docs/master

annotate discussion.roff @ 236:49d3aa0d128a

find changesets by author, revision, files, or words in the commit message
style: Removed unused macro code.
author markus schnalke <meillo@marmaro.de>
date Mon, 16 Jul 2012 11:31:25 +0200
parents 96778c1afc3e
children
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@217 5 It is structured along the goals chosen for the project.
meillo@217 6 A selection of the work undertaken
meillo@217 7 is described.
meillo@217 8 .P
meillo@217 9 This discussion compares the present version of mmh with the state of
meillo@217 10 nmh at the time when the mmh project had started, i.e. fall 2011.
meillo@224 11 Recent changes in nmh are rarely part of the discussion.
meillo@187 12 .P
meillo@232 13 Whenever lines of code are counted, David A. Wheeler's \fIsloccount\fP
meillo@230 14 was used to measure the amount in a comparable way.
meillo@230 15 .P
meillo@187 16 For the reader's convenience, the structure of modern email systems
meillo@217 17 is depicted in the following figure.
meillo@187 18 It illustrates the path a message takes from sender to recipient.
meillo@217 19
meillo@217 20 .sp 1.5
meillo@187 21 .KS
meillo@187 22 .in 2c
meillo@187 23 .so input/mail-agents.pic
meillo@187 24 .KE
meillo@217 25 .sp 1.5
meillo@217 26
meillo@187 27 .LP
meillo@217 28 The ellipses denote mail agents, i.e. different jobs in email processing.
meillo@217 29 These are:
meillo@187 30 .IP "Mail User Agent (MUA)
meillo@217 31 The only program users directly interact with.
meillo@187 32 It includes functions to compose new mail, display received mail,
meillo@187 33 and to manage the mail storage.
meillo@217 34 It is called a \fImail client\fP as well.
meillo@187 35 .IP "Mail Submission Agent (MSA)
meillo@187 36 A special kind of Mail Transfer Agent, used to submit mail into the
meillo@187 37 mail transport system.
meillo@217 38 Often it is also called an MTA.
meillo@187 39 .IP "Mail Transfer Agent (MTA)
meillo@187 40 A node in the mail transport system.
meillo@217 41 It transfers incoming mail to a transport node nearer to the
meillo@217 42 final destination.
meillo@217 43 An MTA may be the final destination itself.
meillo@187 44 .IP "Mail Delivery Agent (MDA)
meillo@217 45 Delivers mail according to a set of rules.
meillo@217 46 Usually, the messages are stored to disk.
meillo@187 47 .IP "Mail Retrieval Agent (MRA)
meillo@217 48 Initiates the transfer of mail from a remote location to the local machine.
meillo@217 49 (The dashed arrow in the figure represents the pull request.)
meillo@217 50 .LP
meillo@217 51 The dashed boxes represent entities that usually reside on single machines.
meillo@217 52 The box on the lower left represents the sender's system.
meillo@187 53 The box on the upper left represents the first mail transfer node.
meillo@224 54 The box on the upper right represents the transfer node responsible
meillo@224 55 for the destination address.
meillo@217 56 The box on the lower right represents the recipient's system.
meillo@187 57 Often, the boxes above the dotted line are servers on the Internet.
meillo@217 58 Many mail clients, including nmh, include all of the components below
meillo@217 59 the dotted line.
meillo@217 60 This is not the case for mmh; it implements the MUA only.
meillo@187 61
meillo@187 62
meillo@187 63
meillo@58 64
meillo@58 65
meillo@58 66
meillo@133 67 .\" --------------------------------------------------------------
meillo@125 68 .H1 "Streamlining
meillo@58 69
meillo@0 70 .P
meillo@217 71 MH once provided a complete email system.
meillo@217 72 The community around nmh tries to keep nmh in similar shape.
meillo@178 73 In fundamental contrast, mmh shall be an MUA only.
meillo@87 74 I believe that the development of all-in-one mail systems is obsolete.
meillo@173 75 Today, email is too complex to be fully covered by a single project.
meillo@173 76 Such a project will not be able to excel in all aspects.
meillo@159 77 Instead, the aspects of email should be covered by multiple projects,
meillo@87 78 which then can be combined to form a complete system.
meillo@169 79 Excellent implementations for the various aspects of email already exist.
meillo@223 80 Just to name three examples: Postfix is a specialized MTA, Procmail
meillo@223 81 is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89 82 I believe that it is best to use such specialized tools instead of
meillo@217 83 providing the same function once more as a side component.
meillo@58 84 .P
meillo@169 85 Doing something well requires focusing on a small set of specific aspects.
meillo@217 86 Under the assumption that development which is focussed on a particular
meillo@217 87 area produces better results there, specialized projects will be superior
meillo@87 88 in their field of focus.
meillo@87 89 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87 90 or modular \(en will never be the best choice in any of the fields.
meillo@217 91 Even in providing the most consistent all-in-one system, they are likely
meillo@217 92 to be beaten by projects that focus exclusively on the creation
meillo@217 93 of a homogeneous system by integrating existing mail components.
meillo@87 94 .P
meillo@217 95 Usually, the limiting resource in the community development of
meillo@217 96 free software is man power.
meillo@217 97 If the development effort is spread over a large development area,
meillo@217 98 it becomes more difficult to compete with the specialists in the
meillo@87 99 various fields.
meillo@87 100 The concrete situation for MH-based mail systems is even tougher,
meillo@169 101 given their small and aged community, concerning both developers and users.
meillo@87 102 .P
meillo@87 103 In consequence, I believe that the available development resources
meillo@100 104 should focus on the point where MH is most unique.
meillo@87 105 This is clearly the user interface \(en the MUA.
meillo@125 106 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60 107
meillo@60 108
meillo@100 109 .H2 "Mail Transfer Facilities
meillo@154 110 .Id mail-transfer-facilities
meillo@60 111 .P
meillo@217 112 The removal of the mail transfer facilities, effectively dropping the
meillo@217 113 MSA and MRA, had been the first work task in the mmh project.
meillo@217 114 The desire for this change initiated the creation of the mmh project.
meillo@60 115 .P
meillo@169 116 Focusing on one mail agent role only, is motivated by Eric Allman's
meillo@105 117 experience with Sendmail.
meillo@217 118 He identified the limitation of Sendmail
meillo@217 119 to the MTA task as one reason for its success:
meillo@105 120 .[ [
meillo@105 121 costales sendmail
meillo@105 122 .], p. xviii]
meillo@105 123 .QS
meillo@105 124 Second, I limited myself to the routing function \(en
meillo@110 125 I wouldn't write user agents or delivery back-ends.
meillo@217 126 This was a departure of the dominant thought of the time,
meillo@105 127 in which routing logic, local delivery, and often the network code
meillo@105 128 were incorporated directly into the user agents.
meillo@105 129 .QE
meillo@105 130 .P
meillo@187 131 In nmh, the MSA is called \fIMessage Transfer Service\fP (MTS).
meillo@105 132 This facility, implemented by the
meillo@105 133 .Pn post
meillo@217 134 command, establishes network connections and spoke SMTP to submit
meillo@159 135 messages to be relayed to the outside world.
meillo@217 136 When email transfer changed, this part needed to be changed as well.
meillo@89 137 Encryption and authentication for network connections
meillo@87 138 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@217 139 This added complexity without improving the core functions.
meillo@217 140 Furthermore, keeping up with recent developments in the field of
meillo@87 141 mail transfer requires development power and specialists.
meillo@217 142 In mmh, this whole facility was simply cut off
meillo@76 143 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76 144 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@217 145 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b .
meillo@87 146 Instead, mmh depends on an external MSA.
meillo@217 147 All outgoing mail in mmh goes through the
meillo@60 148 .Pn sendmail
meillo@87 149 command, which almost any MSA provides.
meillo@87 150 If not, a wrapper program can be written.
meillo@87 151 It must read the message from the standard input, extract the
meillo@87 152 recipient addresses from the message header, and hand the message
meillo@87 153 over to the MSA.
meillo@223 154 For example, a wrapper script for qmail would be:
meillo@87 155 .VS
meillo@87 156 #!/bin/sh
meillo@138 157 exec qmail-inject # ignore command line arguments
meillo@87 158 VE
meillo@87 159 The requirement to parse the recipient addresses out of the message header
meillo@217 160 may be removed in the future.
meillo@217 161 Mmh could pass the recipient addresses as command line arguments.
meillo@100 162 This appears to be the better interface.
meillo@60 163 .P
meillo@60 164 To retrieve mail, the
meillo@60 165 .Pn inc
meillo@217 166 command in nmh acts as MRA.
meillo@217 167 It establishes network connections
meillo@217 168 and speaks POP3 to retrieve mail from remote servers.
meillo@76 169 As with mail submission, the network connections required encryption and
meillo@217 170 authentication, thus TLS and SASL were added to nmh.
meillo@169 171 Support for message retrieval through IMAP will soon become necessary
meillo@169 172 additions, too, and likewise for any other changes in mail transfer.
meillo@217 173 But not in mmh because it has dropped the support for retrieving mail
meillo@217 174 from remote locations
meillo@217 175 .Ci ab7b48411962d26439f92f35ed084d3d6275459c .
meillo@76 176 Instead, it depends on an external tool to cover this task.
meillo@169 177 Mmh has two paths for messages to enter mmh's mail storage:
meillo@100 178 (1) Mail can be incorporated with
meillo@60 179 .Pn inc
meillo@87 180 from the system maildrop, or (2) with
meillo@60 181 .Pn rcvstore
meillo@87 182 by reading them, one at a time, from the standard input.
meillo@60 183 .P
meillo@217 184 With the removal of the MSA and MRA, mmh converted from a complete
meillo@217 185 mail system to only an MUA.
meillo@60 186 Now, of course, mmh depends on third-party software.
meillo@87 187 An external MSA is required to transfer mail to the outside world;
meillo@60 188 an external MRA is required to retrieve mail from remote machines.
meillo@217 189 Excellent implementations of such software exist.
meillo@217 190 They likely are superior to the internal versions that were removed.
meillo@217 191 Additionally, the best suiting programs can be chosen freely.
meillo@60 192 .P
meillo@217 193 As it had already been possible to use an external MSA and MRA,
meillo@217 194 why should the internal version not be kept for convenience?
meillo@228 195 Transferred to a different area, the question,
meillo@224 196 whether there is sense in having a fall-back pager in all
meillo@224 197 the command line tools for the cases when
meillo@60 198 .Pn more
meillo@60 199 or
meillo@60 200 .Pn less
meillo@173 201 are not available, appears to be ridiculous.
meillo@100 202 Of course, MSAs and MRAs are more complex than text pagers
meillo@87 203 and not necessarily available but still the concept of orthogonal
meillo@217 204 design holds: ``Write programs that do one thing and do it well''.
meillo@87 205 .[
meillo@87 206 mcilroy unix phil
meillo@87 207 p. 53
meillo@87 208 .]
meillo@87 209 .[
meillo@87 210 mcilroy bstj foreword
meillo@87 211 .]
meillo@87 212 Here, this part of the Unix philosophy was applied not only
meillo@87 213 to the programs but to the project itself.
meillo@87 214 In other words:
meillo@164 215 Develop projects that focus on one thing and do it well.
meillo@169 216 Projects which have grown complex should be split, for the same
meillo@169 217 reasons that programs which have grown complex should be split.
meillo@100 218 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87 219 separate projects then they should be separated.
meillo@217 220 In my opinion, this is the case.
meillo@217 221 The RFCs suggest this separation by clearly distinguishing the
meillo@217 222 different mail handling tasks [RFC\|821].
meillo@217 223 The small interfaces between the mail agents support the
meillo@217 224 separation as well.
meillo@76 225 .P
meillo@217 226 Once, email had been small and simple.
meillo@100 227 At that time,
meillo@60 228 .Pn /bin/mail
meillo@169 229 had covered everything there was to email and still was small and simple.
meillo@100 230 Later, the essential complexity of email increased.
meillo@224 231 (Essential complexity is the complexity defined by the problem itself
meillo@217 232 .[ [
meillo@87 233 brooks no silver bullet
meillo@224 234 .]].)
meillo@217 235 Consequently, email systems grew.
meillo@100 236 RFCs started to introduce the concept of mail agents to separate the
meillo@217 237 various roles because they became more extensive and because
meillo@217 238 new roles appeared.
meillo@217 239 As mail system implementations grew, parts of them were split off.
meillo@169 240 For instance, a POP server was included in the original MH;
meillo@169 241 it was removed in nmh.
meillo@217 242 Now is the time to go one step further and split off the MSA and MRA,
meillo@217 243 as well.
meillo@87 244 Not only does this decrease the code size of the project,
meillo@169 245 more importantly, it unburdens mmh of the whole field of
meillo@217 246 message transfer, with all its implications for the project.
meillo@169 247 There is no more need for concern with changes in network transfer.
meillo@217 248 This independence is gained by depending on external components
meillo@217 249 that cover the field.
meillo@60 250 .P
meillo@217 251 In general, functionality can be added in three different ways:
meillo@171 252 .LI 1
meillo@217 253 By implementing the function in the project itself.
meillo@171 254 .LI 2
meillo@217 255 By depending on a library that provides the function.
meillo@171 256 .LI 3
meillo@217 257 By depending on a program that provides the function.
meillo@171 258 .LP
meillo@169 259 While implementing the function in the project itself leads to the
meillo@169 260 largest increase in code size and requires the most maintenance
meillo@169 261 and development work,
meillo@217 262 it keeps the project's dependence on other software lowest.
meillo@169 263 Using libraries or external programs requires less maintenance work
meillo@217 264 but introduces dependencies on external projects.
meillo@169 265 Programs have the smallest interfaces and provide the best separation,
meillo@87 266 but possibly limit the information exchange.
meillo@169 267 External libraries are more strongly connected than external programs,
meillo@169 268 thus information can be exchanged in a more flexible manner.
meillo@227 269 Obviously, adding code to a project increases the maintenance work.
meillo@217 270 As implementing complex functions in the project itself adds
meillo@217 271 a lot of code, this should be avoided if possible.
meillo@217 272 Thus, 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@217 294
meillo@223 295 Choices for MSAs range from small forwarders such as \fIssmtp\fP and
meillo@223 296 \fInullmailer\fP, over mid-size MTAs including \fImasqmail\fP and
meillo@223 297 \fIdma\fP, up to full-featured MTAs as for instance \fIPostfix\fP.
meillo@223 298 MRAs are provided for example by \fIfetchmail\fP, \fIgetmail\fP,
meillo@223 299 \fImpop\fP, and \fIfdm\fP.
meillo@60 300
meillo@60 301
meillo@100 302 .H2 "Non-MUA Tools
meillo@60 303 .P
meillo@217 304 One goal of mmh is to remove the tools that do not significantly
meillo@217 305 contribute to the MUA's job.
meillo@217 306 Loosely related and rarely used tools distract from a lean appearance,
meillo@217 307 and require maintenance work without adding much to the core task.
meillo@217 308 By removing these tools, mmh became more streamlined and focused.
meillo@62 309 .BU
meillo@58 310 .Pn conflict
meillo@87 311 was removed
meillo@76 312 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@217 313 because it is a mail system maintenance tool and not MUA-related.
meillo@87 314 It even checked
meillo@58 315 .Fn /etc/passwd
meillo@58 316 and
meillo@58 317 .Fn /etc/group
meillo@87 318 for consistency, which is completely unrelated to email.
meillo@87 319 A tool like
meillo@87 320 .Pn conflict
meillo@87 321 is surely useful, but it should not be shipped with mmh.
meillo@62 322 .BU
meillo@58 323 .Pn rcvtty
meillo@87 324 was removed
meillo@87 325 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89 326 because its use case of writing to the user's terminal
meillo@200 327 on reception of mail is obsolete.
meillo@87 328 If users like to be informed of new mail, the shell's
meillo@58 329 .Ev MAILPATH
meillo@87 330 variable or graphical notifications are technically more appealing.
meillo@217 331 Writing to terminals directly is hardly ever desired today.
meillo@169 332 If, though, one prefers this approach, the standard tool
meillo@58 333 .Pn write
meillo@58 334 can be used in a way similar to:
meillo@82 335 .VS
meillo@58 336 scan -file - | write `id -un`
meillo@82 337 VE
meillo@62 338 .BU
meillo@58 339 .Pn viamail
meillo@87 340 was removed
meillo@87 341 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87 342 when the new attachment system was activated, because
meillo@58 343 .Pn forw
meillo@76 344 could then cover the task itself.
meillo@232 345 The
meillo@58 346 .Pn sendfiles
meillo@232 347 shell script was rewritten as a wrapper around
meillo@232 348 .Pn forw
meillo@232 349 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6 .
meillo@62 350 .BU
meillo@58 351 .Pn msgchk
meillo@87 352 was removed
meillo@87 353 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87 354 because it lost its use case when POP support was removed.
meillo@76 355 A call to
meillo@58 356 .Pn msgchk
meillo@87 357 provided hardly more information than:
meillo@82 358 .VS
meillo@58 359 ls -l /var/mail/meillo
meillo@82 360 VE
meillo@217 361 Yet, it distinguished between old and new mail, but
meillo@169 362 these details can be retrieved with
meillo@76 363 .Pn stat (1),
meillo@62 364 too.
meillo@100 365 A small shell script could be written to print the information
meillo@76 366 in a similar way, if truly necessary.
meillo@76 367 As mmh's
meillo@76 368 .Pn inc
meillo@87 369 only incorporates mail from the user's local maildrop,
meillo@62 370 and thus no data transfers over slow networks are involved,
meillo@169 371 there is hardly any need to check for new mail before incorporating it.
meillo@62 372 .BU
meillo@58 373 .Pn msh
meillo@87 374 was removed
meillo@76 375 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87 376 because the tool was in conflict with the philosophy of MH.
meillo@217 377 It provided an interactive shell to access the features of MH.
meillo@217 378 However, it was not just a shell tailored to the needs of mail handling,
meillo@217 379 but one large program that had several MH tools built in.
meillo@217 380 This conflicted with the major feature of MH of being a tool chest.
meillo@76 381 .Pn msh 's
meillo@159 382 main use case had been accessing Bulletin Boards, which have ceased to
meillo@62 383 be popular.
meillo@62 384 .P
meillo@62 385 Removing
meillo@169 386 .Pn msh
meillo@212 387 together with the truly archaic code relics
meillo@58 388 .Pn vmh
meillo@58 389 and
meillo@169 390 .Pn wmh
meillo@62 391 saved more than 7\|000 lines of C code \(en
meillo@66 392 about 15\|% of the project's original source code amount.
meillo@100 393 Having less code \(en with equal readability, of course \(en
meillo@76 394 for the same functionality is an advantage.
meillo@63 395 Less code means less bugs and less maintenance work.
meillo@76 396 As
meillo@63 397 .Pn rcvtty
meillo@63 398 and
meillo@63 399 .Pn msgchk
meillo@87 400 are assumed to be rarely used and can be implemented in different ways,
meillo@87 401 why should one keep them?
meillo@217 402 Removing them streamlined mmh.
meillo@63 403 .Pn viamail 's
meillo@63 404 use case is now partly obsolete and partly covered by
meillo@63 405 .Pn forw ,
meillo@217 406 hence there is no reason to still maintain it.
meillo@63 407 .Pn conflict
meillo@76 408 is not related to the mail client, and
meillo@63 409 .Pn msh
meillo@63 410 conflicts with the basic concept of MH.
meillo@169 411 These two tools might still be useful, but they should not be part of mmh.
meillo@63 412 .P
meillo@220 413 .Id slocal
meillo@169 414 Finally, there is
meillo@217 415 .Pn slocal ,
meillo@217 416 which is an MDA and thus not directly MUA-related.
meillo@217 417 It should be removed from mmh because including it conflicts with
meillo@178 418 the idea that mmh is an MUA only.
meillo@87 419 However,
meillo@76 420 .Pn slocal
meillo@76 421 provides rule-based processing of messages, like filing them into
meillo@76 422 different folders, which is otherwise not available in mmh.
meillo@87 423 Although
meillo@76 424 .Pn slocal
meillo@169 425 neither pulls in dependencies, nor does it include a separate
meillo@154 426 technical area (cf. Sec.
meillo@154 427 .Cf mail-transfer-facilities ),
meillo@169 428 it still accounts for about 1\|000 lines of code that need to be maintained.
meillo@76 429 As
meillo@76 430 .Pn slocal
meillo@76 431 is almost self-standing, it should be split off into a separate project.
meillo@76 432 This would cut the strong connection between the MUA mmh and the MDA
meillo@76 433 .Pn slocal .
meillo@87 434 For anyone not using MH,
meillo@87 435 .Pn slocal
meillo@87 436 would become yet another independent MDA, like
meillo@87 437 .I procmail .
meillo@100 438 Then
meillo@87 439 .Pn slocal
meillo@217 440 could be installed without a complete MH system.
meillo@76 441 Likewise, mmh users could decide to use
meillo@76 442 .I procmail
meillo@217 443 without having a second, unused MDA, i.e.
meillo@87 444 .Pn slocal ,
meillo@76 445 installed.
meillo@100 446 That appears to be conceptionally the best solution.
meillo@76 447 Yet,
meillo@76 448 .Pn slocal
meillo@87 449 is not split off.
meillo@100 450 I defer the decision over
meillo@78 451 .Pn slocal
meillo@169 452 out of a need for deeper investigation.
meillo@217 453 In the meanwhile, it remains part of mmh
meillo@217 454 as its continued existence is not significant;
meillo@100 455 .Pn slocal
meillo@100 456 is unrelated to the rest of the project.
meillo@0 457
meillo@58 458
meillo@133 459
meillo@134 460 .H2 "Displaying Messages
meillo@155 461 .Id mhshow
meillo@131 462 .P
meillo@133 463 Since the very beginning, already in the first concept paper,
meillo@227 464 .[
meillo@227 465 original memo rand mh shapiro gaines
meillo@227 466 .]
meillo@58 467 .Pn show
meillo@62 468 had been MH's message display program.
meillo@58 469 .Pn show
meillo@76 470 mapped message numbers and sequences to files and invoked
meillo@58 471 .Pn mhl
meillo@89 472 to have the files formatted.
meillo@173 473 With MIME, this approach was not sufficient anymore.
meillo@217 474 MIME messages can consist of multiple parts.
meillo@217 475 Some parts, like binary attachments or text content in foreign charsets,
meillo@217 476 are not directly displayable.
meillo@58 477 .Pn show 's
meillo@76 478 understanding of messages and
meillo@58 479 .Pn mhl 's
meillo@173 480 display capabilities could not cope with the task any longer.
meillo@62 481 .P
meillo@88 482 Instead of extending these tools, additional tools were written from
meillo@217 483 scratch and were added to the MH tool chest.
meillo@88 484 Doing so is encouraged by the tool chest approach.
meillo@88 485 Modular design is a great advantage for extending a system,
meillo@88 486 as new tools can be added without interfering with existing ones.
meillo@62 487 First, the new MIME features were added in form of the single program
meillo@58 488 .Pn mhn .
meillo@58 489 The command
meillo@82 490 .Cl "mhn -show 42
meillo@217 491 had then shown the message number
meillo@217 492 .Fn 42 ,
meillo@217 493 interpreting MIME.
meillo@58 494 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58 495 the split of
meillo@58 496 .Pn mhn
meillo@88 497 into a set of specialized tools, which together covered the
meillo@88 498 multiple aspects of MIME.
meillo@88 499 One of them was
meillo@69 500 .Pn mhshow ,
meillo@88 501 which replaced
meillo@88 502 .Cl "mhn -show" .
meillo@88 503 It was capable of displaying MIME messages appropriately.
meillo@62 504 .P
meillo@232 505 .ZZ
meillo@88 506 From then on, two message display tools were part of nmh,
meillo@76 507 .Pn show
meillo@76 508 and
meillo@76 509 .Pn mhshow .
meillo@88 510 To ease the life of users,
meillo@69 511 .Pn show
meillo@69 512 was extended to automatically hand the job over to
meillo@69 513 .Pn mhshow
meillo@69 514 if displaying the message would be beyond
meillo@69 515 .Pn show 's
meillo@69 516 abilities.
