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author markus schnalke <meillo@marmaro.de>
date Thu, 12 Jul 2012 01:18:02 +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 ..