, included the source file
meillo@123	3993 .Fn uip/annosbr.c
meillo@123	3994 and called
meillo@123	3995 .Fu annotate() .
meillo@123	3996 Because the function
meillo@123	3997 .Fu annotate()
meillo@123	3998 was used like the tool
meillo@123	3999 .Pn anno ,
meillo@123	4000 it had seven parameters, reflecting the command line switches of the tool.
meillo@122	4001 When another pair of command line switches was added to
meillo@122	4002 .Pn anno ,
meillo@122	4003 a rather ugly hack was implemented to avoid adding another parameter
meillo@122	4004 to the function.
meillo@122	4005 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@122	4006 .P
meillo@122	4007 Separation simplifies the understanding of program code
meillo@122	4008 because the area influenced by any particular statement is smaller.
meillo@122	4009 The separating on the program-level is more strict than the separation
meillo@122	4010 on the function level.
meillo@122	4011 In mmh, the relevant code of
meillo@122	4012 .Pn comp
meillo@122	4013 comprises the two files
meillo@122	4014 .Fn uip/comp.c
meillo@122	4015 and
meillo@122	4016 .Fn uip/whatnowproc.c ,
meillo@123	4017 together 210 lines of code.
meillo@122	4018 In nmh,
meillo@122	4019 .Pn comp
meillo@122	4020 comprises six files with 2\\|450 lines.
meillo@123	4021 Not all of the code in these six files was actually used by
meillo@122	4022 .Pn comp ,
meillo@123	4023 but the code reader needed to read all of the code first to know which
meillo@123	4024 parts were used.
meillo@122	4025 .P
meillo@123	4026 As I have read a lot in the code base during the last two years,
meillo@123	4027 I learned about the easy and the difficult parts.
meillo@171	4028 Code is easy to understand if the influenced code area is small
meillo@171	4029 and its boundaries are strictly defined.
meillo@181	4030 Furthermore, the code needs to solve the problem in a straight-forward way.
meillo@123	4031 .P
meillo@123	4032 .\" XXX move this paragraph somewhere else?
meillo@123	4033 Reading
meillo@122	4034 .Pn rmm 's
meillo@122	4035 source code in
meillo@122	4036 .Fn uip/rmm.c
meillo@122	4037 is my recommendation for a beginner's entry point into the code base of nmh.
meillo@122	4038 The reasons are that the task of
meillo@122	4039 .Pn rmm
meillo@122	4040 is straight forward and it consists of one small source code file only,
meillo@122	4041 yet its source includes code constructs typical for MH tools.
meillo@122	4042 With the introduction of the trash folder in mmh,
meillo@122	4043 .Pn rmm
meillo@122	4044 became a bit more complex, because it invokes
meillo@122	4045 .Pn refile .
meillo@122	4046 Still, it is a good example for a simple tool with clear sources.
meillo@122	4047 .P
meillo@122	4048 Understanding
meillo@122	4049 .Pn comp
meillo@180	4050 .\" XXX kate fragen: more vs. as much
meillo@180	4051 requires to read 210 lines of code in mmh, but ten times more in nmh.
meillo@123	4052 Due to the aforementioned hack in
meillo@122	4053 .Pn anno
meillo@122	4054 to save the additional parameter, information passed through the program's
meillo@122	4055 source base in obscure ways.
meillo@123	4056 Thus, understanding
meillo@122	4057 .Pn comp ,
meillo@123	4058 required understanding the inner workings of
meillo@122	4059 .Fn uip/annosbr.c
meillo@122	4060 first.
meillo@123	4061 To be sure to fully understand a program, its whole source code needs
meillo@122	4062 to be examined.
meillo@123	4063 Not doing so is a leap of faith, assuming that the developers
meillo@122	4064 have avoided obscure programming techniques.
meillo@122	4065 By separating the tools on the program-level, the boundaries are
meillo@122	4066 clearly visible and technically enforced.
meillo@122	4067 The interfaces are calls to
meillo@122	4068 .Fu exec()
meillo@122	4069 rather than arbitrary function calls.
meillo@123	4070 .P
meillo@123	4071 But the real problem is another:
meillo@123	4072 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@181	4073 .\" XXX ref
meillo@123	4074 Understanding
meillo@122	4075 .Pn comp
meillo@123	4076 requires understanding
meillo@123	4077 .Fn uip/annosbr.c
meillo@123	4078 and
meillo@123	4079 .Fn uip/sendsbr.c
meillo@123	4080 because
meillo@123	4081 .Pn comp
meillo@123	4082 does annotate and send messages.
meillo@123	4083 In nmh, there surely exists the tool
meillo@122	4084 .Pn send ,
meillo@179	4085 which does mainly send messages.
meillo@123	4086 But
meillo@122	4087 .Pn comp
meillo@123	4088 and
meillo@122	4089 .Pn repl
meillo@122	4090 and
meillo@122	4091 .Pn forw
meillo@122	4092 and
meillo@122	4093 .Pn dist
meillo@122	4094 and
meillo@122	4095 .Pn whatnow
meillo@122	4096 and
meillo@123	4097 .Pn viamail ,
meillo@179	4098 they all (!) have the same message sending function included, as well.