meillo@88 517 In consequence, the user would simply invoke
meillo@69 518 .Pn show
meillo@69 519 (possibly through
meillo@69 520 .Pn next
meillo@69 521 or
meillo@69 522 .Pn prev )
meillo@69 523 and get the message printed with either
meillo@69 524 .Pn show
meillo@69 525 or
meillo@69 526 .Pn mhshow ,
meillo@69 527 whatever was more appropriate.
meillo@69 528 .P
meillo@217 529 Having two similar tools for basically the same task is redundancy.
meillo@217 530 Usually, users do not distinguish between
meillo@88 531 .Pn show
meillo@88 532 and
meillo@88 533 .Pn mhshow
meillo@88 534 in their daily mail reading.
meillo@217 535 Having two separate display programs was therefore unnecessary
meillo@88 536 from a user's point of view.
meillo@88 537 Besides, the development of both programs needed to be in sync,
meillo@76 538 to ensure that the programs behaved in a similar way,
meillo@76 539 because they were used like a single tool.
meillo@76 540 Different behavior would have surprised the user.
meillo@69 541 .P
meillo@69 542 Today, non-MIME messages are rather seen to be a special case of
meillo@100 543 MIME messages, although it is the other way round.
meillo@69 544 As
meillo@69 545 .Pn mhshow
meillo@217 546 already had been able to display non-MIME messages, it appeared natural
meillo@69 547 to drop
meillo@69 548 .Pn show
meillo@69 549 in favor of using
meillo@69 550 .Pn mhshow
meillo@217 551 exclusively
meillo@217 552 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853 .
meillo@88 553 Removing
meillo@88 554 .Pn show
meillo@217 555 is no loss in function, because
meillo@88 556 .Pn mhshow
meillo@88 557 covers it completely.
meillo@217 558 Yet, the old behavior of
meillo@88 559 .Pn show
meillo@88 560 can still be emulated with the simple command line:
meillo@88 561 .VS
meillo@88 562 mhl `mhpath c`
meillo@88 563 VE
meillo@88 564 .P
meillo@76 565 For convenience,
meillo@76 566 .Pn mhshow
meillo@88 567 was renamed to
meillo@88 568 .Pn show
meillo@88 569 after
meillo@88 570 .Pn show
meillo@88 571 was gone.
meillo@88 572 It is clear that such a rename may confuse future developers when
meillo@88 573 trying to understand the history.
meillo@88 574 Nevertheless, I consider the convenience on the user's side,
meillo@217 575 to outweigh the inconvenience for understanding the evolution
meillo@217 576 of the tools.
meillo@69 577 .P
meillo@88 578 To prepare for the transition,
meillo@69 579 .Pn mhshow
meillo@69 580 was reworked to behave more like
meillo@69 581 .Pn show
meillo@217 582 first (cf. Sec.
meillo@217 583 .Cf mhshow ).
meillo@88 584 Once the tools behaved more alike, the replacing appeared to be
meillo@88 585 even more natural.
meillo@88 586 Today, mmh's new
meillo@69 587 .Pn show
meillo@217 588 has become the one single message display program once again,
meillo@159 589 with the difference
meillo@88 590 that today it handles MIME messages as well as non-MIME messages.
meillo@217 591 The outcomes of the transition are one program less to maintain,
meillo@88 592 no second display program for users to deal with,
meillo@88 593 and less system complexity.
meillo@69 594 .P
meillo@88 595 Still, removing the old
meillo@69 596 .Pn show
meillo@88 597 hurts in one regard: It had been such a simple program.
meillo@159 598 Its lean elegance is missing from the new
meillo@159 599 .Pn show ,
meillo@225 600 but there is no alternative;
meillo@159 601 supporting MIME demands higher essential complexity.
meillo@58 602
meillo@131 603
meillo@133 604
meillo@100 605 .H2 "Configure Options
meillo@58 606 .P
meillo@76 607 Customization is a double-edged sword.
meillo@76 608 It allows better suiting setups, but not for free.
meillo@76 609 There is the cost of code complexity to be able to customize.
meillo@76 610 There is the cost of less tested setups, because there are
meillo@171 611 more possible setups and especially corner cases.
meillo@226 612 Steve Johnson confirms:
meillo@226 613 .[ [
meillo@226 614 eric raymond the art of unix programming
meillo@226 615 .], p. 233]
meillo@226 616 .QS
meillo@226 617 Unless it is done very carefully, the addition of an on/off
meillo@226 618 configuration option can lead to a need to double the amount of
meillo@226 619 testing. Since in practice one never does double the amount of testing,
meillo@226 620 the practical effect is to reduce the amount of testing that any
meillo@226 621 given configuration receives. Ten options leads to 1024 times as much
meillo@226 622 testing, and pretty soon you are talking real reliability problems.
meillo@226 623 .QE
meillo@226 624 .LP
meillo@159 625 Additionally, there is the cost of choice itself.
meillo@76 626 The code complexity directly affects the developers.
meillo@173 627 Less tested code affects both users and developers.
meillo@217 628 The problem of choice affects the users, for once by having to choose
meillo@159 629 but also by more complex interfaces that require more documentation.
meillo@159 630 Whenever options add few advantages but increase the complexity of the
meillo@159 631 system, they should be considered for removal.
meillo@72 632 I have reduced the number of project-specific configure options from
meillo@217 633 15 to 3.
meillo@74 634
meillo@76 635 .U3 "Mail Transfer Facilities
meillo@74 636 .P
meillo@227 637 With the removal of the mail transfer facilities (cf. Sec.
meillo@227 638 .Cf mail-transfer-facilities )
meillo@227 639 five configure options vanished:
meillo@85 640 .P
meillo@85 641 The switches
meillo@85 642 .Sw --with-tls
meillo@85 643 and
meillo@85 644 .Sw --with-cyrus-sasl
meillo@89 645 had activated the support for transfer encryption and authentication.
meillo@217 646 They are not needed anymore.
meillo@85 647 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85 648 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85 649 .P
meillo@85 650 The configure switch
meillo@85 651 .Sw --enable-pop
meillo@227 652 had activated the message retrieval facility.
meillo@217 653 Whereas the code area that had been conditionally compiled in
meillo@217 654 for TLS and SASL support was small,
meillo@217 655 the conditionally compiled code area for POP support was much larger.
meillo@217 656 The code base had only changed slightly on toggling TLS or SASL
meillo@217 657 support but it had changed much on toggling POP support.
meillo@85 658 The changes in the code base could hardly be overviewed.
meillo@159 659 By having POP support togglable, a second code base had been created,
meillo@85 660 one that needed to be tested.
meillo@85 661 This situation is basically similar for the conditional TLS and SASL
meillo@85 662 code, but there the changes are minor and can yet be overviewed.
meillo@85 663 Still, conditional compilation of a code base creates variations
meillo@85 664 of the original program.
meillo@85 665 More variations require more testing and maintenance work.
meillo@85 666 .P
meillo@227 667 Two other options had only specified default configuration values:
meillo@100 668 .Sw --with-mts
meillo@217 669 defined the default transport service
meillo@217 670 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226 .
meillo@85 671 With
meillo@100 672 .Sw --with-smtpservers
meillo@227 673 default SMTP servers could be set
meillo@217 674 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9 .
meillo@164 675 Both of them became irrelevant when the SMTP transport service was removed.
meillo@164 676 In mmh, all messages are handed over to
meillo@164 677 .Pn sendmail
meillo@164 678 for transportation.
meillo@164 679
meillo@72 680
meillo@74 681 .U3 "Backup Prefix
meillo@74 682 .P
meillo@76 683 The backup prefix is the string that was prepended to message
meillo@76 684 filenames to tag them as deleted.
meillo@173 685 By default it had been the comma character (`\fL,\fP').
meillo@78 686 In July 2000, Kimmo Suominen introduced
meillo@78 687 the configure option
meillo@78 688 .Sw --with-hash-backup
meillo@173 689 to change the default to the hash character `\f(CW#\fP'.
meillo@217 690 This choice was probably personal preference, but,
meillo@217 691 being related or not, words that start with the hash character
meillo@78 692 introduce a comment in the Unix shell.
meillo@72 693 Thus, the command line
meillo@72 694 .Cl "rm #13 #15
meillo@72 695 calls
meillo@72 696 .Pn rm
meillo@217 697 without arguments because the first hash character starts a comment
meillo@72 698 that reaches until the end of the line.
meillo@72 699 To delete the backup files,
meillo@72 700 .Cl "rm ./#13 ./#15"
meillo@72 701 needs to be used.
meillo@217 702 Thus, using the hash as backup prefix may be seen as a precaution
meillo@217 703 against backup loss.
meillo@78 704 .P
meillo@159 705 First, I removed the configure option but added the profile entry
meillo@217 706 .Pe Backup-Prefix ,
meillo@217 707 which allowed to specify an arbitrary string as backup prefix
meillo@217 708 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086 .
meillo@76 709 This change did not remove the choice but moved it to a location where
meillo@217 710 it suited better, in my eyes.
meillo@76 711 .P
meillo@217 712 Eventually however, the new trash folder concept
meillo@154 713 (cf. Sec.
meillo@154 714 .Cf trash-folder )
meillo@164 715 removed the need for the backup prefix completely.
meillo@78 716 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133 717 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133 718
meillo@76 719
meillo@76 720 .U3 "Editor and Pager
meillo@227 721 .Id editor-pager
meillo@74 722 .P
meillo@74 723 The two configure options
meillo@74 724 .CW --with-editor=EDITOR
meillo@74 725 .CW --with-pager=PAGER
meillo@74 726 were used to specify the default editor and pager at configure time.
meillo@109 727 Doing so at configure time made sense in the eighties,
meillo@76 728 when the set of available editors and pagers varied much across
meillo@76 729 different systems.
meillo@89 730 Today, the situation is more homogeneous.
meillo@74 731 The programs
meillo@74 732 .Pn vi
meillo@74 733 and
meillo@74 734 .Pn more
meillo@76 735 can be expected to be available on every Unix system,
meillo@74 736 as they are specified by POSIX since two decades.
meillo@74 737 (The specifications for
meillo@74 738 .Pn vi
meillo@74 739 and
meillo@74 740 .Pn more
meillo@74 741 appeared in
meillo@74 742 .[
meillo@74 743 posix 1987
meillo@74 744 .]
meillo@74 745 and,
meillo@74 746 .[
meillo@74 747 posix 1992
meillo@74 748 .]
meillo@74 749 respectively.)
meillo@217 750 As a first step, these two tools were hard-coded as defaults
meillo@217 751 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f .
meillo@74 752 Not changed were the
meillo@74 753 .Pe editor
meillo@74 754 and
meillo@74 755 .Pe moreproc
meillo@76 756 profile entries, which allowed the user to override the system defaults.
meillo@217 757 Later, the concept was reworked again to respect the standard
meillo@217 758 environment variables
meillo@74 759 .Ev VISUAL
meillo@74 760 and
meillo@74 761 .Ev PAGER
meillo@76 762 if they are set.
meillo@74 763 Today, mmh determines the editor to use in the following order,
meillo@217 764 taking the first available and non-empty item
meillo@217 765 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b :
meillo@171 766 .LI 1
meillo@74 767 Environment variable
meillo@74 768 .Ev MMHEDITOR
meillo@171 769 .LI 2
meillo@74 770 Profile entry
meillo@74 771 .Pe Editor
meillo@171 772 .LI 3
meillo@74 773 Environment variable
meillo@74 774 .Ev VISUAL
meillo@171 775 .LI 4
meillo@74 776 Environment variable
meillo@74 777 .Ev EDITOR
meillo@171 778 .LI 5
meillo@74 779 Command
meillo@74 780 .Pn vi .
meillo@171 781 .LP
meillo@217 782 The pager to use is determined in a similar order
meillo@217 783 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e :
meillo@171 784 .LI 1
meillo@74 785 Environment variable
meillo@74 786 .Ev MMHPAGER
meillo@171 787 .LI 2
meillo@74 788 Profile entry
meillo@74 789 .Pe Pager
meillo@74 790 (replaces
meillo@74 791 .Pe moreproc )
meillo@171 792 .LI 3
meillo@74 793 Environment variable
meillo@74 794 .Ev PAGER
meillo@171 795 .LI 4
meillo@74 796 Command
meillo@74 797 .Pn more .
meillo@171 798 .LP
meillo@76 799 By respecting the
meillo@74 800 .Ev VISUAL /\c
meillo@74 801 .Ev EDITOR
meillo@74 802 and
meillo@74 803 .Ev PAGER
meillo@76 804 environment variables,
meillo@217 805 the new behavior complies with the common style on Unix systems.
meillo@217 806 It is more uniform and clearer for users.
meillo@72 807
meillo@72 808
meillo@76 809 .U3 "ndbm
meillo@72 810 .P
meillo@74 811 .Pn slocal
meillo@217 812 used to depend on the database library
meillo@217 813 .I ndbm .
meillo@217 814 The database is used to store the
meillo@217 815 .Hd Message-ID
meillo@217 816 header field values of all messages delivered.
meillo@217 817 This enabled
meillo@74 818 .Pn slocal
meillo@74 819 to suppress delivering the same message to the same user twice.
meillo@217 820 This features was enabled by the
meillo@74 821 .Sw -suppressdup
meillo@217 822 switch.
meillo@74 823 .P
meillo@232 824 Because a variety of versions of the database library exist,
meillo@78 825 .[
meillo@78 826 wolter unix incompat notes dbm
meillo@78 827 .]
meillo@217 828 complicated autoconf code was needed to detect them correctly.
meillo@181 829 Furthermore, the configure switches
meillo@74 830 .Sw --with-ndbm=ARG
meillo@74 831 and
meillo@74 832 .Sw --with-ndbmheader=ARG
meillo@74 833 were added to help with difficult setups that would
meillo@217 834 not be detected automatically or not correctly.
meillo@74 835 .P
meillo@74 836 By removing the suppress duplicates feature of
meillo@74 837 .Pn slocal ,
meillo@74 838 the dependency on
meillo@74 839 .I ndbm
meillo@217 840 vanished and 120 lines of complex autoconf code could be saved
meillo@217 841 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf .
meillo@217 842 The change removed functionality but that is considered minor to the
meillo@217 843 improvement of dropping the dependency and the complex autoconf code.
meillo@225 844
meillo@72 845
meillo@217 846 .U3 "MH-E Support
meillo@72 847 .P
meillo@74 848 The configure option
meillo@74 849 .Sw --disable-mhe
meillo@217 850 was removed when the MH-E support was reworked.
meillo@217 851 MH-E is the Emacs front-end to MH.
meillo@76 852 It requires MH to provide minor additional functions.
meillo@76 853 The
meillo@76 854 .Sw --disable-mhe
meillo@217 855 configure option had switched off these extensions.
meillo@217 856 After removing the support for old versions of MH-E,
meillo@74 857 only the
meillo@74 858 .Sw -build
meillo@76 859 switches of
meillo@74 860 .Pn forw
meillo@74 861 and
meillo@74 862 .Pn repl
meillo@217 863 are left to be MH-E extensions.
meillo@76 864 They are now always built in because they add little code and complexity.
meillo@76 865 In consequence, the
meillo@74 866 .Sw --disable-mhe
meillo@76 867 configure option was removed
meillo@217 868 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643 .
meillo@217 869 Dropping the option also removed a variant of the code base
meillo@217 870 that would have needed to be tested.
meillo@217 871 This change was undertaken in January 2012 in nmh and
meillo@217 872 thereafter merged into mmh.
meillo@217 873
meillo@72 874
meillo@74 875 .U3 "Masquerading
meillo@72 876 .P
meillo@74 877 The configure option
meillo@74 878 .Sw --enable-masquerade
meillo@76 879 could take up to three arguments:
meillo@232 880 .CW draft_from ,
meillo@232 881 .CW mmailid ,
meillo@217 882 and
meillo@232 883 .CW username_extension .
meillo@74 884 They activated different types of address masquerading.
meillo@74 885 All of them were implemented in the SMTP-speaking
meillo@74 886 .Pn post
meillo@217 887 command.
meillo@76 888 Address masquerading is an MTA's task and mmh does not cover
meillo@76 889 this field anymore.
meillo@76 890 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74 891 .P
meillo@74 892 The
meillo@74 893 .I mmailid
meillo@74 894 masquerading type is the oldest one of the three and the only one
meillo@74 895 available in the original MH.
meillo@74 896 It provided a
meillo@74 897 .I username
meillo@74 898 to
meillo@74 899 .I fakeusername
meillo@217 900 mapping, based on the
meillo@217 901 .Fn passwd 's
meillo@217 902 GECOS field.
meillo@217 903 Nmh's man page
meillo@181 904 .Mp mh-tailor (5)
meillo@74 905 described the use case as being the following:
meillo@98 906 .QS
meillo@74 907 This is useful if you want the messages you send to always
meillo@74 908 appear to come from the name of an MTA alias rather than your
meillo@74 909 actual account name. For instance, many organizations set up
meillo@74 910 `First.Last' sendmail aliases for all users. If this is
meillo@74 911 the case, the GECOS field for each user should look like:
meillo@74 912 ``First [Middle] Last <First.Last>''
meillo@98 913 .QE
meillo@74 914 .P
meillo@74 915 As mmh sends outgoing mail via the local MTA only,
meillo@76 916 the best location to do such global rewrites is there.
meillo@74 917 Besides, the MTA is conceptionally the right location because it
meillo@74 918 does the reverse mapping for incoming mail (aliasing), too.
meillo@181 919 Furthermore, masquerading set up there is readily available for all
meillo@74 920 mail software on the system.
meillo@76 921 Hence, mmailid masquerading was removed.
meillo@74 922 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74 923 .P
meillo@74 924 The
meillo@74 925 .I username_extension
meillo@76 926 masquerading type did not replace the username but would append a suffix,
meillo@76 927 specified by the
meillo@74 928 .Ev USERNAME_EXTENSION
meillo@76 929 environment variable, to it.
meillo@76 930 This provided support for the
meillo@74 931 .I user-extension
meillo@217 932 feature of qmail
meillo@217 933 .[ [
meillo@217 934 sill qmail handbook
meillo@217 935 .], p. 141]
meillo@217 936 and the similar
meillo@74 937 .I "plussed user
meillo@217 938 processing of Sendmail.
meillo@217 939 .[ [
meillo@217 940 sendmail costales
meillo@217 941 .], p. 476]
meillo@217 942 The decision to remove this username_extension masquerading
meillo@217 943 was motivated by the fact that
meillo@74 944 .Pn spost
meillo@217 945 had not supported it yet.
meillo@217 946 Username extensions can be used in mmh, but less convenient.
meillo@225 947 .\" XXX In the format file: %(getenv USERNAME_EXTENSION)
meillo@217 948 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@74 949 .P
meillo@74 950 The
meillo@74 951 .I draft_from
meillo@74 952 masquerading type instructed
meillo@74 953 .Pn post
meillo@84 954 to use the value of the
meillo@84 955 .Hd From
meillo@84 956 header field as SMTP envelope sender.
meillo@76 957 Sender addresses could be replaced completely.
meillo@76 958 Mmh offers a kind of masquerading similar in effect, but
meillo@74 959 with technical differences.
meillo@76 960 As mmh does not transfer messages itself, the local MTA has final control
meillo@217 961 over the sender's address.
meillo@217 962 Any masquerading mmh introduces may be reverted by the MTA.
meillo@76 963 In times of pedantic spam checking, an MTA will take care to use
meillo@76 964 sensible envelope sender addresses to keep its own reputation up.
meillo@84 965 Nonetheless, the MUA can set the
meillo@84 966 .Hd From
meillo@217 967 header field and thereby propose a sender address to the MTA.
meillo@74 968 The MTA may then decide to take that one or generate the canonical sender
meillo@74 969 address for use as envelope sender address.
meillo@217 970 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@74 971 .P
meillo@74 972 In mmh, the MTA will always extract the recipient and sender from the
meillo@84 973 message header (\c
meillo@74 974 .Pn sendmail 's
meillo@74 975 .Sw -t
meillo@74 976 switch).
meillo@84 977 The
meillo@84 978 .Hd From
meillo@84 979 header field of the draft may be set arbitrary by the user.
meillo@74 980 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74 981
meillo@74 982 .U3 "Remaining Options
meillo@74 983 .P
meillo@74 984 Two configure options remain in mmh.
meillo@232 985 One of them is the file locking method to use:
meillo@74 986 .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@217 987 The idea of removing all methods except the portable
meillo@217 988 .I "dot locking
meillo@76 989 and having that one as the default is appealing, but this change
meillo@76 990 requires deeper technical investigation into the topic.
meillo@232 991 The other remaining option,
meillo@74 992 .Sw --enable-debug ,
meillo@217 993 compiles the programs with debugging symbols.
meillo@74 994 This option is likely to stay.
meillo@72 995
meillo@72 996
meillo@58 997
meillo@63 998
meillo@100 999 .H2 "Command Line Switches
meillo@58 1000 .P
meillo@227 1001 The command line switches of MH tools are similar in style to the
meillo@227 1002 switches in the X Window System.
meillo@227 1003 They consist of a single dash (`\fL-\fP') followed by a word.
meillo@217 1004 For example
meillo@217 1005 .Cl -truncate .
meillo@232 1006 To ease typing, the switch can be abbreviated, given the remaining
meillo@217 1007 prefix is unambiguous.
meillo@212 1008 If no other switch starts with the letter `t', then any of
meillo@212 1009 .Cl "-truncate" ,
meillo@212 1010 .Cl "-trunc" ,
meillo@212 1011 .Cl "-tr" ,
meillo@212 1012 and
meillo@212 1013 .Cl "-t
meillo@212 1014 is equal.
meillo@212 1015 As a result, switches can neither be grouped (as in
meillo@212 1016 .Cl "ls -ltr" )
meillo@232 1017 nor can switch arguments be appended directly to the switch itself
meillo@232 1018 (as in
meillo@212 1019 .Cl "sendmail -q30m" ).
meillo@212 1020 Many switches have negating counter-parts, which start with `no'.
meillo@212 1021 For example
meillo@212 1022 .Cl "-notruncate
meillo@212 1023 inverts the
meillo@212 1024 .Cl "-truncate
meillo@212 1025 switch.
meillo@212 1026 They exist to override the effect of default switches in the profile.
meillo@93 1027 Every program in mmh has two generic switches:
meillo@93 1028 .Sw -help ,
meillo@93 1029 to print a short message on how to use the program, and
meillo@159 1030 .Sw -Version
meillo@164 1031 (with capital `V'), to tell what version of mmh the program belongs to.
meillo@93 1032 .P
meillo@93 1033 Switches change the behavior of programs.
meillo@93 1034 Programs that do one thing in one way require no switches.
meillo@93 1035 In most cases, doing something in exactly one way is too limiting.
meillo@217 1036 If one task should be accomplished in various ways,
meillo@217 1037 switches are a good approach to alter the behavior of a program.
meillo@93 1038 Changing the behavior of programs provides flexibility and customization
meillo@217 1039 to users, but at the same time it complicates the code,
meillo@217 1040 the documentation, and the usage of the program.
meillo@93 1041 Therefore, the number of switches should be kept small.
meillo@217 1042 A small set of well-chosen switches is best.
meillo@217 1043 Usually, the number of switches increases over time.
meillo@93 1044 Already in 1985, Rose and Romine have identified this as a major
meillo@93 1045 problem of MH:
meillo@93 1046 .[ [
meillo@93 1047 rose romine real work
meillo@93 1048 .], p. 12]
meillo@98 1049 .QS
meillo@93 1050 A complaint often heard about systems which undergo substantial development
meillo@93 1051 by many people over a number of years, is that more and more options are
meillo@93 1052 introduced which add little to the functionality but greatly increase the
meillo@93 1053 amount of information a user needs to know in order to get useful work done.
meillo@93 1054 This is usually referred to as creeping featurism.
meillo@93 1055 .QP
meillo@93 1056 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93 1057 ten or so well-meaning programmers (the present authors included),
meillo@93 1058 suffers mightily from this.
meillo@98 1059 .QE
meillo@93 1060 .P
meillo@217 1061 Being reluctant to adding new switches (or \fIoptions\fP,
meillo@217 1062 as Rose and Romine call them) is one part of a counter-action,
meillo@97 1063 the other part is removing hardly used switches.
meillo@217 1064 Nmh's tools have lots of switches already implemented.
meillo@217 1065 Hence, cleaning up by removing some of them was the more important part
meillo@97 1066 of the counter-action.
meillo@93 1067 Removing existing functionality is always difficult because it
meillo@93 1068 breaks programs that use these functions.
meillo@93 1069 Also, for every obsolete feature, there'll always be someone who still
meillo@93 1070 uses it and thus opposes its removal.
meillo@93 1071 This puts the developer into the position,
meillo@93 1072 where sensible improvements to style are regarded as destructive acts.
meillo@97 1073 Yet, living with the featurism is far worse, in my eyes, because
meillo@97 1074 future needs will demand adding further features,
meillo@93 1075 worsening the situation more and more.
meillo@93 1076 Rose and Romine added in a footnote,
meillo@93 1077 ``[...]
meillo@93 1078 .Pn send
meillo@217 1079 will no doubt acquire an endless number of switches in the years to come''
meillo@217 1080 .[ [
meillo@217 1081 rose romine real work
meillo@217 1082 .], p. 12].
meillo@97 1083 Although clearly humorous, the comment points to the nature of the problem.
meillo@97 1084 Refusing to add any new switches would encounter the problem at its root,
meillo@97 1085 but this is not practical.
meillo@97 1086 New needs will require new switches and it would be unwise to block
meillo@97 1087 them strictly.
meillo@97 1088 Nevertheless, removing obsolete switches still is an effective approach
meillo@97 1089 to deal with the problem.
meillo@97 1090 Working on an experimental branch without an established user base,
meillo@97 1091 eased my work because I did not offend users when I removed existing
meillo@110 1092 functions.
meillo@93 1093 .P
meillo@93 1094 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93 1095 .Pn send .
meillo@97 1096 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@182 1097 At the time of writing, no more than 4 visible switches and 1 hidden switch
meillo@97 1098 have remained in mmh's
meillo@97 1099 .Pn send .
meillo@217 1100 These numbers include the two generic switches,
meillo@182 1101 .Sw -help
meillo@182 1102 and
meillo@183 1103 .Sw -Version .
meillo@217 1104 .P
meillo@183 1105 Hidden switches are ones not documented.
meillo@183 1106 In mmh, 12 tools have hidden switches.
meillo@183 1107 9 of them are
meillo@183 1108 .Sw -debug
meillo@183 1109 switches, the other 6 provide special interfaces for internal use.
meillo@93 1110 .P
meillo@217 1111 The following figure displays the number of switches for each of the tools
meillo@159 1112 that is available in both nmh and mmh.
meillo@100 1113 The tools are sorted by the number of switches they had in nmh.
meillo@217 1114 Both visible and hidden switches were counted,
meillo@97 1115 but not the generic help and version switches.
meillo@93 1116 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93 1117 now it has no more than 5 \(en only half as many.
meillo@93 1118 If the `no' switches and similar inverse variant are folded onto
meillo@100 1119 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100 1120 has 4 now.
meillo@93 1121 The total number of functional switches in mmh dropped from 465
meillo@182 1122 to 233.
meillo@58 1123
meillo@232 1124 .sp
meillo@93 1125 .KS
meillo@93 1126 .in 1c
meillo@93 1127 .so input/switches.grap
meillo@93 1128 .KE
meillo@232 1129 .sp
meillo@58 1130
meillo@93 1131 .P
meillo@232 1132 .ZZ
meillo@93 1133 A part of the switches vanished after functions were removed.
meillo@93 1134 This was the case for network mail transfer, for instance.
meillo@97 1135 Sometimes, however, the work flow was the other way:
meillo@97 1136 I looked through the
meillo@97 1137 .Mp mh-chart (7)
meillo@97 1138 man page to identify the tools with apparently too many switches.
meillo@232 1139 Then I valued the benefit of each switch by examining
meillo@217 1140 the tool's man page and source code, aided by literature research
meillo@217 1141 and testing.
meillo@97 1142
meillo@58 1143
meillo@93 1144 .U3 "Draft Folder Facility
meillo@93 1145 .P
meillo@100 1146 A change early in the project was the complete transition from
meillo@217 1147 the single draft message to the draft folder facility
meillo@227 1148 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@227 1149 (cf. Sec.
meillo@227 1150 .Cf draft-folder ).
meillo@109 1151 The draft folder facility was introduced in the mid-eighties, when
meillo@100 1152 Rose and Romine called it a ``relatively new feature''.
meillo@93 1153 .[
meillo@93 1154 rose romine real work
meillo@93 1155 .]
meillo@217 1156 Since then, the facility was included, inactive by default.
meillo@217 1157 By making it permanently active and by related rework of the tools, the
meillo@93 1158 .Sw -[no]draftfolder ,
meillo@93 1159 and
meillo@93 1160 .Sw -draftmessage
meillo@217 1161 switches could be removed from
meillo@93 1162 .Pn comp ,
meillo@93 1163 .Pn repl ,
meillo@93 1164 .Pn forw ,
meillo@93 1165 .Pn dist ,
meillo@93 1166 .Pn whatnow ,
meillo@93 1167 and
meillo@217 1168 .Pn send
meillo@217 1169 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@217 1170 The only flexibility lost with this change is having multiple
meillo@97 1171 draft folders within one profile.
meillo@97 1172 I consider this a theoretical problem only.
meillo@159 1173 At the same time, the
meillo@93 1174 .Sw -draft
meillo@93 1175 switch of
meillo@93 1176 .Pn anno ,
meillo@93 1177 .Pn refile ,
meillo@93 1178 and
meillo@93 1179 .Pn send
meillo@93 1180 was removed.
meillo@159 1181 The special treatment of \fIthe\fP draft message became irrelevant after
meillo@217 1182 the rework of the draft system
meillo@159 1183 (cf. Sec.
meillo@217 1184 .Cf draft-folder ).
meillo@93 1185
meillo@95 1186
meillo@102 1187 .U3 "In Place Editing
meillo@93 1188 .P
meillo@93 1189 .Pn anno
meillo@93 1190 had the switches
meillo@93 1191 .Sw -[no]inplace
meillo@100 1192 to either annotate the message in place and thus preserve hard links,
meillo@217 1193 or annotate a copy to replace the original message.
meillo@217 1194 The latter approach broke hard links.
meillo@97 1195 Following the assumption that linked messages should truly be the
meillo@217 1196 same message and annotating it should not break the link, the
meillo@93 1197 .Sw -[no]inplace
meillo@93 1198 switches were removed and the previous default
meillo@93 1199 .Sw -inplace
meillo@217 1200 was made the definitive behavior
meillo@217 1201 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0 .
meillo@93 1202 The
meillo@93 1203 .Sw -[no]inplace
meillo@93 1204 switches of
meillo@93 1205 .Pn repl ,
meillo@93 1206 .Pn forw ,
meillo@93 1207 and
meillo@93 1208 .Pn dist
meillo@217 1209 could be removed, as well, as they were simply passed through to
meillo@93 1210 .Pn anno .
meillo@93 1211 .P
meillo@93 1212 .Pn burst
meillo@93 1213 also had
meillo@93 1214 .Sw -[no]inplace
meillo@217 1215 switches, but with a different meaning.
meillo@95 1216 With
meillo@95 1217 .Sw -inplace ,
meillo@95 1218 the digest had been replaced by the table of contents (i.e. the
meillo@110 1219 introduction text) and the burst messages were placed right
meillo@95 1220 after this message, renumbering all following messages.
meillo@95 1221 Also, any trailing text of the digest was lost, though,
meillo@95 1222 in practice, it usually consists of an end-of-digest marker only.
meillo@217 1223 Nonetheless, this behavior appeared less elegant than the
meillo@95 1224 .Sw -noinplace
meillo@95 1225 behavior, which already had been the default.
meillo@95 1226 Nmh's
meillo@95 1227 .Mp burst (1)
meillo@95 1228 man page reads:
meillo@98 1229 .QS
meillo@164 1230 If
meillo@164 1231 .Sw -noinplace
meillo@164 1232 is given, each digest is preserved, no table
meillo@93 1233 of contents is produced, and the messages contained within
meillo@93 1234 the digest are placed at the end of the folder. Other messages
meillo@93 1235 are not tampered with in any way.
meillo@98 1236 .QE
meillo@95 1237 .LP
meillo@93 1238 The decision to drop the
meillo@93 1239 .Sw -inplace
meillo@95 1240 behavior was supported by the code complexity and the possible data loss
meillo@95 1241 it caused.
meillo@93 1242 .Sw -noinplace
meillo@95 1243 was chosen to be the definitive behavior.
meillo@97 1244 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93 1245
meillo@95 1246
meillo@95 1247 .U3 "Forms and Format Strings
meillo@93 1248 .P
meillo@95 1249 Historically, the tools that had
meillo@95 1250 .Sw -form
meillo@95 1251 switches to supply a form file had
meillo@95 1252 .Sw -format
meillo@95 1253 switches as well to supply the contents of a form file as a string
meillo@95 1254 on the command line directly.
meillo@95 1255 In consequence, the following two lines equaled:
meillo@95 1256 .VS
meillo@95 1257 scan -form scan.mailx
meillo@217 1258 scan -format "`cat /path/to/scan.mailx`"
meillo@95 1259 VE
meillo@95 1260 The
meillo@95 1261 .Sw -format
meillo@95 1262 switches were dropped in favor for extending the
meillo@95 1263 .Sw -form
meillo@217 1264 switches
meillo@217 1265 .Ci f51956be123db66b00138f80464d06f030dbb88d .
meillo@217 1266 If their argument starts with an equal sign (`\fL=\fP'),
meillo@95 1267 then the rest of the argument is taken as a format string,
meillo@95 1268 otherwise the arguments is treated as the name of a format file.
meillo@95 1269 Thus, now the following two lines equal:
meillo@95 1270 .VS
meillo@95 1271 scan -form scan.mailx
meillo@217 1272 scan -form "=`cat /path/to/scan.mailx`"
meillo@95 1273 VE
meillo@95 1274 This rework removed the prefix collision between
meillo@95 1275 .Sw -form
meillo@95 1276 and
meillo@95 1277 .Sw -format .
meillo@217 1278 Typing `\fL-fo\fP' is sufficient to specify form file or format string.
meillo@95 1279 .P
meillo@95 1280 The different meaning of
meillo@95 1281 .Sw -format
meillo@95 1282 for
meillo@217 1283 .Pn forw
meillo@217 1284 and
meillo@95 1285 .Pn repl
meillo@95 1286 was removed in mmh.
meillo@95 1287 .Pn forw
meillo@95 1288 was completely switched to MIME-type forwarding, thus removing the
meillo@217 1289 .Sw -[no]format
meillo@217 1290 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1 .
meillo@95 1291 For
meillo@95 1292 .Pn repl ,
meillo@95 1293 the
meillo@95 1294 .Sw -[no]format
meillo@95 1295 switches were reworked to
meillo@95 1296 .Sw -[no]filter
meillo@217 1297 switches
meillo@217 1298 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6 .
meillo@95 1299 The
meillo@95 1300 .Sw -format
meillo@95 1301 switches of
meillo@95 1302 .Pn send
meillo@95 1303 and
meillo@95 1304 .Pn post ,
meillo@217 1305 which had a third meaning, were removed likewise
meillo@217 1306 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9 .
meillo@95 1307 Eventually, the ambiguity of the
meillo@95 1308 .Sw -format
meillo@217 1309 switches is resolved by not having such switches anymore in mmh.
meillo@95 1310
meillo@95 1311
meillo@95 1312 .U3 "MIME Tools
meillo@95 1313 .P
meillo@217 1314 The MIME tools, which once were part of
meillo@100 1315 .Pn mhn
meillo@164 1316 (whatever that stood for),
meillo@95 1317 had several switches that added little practical value to the programs.
meillo@95 1318 The
meillo@95 1319 .Sw -[no]realsize
meillo@95 1320 switches of
meillo@95 1321 .Pn mhbuild
meillo@95 1322 and
meillo@95 1323 .Pn mhlist
meillo@217 1324 were removed
meillo@217 1325 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c .
meillo@217 1326 Real size calculations are done always now because nmh's
meillo@159 1327 .Mp mhbuild (1)
meillo@217 1328 man page states that
meillo@217 1329 ``This provides an accurate count at the expense of a small delay''
meillo@228 1330 with the small delay not being noticeable on modern systems.
meillo@95 1331 .P
meillo@95 1332 The
meillo@95 1333 .Sw -[no]check
meillo@95 1334 switches were removed together with the support for
meillo@95 1335 .Hd Content-MD5
meillo@217 1336 header fields [RFC\|1864]
meillo@154 1337 (cf. Sec.
meillo@154 1338 .Cf content-md5 )
meillo@217 1339 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda .
meillo@95 1340 .P
meillo@95 1341 The
meillo@95 1342 .Sw -[no]ebcdicsafe
meillo@95 1343 and
meillo@95 1344 .Sw -[no]rfc934mode
meillo@95 1345 switches of
meillo@95 1346 .Pn mhbuild
meillo@217 1347 were removed because they are considered obsolete
meillo@97 1348 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@217 1349 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88 .
meillo@95 1350 .P
meillo@95 1351 Content caching of external MIME parts, activated with the
meillo@95 1352 .Sw -rcache
meillo@95 1353 and
meillo@95 1354 .Sw -wcache
meillo@217 1355 switches was completely removed
meillo@217 1356 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269 .
meillo@97 1357 External MIME parts are rare today, having a caching facility
meillo@159 1358 for them appears to be unnecessary.
meillo@95 1359 .P
meillo@95 1360 In pre-MIME times,
meillo@95 1361 .Pn mhl
meillo@95 1362 had covered many tasks that are part of MIME handling today.
meillo@95 1363 Therefore,
meillo@95 1364 .Pn mhl
meillo@95 1365 could be simplified to a large extend, reducing the number of its
meillo@217 1366 switches from 21 to 6
meillo@97 1367 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@217 1368 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70 .
meillo@95 1369
meillo@95 1370
meillo@95 1371
meillo@95 1372
meillo@95 1373 .U3 "Header Printing
meillo@95 1374 .P
meillo@95 1375 .Pn folder 's
meillo@95 1376 data output is self-explaining enough that
meillo@159 1377 displaying the header line makes little sense.
meillo@95 1378 Hence, the
meillo@95 1379 .Sw -[no]header
meillo@217 1380 switch was removed and headers are never printed
meillo@217 1381 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7 .
meillo@95 1382 .P
meillo@95 1383 In
meillo@95 1384 .Pn mhlist ,
meillo@95 1385 the
meillo@95 1386 .Sw -[no]header
meillo@217 1387 switches were removed, as well
meillo@217 1388 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f .
meillo@217 1389 In this case, the headers are printed always because the output
meillo@217 1390 is not self-explaining.
meillo@95 1391 .P
meillo@95 1392 .Pn scan
meillo@95 1393 also had
meillo@95 1394 .Sw -[no]header
meillo@95 1395 switches.
meillo@217 1396 Printing this header had been sensible until the introduction of
meillo@217 1397 format strings made it impossible to display column headings.
meillo@95 1398 Only the folder name and the current date remained to be printed.
meillo@217 1399 As this information can be perfectly generated with
meillo@95 1400 .Pn folder
meillo@95 1401 and
meillo@95 1402 .Pn date ,
meillo@217 1403 the switches were removed
meillo@217 1404 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e .
meillo@95 1405 .P
meillo@95 1406 By removing all
meillo@95 1407 .Sw -header
meillo@95 1408 switches, the collision with
meillo@95 1409 .Sw -help
meillo@95 1410 on the first two letters was resolved.
meillo@95 1411 Currently,
meillo@95 1412 .Sw -h
meillo@95 1413 evaluates to
meillo@95 1414 .Sw -help
meillo@95 1415 for all tools of mmh.
meillo@95 1416
meillo@95 1417
meillo@139 1418 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95 1419 .P
meillo@95 1420 The
meillo@95 1421 .Sw -noedit
meillo@100 1422 switch of
meillo@95 1423 .Pn comp ,
meillo@95 1424 .Pn repl ,
meillo@95 1425 .Pn forw ,
meillo@95 1426 .Pn dist ,
meillo@95 1427 and
meillo@95 1428 .Pn whatnow
meillo@232 1429 was removed and replaced by the ability to specify
meillo@95 1430 .Sw -editor
meillo@217 1431 with an empty argument
meillo@217 1432 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9 .
meillo@232 1433 (Using
meillo@159 1434 .Cl "-editor /bin/true
meillo@217 1435 is nearly the same. It differs only in setting the previous editor.)
meillo@95 1436 .P
meillo@95 1437 The more important change is the removal of the
meillo@95 1438 .Sw -nowhatnowproc
meillo@217 1439 switch
meillo@217 1440 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622 .
meillo@217 1441 This switch had once introduced an awkward behavior,
meillo@217 1442 as explained in nmh's man page for
meillo@95 1443 .Mp comp (1):
meillo@98 1444 .QS
meillo@164 1445 The
meillo@164 1446 .Sw -editor
meillo@164 1447 .Ar editor
meillo@164 1448 switch indicates the editor to use for
meillo@164 1449 the initial edit. Upon exiting from the editor,
meillo@164 1450 .Pn comp
meillo@164 1451 will invoke the
meillo@164 1452 .Pn whatnow
meillo@164 1453 program. See
meillo@164 1454 .Mp whatnow (1)
meillo@164 1455 for a discussion of available options.
meillo@164 1456 The invocation of this program can be
meillo@164 1457 inhibited by using the
meillo@164 1458 .Sw -nowhatnowproc
meillo@164 1459 switch. (In truth of fact, it is the
meillo@164 1460 .Pn whatnow
meillo@164 1461 program which starts the initial edit.
meillo@164 1462 Hence,
meillo@232 1463 .Sw \%-nowhatnowproc
meillo@164 1464 will prevent any edit from occurring.)
meillo@98 1465 .QE
meillo@95 1466 .P
meillo@95 1467 Effectively, the
meillo@95 1468 .Sw -nowhatnowproc
meillo@217 1469 switch caused only only a draft message to be created.
meillo@95 1470 As
meillo@159 1471 .Cl "-whatnowproc /bin/true
meillo@217 1472 does the same, the
meillo@95 1473 .Sw -nowhatnowproc
meillo@95 1474 switch was removed for being redundant.
meillo@95 1475
meillo@95 1476
meillo@95 1477
meillo@95 1478 .U3 "Various
meillo@95 1479 .BU
meillo@139 1480 With the removal of MMDF maildrop format support,
meillo@139 1481 .Pn packf
meillo@139 1482 and
meillo@139 1483 .Pn rcvpack
meillo@232 1484 no longer needed the
meillo@139 1485 .Sw -mbox
meillo@139 1486 and
meillo@139 1487 .Sw -mmdf
meillo@139 1488 switches.
meillo@217 1489 The behavior of
meillo@139 1490 .Sw -mbox
meillo@232 1491 became the definitive behavior
meillo@217 1492 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0 .
meillo@171 1493 Further rework in both tools made the
meillo@139 1494 .Sw -file
meillo@217 1495 switch unnecessary
meillo@217 1496 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e .
meillo@139 1497
meillo@139 1498 .BU
meillo@217 1499 Mmh's tools do no longer clear the screen (\c
meillo@139 1500 .Pn scan 's
meillo@139 1501 and
meillo@139 1502 .Pn mhl 's
meillo@139 1503 .Sw -[no]clear
meillo@139 1504 switches
meillo@139 1505 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139 1506 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@232 1507 The message formating tool
meillo@139 1508 .Pn mhl
meillo@232 1509 does neither ring the bell (\c
meillo@139 1510 .Sw -[no]bell
meillo@139 1511 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@217 1512 nor does it page the output itself (\c
meillo@139 1513 .Sw -length
meillo@232 1514 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 )
meillo@232 1515 anymore.
meillo@139 1516 Generally, the pager to use is no longer specified with the
meillo@139 1517 .Sw -[no]moreproc
meillo@139 1518 command line switches for
meillo@139 1519 .Pn mhl
meillo@139 1520 and
meillo@139 1521 .Pn show /\c
meillo@217 1522 .Pn mhshow
meillo@217 1523 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a .
meillo@139 1524
meillo@139 1525 .BU
meillo@96 1526 In order to avoid prefix collisions among switch names, the
meillo@95 1527 .Sw -version
meillo@95 1528 switch was renamed to
meillo@95 1529 .Sw -Version
meillo@217 1530 (with capital `V')
meillo@217 1531 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a .
meillo@95 1532 Every program has the
meillo@95 1533 .Sw -version
meillo@95 1534 switch but its first three letters collided with the
meillo@95 1535 .Sw -verbose
meillo@95 1536 switch, present in many programs.
meillo@95 1537 The rename solved this problem once for all.
meillo@95 1538 Although this rename breaks a basic interface, having the
meillo@95 1539 .Sw -V
meillo@95 1540 abbreviation to display the version information, isn't all too bad.
meillo@139 1541
meillo@95 1542 .BU
meillo@95 1543 .Sw -[no]preserve
meillo@95 1544 of
meillo@95 1545 .Pn refile
meillo@168 1546 was removed
meillo@168 1547 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 1548 because what use was it anyway?
meillo@168 1549 Quoting nmh's man page
meillo@165 1550 .Mp refile (1):
meillo@98 1551 .QS
meillo@95 1552 Normally when a message is refiled, for each destination
meillo@95 1553 folder it is assigned the number which is one above the current
meillo@95 1554 highest message number in that folder. Use of the
meillo@164 1555 .Sw -preserv
meillo@164 1556 [sic!] switch will override this message renaming, and try
meillo@95 1557 to preserve the number of the message. If a conflict for a
meillo@164 1558 particular folder occurs when using the
meillo@164 1559 .Sw -preserve
meillo@164 1560 switch, then
meillo@164 1561 .Pn refile
meillo@164 1562 will use the next available message number which
meillo@95 1563 is above the message number you wish to preserve.
meillo@98 1564 .QE
meillo@139 1565
meillo@95 1566 .BU
meillo@95 1567 The removal of the
meillo@95 1568 .Sw -[no]reverse
meillo@95 1569 switches of
meillo@95 1570 .Pn scan
meillo@97 1571 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@217 1572 is a bug fix.
meillo@217 1573 This is supported by the comments
meillo@95 1574 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95 1575 by Rose and
meillo@95 1576 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@217 1577 This should be considered a bug'' by Romine in the changelogs.
meillo@217 1578 The question remains why neither Rose nor Romine have fixed this
meillo@217 1579 bug in the eighties when they wrote these comments.
meillo@93 1580
meillo@93 1581
meillo@93 1582
meillo@102 1583
meillo@102 1584
meillo@95 1585
meillo@95 1586
meillo@133 1587 .\" --------------------------------------------------------------
meillo@74 1588 .H1 "Modernizing
meillo@102 1589 .P
meillo@164 1590 In the more than thirty years of MH's existence, its code base was
meillo@159 1591 increasingly extended.
meillo@118 1592 New features entered the project and became alternatives to the
meillo@118 1593 existing behavior.
meillo@217 1594 Relics from several decades have gathered in the code base
meillo@118 1595 but seldom obsolete features were dropped.
meillo@118 1596 This section describes the removing of old code
meillo@118 1597 and the modernizing of the default setup.
meillo@118 1598 It focuses on the functional aspect only;
meillo@154 1599 the non-functional aspects of code style are discussed in Sec.
meillo@154 1600 .Cf code-style .
meillo@58 1601
meillo@58 1602
meillo@212 1603 .H2 "Code Relics
meillo@0 1604 .P
meillo@217 1605 My position regarding the removal of obsolete code
meillo@159 1606 is much more revolutional than the nmh community appreciates.