meillo@123	4099 In result,
meillo@123	4100 .Pn comp
meillo@123	4101 sends messages without using
meillo@123	4102 .Pn send .
meillo@123	4103 The situation is the same as if
meillo@123	4104 .Pn grep
meillo@123	4105 would page without
meillo@123	4106 .Pn more
meillo@123	4107 just because both programs are part of the same code base.
meillo@123	4108 .P
meillo@173	4109 The clear separation on the surface \(en the tool chest approach \(en
meillo@123	4110 is violated on the level below.
meillo@122	4111 This violation is for the sake of time performance.
meillo@122	4112 On systems where
meillo@122	4113 .Fu fork()
meillo@122	4114 and
meillo@122	4115 .Fu exec()
meillo@122	4116 are expensive, the quicker response might be noticable.
meillo@124	4117 In the old times, sacrificing readability and conceptional beauty for
meillo@124	4118 speed might even have been a must to prevent MH from being unusably slow.
meillo@122	4119 Whatever the reasons had been, today they are gone.
meillo@123	4120 No longer should we sacrifice readability or conceptional beauty.
meillo@122	4121 No longer should we violate the Unix philosophy's ``one tool, one job''
meillo@122	4122 guideline.
meillo@181	4123 .\" XXX ref
meillo@123	4124 No longer should we keep speed improvements that became unnecessary.
meillo@122	4125 .P
meillo@123	4126 Therefore, mmh's
meillo@123	4127 .Pn comp
meillo@123	4128 does no longer send messages.
meillo@123	4129 In mmh, different jobs are divided among separate programs that
meillo@122	4130 invoke each other as needed.
meillo@123	4131 In consequence,
meillo@123	4132 .Pn comp
meillo@123	4133 invokes
meillo@123	4134 .Pn whatnow
meillo@123	4135 which thereafter invokes
meillo@123	4136 .Pn send .
meillo@168	4137 .Ci 3df5ab3c116e6d4a2fb4bb5cc9dfc5f781825815
meillo@168	4138 .Ci c73c00bfccd22ec77e9593f47462aeca4a8cd9c0
meillo@123	4139 The clear separation on the surface is maintained on the level below.
meillo@123	4140 Human users and the tools use the same interface \(en
meillo@123	4141 annotations, for example, are made by invoking
meillo@123	4142 .Pn anno ,
meillo@123	4143 no matter if requested by programs or by human beings.
meillo@168	4144 .Ci 469a4163c2a1a43731d412eaa5d9cae7d670c48b
meillo@168	4145 .Ci aed384169af5204b8002d06e7a22f89197963d2d
meillo@168	4146 .Ci 3caf9e298a8861729ca8b8a84f57022b6f3ea742
meillo@123	4147 The decrease of tools built from multiple source files and thus
meillo@123	4148 the decrease of
meillo@123	4149 .Fn uip/*sbr.c
meillo@123	4150 files confirm the improvement.
meillo@168	4151 .Ci 9e6d91313f01c96b4058d6bf419a8ca9a207bc33
meillo@168	4152 .ci 81744a46ac9f845d6c2b9908074d269275178d2e
meillo@168	4153 .Ci f0f858069d21111f0dbea510044593f89c9b0829
meillo@168	4154 .Ci 0503a6e9be34f24858b55b555a5c948182b9f24b
meillo@168	4155 .Ci 27826f9353e0f0b04590b7d0f8f83e60462b90f0
meillo@168	4156 .Ci d1da1f94ce62160aebb30df4063ccbc53768656b
meillo@168	4157 .Ci c42222869e318fff5dec395eca3e776db3075455
meillo@123	4158 .P
meillo@145	4159 .\" XXX move this paragraph up somewhere
meillo@123	4160 One disadvantage needs to be taken with this change:
meillo@123	4161 The compiler can no longer check the integrity of the interfaces.
meillo@123	4162 By changing the command line interfaces of tools, it is
meillo@123	4163 the developer's job to adjust the invocations of these tools as well.
meillo@123	4164 As this is a manual task and regression tests, which could detect such
meillo@124	4165 problems, are not available yet, it is prone to errors.
meillo@123	4166 These errors will not be detected at compile time but at run time.
meillo@171	4167 Installing regression tests is a pending task.
meillo@123	4168 In the best case, a uniform way of invoking tools from other tools
meillo@123	4169 can be developed to allow automated testing at compile time.
meillo@145	4170
meillo@145	4171
meillo@145	4172 .ig
meillo@145	4173 XXX consider writing about mhl vs. mhlproc
meillo@145	4174
meillo@145	4175 sbr/showfile.c
meillo@145	4176
meillo@145	4177 23 /*
meillo@145	4178 24 ** If you have your lproc listed as "mhl",
meillo@145	4179 25 ** then really invoked the mhlproc instead
meillo@145	4180 26 ** (which is usually mhl anyway).
meillo@145	4181 27 */
meillo@145	4182
meillo@145	4183 Sat Nov 24 19:09:14 1984 /mtr (agent: Marshall Rose) <uci@udel-dewey>
meillo@145	4184
meillo@145	4185 sbr/showfile.c: if lproc is "mhl", use mhlproc for consistency
meillo@145	4186 (Actually, user should use "lproc: show", "showproc: mhl".)
meillo@145	4187 ..