meillo@217 1607 Working on an experimental version, I was able to quickly drop
meillo@217 1608 functionality that I considered ancient.
meillo@104 1609 The need for consensus with peers would have slowed this process down.
meillo@104 1610 Without the need to justify my decisions, I was able to rush forward.
meillo@217 1611 .P
meillo@110 1612 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104 1613 do the work:
meillo@104 1614 .[
meillo@104 1615 paul vixie edginess nmh-workers
meillo@104 1616 .]
meillo@104 1617 .QS
meillo@104 1618 let's stop walking on egg shells with this code base. there's no need to
meillo@104 1619 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104 1620 we don't need a separate branch for removing vmh
meillo@104 1621 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@164 1622 or depending on pure ansi/posix ``libc''.
meillo@104 1623 .QP
meillo@164 1624 these things should each be a day or two of work and the ``main branch''
meillo@104 1625 should just be modern. [...]
meillo@104 1626 let's push forward, aggressively.
meillo@104 1627 .QE
meillo@104 1628 .LP
meillo@104 1629 I did so already in the months before.
meillo@104 1630 I pushed forward.
meillo@104 1631 I simply dropped the cruft.
meillo@104 1632 .P
meillo@104 1633 The decision to drop a feature was based on literature research and
meillo@159 1634 careful thinking, but whether having had contact with this particular
meillo@104 1635 feature within my own computer life served as a rule of thumb.
meillo@159 1636 I explained my reasons in the commit messages
meillo@109 1637 in the version control system.
meillo@104 1638 Hence, others can comprehend my view and argue for undoing the change
meillo@104 1639 if I have missed an important aspect.
meillo@109 1640 I was quick in dropping parts.
meillo@179 1641 I rather include falsely dropped parts again, than going at a slower pace.
meillo@179 1642 Mmh is experimental work; it requires tough decisions.
meillo@12 1643
meillo@102 1644
meillo@217 1645 .U3 "Process Forking
meillo@12 1646 .P
meillo@109 1647 Being a tool chest, MH creates many processes.
meillo@104 1648 In earlier times
meillo@104 1649 .Fu fork()
meillo@104 1650 had been an expensive system call, because the process's image needed
meillo@159 1651 to be completely duplicated at once.
meillo@200 1652 This expensive work was especially unnecessary in the commonly occurring
meillo@159 1653 case wherein the image is replaced by a call to
meillo@104 1654 .Fu exec()
meillo@104 1655 right after having forked the child process.
meillo@104 1656 The
meillo@104 1657 .Fu vfork()
meillo@104 1658 system call was invented to speed up this particular case.
meillo@104 1659 It completely omits the duplication of the image.
meillo@104 1660 On old systems this resulted in significant speed ups.
meillo@104 1661 Therefore MH used
meillo@104 1662 .Fu vfork()
meillo@104 1663 whenever possible.
meillo@12 1664 .P
meillo@104 1665 Modern memory management units support copy-on-write semantics, which make
meillo@104 1666 .Fu fork()
meillo@104 1667 almost as fast as
meillo@104 1668 .Fu vfork() .
meillo@104 1669 The man page of
meillo@104 1670 .Mp vfork (2)
meillo@104 1671 in FreeBSD 8.0 states:
meillo@104 1672 .QS
meillo@104 1673 This system call will be eliminated when proper system sharing mechanisms
meillo@104 1674 are implemented. Users should not depend on the memory sharing semantics
meillo@104 1675 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104 1676 .QE
meillo@104 1677 .LP
meillo@104 1678 Vixie supports the removal with the note that ``the last
meillo@104 1679 system on which fork was so slow that an mh user would notice it, was
meillo@104 1680 Eunice. that was 1987''.
meillo@104 1681 .[
meillo@104 1682 nmh-workers vixie edginess
meillo@104 1683 .]
meillo@104 1684 I replaced all calls to
meillo@104 1685 .Fu vfork()
meillo@104 1686 with calls to
meillo@217 1687 .Fu fork()
meillo@217 1688 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d .
meillo@104 1689 .P
meillo@104 1690 Related to the costs of
meillo@104 1691 .Fu fork()
meillo@104 1692 is the probability of its success.
meillo@109 1693 In the eighties, on heavy loaded systems, calls to
meillo@104 1694 .Fu fork()
meillo@104 1695 were prone to failure.
meillo@104 1696 Hence, many of the
meillo@104 1697 .Fu fork()
meillo@104 1698 calls in the code were wrapped into loops to retry the
meillo@104 1699 .Fu fork()
meillo@217 1700 several times, to increase the chances to succeed eventually.
meillo@109 1701 On modern systems, a failing
meillo@104 1702 .Fu fork()
meillo@109 1703 call is unusual.
meillo@104 1704 Hence, in the rare case when
meillo@104 1705 .Fu fork()
meillo@217 1706 fails, mmh programs simply abort
meillo@217 1707 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6 .
meillo@12 1708
meillo@12 1709
meillo@109 1710 .U3 "Header Fields
meillo@104 1711 .BU
meillo@84 1712 The
meillo@84 1713 .Hd Encrypted
meillo@104 1714 header field was introduced by RFC\|822,
meillo@109 1715 but already marked as legacy in RFC\|2822.
meillo@109 1716 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104 1717 messages [RFC\|4880, RFC\|3156].
meillo@109 1718 Hence, the support for
meillo@104 1719 .Hd Encrypted
meillo@217 1720 header fields is removed in mmh
meillo@217 1721 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857 .
meillo@104 1722 .BU
meillo@159 1723 The native support for
meillo@84 1724 .Hd Face
meillo@217 1725 header fields has been removed, as well
meillo@217 1726 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23 .
meillo@104 1727 This feature is similar to the
meillo@84 1728 .Hd X-Face
meillo@84 1729 header field in its intent,
meillo@21 1730 but takes a different approach to store the image.
meillo@84 1731 Instead of encoding the image data directly into the header field,
meillo@109 1732 it contains the hostname and UDP port where the image
meillo@109 1733 date can be retrieved.
meillo@159 1734 There is even a third Face system,
meillo@109 1735 which is the successor of
meillo@109 1736 .Hd X-Face ,
meillo@109 1737 although it re-uses the
meillo@104 1738 .Hd Face
meillo@217 1739 header field name.
meillo@109 1740 It was invented in 2005 and supports colored PNG images.
meillo@104 1741 None of the Face systems described here is popular today.
meillo@104 1742 Hence, mmh has no direct support for them.
meillo@104 1743 .BU
meillo@154 1744 .Id content-md5
meillo@104 1745 The
meillo@104 1746 .Hd Content-MD5
meillo@104 1747 header field was introduced by RFC\|1864.
meillo@104 1748 It provides detection of data corruption during the transfer.
meillo@104 1749 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104 1750 [RFC\|1864].
meillo@104 1751 The proper approach to verify content integrity in an
meillo@227 1752 end-to-end relationship is the use of digital signatures [RFC\|4880].
meillo@104 1753 On the other hand, transfer protocols should detect corruption during
meillo@109 1754 the transmission.
meillo@109 1755 The TCP includes a checksum field therefore.
meillo@104 1756 These two approaches in combinations render the
meillo@104 1757 .Hd Content-MD5
meillo@104 1758 header field superfluous.
meillo@109 1759 Not a single one out of 4\|200 messages from two decades
meillo@217 1760 in the nmh-workers mailing list archive
meillo@217 1761 .[
meillo@217 1762 nmh-workers mailing list archive website
meillo@217 1763 .]
meillo@232 1764 contained a
meillo@104 1765 .Hd Content-MD5
meillo@104 1766 header field.
meillo@104 1767 Neither did any of the 60\|000 messages in my personal mail storage.
meillo@217 1768 Removing the support for this header field
meillo@217 1769 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda ,
meillo@104 1770 removed the last place where MD5 computation was needed.
meillo@104 1771 Hence, the MD5 code could be removed as well.
meillo@104 1772 Over 500 lines of code vanished by this one change.
meillo@104 1773
meillo@104 1774
meillo@104 1775 .U3 "MMDF maildrop support
meillo@21 1776 .P
meillo@217 1777 This type of maildrop format is conceptionally similar to the mbox format,
meillo@139 1778 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139 1779 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104 1780 Mbox is the de-facto standard maildrop format on Unix,
meillo@159 1781 whereas the MMDF maildrop format is now forgotten.
meillo@217 1782 Mbox remains as the only packed mailbox format, supported in mmh.
meillo@104 1783 .P
meillo@109 1784 The simplifications within the code were moderate.
meillo@109 1785 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109 1786 But also, switches of
meillo@109 1787 .Pn packf
meillo@104 1788 and
meillo@109 1789 .Pn rcvpack
meillo@217 1790 could be removed
meillo@217 1791 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0 .
meillo@109 1792 In the message parsing function
meillo@109 1793 .Fn sbr/m_getfld.c ,
meillo@217 1794 knowledge of MMDF packed mail boxes was removed
meillo@217 1795 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754 .
meillo@109 1796 Further code structure simplifications may be possible there,
meillo@109 1797 because only one single packed mailbox format is left to be supported.
meillo@104 1798 I have not worked on them yet because
meillo@104 1799 .Fu m_getfld()
meillo@104 1800 is heavily optimized and thus dangerous to touch.
meillo@104 1801 The risk of damaging the intricate workings of the optimized code is
meillo@104 1802 too high.
meillo@104 1803
meillo@12 1804
meillo@101 1805 .U3 "Prompter's Control Keys
meillo@20 1806 .P
meillo@20 1807 The program
meillo@20 1808 .Pn prompter
meillo@104 1809 queries the user to fill in a message form.
meillo@217 1810 When used as
meillo@104 1811 .Cl "comp -editor prompter" ,
meillo@20 1812 the resulting behavior is similar to
meillo@20 1813 .Pn mailx .
meillo@51 1814 Apparently,
meillo@20 1815 .Pn prompter
meillo@173 1816 had not been touched lately.
meillo@104 1817 Otherwise it's hardly explainable why it
meillo@20 1818 still offered the switches
meillo@84 1819 .Sw -erase
meillo@84 1820 .Ar chr
meillo@20 1821 and
meillo@84 1822 .Sw -kill
meillo@84 1823 .Ar chr
meillo@20 1824 to name the characters for command line editing.
meillo@21 1825 The times when this had been necessary are long time gone.
meillo@20 1826 Today these things work out-of-the-box, and if not, are configured
meillo@20 1827 with the standard tool
meillo@20 1828 .Pn stty .
meillo@104 1829 The switches are removed now
meillo@104 1830 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20 1831
meillo@104 1832
meillo@109 1833 .U3 "Hardcopy Terminal Support
meillo@21 1834 .P
meillo@109 1835 More of a funny anecdote is a check for being connected to a
meillo@109 1836 hardcopy terminal.
meillo@159 1837 It remained in the code until spring 2012, when I finally removed it
meillo@104 1838 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@109 1839 The check only prevented a pager to be placed between the printing
meillo@104 1840 program (\c
meillo@104 1841 .Pn mhl )
meillo@104 1842 and the terminal.
meillo@109 1843 In nmh, this could have been ensured statically with the
meillo@104 1844 .Sw -nomoreproc
meillo@109 1845 at the command line, too.
meillo@121 1846 In mmh, setting the profile entry
meillo@104 1847 .Pe Pager
meillo@104 1848 or the environment variable
meillo@104 1849 .Ev PAGER
meillo@104 1850 to
meillo@109 1851 .Pn cat
meillo@159 1852 is sufficient.
meillo@104 1853
meillo@104 1854
meillo@21 1855
meillo@12 1856
meillo@58 1857 .H2 "Attachments
meillo@22 1858 .P
meillo@101 1859 The mind model of email attachments is unrelated to MIME.
meillo@217 1860 Although the MIME RFCs [RFC\|2045\(en2049] define the technical
meillo@217 1861 requirements for having attachments, they do not mention the term.
meillo@101 1862 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101 1863 [RFC\|2045], a more general concept.
meillo@101 1864 Multi-part messages are messages
meillo@101 1865 ``in which one or more different
meillo@101 1866 sets of data are combined in a single body''
meillo@101 1867 [RFC\|2046].
meillo@101 1868 MIME keeps its descriptions generic;
meillo@101 1869 it does not imply specific usage models.
meillo@217 1870 Today, one usage model is prevalent: attachments.
meillo@101 1871 The idea is having a main text document with files of arbitrary kind
meillo@101 1872 attached to it.
meillo@101 1873 In MIME terms, this is a multi-part message having a text part first
meillo@110 1874 and parts of arbitrary type following.
meillo@101 1875 .P
meillo@232 1876 .ZZ
meillo@101 1877 MH's MIME support is a direct implementation of the RFCs.
meillo@101 1878 The perception of the topic described in the RFCs is clearly visible
meillo@101 1879 in MH's implementation.
meillo@159 1880 As a result,
meillo@159 1881 MH had all the MIME features but no idea of attachments.
meillo@173 1882 But users do not need all the MIME features,
meillo@109 1883 they want convenient attachment handling.
meillo@109 1884
meillo@102 1885
meillo@102 1886 .U3 "Composing MIME Messages
meillo@102 1887 .P
meillo@102 1888 In order to improve the situation on the message composing side,
meillo@217 1889 Jon Steinhart had added an attachment system to nmh in 2002
meillo@217 1890 .Ci 7480dbc14bc90f2d872d434205c0784704213252 .
meillo@102 1891 In the file
meillo@102 1892 .Fn docs/README-ATTACHMENTS ,
meillo@217 1893 he described his motivation to do so:
meillo@101 1894 .QS
meillo@159 1895 Although nmh contains the necessary functionality for MIME message
meillo@159 1896 handing [sic!], the interface to this functionality is pretty obtuse.
meillo@101 1897 There's no way that I'm ever going to convince my partner to write
meillo@101 1898 .Pn mhbuild
meillo@101 1899 composition files!
meillo@101 1900 .QE
meillo@102 1901 .LP
meillo@102 1902 With this change, the mind model of attachments entered nmh.
meillo@102 1903 In the same document:
meillo@101 1904 .QS
meillo@101 1905 These changes simplify the task of managing attachments on draft files.
meillo@101 1906 They allow attachments to be added, listed, and deleted.
meillo@101 1907 MIME messages are automatically created when drafts with attachments
meillo@101 1908 are sent.
meillo@101 1909 .QE
meillo@102 1910 .LP
meillo@217 1911 Unfortunately, the attachment system, like every new facilities in nmh,
meillo@110 1912 was inactive by default.
meillo@101 1913 .P
meillo@217 1914 During my time in Argentina, I tried to improve the attachment system.
meillo@217 1915 But, after long discussions my patch died as a proposal on the
meillo@217 1916 mailing list because of great opposition in the nmh community.
meillo@101 1917 .[
meillo@101 1918 nmh-workers attachment proposal
meillo@101 1919 .]
meillo@217 1920 In January 2012, I extended the patch and applied it to mmh
meillo@217 1921 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1 .
meillo@102 1922 In mmh, the attachment system is active by default.
meillo@102 1923 Instead of command line switches, the
meillo@102 1924 .Pe Attachment-Header
meillo@102 1925 profile entry is used to specify
meillo@102 1926 the name of the attachment header field.
meillo@102 1927 It is pre-defined to
meillo@102 1928 .Hd Attach .
meillo@101 1929 .P
meillo@159 1930 To add an attachment to a draft, a header line needs to be added:
meillo@101 1931 .VS
meillo@101 1932 To: bob
meillo@101 1933 Subject: The file you wanted
meillo@101 1934 Attach: /path/to/the/file-bob-wanted
meillo@101 1935 --------
meillo@101 1936 Here it is.
meillo@101 1937 VE
meillo@101 1938 The header field can be added to the draft manually in the editor,
meillo@102 1939 or by using the `attach' command at the WhatNow prompt, or
meillo@102 1940 non-interactively with
meillo@101 1941 .Pn anno :
meillo@101 1942 .VS
meillo@102 1943 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101 1944 VE
meillo@102 1945 Drafts with attachment headers are converted to MIME automatically by
meillo@102 1946 .Pn send .
meillo@102 1947 The conversion to MIME is invisible to the user.
meillo@159 1948 The draft stored in the draft folder is always in source form with
meillo@101 1949 attachment headers.
meillo@179 1950 If the MIMEification fails (e.g. because the file to attach
meillo@179 1951 is not accessible) the original draft is not changed.
meillo@101 1952 .P
meillo@102 1953 The attachment system handles the forwarding of messages, too.
meillo@173 1954 If the attachment header value starts with a plus character (`\fL+\fP'),
meillo@101 1955 like in
meillo@101 1956 .Cl "Attach: +bob 30 42" ,
meillo@159 1957 the given messages in the specified folder will be attached.
meillo@101 1958 This allowed to simplify
meillo@217 1959 .Pn forw
meillo@217 1960 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550 .
meillo@101 1961 .P
meillo@101 1962 Closely related to attachments is non-ASCII text content,
meillo@217 1963 because it requires MIME as well.
meillo@102 1964 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101 1965 to have the draft converted to MIME.
meillo@102 1966 This was necessary whenever the draft contained non-ASCII characters.
meillo@101 1967 If the user did not call `mime', a broken message would be sent.
meillo@101 1968 Therefore, the
meillo@101 1969 .Pe automimeproc
meillo@101 1970 profile entry could be specified to have the `mime' command invoked
meillo@102 1971 automatically each time.
meillo@179 1972 Unfortunately, this approach conflicted with the attachment system
meillo@101 1973 because the draft would already be in MIME format at the time
meillo@101 1974 when the attachment system wanted to MIMEify it.
meillo@102 1975 To use nmh's attachment system, `mime' must not be called at the
meillo@102 1976 WhatNow prompt and
meillo@101 1977 .Pe automimeproc
meillo@102 1978 must not be set in the profile.
meillo@101 1979 But then the case of non-ASCII text without attachment headers was
meillo@101 1980 not caught.
meillo@102 1981 All in all, the solution was complex and irritating.
meillo@168 1982 My patch from December 2010
meillo@168 1983 .[
meillo@168 1984 nmh-workers attachment proposal
meillo@168 1985 .]
meillo@168 1986 would have simplified the situation.
meillo@102 1987 .P
meillo@101 1988 Mmh's current solution is even more elaborate.
meillo@101 1989 Any necessary MIMEification is done automatically.
meillo@101 1990 There is no `mime' command at the WhatNow prompt anymore.
meillo@102 1991 The draft will be converted automatically to MIME when either an
meillo@102 1992 attachment header or non-ASCII text is present.
meillo@173 1993 Furthermore, the hash character (`\fL#\fP') is not special any more
meillo@159 1994 at line beginnings in the draft message.
meillo@159 1995 Users need not concern themselves with the whole topic at all.
meillo@232 1996 The approach taken in mmh is tailored towards today's most common case:
meillo@232 1997 a text part, possibly with attachments.
meillo@232 1998 This case was simplified.
meillo@101 1999 .P
meillo@102 2000 Although the new approach does not anymore support arbitrary MIME
meillo@102 2001 compositions directly, the full power of
meillo@101 2002 .Pn mhbuild
meillo@101 2003 can still be accessed.
meillo@217 2004 Given no attachment headers are included, users can create
meillo@101 2005 .Pn mhbuild
meillo@102 2006 composition drafts like in nmh.
meillo@217 2007 Then, at the WhatNow prompt, they can invoke
meillo@101 2008 .Cl "edit mhbuild
meillo@217 2009 to convert the draft to MIME.
meillo@217 2010 Because the resulting draft neither contains non-ASCII characters
meillo@102 2011 nor has it attachment headers, the attachment system will not touch it.
meillo@102 2012
meillo@112 2013
meillo@102 2014 .U3 "MIME Type Guessing
meillo@102 2015 .P
meillo@159 2016 From the programmer's point of view, the use of
meillo@101 2017 .Pn mhbuild
meillo@159 2018 composition drafts had one notable advantage over attachment headers:
meillo@159 2019 The user provides the appropriate MIME types for files to include.
meillo@217 2020 The new attachment system needs to find out the correct MIME type itself.
meillo@217 2021 This is a difficult task.
meillo@102 2022 Determining the correct MIME type of content is partly mechanical,
meillo@102 2023 partly intelligent work.
meillo@102 2024 Forcing the user to find out the correct MIME type,
meillo@102 2025 forces him to do partly mechanical work.
meillo@179 2026 Letting the computer do the work can lead to bad choices for difficult
meillo@102 2027 content.
meillo@217 2028 For mmh, the latter option was chosen to spare the user the work
meillo@217 2029 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6 .
meillo@102 2030 .P
meillo@102 2031 Determining the MIME type by the suffix of the file name is a dumb
meillo@102 2032 approach, yet it is simple to implement and provides good results
meillo@102 2033 for the common cases.
meillo@217 2034 If no MIME type can be determined, text content is sent as `text/plain',
meillo@217 2035 anything else under the generic fall-back type `application/octet-stream'.
meillo@102 2036 Mmh implements this approach in the
meillo@102 2037 .Pn print-mimetype
meillo@217 2038 script
meillo@217 2039 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44 .
meillo@102 2040 .P
meillo@112 2041 A far better, though less portable, approach is the use of
meillo@102 2042 .Pn file .
meillo@102 2043 This standard tool tries to determine the type of files.
meillo@102 2044 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102 2045 Additionally, its output was only intended for human beings,
meillo@102 2046 but not to be used by programs.
meillo@102 2047 Nevertheless, modern versions of GNU
meillo@102 2048 .Pn file ,
meillo@217 2049 which are prevalent on the popular GNU/Linux systems,
meillo@159 2050 provide MIME type output in machine-readable form.
meillo@217 2051 Although this solution is system-dependent,
meillo@102 2052 it solves the difficult problem well.
meillo@102 2053 On systems where GNU
meillo@102 2054 .Pn file ,
meillo@102 2055 version 5.04 or higher, is available it should be used.
meillo@102 2056 One needs to specify the following profile entry to do so:
meillo@102 2057 .VS
meillo@102 2058 Mime-Type-Query: file -b --mime
meillo@102 2059 VE
meillo@102 2060 .LP
meillo@102 2061 Other versions of
meillo@102 2062 .Pn file
meillo@217 2063 might possibly be usable with wrapper scripts that reformat the output.
meillo@102 2064 The diversity among
meillo@102 2065 .Pn file
meillo@102 2066 implementations is great; one needs to check the local variant.
meillo@102 2067 .P
meillo@102 2068 It is not possible in mmh to override the automatic MIME type guessing
meillo@102 2069 for a specific file.
meillo@159 2070 To do so, either the user would need to know in advance for which file
meillo@217 2071 the automatic guessing fails or the system would require interaction.
meillo@102 2072 I consider both cases impractical.
meillo@102 2073 The existing solution should be sufficient.
meillo@102 2074 If not, the user may always fall back to
meillo@102 2075 .Pn mhbuild
meillo@217 2076 composition drafts and bypass the attachment system.
meillo@101 2077
meillo@102 2078
meillo@102 2079 .U3 "Storing Attachments
meillo@102 2080 .P
meillo@169 2081 Extracting MIME parts of a message and storing them to disk is performed by
meillo@108 2082 .Pn mhstore .
meillo@108 2083 The program has two operation modes,
meillo@108 2084 .Sw -auto
meillo@108 2085 and
meillo@108 2086 .Sw -noauto .
meillo@108 2087 With the former one, each part is stored under the filename given in the
meillo@108 2088 MIME part's meta information, if available.
meillo@108 2089 This naming information is usually available for modern attachments.
meillo@108 2090 If no filename is available, this MIME part is stored as if
meillo@108 2091 .Sw -noauto
meillo@108 2092 would have been specified.
meillo@108 2093 In the
meillo@108 2094 .Sw -noauto
meillo@232 2095 mode, the parts are processed according to the rules that are defined by
meillo@108 2096 .Pe mhstore-store-*
meillo@108 2097 profile entries.
meillo@108 2098 These rules define generic filename templates for storing
meillo@108 2099 or commands to post-process the contents in arbitrary ways.
meillo@108 2100 If no matching rule is available the part is stored under a generic
meillo@108 2101 filename, built from message number, MIME part number, and MIME type.
meillo@108 2102 .P
meillo@108 2103 The
meillo@108 2104 .Sw -noauto
meillo@108 2105 mode had been the default in nmh because it was considered safe,
meillo@108 2106 in contrast to the
meillo@108 2107 .Sw -auto
meillo@108 2108 mode.
meillo@108 2109 In mmh,
meillo@108 2110 .Sw -auto
meillo@108 2111 is not dangerous anymore.
meillo@108 2112 Two changes were necessary:
meillo@171 2113 .LI 1
meillo@108 2114 Any directory path is removed from the proposed filename.
meillo@108 2115 Thus, the files are always stored in the expected directory.
meillo@108 2116 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@171 2117 .LI 2
meillo@108 2118 Tar files are not extracted automatically any more.
meillo@108 2119 Thus, the rest of the file system will not be touched.
meillo@108 2120 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@217 2121 .P
meillo@217 2122 In mmh, the result of
meillo@108 2123 .Cl "mhstore -auto
meillo@110 2124 can be foreseen from the output of
meillo@108 2125 .Cl "mhlist -verbose" .
meillo@217 2126 Although the
meillo@108 2127 .Sw -noauto
meillo@217 2128 mode is considered to be more powerful, it is less convenient and
meillo@108 2129 .Sw -auto
meillo@217 2130 is safe now.
meillo@217 2131 Additionally, storing attachments under their original name
meillo@217 2132 is intuitive.
meillo@108 2133 Hence,
meillo@108 2134 .Sw -auto
meillo@217 2135 serves better as the default option
meillo@217 2136 .Ci 3410b680416c49a7617491af38bc1929855a331d .
meillo@108 2137 .P
meillo@108 2138 Files are stored into the directory given by the
meillo@108 2139 .Pe Nmh-Storage
meillo@108 2140 profile entry, if set, or
meillo@108 2141 into the current working directory, otherwise.
meillo@108 2142 Storing to different directories is only possible with
meillo@108 2143 .Pe mhstore-store-*
meillo@108 2144 profile entries.
meillo@108 2145 .P
meillo@217 2146 Still existing files get overwritten silently in both modes.
meillo@108 2147 This can be considered a bug.
meillo@108 2148 Yet, each other behavior has its draw-backs, too.
meillo@108 2149 Refusing to replace files requires adding a
meillo@108 2150 .Sw -force
meillo@217 2151 switch.
meillo@108 2152 Users will likely need to invoke
meillo@108 2153 .Pn mhstore
meillo@108 2154 a second time with
meillo@159 2155 .Sw -force .
meillo@159 2156 Eventually, only the user can decide in the specific case.
meillo@108 2157 This requires interaction, which I like to avoid if possible.
meillo@108 2158 Appending a unique suffix to the filename is another bad option.
meillo@108 2159 For now, the behavior remains as it is.
meillo@108 2160 .P
meillo@108 2161 In mmh, only MIME parts of type message are special in
meillo@108 2162 .Pn mhstore 's
meillo@108 2163 .Sw -auto
meillo@108 2164 mode.
meillo@108 2165 Instead of storing message/rfc822 parts as files to disk,
meillo@108 2166 they are stored as messages into the current mail folder.
meillo@159 2167 The same applies to message/partial, although the parts are
meillo@159 2168 automatically reassembled beforehand.
meillo@159 2169 MIME parts of type message/external-body are not automatically retrieved
meillo@159 2170 anymore.
meillo@159 2171 Instead, information on how to retrieve them is output.
meillo@217 2172 Not supporting this rare case saved nearly one thousand lines of code
meillo@217 2173 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32 .
meillo@217 2174 The MIME type `application/octet-stream; type=tar' is not special anymore.
meillo@217 2175 The automatically extracting of such MIME parts had been the
meillo@217 2176 dangerous part of the
meillo@108 2177 .Sw -auto
meillo@217 2178 mode
meillo@217 2179 .Ci 94c80042eae3383c812d9552089953f9846b1bb6 .
meillo@108 2180
meillo@102 2181
meillo@102 2182
meillo@102 2183 .U3 "Showing MIME Messages
meillo@227 2184 .Id showing-mime-msgs
meillo@102 2185 .P
meillo@114 2186 The program
meillo@114 2187 .Pn mhshow
meillo@217 2188 was written to display MIME messages.
meillo@114 2189 It implemented the conceptional view of the MIME RFCs.
meillo@114 2190 Nmh's
meillo@114 2191 .Pn mhshow
meillo@217 2192 handles each MIME part independently, presenting them separately
meillo@114 2193 to the user.
meillo@114 2194 This does not match today's understanding of email attachments,
meillo@114 2195 where displaying a message is seen to be a single, integrated operation.
meillo@114 2196 Today, email messages are expected to consist of a main text part
meillo@114 2197 plus possibly attachments.
meillo@217 2198 They are no more seen to be arbitrary MIME hierarchies with
meillo@114 2199 information on how to display the individual parts.
meillo@114 2200 I adjusted
meillo@114 2201 .Pn mhshow 's
meillo@114 2202 behavior to the modern view on the topic.
meillo@114 2203 .P
meillo@224 2204 One should note that this section completely ignores the original
meillo@114 2205 .Pn show
meillo@114 2206 program, because it was not capable to display MIME messages
meillo@227 2207 and is no longer part of mmh
meillo@227 2208 (cf. Sec.
meillo@227 2209 .Cf mhshow ).
meillo@114 2210 Although
meillo@114 2211 .Pn mhshow
meillo@114 2212 was renamed to
meillo@114 2213 .Pn show
meillo@114 2214 in mmh, this section uses the name
meillo@114 2215 .Pn mhshow ,
meillo@224 2216 in order to avoid confusion.
meillo@114 2217 .P
meillo@114 2218 In mmh, the basic idea is that
meillo@114 2219 .Pn mhshow
meillo@114 2220 should display a message in one single pager session.
meillo@114 2221 Therefore,
meillo@114 2222 .Pn mhshow
meillo@114 2223 invokes a pager session for all its output,
meillo@217 2224 whenever it prints to a terminal
meillo@217 2225 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e .
meillo@114 2226 In consequence,
meillo@114 2227 .Pn mhl
meillo@217 2228 does no more invoke a pager
meillo@217 2229 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70 .
meillo@114 2230 With
meillo@114 2231 .Pn mhshow
meillo@114 2232 replacing the original
meillo@114 2233 .Pn show ,
meillo@217 2234 the output of
meillo@114 2235 .Pn mhl
meillo@217 2236 no longer goes to the terminal directly, but through
meillo@114 2237 .Pn mhshow .
meillo@114 2238 Hence,
meillo@114 2239 .Pn mhl
meillo@114 2240 does not need to invoke a pager.
meillo@114 2241 The one and only job of
meillo@114 2242 .Pn mhl
meillo@114 2243 is to format messages or parts of them.
meillo@114 2244 The only place in mmh, where a pager is invoked is
meillo@114 2245 .Pn mhshow .
meillo@114 2246 .P
meillo@227 2247 Only text content is displayed.
meillo@227 2248 Other kinds of attachments are ignored.
meillo@217 2249 Non-text content needs to be converted to text by appropriate
meillo@217 2250 .Pe mhshow-show-*
meillo@217 2251 profile entries before, if this is possible and wanted.
meillo@217 2252 A common example for this are PDF files.
meillo@227 2253 .P
meillo@227 2254 MIME parts are always displayed serially.
meillo@114 2255 The request to display the MIME type `multipart/parallel' in parallel
meillo@114 2256 is ignored.
meillo@217 2257 It is simply treated as `multipart/mixed'
meillo@217 2258 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6 .
meillo@232 2259 This was already possible to request with the
meillo@114 2260 .Sw -serialonly
meillo@114 2261 switch of
meillo@232 2262 .Pn mhshow ,
meillo@232 2263 which is now removed.
meillo@179 2264 As MIME parts are always processed exclusively, i.e. serially,
meillo@217 2265 the `\fL%e\fP' escape in
meillo@114 2266 .Pe mhshow-show-*
meillo@217 2267 profile entries became useless and was thus removed
meillo@217 2268 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae .
meillo@114 2269 For parallel display, the attachments need to be stored to disk first.
meillo@114 2270 .P
meillo@114 2271 To display text content in foreign charsets, they need to be converted
meillo@114 2272 to the native charset.
meillo@114 2273 Therefore,
meillo@114 2274 .Pe mhshow-charset-*
meillo@217 2275 profile entries were needed.
meillo@169 2276 In mmh, the conversion is performed automatically by piping the
meillo@169 2277 text through the
meillo@114 2278 .Pn iconv
meillo@217 2279 command, if necessary
meillo@217 2280 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60 .
meillo@114 2281 Custom
meillo@114 2282 .Pe mhshow-show-*
meillo@114 2283 rules for textual content might need a
meillo@114 2284 .Cl "iconv -f %c %f |
meillo@114 2285 prefix to have the text converted to the native charset.
meillo@114 2286 .P
meillo@121 2287 Although the conversion of foreign charsets to the native one
meillo@114 2288 has improved, it is not consistent enough.
meillo@114 2289 Further work needs to be done and
meillo@114 2290 the basic concepts in this field need to be re-thought.
meillo@114 2291 Though, the default setup of mmh displays message in foreign charsets
meillo@114 2292 correctly without the need to configure anything.
meillo@114 2293
meillo@114 2294
meillo@114 2295 .ig
meillo@114 2296
meillo@114 2297 .P
meillo@114 2298 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@173 2299 These tools will not download the contents automatically anymore. Instead,
meillo@114 2300 they print the information needed to get the contents. If someone should
meillo@114 2301 really receive one of those rare message/external-body messages, he can
meillo@114 2302 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114 2303 it!
meillo@114 2304 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114 2305 ~/.netrc are gone now.)
meillo@114 2306 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114 2307
meillo@114 2308 ..
meillo@102 2309
meillo@58 2310
meillo@58 2311
meillo@166 2312 .H2 "Signing and Encrypting
meillo@22 2313 .P
meillo@166 2314 Nmh offers no direct support for digital signatures and message encryption.
meillo@157 2315 This functionality needed to be added through third-party software.
meillo@217 2316 In mmh, the functionality is included because it
meillo@217 2317 is a part of modern email and is likely wanted by users of mmh.
meillo@217 2318 A fresh mmh installation supports signing and encrypting
meillo@157 2319 out-of-the-box.
meillo@157 2320 Therefore, Neil Rickert's
meillo@157 2321 .Pn mhsign
meillo@157 2322 and
meillo@157 2323 .Pn mhpgp
meillo@157 2324 scripts
meillo@157 2325 .[
meillo@157 2326 neil rickert mhsign mhpgp
meillo@157 2327 .]
meillo@217 2328 were included
meillo@177 2329 .Ci f45cdc98117a84f071759462c7ae212f4bc5ab2e
meillo@177 2330 .Ci 58cf09aa36e9f7f352a127158bbf1c5678bc6ed8 .
meillo@177 2331 The scripts fit well because they are lightweight and
meillo@177 2332 similar of style to the existing tools.
meillo@217 2333 Additionally, no licensing difficulties appeared
meillo@157 2334 as they are part of the public domain.
meillo@112 2335 .P
meillo@157 2336 .Pn mhsign
meillo@157 2337 handles the signing and encrypting part.
meillo@157 2338 It comprises about 250 lines of shell code and interfaces between
meillo@223 2339 .Pn gnupg
meillo@217 2340 and the MH system.
meillo@177 2341 It was meant to be invoked manually at the WhatNow prompt, but in mmh,
meillo@157 2342 .Pn send
meillo@177 2343 invokes
meillo@217 2344 .Pn mhsign
meillo@177 2345 automatically
meillo@177 2346 .Ci c7b5e1df086bcc37ff40163ee67571f076cf6683 .
meillo@177 2347 Special header fields were introduced to request this action.
meillo@157 2348 If a draft contains the
meillo@157 2349 .Hd Sign
meillo@157 2350 header field,
meillo@157 2351 .Pn send
meillo@177 2352 will initiate the signing.
meillo@217 2353 The signing key is either chosen automatically or it is specified by the
meillo@157 2354 .Pe Pgpkey
meillo@157 2355 profile entry.
meillo@157 2356 .Pn send
meillo@217 2357 always create signatures using the PGP/MIME standard [RFC\|4880],
meillo@217 2358 but by invoking
meillo@217 2359 .Pn mhsign
meillo@217 2360 manually, old-style non-MIME signatures can be created as well.
meillo@177 2361 To encrypt an outgoing message, the draft needs to contain an
meillo@157 2362 .Hd Enc
meillo@157 2363 header field.
meillo@177 2364 Public keys of all recipients are searched for in the gnupg keyring and
meillo@177 2365 in a file called
meillo@177 2366 .Fn pgpkeys ,
meillo@177 2367 which contains exceptions and overrides.
meillo@157 2368 Unless public keys are found for all recipients,
meillo@177 2369 .Pn mhsign
meillo@177 2370 will refuse to encrypt it.
meillo@157 2371 Currently, messages with hidden (BCC) recipients can not be encrypted.
meillo@171 2372 This work is pending because it requires a structurally more complex
meillo@171 2373 approach.
meillo@157 2374 .P
meillo@177 2375 .Pn mhpgp
meillo@177 2376 is the companion to
meillo@177 2377 .Pn mhsign .
meillo@177 2378 It verifies signatures and decrypts messages.
meillo@217 2379 Encrypted messages can be either temporarily decrypted and displayed
meillo@177 2380 or permanently decrypted and stored into the current folder.
meillo@177 2381 Currently,
meillo@177 2382 .Pn mhpgp
meillo@177 2383 needs to be invoked manually.
meillo@177 2384 The integration into
meillo@177 2385 .Pn show
meillo@177 2386 and
meillo@177 2387 .Pn mhstore
meillo@217 2388 to verify signatures and decrypt messages as needed
meillo@217 2389 is planned but not yet realized.
meillo@177 2390 .P
meillo@217 2391 Both scripts were written for nmh.
meillo@217 2392 Hence they needed to be adjust
meillo@177 2393 according to the differences between nmh and mmh.
meillo@177 2394 For instance, they use the backup prefix no longer.
meillo@181 2395 Furthermore, compatibility support for old PGP features was dropped.
meillo@177 2396 .P
meillo@157 2397 The integrated message signing and encrypting support is one of the
meillo@157 2398 most recent features in mmh.
meillo@217 2399 It has not had the time to mature.
meillo@177 2400 User feedback and personal experience need to be accumulated to
meillo@177 2401 direct the further development of the facility.
meillo@217 2402 Already it seems to be worthwhile to consider adding
meillo@157 2403 .Sw -[no]sign
meillo@157 2404 and
meillo@157 2405 .Sw -[no]enc
meillo@157 2406 switches to
meillo@157 2407 .Pn send ,
meillo@177 2408 to be able to override the corresponding header fields.
meillo@177 2409 A profile entry:
meillo@157 2410 .VS
meillo@157 2411 send: -sign
meillo@157 2412 VE
meillo@177 2413 would then activate signing for all outgoing messages.
meillo@177 2414 With the present approach, a
meillo@177 2415 .Hd Send
meillo@177 2416 header component needs to be added to each draft template
meillo@177 2417 to achieve the same result.
meillo@177 2418 Adding the switches would ease the work greatly and keep the
meillo@177 2419 template files clean.
meillo@157 2420
meillo@58 2421
meillo@58 2422
meillo@102 2423
meillo@133 2424 .H2 "Draft and Trash Folder
meillo@131 2425 .P
meillo@58 2426
meillo@131 2427 .U3 "Draft Folder
meillo@154 2428 .Id draft-folder
meillo@131 2429 .P
meillo@131 2430 In the beginning, MH had the concept of a draft message.
meillo@217 2431 This was a file named
meillo@131 2432 .Fn draft
meillo@217 2433 in the MH directory, which was treated special.
meillo@131 2434 On composing a message, this draft file was used.
meillo@131 2435 When starting to compose another message before the former one was sent,
meillo@131 2436 the user had to decide among:
meillo@171 2437 .LI 1
meillo@168 2438 Using the old draft to finish and send it before starting with a new one.
meillo@171 2439 .LI 2
meillo@168 2440 Discarding the old draft and replacing it with a new one.
meillo@171 2441 .LI 3
meillo@168 2442 Preserving the old draft by refiling it to a folder.
meillo@171 2443 .LP
meillo@217 2444 Working on multiple drafts was only possible in alternation.
meillo@217 2445 For that, the current draft needed to be refiled to a folder and
meillo@168 2446 another one re-used for editing.
meillo@131 2447 Working on multiple drafts at the same time was impossible.
meillo@131 2448 The usual approach of switching to a different MH context did not
meillo@168 2449 help anything.
meillo@131 2450 .P
meillo@131 2451 The draft folder facility exists to
meillo@131 2452 allow true parallel editing of drafts, in a straight forward way.
meillo@131 2453 It was introduced by Marshall T. Rose, already in 1984.
meillo@131 2454 Similar to other new features, the draft folder was inactive by default.
meillo@131 2455 Even in nmh, the highly useful draft folder was not available
meillo@131 2456 out-of-the-box.
meillo@131 2457 At least, Richard Coleman added the man page
meillo@131 2458 .Mp mh-draft (5)
meillo@131 2459 to better document the feature.
meillo@131 2460 .P
meillo@131 2461 Not using the draft folder facility has the single advantage of having
meillo@131 2462 the draft file at a static location.
meillo@131 2463 This is simple in simple cases but the concept does not scale for more
meillo@131 2464 complex cases.
meillo@217 2465 The concept of the draft message is too limited for the problem
meillo@217 2466 it tries to solve.
meillo@131 2467 Therefore the draft folder was introduced.
meillo@131 2468 It is the more powerful and more natural concept.
meillo@131 2469 The draft folder is a folder like any other folder in MH.
meillo@131 2470 Its messages can be listed like any other messages.
meillo@131 2471 A draft message is no longer a special case.
meillo@131 2472 Tools do not need special switches to work on the draft message.
meillo@171 2473 Hence corner cases were removed.
meillo@131 2474 .P
meillo@131 2475 The trivial part of the work was activating the draft folder with a
meillo@131 2476 default name.
meillo@131 2477 I chose the name
meillo@217 2478 .Fn +drafts ,
meillo@131 2479 for obvious reasons.
meillo@131 2480 In consequence, the command line switches
meillo@131 2481 .Sw -draftfolder
meillo@131 2482 and
meillo@131 2483 .Sw -draftmessage
meillo@131 2484 could be removed.
meillo@232 2485 More difficult, but also more improving, was the updating of the
meillo@232 2486 tools to the new concept.
meillo@217 2487 By fully switching to the draft folder, the tools could be
meillo@217 2488 simplified by dropping the awkward draft message handling code.
meillo@131 2489 .Sw -draft
meillo@131 2490 switches were removed because operating on a draft message is no longer
meillo@131 2491 special.
meillo@131 2492 It became indistinguishable to operating on any other message.
meillo@168 2493 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@168 2494 .P
meillo@168 2495 There is no more need to query the user for draft handling
meillo@168 2496 .Ci 2d48b455c303a807041c35e4248955f8bec59eeb .
meillo@131 2497 It is always possible to add another new draft.
meillo@131 2498 Refiling drafts is without difference to refiling other messages.
meillo@168 2499 All of these special cases are gone.
meillo@131 2500 Yet, one draft-related switch remained.
meillo@131 2501 .Pn comp
meillo@131 2502 still has
meillo@131 2503 .Sw -[no]use
meillo@131 2504 for switching between two modes:
meillo@171 2505 .LI 1
meillo@217 2506 Modifying an existing draft, with
meillo@217 2507 .Sw -use .
meillo@171 2508 .LI 2
meillo@217 2509 Composing a new draft, possibly taking some existing message as template,
meillo@217 2510 with
meillo@217 2511 .Sw -nouse ,
meillo@217 2512 the default.
meillo@232 2513 .ZZ
meillo@232 2514 .RT
meillo@232 2515 .sp \n(PDu
meillo@131 2516 In either case, the behavior of
meillo@131 2517 .Pn comp
meillo@131 2518 is deterministic.
meillo@131 2519 .P
meillo@131 2520 .Pn send
meillo@131 2521 now operates on the current message in the draft folder by default.
meillo@131 2522 As message and folder can both be overridden by specifying them on
meillo@131 2523 the command line, it is possible to send any message in the mail storage
meillo@131 2524 by simply specifying its number and folder.
meillo@131 2525 In contrast to the other tools,
meillo@131 2526 .Pn send
meillo@131 2527 takes the draft folder as its default folder.
meillo@131 2528 .P
meillo@131 2529 Dropping the draft message concept in favor for the draft folder concept,
meillo@217 2530 replaced special cases with regular cases.
meillo@131 2531 This simplified the source code of the tools, as well as the concepts.
meillo@131 2532 In mmh, draft management does not break with the MH concepts
meillo@131 2533 but applies them.
meillo@133 2534 .Cl "scan +drafts" ,
meillo@133 2535 for instance, is a truly natural request.
meillo@217 2536 .P
meillo@169 2537 Most of the work was already performed by Rose in the eighties.
meillo@133 2538 The original improvement of mmh is dropping the old draft message approach
meillo@217 2539 and thus simplifying the tools, the documentation,
meillo@217 2540 and the system as a whole.
meillo@131 2541 Although my part in the draft handling improvement was small,
meillo@217 2542 it was important.
meillo@131 2543
meillo@131 2544
meillo@131 2545 .U3 "Trash Folder
meillo@154 2546 .Id trash-folder
meillo@131 2547 .P
meillo@131 2548 Similar to the situation for drafts is the situation for removed messages.
meillo@131 2549 Historically, a message was ``deleted'' by prepending a specific
meillo@173 2550 \fIbackup prefix\fP, usually the comma character,
meillo@173 2551 to the file name.
meillo@164 2552 The specific file would then be ignored by MH because only files with
meillo@164 2553 names consisting of digits only are treated as messages.
meillo@131 2554 Although files remained in the file system,
meillo@168 2555 the messages were no longer visible in MH.
meillo@168 2556 To truly delete them, a maintenance job was needed.
meillo@168 2557 Usually a cron job was installed to delete them after a grace time.
meillo@131 2558 For instance:
meillo@131 2559 .VS
meillo@131 2560 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131 2561 VE
meillo@168 2562 In such a setup, the original message could be restored
meillo@131 2563 within the grace time interval by stripping the
meillo@217 2564 backup prefix from the file name \(en usually but not always.
meillo@168 2565 If the last message of a folder with six messages (\fL1-6\fP) was removed,
meillo@131 2566 message
meillo@131 2567 .Fn 6 ,
meillo@168 2568 became file
meillo@131 2569 .Fn ,6 .
meillo@168 2570 If then a new message entered the same folder, it would be named with
meillo@168 2571 the number one above the highest existing message number.
meillo@168 2572 In this case the message would be named
meillo@217 2573 .Fn 6 ,
meillo@217 2574 reusing the number.
meillo@168 2575 If this new message would be removed as well,
meillo@217 2576 then the backup of the former message becomes overwritten.
meillo@168 2577 Hence, the ability to restore removed messages did not only depend on
meillo@181 2578 the sweeping cron job but also on the removing of further messages.
meillo@131 2579 It is undesirable to have such obscure and complex mechanisms.
meillo@168 2580 The user should be given a small set of clear assertions, such as
meillo@131 2581 ``Removed files are restorable within a seven-day grace time.''
meillo@131 2582 With the addition ``... unless a message with the same name in the
meillo@131 2583 same folder is removed before.'' the statement becomes complex.
meillo@217 2584 A user will hardly be able to keep track of all removals to know
meillo@131 2585 if the assertion still holds true for a specific file.
meillo@164 2586 In practice, the real mechanism is unclear to the user.
meillo@131 2587 .P
meillo@217 2588 Furthermore, the backup files were scattered within the whole mail storage.
meillo@217 2589 This complicated managing them.
meillo@217 2590 It was possible with the help of
meillo@131 2591 .Pn find ,
meillo@217 2592 but everything is more convenient
meillo@217 2593 if the deleted messages are collected in one place.
meillo@131 2594 .P
meillo@131 2595 The profile entry
meillo@131 2596 .Pe rmmproc
meillo@131 2597 (previously named
meillo@131 2598 .Pe Delete-Prog )
meillo@131 2599 was introduced very early to improve the situation.
meillo@164 2600 It could be set to any command, which would be executed to remove
meillo@131 2601 the specified messages.
meillo@217 2602 This had overridden the default action, described above.
meillo@217 2603 Refiling the to-be-removed files to a trash folder was the usual example.
meillo@131 2604 Nmh's man page
meillo@131 2605 .Mp rmm (1)
meillo@131 2606 proposes to set the
meillo@131 2607 .Pe rmmproc
meillo@131 2608 to
meillo@131 2609 .Cl "refile +d
meillo@217 2610 to move messages to the trash folder
meillo@217 2611 .Fn +d
meillo@131 2612 instead of renaming them with the backup prefix.
meillo@217 2613 The man page additionally proposes the expunge command
meillo@131 2614 .Cl "rm `mhpath +d all`
meillo@168 2615 to empty the trash folder.
meillo@131 2616 .P
meillo@217 2617 Removing messages in such a way has advantages:
meillo@217 2618 .LI 1
meillo@131 2619 The mail storage is prevented from being cluttered with removed messages
meillo@131 2620 because they are all collected in one place.
meillo@131 2621 Existing and removed messages are thus separated more strictly.
meillo@217 2622 .LI 2
meillo@131 2623 No backup files are silently overwritten.
meillo@217 2624 .LI 3
meillo@217 2625 Most important, however, removed messages are kept in the MH domain.
meillo@131 2626 Messages in the trash folder can be listed like those in any other folder.
meillo@131 2627 Deleted messages can be displayed like any other messages.
meillo@169 2628 .Pn refile
meillo@169 2629 can restore deleted messages.
meillo@131 2630 All operations on deleted files are still covered by the MH tools.
meillo@131 2631 The trash folder is just like any other folder in the mail storage.
meillo@131 2632 .P
meillo@131 2633 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131 2634 in favor for replacing it by the better suiting trash folder system.
meillo@131 2635 Hence,
meillo@131 2636 .Pn rmm
meillo@131 2637 calls
meillo@131 2638 .Pn refile
meillo@131 2639 to move the to-be-removed message to the trash folder,
meillo@131 2640 .Fn +trash
meillo@131 2641 by default.
meillo@164 2642 To sweep it clean, the user can use
meillo@131 2643 .Cl "rmm -unlink +trash a" ,
meillo@131 2644 where the
meillo@131 2645 .Sw -unlink
meillo@131 2646 switch causes the files to be unlinked.
meillo@168 2647 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 2648 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@131 2649 .P
meillo@217 2650 Dropping the legacy approach and converting to the new approach
meillo@217 2651 completely, simplified the code base.
meillo@131 2652 The relationship between
meillo@131 2653 .Pn rmm
meillo@131 2654 and
meillo@131 2655 .Pn refile
meillo@131 2656 was inverted.
meillo@131 2657 In mmh,
meillo@131 2658 .Pn rmm
meillo@131 2659 invokes
meillo@217 2660 .Pn refile .
meillo@217 2661 That used to be the other way round.
meillo@131 2662 Yet, the relationship is simpler now.
meillo@164 2663 Loops, like described in nmh's man page for
meillo@131 2664 .Mp refile (1),
meillo@164 2665 can no longer occur:
meillo@131 2666 .QS
meillo@131 2667 Since
meillo@131 2668 .Pn refile
meillo@131 2669 uses your
meillo@131 2670 .Pe rmmproc
meillo@131 2671 to delete the message, the
meillo@131 2672 .Pe rmmproc
meillo@131 2673 must NOT call
meillo@131 2674 .Pn refile
meillo@131 2675 without specifying
meillo@131 2676 .Sw -normmproc
meillo@131 2677 or you will create an infinite loop.
meillo@131 2678 .QE
meillo@131 2679 .LP
meillo@131 2680 .Pn rmm
meillo@131 2681 either unlinks a message with
meillo@131 2682 .Fu unlink()
meillo@131 2683 or invokes
meillo@131 2684 .Pn refile
meillo@131 2685 to move it to the trash folder.
meillo@131 2686 .Pn refile
meillo@131 2687 does not invoke any tools.
meillo@131 2688 .P
meillo@136 2689 By generalizing the message removal in the way that it became covered
meillo@136 2690 by the MH concepts made the whole system more powerful.
meillo@131 2691
meillo@131 2692
meillo@131 2693
meillo@131 2694
meillo@131 2695
meillo@133 2696 .H2 "Modern Defaults
meillo@133 2697 .P
meillo@133 2698 Nmh has a bunch of convenience-improving features inactive by default,
meillo@217 2699 although one can expect every new user to want them active.
meillo@133 2700 The reason they are inactive by default is the wish to stay compatible
meillo@133 2701 with old versions.
meillo@217 2702 But what are old versions?
meillo@136 2703 Still, the highly useful draft folder facility has not been activated
meillo@136 2704 by default although it was introduced over twenty-five years ago.
meillo@133 2705 .[
meillo@133 2706 rose romine real work
meillo@133 2707 .]
meillo@136 2708 The community seems not to care.
meillo@217 2709 .P
meillo@217 2710 In nmh, new users are required to first build up
meillo@217 2711 a profile before they can access the modern features.
meillo@136 2712 Without an extensive profile, the setup is hardly usable
meillo@133 2713 for modern emailing.
meillo@133 2714 The point is not the customization of the setup,
meillo@136 2715 but the need to activate generally useful facilities.
meillo@217 2716 Yet, the real problem lies less in enabling the features,
meillo@217 2717 as this is straight forward as soon as one knows what he wants.
meillo@168 2718 The real problem is that new users need deep insight into the project
meillo@217 2719 to discover the available but inactive features.
meillo@133 2720 To give an example, I needed one year of using nmh
meillo@133 2721 before I became aware of the existence of the attachment system.
meillo@133 2722 One could argue that this fact disqualifies my reading of the
meillo@133 2723 documentation.
meillo@133 2724 If I would have installed nmh from source back then, I could agree.
meillo@217 2725 Yet, I had used a pre-packaged version and had expected that it would
meillo@133 2726 just work.
meillo@133 2727 Nevertheless, I had been convinced by the concepts of MH already
meillo@133 2728 and I am a software developer,
meillo@133 2729 still I required a lot of time to discover the cool features.
meillo@133 2730 How can we expect users to be even more advanced than me,
meillo@217 2731 just to enable them to use MH in a convenient and modern way?
meillo@133 2732 Unless they are strongly convinced of the concepts, they will fail.
meillo@133 2733 I have seen friends of me giving up disappointed
meillo@133 2734 before they truly used the system,
meillo@133 2735 although they had been motivated in the beginning.
meillo@217 2736 New users suffer hard enough to get used to the tool chest approach,
meillo@179 2737 we developers should spare them further inconveniences.
meillo@133 2738 .P
meillo@136 2739 Maintaining compatibility for its own sake is bad,
meillo@217 2740 because the code base will collect more and more compatibility code.
meillo@200 2741 Sticking to the compatibility code means remaining limited;
meillo@168 2742 whereas adjusting to the changes renders the compatibility unnecessary.
meillo@217 2743 Keeping unused alternatives in the code for longer than a short
meillo@217 2744 grace time is a bad choice as they likely
meillo@217 2745 gather bugs by not being constantly tested.
meillo@136 2746 Also, the increased code size and the greater number of conditions
meillo@136 2747 increase the maintenance costs.
meillo@133 2748 If any MH implementation would be the back-end of widespread
meillo@133 2749 email clients with large user bases, compatibility would be more
meillo@133 2750 important.
meillo@133 2751 Yet, it appears as if this is not the case.
meillo@133 2752 Hence, compatibility is hardly important for technical reasons.
meillo@217 2753 Its importance originates from personal reasons rather.
meillo@133 2754 Nmh's user base is small and old.
meillo@217 2755 Changing the interfaces causes inconvenience to long-term users of MH.
meillo@217 2756 It forces them to change their many years old MH configurations.
meillo@168 2757 I do understand this aspect, but by sticking to the old users,
meillo@217 2758 new users are kept from entering the world of MH.
meillo@217 2759 But the future lies in new users.
meillo@168 2760 In consequence, mmh invites new users by providing a convenient
meillo@168 2761 and modern setup, readily usable out-of-the-box.
meillo@133 2762 .P
meillo@136 2763 In mmh, all modern features are active by default and many previous
meillo@217 2764 approaches are removed or only accessible in a manual way.
meillo@136 2765 New default features include:
meillo@133 2766 .BU
meillo@133 2767 The attachment system (\c
meillo@217 2768 .Hd Attach )
meillo@217 2769 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1 .
meillo@133 2770 .BU
meillo@133 2771 The draft folder facility (\c
meillo@217 2772 .Fn +drafts )
meillo@217 2773 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@133 2774 .BU
meillo@133 2775 The unseen sequence (`u')
meillo@133 2776 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@217 2777 and the sequence negation prefix (`!')
meillo@217 2778 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc .
meillo@133 2779 .BU
meillo@217 2780 Quoting the original message in the reply
meillo@217 2781 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6 .
meillo@133 2782 .BU
meillo@217 2783 Forwarding messages using MIME
meillo@217 2784 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1 .
meillo@171 2785 .LP
meillo@217 2786 An mmh setup with a profile that defines only the path to the
meillo@136 2787 mail storage, is already convenient to use.
meillo@217 2788 Again, Paul Vixie's supports the direction I took:
meillo@136 2789 ``the `main branch' should just be modern''.
meillo@136 2790 .[
meillo@136 2791 paul vixie edginess nmh-workers
meillo@136 2792 .]
meillo@131 2793
meillo@133 2794
meillo@133 2795
meillo@133 2796
meillo@133 2797
meillo@133 2798 .\" --------------------------------------------------------------
meillo@131 2799 .H1 "Styling
meillo@22 2800 .P
meillo@118 2801 Kernighan and Pike have emphasized the importance of style in the
meillo@232 2802 preface of \fIThe Practice of Programming\fP:
meillo@118 2803 .[ [
meillo@118 2804 kernighan pike practice of programming
meillo@118 2805 .], p. x]
meillo@118 2806 .QS
meillo@118 2807 Chapter 1 discusses programming style.
meillo@219 2808 Good style is so important to good programming that we have chosen
meillo@118 2809 to cover it first.
meillo@118 2810 .QE
meillo@168 2811 This section covers changes in mmh that were guided by the desire
meillo@118 2812 to improve on style.
meillo@219 2813 Many of them follow the advice given in the quoted book.
meillo@118 2814
meillo@118 2815
meillo@127 2816
meillo@127 2817
meillo@127 2818 .H2 "Code Style
meillo@154 2819 .Id code-style
meillo@118 2820 .P
meillo@118 2821 .U3 "Indentation Style
meillo@118 2822 .P
meillo@219 2823 Indentation styles are the holy cow of programming.
meillo@219 2824 Kernighan and Pike write:
meillo@118 2825 .[ [
meillo@118 2826 kernighan pike practice of programming
meillo@118 2827 .], p. 10]
meillo@118 2828 .QS
meillo@118 2829 Programmers have always argued about the layout of programs,
meillo@118 2830 but the specific style is much less important than its consistent
meillo@118 2831 application.
meillo@121 2832 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118 2833 time arguing.
meillo@118 2834 .QE
meillo@118 2835 .P
meillo@118 2836 I agree that the constant application is most important,
meillo@118 2837 but I believe that some styles have advantages over others.
meillo@118 2838 For instance the indentation with tab characters only.
meillo@219 2839 The number of tabs corresponds to the nesting level \(en
meillo@118 2840 one tab, one level.
meillo@219 2841 Tab characters provide flexible visual appearance because developers
meillo@228 2842 can adjust their width as preferred.
meillo@219 2843 There is no more need to check for the correct mixture of
meillo@219 2844 tabs and spaces.
meillo@219 2845 Two simple rules ensure the integrity and flexibility of the visual
meillo@219 2846 appearance:
meillo@219 2847 .LI 1
meillo@219 2848 Leading whitespace must consist of tabs only.
meillo@219 2849 .LI 2
meillo@219 2850 All other whitespace should be spaces.
meillo@219 2851 .LP
meillo@121 2852 Although reformatting existing code should be avoided, I did it.
meillo@200 2853 I did not waste time arguing; I just reformatted the code.
meillo@118 2854 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118 2855
meillo@118 2856 .U3 "Comments
meillo@118 2857 .P
meillo@219 2858 Kernighan and Pike demand: ``Don't belabor the obvious''.
meillo@118 2859 .[ [
meillo@118 2860 kernighan pike practice of programming
meillo@118 2861 .], p. 23]
meillo@219 2862 Following the advice, I removed unnecessary comments.
meillo@219 2863 For instance, I removed all comments in the following code excerpt
meillo@219 2864 .Ci 426543622b377fc5d091455cba685e114b6df674 :
meillo@118 2865 .VS
meillo@120 2866 context_replace(curfolder, folder); /* update current folder */
meillo@120 2867 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120 2868 seq_save(mp); /* synchronize message sequences */
meillo@120 2869 folder_free(mp); /* free folder/message structure */
meillo@120 2870 context_save(); /* save the context file */
meillo@120 2871
meillo@120 2872 [...]
meillo@120 2873
meillo@120 2874 int c; /* current character */
meillo@120 2875 char *cp; /* miscellaneous character pointer */
meillo@120 2876
meillo@120 2877 [...]
meillo@120 2878
meillo@120 2879 /* NUL-terminate the field */
meillo@120 2880 *cp = '\0';
meillo@118 2881 VE
meillo@118 2882 .P
meillo@219 2883 The information in each of the comments was present in the code
meillo@219 2884 statements already, except for the NUL-termination, which became
meillo@219 2885 obvious from the context.
meillo@136 2886
meillo@118 2887
meillo@118 2888 .U3 "Names
meillo@118 2889 .P
meillo@219 2890 Regarding this topic, Kernighan and Pike suggest:
meillo@118 2891 ``Use active names for functions''.
meillo@118 2892 .[ [
meillo@118 2893 kernighan pike practice of programming
meillo@118 2894 .], p. 4]
meillo@118 2895 One application of this rule was the rename of
meillo@118 2896 .Fu check_charset()
meillo@118 2897 to
meillo@219 2898 .Fu is_native_charset()
meillo@219 2899 .Ci 8d77b48284c58c135a6b2787e721597346ab056d .
meillo@219 2900 The same change additionally fixed a violation of ``Be accurate'',
meillo@181 2901 .[ [
meillo@181 2902 kernighan pike practice of programming
meillo@181 2903 .], p. 4]
meillo@219 2904 as the code did not match the expectation the function suggested.
meillo@219 2905 It did not compare charset names but prefixes of them only.
meillo@219 2906 In case the native charset was `ISO-8859-1', then
meillo@219 2907 .VS
meillo@219 2908 check_charset("ISO-8859-11", strlen("ISO-8859-11"))
meillo@219 2909 VE
meillo@219 2910 had returned true although the upper halves of the code pages
meillo@219 2911 are different.
meillo@118 2912 .P
meillo@118 2913 More important than using active names is using descriptive names.
meillo@145 2914 .VS
meillo@145 2915 m_unknown(in); /* the MAGIC invocation... */
meillo@145 2916 VE
meillo@145 2917 Renaming the obscure
meillo@118 2918 .Fu m_unknown()
meillo@219 2919 function was a delightful event, although it made the code less funny
meillo@219 2920 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846 .
meillo@118 2921 .P
meillo@118 2922 Magic numbers are generally considered bad style.
meillo@118 2923 Obviously, Kernighan and Pike agree:
meillo@118 2924 ``Give names to magic numbers''.
meillo@118 2925 .[ [
meillo@118 2926 kernighan pike practice of programming
meillo@118 2927 .], p. 19]
meillo@219 2928 .P
meillo@219 2929 The argument
meillo@219 2930 .CW outnum
meillo@219 2931 of the function
meillo@219 2932 .Fu scan()
meillo@219 2933 in
meillo@219 2934 .Fn uip/scansbr.c
meillo@219 2935 holds the number of the message to be created.
meillo@219 2936 As well it encodes program logic with negative numbers and zero.
meillo@219 2937 This led to obscure code.
meillo@219 2938 I clarified the code by introducing two variables that extracted
meillo@219 2939 the hidden information:
meillo@219 2940 .VS
meillo@219 2941 int incing = (outnum > 0);
meillo@219 2942 int ismbox = (outnum != 0);
meillo@219 2943 VE
meillo@219 2944 The readable names are thus used in conditions;
meillo@219 2945 the variable
meillo@219 2946 .CW outnum
meillo@219 2947 is used only to extract ordinary message numbers
meillo@219 2948 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f .
meillo@219 2949 .P
meillo@219 2950 Through the clarity improvement of the change detours in the program
meillo@219 2951 logic of related code parts became apparent.
meillo@219 2952 The implementation was simplified.
meillo@219 2953 This possibility to improve had been invisible before
meillo@219 2954 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723 .
meillo@219 2955 .P
meillo@219 2956 The names just described were a first step, yet the situation
meillo@219 2957 was further improved by giving names to the magic values of
meillo@219 2958 .CW outnum :
meillo@118 2959 .VS
meillo@118 2960 #define SCN_MBOX (-1)
meillo@118 2961 #define SCN_FOLD 0
meillo@118 2962 VE
meillo@219 2963 The two variables were updated thereafter as well:
meillo@219 2964 .VS
meillo@219 2965 int incing = (outnum != SCN_MBOX && outnum != SCN_FOLD);
meillo@219 2966 int scanfolder = (outnum == SCN_FOLD);
meillo@219 2967 VE
meillo@219 2968 Furthermore,
meillo@219 2969 .CW ismbox
meillo@219 2970 was replaced by
meillo@219 2971 .CW scanfolder
meillo@219 2972 because that matched better to the program logic.
meillo@118 2973 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@219 2974
meillo@118 2975
meillo@133 2976
meillo@133 2977
meillo@133 2978 .H2 "Structural Rework
meillo@133 2979 .P
meillo@232 2980 .ZZ
meillo@219 2981 Although the stylistic changes described already improve the
meillo@219 2982 readability of the source code, all of them were changes ``in the small''.
meillo@219 2983 Structural changes, in contrast, affect much larger code areas.
meillo@219 2984 They are more difficult to accomplish but lead to larger improvements,
meillo@219 2985 especially as they often influence the outer shape of the tools as well.
meillo@118 2986 .P
meillo@118 2987 At the end of their chapter on style,
meillo@118 2988 Kernighan and Pike ask: ``But why worry about style?''
meillo@181 2989 .[ [
meillo@181 2990 kernighan pike practice of programming
meillo@219 2991 .], p. 28].
meillo@219 2992 Following are two examples of structural rework that demonstrate
meillo@136 2993 why style is important in the first place.
meillo@136 2994
meillo@136 2995
meillo@136 2996 .U3 "Rework of \f(CWanno\fP
meillo@118 2997 .P
meillo@120 2998 Until 2002,
meillo@120 2999 .Pn anno
meillo@219 3000 had six functional command line switches:
meillo@120 3001 .Sw -component
meillo@120 3002 and
meillo@120 3003 .Sw -text ,
meillo@219 3004 each with an argument,
meillo@120 3005 and the two pairs of flags,
meillo@120 3006 .Sw -[no]date
meillo@120 3007 and
meillo@120 3008 .Sw -[no]inplace .
meillo@120 3009 Then Jon Steinhart introduced his attachment system.
meillo@120 3010 In need for more advanced annotation handling, he extended
meillo@232 3011 .Pn anno
meillo@232 3012 and added five more switches:
meillo@120 3013 .Sw -draft ,
meillo@120 3014 .Sw -list ,
meillo@232 3015 .Sw \%-delete ,
meillo@120 3016 .Sw -append ,
meillo@120 3017 and
meillo@120 3018 .Sw -number ,
meillo@219 3019 the last one taking an argument
meillo@219 3020 .Ci 7480dbc14bc90f2d872d434205c0784704213252 .
meillo@120 3021 Later,
meillo@120 3022 .Sw -[no]preserve
meillo@219 3023 was added as well
meillo@219 3024 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f .
meillo@120 3025 Then, the Synopsis section of the man page
meillo@120 3026 .Mp anno (1)
meillo@120 3027 read:
meillo@120 3028 .VS
meillo@219 3029 anno [+folder] [msgs] [-component f(CIfieldfP] [-inplace | -noinplace]
meillo@120 3030 [-date | -nodate] [-draft] [-append] [-list] [-delete]
meillo@219 3031 [-number [f(CInumfP|fPallfP]] [-preserve | -nopreserve] [-version]
meillo@219 3032 [-help] [-text f(CIbodyfP]
meillo@120 3033 VE
meillo@120 3034 .LP
meillo@120 3035 The implementation followed the same structure.
meillo@120 3036 Problems became visible when
meillo@120 3037 .Cl "anno -list -number 42
meillo@219 3038 worked on the current message instead of on message number 42,
meillo@120 3039 and
meillo@120 3040 .Cl "anno -list -number l:5
meillo@124 3041 did not work on the last five messages but failed with the mysterious
meillo@120 3042 error message: ``anno: missing argument to -list''.
meillo@121 3043 Yet, the invocation matched the specification in the man page.
meillo@120 3044 There, the correct use of
meillo@120 3045 .Sw -number
meillo@120 3046 was defined as being
meillo@120 3047 .Cl "[-number [num|all]]
meillo@120 3048 and the textual description for the combination with
meillo@120 3049 .Sw -list
meillo@120 3050 read:
meillo@120 3051 .QS
meillo@164 3052 The
meillo@164 3053 .Sw -list
meillo@164 3054 option produces a listing of the field bodies for
meillo@120 3055 header fields with names matching the specified component,
meillo@164 3056 one per line. The listing is numbered, starting at 1, if the
meillo@164 3057 .Sw -number
meillo@164 3058 option is also used.
meillo@120 3059 .QE
meillo@120 3060 .LP
meillo@120 3061 The problem was manifold.
meillo@120 3062 Semantically, the argument to the
meillo@120 3063 .Sw -number
meillo@120 3064 switch is only necessary in combination with
meillo@120 3065 .Sw -delete ,
meillo@120 3066 but not with
meillo@120 3067 .Sw -list .
meillo@219 3068 The code, however, required a numeric argument in any case.
meillo@219 3069 If the argument was missing or non-numeric,
meillo@219 3070 .Pn anno
meillo@219 3071 aborted with an error message that additionally had an off-by-one error.
meillo@219 3072 It printed the name of the switch one before the concerned one.
meillo@120 3073 .P
meillo@219 3074 Trying to fix these problems on the surface would not have solved them.
meillo@219 3075 They originate from a discrepance between the
meillo@120 3076 structure of the problem and the structure implemented in the program.
meillo@219 3077 Such structural differences can only be solved by adjusting the
meillo@219 3078 structure of the implementation to the structure of the problem.
meillo@120 3079 .P
meillo@232 3080 Steinhart had added the
meillo@120 3081 .Sw -list
meillo@120 3082 and
meillo@120 3083 .Sw -delete
meillo@232 3084 switches in the same way as the other switches though
meillo@219 3085 they are of structural different type.
meillo@120 3086 Semantically,
meillo@120 3087 .Sw -list
meillo@120 3088 and
meillo@232 3089 .Sw \%-delete
meillo@219 3090 introduce operation modes.
meillo@120 3091 Historically,
meillo@120 3092 .Pn anno
meillo@120 3093 had only one operation mode: adding header fields.
meillo@219 3094 With the extension, two more modes were added:
meillo@120 3095 listing and deleting header fields.
meillo@120 3096 The structure of the code changes did not pay respect to this
meillo@219 3097 fundamental change.
meillo@120 3098 Neither the implementation nor the documentation did clearly
meillo@219 3099 declare the exclusive operation modes as such.
meillo@120 3100 Having identified the problem, I solved it by putting structure into
meillo@120 3101 .Pn anno
meillo@219 3102 and its documentation
meillo@219 3103 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11 .
meillo@120 3104 .P
meillo@173 3105 The difference is visible in both the code and the documentation.
meillo@219 3106 For instance in the following code excerpt:
meillo@120 3107 .VS
meillo@120 3108 int delete = -2; /* delete header element if set */
meillo@120 3109 int list = 0; /* list header elements if set */
meillo@120 3110 [...]
meillo@121 3111 case DELETESW: /* delete annotations */
meillo@121 3112 delete = 0;
meillo@121 3113 continue;
meillo@121 3114 case LISTSW: /* produce a listing */
meillo@121 3115 list = 1;
meillo@121 3116 continue;
meillo@120 3117 VE
meillo@121 3118 .LP
meillo@219 3119 which was replaced by:
meillo@120 3120 .VS
meillo@120 3121 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120 3122 [...]
meillo@121 3123 case DELETESW: /* delete annotations */
meillo@121 3124 mode = MODE_DEL;
meillo@121 3125 continue;
meillo@121 3126 case LISTSW: /* produce a listing */
meillo@121 3127 mode = MODE_LIST;
meillo@121 3128 continue;
meillo@120 3129 VE
meillo@120 3130 .LP
meillo@121 3131 The replacement code does not only reflect the problem's structure better,
meillo@121 3132 it is easier to understand as well.
meillo@121 3133 The same applies to the documentation.
meillo@120 3134 The man page was completely reorganized to propagate the same structure.
meillo@219 3135 This is already visible in the Synopsis section:
meillo@120 3136 .VS
meillo@219 3137 anno [+folder] [msgs] [-component f(CIfieldfP] [-text fPbodyfP]
meillo@120 3138 [-append] [-date | -nodate] [-preserve | -nopreserve]
meillo@120 3139 [-Version] [-help]
meillo@120 3140
meillo@219 3141 anno -delete [+folder] [msgs] [-component fPfieldfP] [-text
meillo@219 3142 fPbodyfP] [-number fPnum fP| fPall fP] [-preserve | -nopreserve]
meillo@120 3143 [-Version] [-help]
meillo@120 3144
meillo@219 3145 anno -list [+folder] [msgs] [-component fPfieldfP] [-number]
meillo@120 3146 [-Version] [-help]
meillo@120 3147 VE
meillo@118 3148
meillo@58 3149
meillo@58 3150
meillo@133 3151 .U3 "Path Conversion
meillo@133 3152 .P
meillo@134 3153 Four kinds of path names can appear in MH:
meillo@171 3154 .LI 1
meillo@134 3155 Absolute Unix directory paths, like
meillo@134 3156 .Fn /etc/passwd .
meillo@171 3157 .LI 2
meillo@134 3158 Relative Unix directory paths, like
meillo@134 3159 .Fn ./foo/bar .
meillo@171 3160 .LI 3
meillo@134 3161 Absolute MH folder paths, like
meillo@219 3162 .Fn +projects/mmh .
meillo@171 3163 .LI 4
meillo@134 3164 Relative MH folder paths, like
meillo@134 3165 .Fn @subfolder .
meillo@171 3166 .LP
meillo@219 3167 Relative MH folder paths, are hardly documented
meillo@219 3168 although they are useful for large mail storages.
meillo@134 3169 The current mail folder is specified as `\c
meillo@134 3170 .Fn @ ',
meillo@134 3171 just like the current directory is specified as `\c
meillo@134 3172 .Fn . '.
meillo@134 3173 .P
meillo@134 3174 To allow MH tools to understand all four notations,
meillo@219 3175 they need to be able to convert between them.
meillo@134 3176 In nmh, these path name conversion functions were located in the files
meillo@134 3177 .Fn sbr/path.c
meillo@134 3178 (``return a pathname'') and
meillo@134 3179 .Fn sbr/m_maildir.c
meillo@134 3180 (``get the path for the mail directory'').
meillo@134 3181 The seven functions in the two files were documented with no more
meillo@134 3182 than two comments, which described obvious information.
meillo@219 3183 The signatures of the four exported functions did not explain their
meillo@219 3184 semantics:
meillo@219 3185 .LI 1
meillo@219 3186 .CW "char *path(char *, int);
meillo@219 3187 .LI 2
meillo@219 3188 .CW "char *pluspath(char *);
meillo@219 3189 .LI 3
meillo@219 3190 .CW "char *m_mailpath(char *);
meillo@219 3191 .LI 4
meillo@219 3192 .CW "char *m_maildir(char *);
meillo@134 3193 .P
meillo@219 3194 My investigations provided the following descriptions:
meillo@171 3195 .LI 1
meillo@134 3196 The second parameter of
meillo@134 3197 .Fu path()
meillo@219 3198 defines the type as which the path given in the first parameter should
meillo@219 3199 be treated.
meillo@134 3200 Directory paths are converted to absolute directory paths.
meillo@134 3201 Folder paths are converted to absolute folder paths.
meillo@173 3202 Folder paths must not include a leading `\fL@\fP' character.
meillo@134 3203 Leading plus characters are preserved.
meillo@134 3204 The result is a pointer to newly allocated memory.
meillo@171 3205 .LI 2
meillo@134 3206 .Fu pluspath()
meillo@134 3207 is a convenience-wrapper to
meillo@134 3208 .Fu path() ,
meillo@134 3209 to convert folder paths only.
meillo@134 3210 This function can not be used for directory paths.
meillo@134 3211 An empty string parameter causes a buffer overflow.
meillo@171 3212 .LI 3
meillo@134 3213 .Fu m_mailpath()
meillo@134 3214 converts directory paths to absolute directory paths.
meillo@173 3215 The characters `\fL+\fP' or `\fL@\fP' at the beginning of the path name are
meillo@134 3216 treated literal, i.e. as the first character of a relative directory path.
meillo@134 3217 Hence, this function can not be used for folder paths.
meillo@219 3218 In any case, the result is an absolute directory path,
meillo@219 3219 returned as a pointer to newly allocated memory.
meillo@171 3220 .LI 4
meillo@134 3221 .Fu m_maildir()
meillo@134 3222 returns the parameter unchanged if it is an absolute directory path
meillo@173 3223 or begins with the entry `\fL.\fP' or `\fL..\fP'.
meillo@134 3224 All other strings are prepended with the current working directory.
meillo@219 3225 Hence, this function can not be used for folder paths.
meillo@134 3226 The result is either an absolute directory path or a relative
meillo@219 3227 directory path, starting with dot or dot-dot.
meillo@134 3228 In contrast to the other functions, the result is a pointer to
meillo@134 3229 static memory.
meillo@134 3230 .P
meillo@134 3231 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@219 3232 Additionally, no clear terminology was used to name the different
meillo@219 3233 kinds of path names.
meillo@219 3234 Sometimes, the names were even misleading, much as the first argument of
meillo@134 3235 .Fu m_mailpath() ,
meillo@219 3236 which was named
meillo@219 3237 .CW folder ,
meillo@219 3238 although
meillo@134 3239 .Fu m_mailpath()
meillo@219 3240 could not be used with MH folder arguments.
meillo@134 3241 .P
meillo@219 3242 I clarified the path name conversion by complete rework.
meillo@134 3243 First of all, the terminology needed to be defined.
meillo@134 3244 A path name is either in the Unix domain, then it is called
meillo@227 3245 \fIdirectory path\fP or it is in the MH domain,
meillo@227 3246 then it is called \fIfolder path\fP.
meillo@134 3247 The two terms need to be used with strict distinction.
meillo@134 3248 Second, I exploited the concept of path type indicators.
meillo@219 3249 By requiring every path name to start with a distinct type identifier,
meillo@219 3250 the conversion between the types could be fully automated.
meillo@227 3251 This allows the tools to accept path names of any type from the user.
meillo@134 3252 Therefore, it was necessary to require relative directory paths to be
meillo@134 3253 prefixed with a dot character.
meillo@134 3254 In consequence, the dot character could no longer be an alias for the
meillo@227 3255 current message
meillo@227 3256 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01 .
meillo@134 3257 Third, I created three new functions to replace the previous mess:
meillo@171 3258 .LI 1
meillo@134 3259 .Fu expandfol()
meillo@219 3260 converts folder paths to absolute folder paths.
meillo@134 3261 Directory paths are simply passed through.
meillo@134 3262 This function is to be used for folder paths only, thus the name.
meillo@134 3263 The result is a pointer to static memory.
meillo@171 3264 .LI 2
meillo@134 3265 .Fu expanddir()
meillo@134 3266 converts directory paths to absolute directory paths.
meillo@134 3267 Folder paths are treated as relative directory paths.
meillo@134 3268 This function is to be used for directory paths only, thus the name.
meillo@134 3269 The result is a pointer to static memory.
meillo@171 3270 .LI 3
meillo@134 3271 .Fu toabsdir()
meillo@134 3272 converts any type of path to an absolute directory path.
meillo@134 3273 This is the function of choice for path conversion.
meillo@134 3274 Absolute directory paths are the most general representation of a
meillo@134 3275 path name.
meillo@134 3276 The result is a pointer to static memory.
meillo@134 3277 .P
meillo@134 3278 The new functions have names that indicate their use.
meillo@134 3279 Two of the functions convert relative to absolute path names of the
meillo@134 3280 same type.
meillo@134 3281 The third function converts any path name type to the most general one,
meillo@134 3282 the absolute directory path.
meillo@134 3283 All of the functions return pointers to static memory.
meillo@219 3284 The file
meillo@219 3285 .Fn sbr/path.c
meillo@219 3286 contains the implementation of the functions;
meillo@134 3287 .Fn sbr/m_maildir.c
meillo@219 3288 was removed.
meillo@168 3289 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3290 .P
meillo@134 3291 Along with the path conversion rework, I also replaced
meillo@134 3292 .Fu getfolder(FDEF)
meillo@134 3293 with
meillo@134 3294 .Fu getdeffol()
meillo@134 3295 and
meillo@134 3296 .Fu getfolder(FCUR)
meillo@134 3297 with
meillo@134 3298 .Fu getcurfol() ,
meillo@219 3299 which only wraps
meillo@219 3300 .Fu expandfol(""@"")
meillo@219 3301 for convenience.
meillo@134 3302 This code was moved from
meillo@134 3303 .Fn sbr/getfolder.c
meillo@219 3304 into
meillo@219 3305 .Fn sbr/path.c
meillo@219 3306 as well.
meillo@168 3307 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3308 .P
meillo@134 3309 The related function
meillo@134 3310 .Fu etcpath()
meillo@219 3311 is now included in
meillo@134 3312 .Fn sbr/path.c ,
meillo@168 3313 too
meillo@168 3314 .Ci b4c29794c12099556151d93a860ee51badae2e35 .
meillo@134 3315 Previously, it had been located in
meillo@219 3316 .Fn config/config.c .
meillo@134 3317 .P
meillo@219 3318 Now,
meillo@134 3319 .Fn sbr/path.c
meillo@219 3320 contains all path handling code.
meillo@219 3321 Besides being less code, its readability is highly improved.
meillo@219 3322 The functions follow a common style and are well documented.
meillo@133 3323
meillo@133 3324
meillo@133 3325
meillo@133 3326
meillo@133 3327 .H2 "Profile Reading
meillo@133 3328 .P
meillo@220 3329 The MH profile contains the configuration of a user-specific MH setup.
meillo@220 3330 MH tools read the profile right after starting up
meillo@220 3331 because it contains the location of the user's mail storage
meillo@138 3332 and similar settings that influence the whole setup.
meillo@220 3333 Furthermore, the profile contains the default switches for the tools
meillo@220 3334 as well.
meillo@220 3335 The context file is read along with the profile.
meillo@138 3336 .P
meillo@138 3337 For historic reasons, some MH tools did not read the profile and context.
meillo@138 3338 Among them were
meillo@138 3339 .Pn post /\c
meillo@138 3340 .Pn spost ,
meillo@138 3341 .Pn mhmail ,
meillo@138 3342 and
meillo@138 3343 .Pn slocal .
meillo@138 3344 The reason why these tools ignored the profile were not clearly stated.
meillo@220 3345 During a discussion on the nmh-workers mailing list,
meillo@181 3346 David Levine posted an explanation, quoting John Romine:
meillo@138 3347 .[
meillo@138 3348 nmh-workers levine post profile
meillo@138 3349 .]
meillo@220 3350
meillo@138 3351 .QS
meillo@138 3352 I asked John Romine and here's what he had to say, which
meillo@138 3353 agrees and provides an example that convinces me:
meillo@138 3354 .QS
meillo@164 3355 My take on this is that
meillo@164 3356 .Pn post
meillo@164 3357 should not be called by users directly, and it doesn't read the
meillo@164 3358 .Fn .mh_profile
meillo@138 3359 (only front-end UI programs read the profile).
meillo@138 3360 .QP
meillo@164 3361 For example, there can be contexts where
meillo@164 3362 .Pn post
meillo@164 3363 is called by a helper program (like `\c
meillo@164 3364 .Pn mhmail ')
meillo@164 3365 which may be run by a non-MH user.
meillo@164 3366 We don't want this to prompt the user to create an MH profile, etc.
meillo@138 3367 .QP
meillo@164 3368 My suggestion would be to have
meillo@164 3369 .Pn send
meillo@164 3370 pass a (hidden) `\c
meillo@164 3371 .Sw -fileproc
meillo@164 3372 .Ar proc '
meillo@164 3373 option to
meillo@164 3374 .Pn post
meillo@164 3375 if needed.
meillo@164 3376 You could also
meillo@164 3377 use an environment variable (I think
meillo@164 3378 .Pn send /\c
meillo@164 3379 .Pn whatnow
meillo@164 3380 do this).
meillo@138 3381 .QE
meillo@220 3382 .sp \n(PDu
meillo@164 3383 I think that's the way to go.
meillo@164 3384 My personal preference is to use a command line option,
meillo@164 3385 not an environment variable.
meillo@138 3386 .QE
meillo@220 3387
meillo@138 3388 .P
meillo@220 3389 To solve the problem that
meillo@138 3390 .Pn post
meillo@220 3391 does not honor the
meillo@138 3392 .Pe fileproc
meillo@138 3393 profile entry,
meillo@138 3394 the community roughly agreed that a switch
meillo@138 3395 .Sw -fileproc
meillo@138 3396 should be added to
meillo@138 3397 .Pn post
meillo@138 3398 to be able to pass a different fileproc.
meillo@138 3399 I strongly disagree with this approach because it does not solve
meillo@138 3400 the problem; it only removes a single symptom.
meillo@220 3401 The actual problem is that
meillo@138 3402 .Pn post
meillo@220 3403 does not behave as expected,
meillo@220 3404 though all programs should behave as expected.
meillo@220 3405 Clear and general concepts are a precondition for this.
meillo@220 3406 Thus, there should be no separation into ``front-end UI programs''
meillo@220 3407 and ones that ``should not be called by users directly''.
meillo@220 3408 The real solution is having all MH tools read the profile.
meillo@138 3409 .P
meillo@220 3410 But the problem has a further aspect,
meillo@220 3411 which originates from
meillo@220 3412 .Pn mhmail
meillo@220 3413 mainly.
meillo@138 3414 .Pn mhmail
meillo@138 3415 was intended to be a replacement for
meillo@138 3416 .Pn mailx
meillo@138 3417 on systems with MH installations.
meillo@220 3418 In difference to
meillo@220 3419 .Pn mailx ,
meillo@138 3420 .Pn mhmail
meillo@220 3421 used MH's
meillo@138 3422 .Pn post
meillo@220 3423 to send the message.
meillo@220 3424 The idea was that using
meillo@138 3425 .Pn mhmail
meillo@220 3426 should not be influenced whether the user had
meillo@138 3427 MH set up for himself or not.
meillo@220 3428 Therefore
meillo@138 3429 .Pn mhmail
meillo@220 3430 had not read the profile.
meillo@138 3431 As
meillo@138 3432 .Pn mhmail
meillo@138 3433 used
meillo@138 3434 .Pn post ,
meillo@138 3435 .Pn post
meillo@220 3436 was not allowed to read the profile neither.
meillo@138 3437 This is the reason for the actual problem.
meillo@220 3438 Yet, this was not considered much of a problem because
meillo@138 3439 .Pn post
meillo@138 3440 was not intended to be used by users directly.
meillo@220 3441 To invoke
meillo@220 3442 .Pn post ,
meillo@138 3443 .Pn send
meillo@220 3444 was used an a front-end.
meillo@138 3445 .Pn send
meillo@138 3446 read the profile and passed all relevant values on the command line to
meillo@138 3447 .Pn post
meillo@138 3448 \(en an awkward solution.
meillo@138 3449 .P
meillo@138 3450 The important insight is that
meillo@138 3451 .Pn mhmail
meillo@220 3452 is a wolf in sheep's clothing.
meillo@220 3453 This alien tool broke the concepts because it was treated like
meillo@220 3454 a normal MH tool.
meillo@138 3455 Instead it should have been treated accordingly to its foreign style.
meillo@220 3456 .P
meillo@220 3457 The solution is not to prevent the tools from reading the profile but
meillo@220 3458 to instruct them to read a different profile.
meillo@138 3459 .Pn mhmail
meillo@220 3460 could have set up a well-defined profile and caused the following
meillo@138 3461 .Pn post
meillo@220 3462 to use this profile by exporting an environment variable.
meillo@220 3463 With this approach, no special cases would have been introduced
meillo@220 3464 and no surprises would have been caused.
meillo@220 3465 By writing a wrapper program to provide a clean temporary profile,
meillo@220 3466 the concept could have been generalized orthogonally to the whole
meillo@220 3467 MH tool chest.
meillo@220 3468 .P
meillo@220 3469 In mmh, the wish to have
meillo@220 3470 .Pn mhmail
meillo@220 3471 as a replacement for
meillo@220 3472 .Pn mailx
meillo@220 3473 is considered obsolete.
meillo@220 3474 Mmh's
meillo@220 3475 .Pn mhmail
meillo@220 3476 does no longer cover this use-case
meillo@220 3477 .Ci d36e56e695fe1c482c7920644bfbb6386ac9edb0 .
meillo@220 3478 Currently,
meillo@220 3479 .Pn mhmail
meillo@220 3480 is in a transition state
meillo@220 3481 .Ci 32d4f9daaa70519be3072479232ff7be0500d009 .
meillo@220 3482 It may become a front-end to
meillo@220 3483 .Pn comp ,
meillo@220 3484 which provides an alternative interface which can be more convenient
meillo@220 3485 in some cases.
meillo@220 3486 This would convert
meillo@220 3487 .Pn mhmail
meillo@220 3488 into an ordinary MH tool.
meillo@220 3489 If, however, this idea does not convince, then
meillo@220 3490 .Pn mhmail
meillo@220 3491 will be removed.
meillo@220 3492 .P
meillo@232 3493 .ZZ -1
meillo@220 3494 In the mmh tool chest, every program reads the profile.
meillo@220 3495 (\c
meillo@220 3496 .Pn slocal
meillo@220 3497 is not considered part of the mmh tool chest (cf. Sec.
meillo@220 3498 .Cf slocal ).)
meillo@220 3499 Mmh has no
meillo@220 3500 .Pn post
meillo@220 3501 program, but it has
meillo@220 3502 .Pn spost ,
meillo@220 3503 which now does read the profile
meillo@220 3504 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8 .
meillo@220 3505 Following this change,
meillo@220 3506 .Pn send
meillo@220 3507 and
meillo@220 3508 .Pn spost
meillo@220 3509 can be considered for merging.
meillo@220 3510 Besides
meillo@220 3511 .Pn send ,
meillo@220 3512 .Pn spost
meillo@220 3513 is only invoked directly by the to-be-changed
meillo@220 3514 .Pn mhmail
meillo@220 3515 implementation and by
meillo@220 3516 .Pn rcvdist ,
meillo@220 3517 which requires rework anyway.
meillo@220 3518
meillo@220 3519 .P
meillo@220 3520 Jeffrey Honig quoted Marshall T. Rose explaining the decision that
meillo@220 3521 .Pn post
meillo@220 3522 ignores the profile:
meillo@138 3523 .[
meillo@197 3524 nmh-workers honig post profile
meillo@138 3525 .]
meillo@138 3526 .QS
meillo@138 3527 when you run mh commands in a script, you want all the defaults to be
meillo@138 3528 what the man page says.
meillo@138 3529 when you run a command by hand, then you want your own defaults...
meillo@138 3530 .QE
meillo@138 3531 .LP
meillo@228 3532 The explanation neither matches the problem concerned exactly
meillo@220 3533 nor is the interpretation clear.
meillo@220 3534 If the described desire addresses the technical level,
meillo@232 3535 then it conflicts with the Unix philosophy,
meillo@220 3536 precisely because the indistinquishability of human and script
meillo@220 3537 input is the main reason for the huge software leverage in Unix.
meillo@220 3538 If, however, the described desire addresses the user's view,
meillo@220 3539 then different technical solutions are more appropriate.
meillo@220 3540 The two cases can be regarded simply as two different MH setups.
meillo@220 3541 Hence, mapping the problem of different behavior between interactive and
meillo@220 3542 automated use on the concept of switching between different profiles,
meillo@220 3543 marks it already solved.
meillo@133 3544
meillo@133 3545
meillo@127 3546
meillo@121 3547 .H2 "Standard Libraries
meillo@22 3548 .P
meillo@121 3549 MH is one decade older than the POSIX and ANSI C standards.
meillo@121 3550 Hence, MH included own implementations of functions
meillo@220 3551 that were neither standardized nor widely available, back then.
meillo@220 3552 Today, twenty years after POSIX and ANSI C were published,
meillo@220 3553 developers can expect that systems comply with these standards.
meillo@121 3554 In consequence, MH-specific replacements for standard functions
meillo@121 3555 can and should be dropped.
meillo@220 3556 Kernighan and Pike advise: ``Use standard libraries''.
meillo@121 3557 .[ [
meillo@121 3558 kernighan pike practice of programming
meillo@121 3559 .], p. 196]
meillo@121 3560 Actually, MH had followed this advice in history,
meillo@220 3561 but it had not adjusted to more recent changes in this field.
meillo@121 3562 The
meillo@121 3563 .Fu snprintf()
meillo@121 3564 function, for instance, was standardized with C99 and is available
meillo@121 3565 almost everywhere because of its high usefulness.
meillo@220 3566 Thus, the project's own implementation of
meillo@121 3567 .Fu snprintf()
meillo@123 3568 was dropped in March 2012 in favor for using the one of the
meillo@220 3569 standard library
meillo@220 3570 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@123 3571 Such decisions limit the portability of mmh
meillo@173 3572 if systems do not support these standardized and widespread functions.
meillo@123 3573 This compromise is made because mmh focuses on the future.
meillo@121 3574 .P
meillo@232 3575 .ZZ
meillo@220 3576 As I am still in my twenties, have no programming experience from
meillo@220 3577 past decades.
meillo@220 3578 I have not followed the evolution of C through time.
meillo@220 3579 I have not suffered from the the Unix wars.
meillo@121 3580 I have not longed for standardization.
meillo@121 3581 All my programming experience is from a time when ANSI C and POSIX
meillo@121 3582 were well established already.
meillo@220 3583 Thus, I needed to learn about the history in retrospective.
meillo@121 3584 I have only read a lot of books about the (good) old times.
meillo@220 3585 This put me in a difficult position when working with old code.
meillo@123 3586 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123 3587 programming styles, whereas older programmers know these things by
meillo@123 3588 heart from their own experience.
meillo@123 3589 Being aware of the situation, I rather let people with more historic
meillo@220 3590 experience do the transition from ancient code constructs to
meillo@220 3591 standardized ones.
meillo@121 3592 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121 3593 He converted project-specific functions to POSIX replacements,
meillo@121 3594 also removing the conditionals compilation of now standardized features.
meillo@220 3595 Ken Hornstein and David Levine had their part in this work, as well.
meillo@220 3596 Often, I only pulled the changes over from nmh into mmh.
meillo@220 3597 These changes include many commits, among them:
meillo@121 3598 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121 3599 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102 3600 .P
meillo@220 3601 Nevertheless, I worked on the task as well, tidying up the
meillo@220 3602 \fIMH standard library\fP,
meillo@220 3603 .Fn libmh.a .
meillo@220 3604 It is located in the
meillo@123 3605 .Fn sbr
meillo@220 3606 (``subroutines'') directory in the source tree and
meillo@220 3607 includes functions that mmh tools usually need.
meillo@123 3608 Among them are MH-specific functions for profile, context, sequence,
meillo@123 3609 and folder handling, but as well
meillo@123 3610 MH-independent functions, such as auxiliary string functions,
meillo@123 3611 portability interfaces and error-checking wrappers for critical
meillo@123 3612 functions of the standard library.
meillo@220 3613 .BU
meillo@123 3614 I have replaced the
meillo@121 3615 .Fu atooi()
meillo@121 3616 function with calls to
meillo@220 3617 .Fu strtoul() ,
meillo@220 3618 setting the third parameter, the base, to eight.
meillo@123 3619 .Fu strtoul()
meillo@220 3620 is part of C89 and thus considered safe to use
meillo@220 3621 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74 .
meillo@220 3622 .BU
meillo@121 3623 I did remove project-included fallback implementations of
meillo@121 3624 .Fu memmove()
meillo@121 3625 and
meillo@220 3626 .Fu strerror()
meillo@220 3627 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215 ,
meillo@121 3628 although Peter Maydell had re-included them into nmh in 2008
meillo@121 3629 to support SunOS 4.
meillo@121 3630 Nevertheless, these functions are part of ANSI C.
meillo@121 3631 Systems that do not even provide full ANSI C support should not
meillo@121 3632 put a load on mmh.
meillo@220 3633 .BU
meillo@121 3634 The
meillo@121 3635 .Fu copy()
meillo@180 3636 function copies the string in parameter one to the location in
meillo@180 3637 parameter two.
meillo@121 3638 In contrast to
meillo@121 3639 .Fu strcpy() ,
meillo@121 3640 it returns a pointer to the terminating null-byte in the destination area.
meillo@123 3641 The code was adjusted to replace
meillo@121 3642 .Fu copy()
meillo@123 3643 with
meillo@121 3644 .Fu strcpy() ,
meillo@121 3645 except within
meillo@121 3646 .Fu concat() ,
meillo@121 3647 where
meillo@121 3648 .Fu copy()
meillo@123 3649 was more convenient.
meillo@123 3650 Therefore, the definition of
meillo@121 3651 .Fu copy()
meillo@123 3652 was moved into the source file of
meillo@121 3653 .Fu concat()
meillo@220 3654 and its visibility it limited to that
meillo@220 3655 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb .
meillo@220 3656 .BU
meillo@121 3657 The function
meillo@121 3658 .Fu r1bindex()
meillo@121 3659 had been a generalized version of
meillo@121 3660 .Fu basename()
meillo@121 3661 with minor differences.
meillo@121 3662 As all calls to
meillo@121 3663 .Fu r1bindex()
meillo@220 3664 had the slash (`\fL/\fP') as delimiter anyway,
meillo@121 3665 replacing
meillo@121 3666 .Fu r1bindex()
meillo@121 3667 with the more specific and better-named function
meillo@121 3668 .Fu basename()
meillo@121 3669 became desirable.
meillo@121 3670 Unfortunately, many of the 54 calls to
meillo@121 3671 .Fu r1bindex()
meillo@123 3672 depended on a special behavior,
meillo@121 3673 which differed from the POSIX specification for
meillo@121 3674 .Fu basename() .
meillo@121 3675 Hence,
meillo@121 3676 .Fu r1bindex()
meillo@121 3677 was kept but renamed to
meillo@123 3678 .Fu mhbasename() ,
meillo@220 3679 setting the delimiter to the slash
meillo@220 3680 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60 .
meillo@121 3681 For possible uses of
meillo@121 3682 .Fu r1bindex()
meillo@121 3683 with a different delimiter,
meillo@121 3684 the ANSI C function
meillo@121 3685 .Fu strrchr()
meillo@121 3686 provides the core functionality.
meillo@220 3687 .BU
meillo@232 3688 .ZZ
meillo@121 3689 The
meillo@121 3690 .Fu ssequal()
meillo@121 3691 function \(en apparently for ``substring equal'' \(en
meillo@121 3692 was renamed to
meillo@121 3693 .Fu isprefix() ,
meillo@220 3694 because this is what it actually checked
meillo@220 3695 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711.
meillo@220 3696 Its source file had included both of the following comments, no joke.
meillo@220 3697 .in -\n(PIu
meillo@121 3698 .VS
meillo@121 3699 /*
meillo@121 3700 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121 3701 * It is actually checking if s1 is a PREFIX of s2.
meillo@121 3702 * All calls to this function need to be checked to see
meillo@121 3703 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121 3704 * should be kept if it's sufficient.
meillo@121 3705 */
meillo@232 3706 sp .5
meillo@121 3707 /*
meillo@121 3708 * Check if s1 is a substring of s2.
meillo@121 3709 * If yes, then return 1, else return 0.
meillo@121 3710 */
meillo@121 3711 VE
meillo@220 3712 .in +\n(PIu
meillo@220 3713 Eventually, the function was completely replaced with calls to
meillo@220 3714 .Fu strncmp()
meillo@220 3715 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb .
meillo@121 3716
meillo@102 3717
meillo@102 3718
meillo@102 3719
meillo@133 3720
meillo@133 3721 .H2 "User Data Locations
meillo@133 3722 .P
meillo@133 3723 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133 3724 The profile is a file named
meillo@133 3725 .Fn \&.mh_profile
meillo@133 3726 in the user's home directory.
meillo@133 3727 It contains the static configuration.
meillo@133 3728 It also contains the location of the MH directory in the profile entry
meillo@133 3729 .Pe Path .
meillo@133 3730 The MH directory contains the mail storage and is the first
meillo@220 3731 place to search for form files, scan formats, and similar
meillo@133 3732 configuration files.
meillo@133 3733 The location of the MH directory can be chosen freely by the user.
meillo@220 3734 The usual name is a directory named
meillo@133 3735 .Fn Mail
meillo@220 3736 in the user's home directory.
meillo@133 3737 .P
meillo@200 3738 The way MH data is split between profile and MH directory is a legacy.
meillo@133 3739 It is only sensible in a situation where the profile is the only
meillo@133 3740 configuration file.
meillo@133 3741 Why else should the mail storage and the configuration files be intermixed?
meillo@220 3742 They are of different kind:
meillo@220 3743 One kind is the data to be operated on and the other kind is
meillo@220 3744 the configuration to change how tools operate.
meillo@133 3745 Splitting the configuration between the profile and the MH directory
meillo@220 3746 is inappropriate, as well.
meillo@220 3747 I improved the situation by breaking compatibility.
meillo@133 3748 .P
meillo@220 3749 In mmh, personal data is grouped by type.
meillo@220 3750 This results in two distinct parts:
meillo@171 3751 the mail storage and the configuration.
meillo@220 3752 The mail storage directory still contains all the messages,
meillo@133 3753 but, in exception of public sequences files, nothing else.
meillo@133 3754 In difference to nmh, the auxiliary configuration files are no longer
meillo@133 3755 located there.
meillo@133 3756 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@220 3757 but the user's \fImail storage\fP.
meillo@133 3758 Its location is still user-chosen, with the default name
meillo@220 3759 .Fn Mail
meillo@133 3760 in the user's home directory.
meillo@220 3761 The configuration is grouped together in the hidden directory
meillo@133 3762 .Fn \&.mmh
meillo@133 3763 in the user's home directory.
meillo@133 3764 This \fImmh directory\fP contains the context file, personal forms,
meillo@133 3765 scan formats, and the like, but also the user's profile, now named
meillo@133 3766 .Fn profile .
meillo@220 3767 The path to the profile is no longer
meillo@133 3768 .Fn $HOME/.mh_profile
meillo@220 3769 but
meillo@133 3770 .Fn $HOME/.mmh/profile .
meillo@220 3771 (The alternative of having file
meillo@133 3772 .Fn $HOME/.mh_profile
meillo@220 3773 and a configuration directory
meillo@133 3774 .Fn $HOME/.mmh
meillo@220 3775 appeared to be inconsistent.)
meillo@220 3776 .P
meillo@133 3777 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133 3778 Unix users.
meillo@220 3779 The main achievement of the change is the clear and sensible separation
meillo@220 3780 of the mail storage and the configuration.
meillo@168 3781 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3782 .P
meillo@220 3783 As MH allows users to have multiple MH setups,
meillo@220 3784 it is necessary to switch the profile.
meillo@133 3785 The profile is the single entry point to access the rest of a
meillo@133 3786 personal MH setup.
meillo@133 3787 In nmh, the environment variable
meillo@133 3788 .Ev MH
meillo@220 3789 is used to specify a different profile.
meillo@220 3790 To operate in the same MH setup with a separate context, the
meillo@133 3791 .Ev MHCONTEXT
meillo@220 3792 environment variable is used.
meillo@220 3793 This allows having a separate current folder in each terminal at
meillo@220 3794 the same time, for instance.
meillo@220 3795 In mmh, three environment variables replace the two of nmh.
meillo@133 3796 .Ev MMH
meillo@133 3797 overrides the default location of the mmh directory (\c
meillo@133 3798 .Fn .mmh ).
meillo@133 3799 .Ev MMHP
meillo@133 3800 and
meillo@133 3801 .Ev MMHC
meillo@220 3802 override the paths to the profile and context file, respectively.
meillo@133 3803 This approach allows the set of personal configuration files to be chosen
meillo@220 3804 independently of the profile, context, and mail storage.
meillo@133 3805 The new approach has no functional disadvantages,
meillo@133 3806 as every setup I can imagine can be implemented with both approaches,
meillo@220 3807 possibly even easier with the new one.
meillo@220 3808 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3809
meillo@133 3810
meillo@133 3811
meillo@133 3812
meillo@133 3813
meillo@118 3814 .H2 "Modularization
meillo@220 3815 .Id modularization
meillo@118 3816 .P
meillo@123 3817 The source code of the mmh tools is located in the
meillo@122 3818 .Fn uip
meillo@123 3819 (``user interface programs'') directory.
meillo@180 3820 Each tool has a source file with the name of the command.
meillo@122 3821 For example,
meillo@122 3822 .Pn rmm
meillo@122 3823 is built from
meillo@122 3824 .Fn uip/rmm.c .
meillo@123 3825 Some source files are used for multiple programs.
meillo@122 3826 For example
meillo@122 3827 .Fn uip/scansbr.c
meillo@173 3828 is used for both
meillo@122 3829 .Pn scan
meillo@122 3830 and
meillo@122 3831 .Pn inc .
meillo@122 3832 In nmh, 49 tools were built from 76 source files.
meillo@123 3833 This is a ratio of 1.6 source files per program.
meillo@123 3834 32 programs depended on multiple source files;
meillo@123 3835 17 programs depended on one source file only.
meillo@122 3836 In mmh, 39 tools are built from 51 source files.
meillo@123 3837 This is a ratio of 1.3 source files per program.
meillo@123 3838 18 programs depend on multiple source files;
meillo@123 3839 21 programs depend on one source file only.
meillo@123 3840 (These numbers and the ones in the following text ignore the MH library
meillo@123 3841 as well as shell scripts and multiple names for the same program.)
meillo@122 3842 .P
meillo@123 3843 Splitting the source code of a large program into multiple files can
meillo@220 3844 increase the readability of its source code,
meillo@220 3845 but most of the mmh tools are small and straight-forward programs.
meillo@220 3846 In exception of the MIME handling tools (i.e.
meillo@122 3847 .Pn mhbuild ,
meillo@122 3848 .Pn mhstore ,
meillo@122 3849 .Pn show ,
meillo@220 3850 etc.),
meillo@220 3851 .Pn pick
meillo@220 3852 is the only tool with more than one thousand lines of source code.
meillo@220 3853 Splitting programs with less than one thousand lines of code into
meillo@220 3854 multiple source files leads seldom to better readability.
meillo@220 3855 For such tools, splitting still makes sense
meillo@220 3856 when parts of the code are reused in other programs
meillo@179 3857 and the reused code fragment is (1) not general enough
meillo@179 3858 for including it in the MH library
meillo@179 3859 or (2) has dependencies on a library that only few programs need.
meillo@122 3860 .Fn uip/packsbr.c ,
meillo@122 3861 for instance, provides the core program logic for the
meillo@122 3862 .Pn packf
meillo@122 3863 and
meillo@122 3864 .Pn rcvpack
meillo@122 3865 programs.
meillo@122 3866 .Fn uip/packf.c
meillo@122 3867 and
meillo@122 3868 .Fn uip/rcvpack.c
meillo@122 3869 mainly wrap the core function appropriately.
meillo@122 3870 No other tools use the folder packing functions.
meillo@123 3871 As another example,
meillo@123 3872 .Fn uip/termsbr.c
meillo@220 3873 accesses terminal properties, which requires linking with the
meillo@220 3874 \fItermcap\fP or a \fIcurses\fP library.
meillo@220 3875 If
meillo@123 3876 .Fn uip/termsbr.c
meillo@220 3877 is included in the MH library, then every program needs to be linked
meillo@220 3878 with termcap or curses, although only few of the programs use
meillo@220 3879 the library.
meillo@122 3880 .P
meillo@122 3881 The task of MIME handling is complex enough that splitting its code
meillo@122 3882 into multiple source files improves the readability.
meillo@122 3883 The program
meillo@122 3884 .Pn mhstore ,
meillo@122 3885 for instance, is compiled out of seven source files with 2\|500
meillo@122 3886 lines of code in summary.
meillo@122 3887 The main code file
meillo@122 3888 .Fn uip/mhstore.c
meillo@220 3889 consists of 800 lines; the other 1\|700 lines are code reused in
meillo@123 3890 other MIME handling tools.
meillo@123 3891 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123 3892 a MH-MIME library, as a companion to the MH standard library.
meillo@220 3893 This is left to be done.
meillo@122 3894 .P
meillo@169 3895 The work already accomplished focussed on the non-MIME tools.
meillo@122 3896 The amount of code compiled into each program was reduced.
meillo@123 3897 This eases the understanding of the code base.
meillo@122 3898 In nmh,
meillo@122 3899 .Pn comp
meillo@122 3900 was built from six source files:
meillo@122 3901 .Fn comp.c ,
meillo@122 3902 .Fn whatnowproc.c ,
meillo@122 3903 .Fn whatnowsbr.c ,
meillo@122 3904 .Fn sendsbr.c ,
meillo@122 3905 .Fn annosbr.c ,
meillo@122 3906 and
meillo@122 3907 .Fn distsbr.c .
meillo@122 3908 In mmh, it builds from only two:
meillo@122 3909 .Fn comp.c
meillo@122 3910 and
meillo@122 3911 .Fn whatnowproc.c .
meillo@123 3912 In nmh's
meillo@123 3913 .Pn comp ,
meillo@123 3914 the core function of
meillo@122 3915 .Pn whatnow ,
meillo@122 3916 .Pn send ,
meillo@122 3917 and
meillo@122 3918 .Pn anno
meillo@220 3919 were all compiled into
meillo@122 3920 .Pn comp .
meillo@123 3921 This saved the need to execute these programs with
meillo@220 3922 the expensive system calls
meillo@122 3923 .Fu fork()
meillo@122 3924 and
meillo@220 3925 .Fu exec() .
meillo@171 3926 Whereas this approach improved the time performance,
meillo@171 3927 it interwove the source code.
meillo@122 3928 Core functionalities were not encapsulated into programs but into
meillo@122 3929 function, which were then wrapped by programs.
meillo@122 3930 For example,
meillo@122 3931 .Fn uip/annosbr.c
meillo@122 3932 included the function
meillo@122 3933 .Fu annotate() .
meillo@122 3934 Each program that wanted to annotate messages, included the source file
meillo@123 3935 .Fn uip/annosbr.c
meillo@123 3936 and called
meillo@123 3937 .Fu annotate() .
meillo@123 3938 Because the function
meillo@123 3939 .Fu annotate()
meillo@123 3940 was used like the tool
meillo@123 3941 .Pn anno ,
meillo@123 3942 it had seven parameters, reflecting the command line switches of the tool.
meillo@122 3943 When another pair of command line switches was added to
meillo@122 3944 .Pn anno ,
meillo@122 3945 a rather ugly hack was implemented to avoid adding another parameter
meillo@220 3946 to the function
meillo@220 3947 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f .
meillo@122 3948 .P
meillo@122 3949 In mmh, the relevant code of
meillo@122 3950 .Pn comp
meillo@122 3951 comprises the two files
meillo@122 3952 .Fn uip/comp.c
meillo@122 3953 and
meillo@122 3954 .Fn uip/whatnowproc.c ,
meillo@220 3955 together 210 lines of code,
meillo@220 3956 whereas in nmh,
meillo@122 3957 .Pn comp
meillo@122 3958 comprises six files with 2\|450 lines.
meillo@220 3959 Not all of the code in these six files is actually used by
meillo@122 3960 .Pn comp ,
meillo@220 3961 but the reader needed to read it all to know which parts are relevant.
meillo@220 3962 Understanding nmh's
meillo@122 3963 .Pn comp ,
meillo@123 3964 required understanding the inner workings of
meillo@122 3965 .Fn uip/annosbr.c
meillo@122 3966 first.
meillo@123 3967 To be sure to fully understand a program, its whole source code needs
meillo@122 3968 to be examined.
meillo@123 3969 Not doing so is a leap of faith, assuming that the developers
meillo@122 3970 have avoided obscure programming techniques.
meillo@220 3971 Here, it should be recalled that information passed in obscure ways
meillo@220 3972 through the program's source base, due to the aforementioned hack
meillo@220 3973 to save an additional parameter in nmh's
meillo@220 3974 .Pn anno .
meillo@220 3975 .P
meillo@220 3976 In mmh, understanding
meillo@220 3977 .Pn comp
meillo@220 3978 requires to read only 210 lines of code to read, whereas the amount
meillo@220 3979 is ten times more for nmh's
meillo@220 3980 .Pn comp .
meillo@220 3981 .P
meillo@220 3982 By separating the tools on the program-level,
meillo@220 3983 the boundaries are clearly visible, as the interfaces are calls to
meillo@122 3984 .Fu exec()
meillo@122 3985 rather than arbitrary function calls.
meillo@220 3986 Additionally, this kind of separation is more strict because
meillo@220 3987 it is technically enforced by the operating system;
meillo@220 3988 it can not be simply bypassed with global variables.
meillo@220 3989 Good separation simplifies the understanding of program code
meillo@220 3990 because the area influenced by any particular statement is small.
meillo@220 3991 As I have read a lot in nmh's code base during the last two years,
meillo@220 3992 I have learned about the easy and the difficult parts.
meillo@220 3993 In my observation, the understanding of code is enormously eased
meillo@220 3994 if the influenced area is small and clearly bounded.
meillo@123 3995 .P
meillo@220 3996 Yet, the real problem is another:
meillo@123 3997 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123 3998 Understanding
meillo@122 3999 .Pn comp
meillo@123 4000 requires understanding
meillo@123 4001 .Fn uip/annosbr.c
meillo@123 4002 and
meillo@123 4003 .Fn uip/sendsbr.c
meillo@123 4004 because
meillo@123 4005 .Pn comp
meillo@220 4006 annotates and sends messages.
meillo@220 4007 In nmh, there surely exist the tools
meillo@220 4008 .Pn anno
meillo@220 4009 and
meillo@122 4010 .Pn send ,
meillo@220 4011 which cover these jobs,
meillo@220 4012 but
meillo@122 4013 .Pn comp
meillo@123 4014 and
meillo@122 4015 .Pn repl
meillo@122 4016 and
meillo@122 4017 .Pn forw
meillo@122 4018 and
meillo@122 4019 .Pn dist
meillo@122 4020 and
meillo@122 4021 .Pn whatnow
meillo@122 4022 and
meillo@220 4023 .Pn viamail
meillo@220 4024 \(en they all (!) \(en
meillo@220 4025 have the same annotating and sending functions included, once more.
meillo@220 4026 As a result,
meillo@123 4027 .Pn comp
meillo@123 4028 sends messages without using
meillo@123 4029 .Pn send .
meillo@123 4030 The situation is the same as if
meillo@123 4031 .Pn grep
meillo@220 4032 would page its output without using
meillo@123 4033 .Pn more
meillo@123 4034 just because both programs are part of the same code base.
meillo@123 4035 .P
meillo@220 4036 The clear separation on the surface of nmh
meillo@220 4037 \(en the tool chest approach \(en
meillo@123 4038 is violated on the level below.
meillo@122 4039 This violation is for the sake of time performance.
meillo@220 4040 Decades ago, sacrificing readability and conceptional beauty
meillo@220 4041 for speed might have been necessary to prevent MH from being
meillo@220 4042 unusably slow, but today this is not the case anymore.
meillo@220 4043 No longer should speed improvements that became unnecessary be kept.
meillo@220 4044 No longer should readability or conceptional beauty be sacrificed.
meillo@220 4045 No longer should the Unix philosophy's ``one tool, one job''
meillo@220 4046 guideline be violated.
meillo@123 4047 Therefore, mmh's
meillo@123 4048 .Pn comp
meillo@220 4049 no longer sends messages.
meillo@220 4050 .P
meillo@123 4051 In mmh, different jobs are divided among separate programs that
meillo@122 4052 invoke each other as needed.
meillo@123 4053 In consequence,
meillo@123 4054 .Pn comp
meillo@123 4055 invokes
meillo@123 4056 .Pn whatnow
meillo@123 4057 which thereafter invokes
meillo@220 4058 .Pn send
meillo@168 4059 .Ci 3df5ab3c116e6d4a2fb4bb5cc9dfc5f781825815
meillo@220 4060 .Ci c73c00bfccd22ec77e9593f47462aeca4a8cd9c0 .
meillo@123 4061 The clear separation on the surface is maintained on the level below.
meillo@220 4062 Human users and other tools use the same interface \(en
meillo@123 4063 annotations, for example, are made by invoking
meillo@123 4064 .Pn anno ,
meillo@220 4065 no matter if requested by programs or by human beings
meillo@168 4066 .Ci 469a4163c2a1a43731d412eaa5d9cae7d670c48b
meillo@168 4067 .Ci aed384169af5204b8002d06e7a22f89197963d2d
meillo@220 4068 .Ci 3caf9e298a8861729ca8b8a84f57022b6f3ea742 .
meillo@232 4069 .P
meillo@232 4070 .ZZ -1
meillo@123 4071 The decrease of tools built from multiple source files and thus
meillo@123 4072 the decrease of
meillo@123 4073 .Fn uip/*sbr.c
meillo@220 4074 files confirm the improvement
meillo@168 4075 .Ci 9e6d91313f01c96b4058d6bf419a8ca9a207bc33
meillo@168 4076 .ci 81744a46ac9f845d6c2b9908074d269275178d2e
meillo@168 4077 .Ci f0f858069d21111f0dbea510044593f89c9b0829
meillo@168 4078 .Ci 0503a6e9be34f24858b55b555a5c948182b9f24b
meillo@168 4079 .Ci 27826f9353e0f0b04590b7d0f8f83e60462b90f0
meillo@168 4080 .Ci d1da1f94ce62160aebb30df4063ccbc53768656b
meillo@220 4081 .Ci c42222869e318fff5dec395eca3e776db3075455 .
meillo@220 4082 This is also visible in the complexity of the build dependency graphs:
meillo@145 4083
meillo@220 4084 .sp
meillo@220 4085 Nmh:
meillo@220 4086 .BP input/deps-nmh.eps .5i
meillo@220 4087 .EP
meillo@220 4088 .sp
meillo@220 4089 Mmh:
meillo@220 4090 .BP input/deps-mmh.eps .8i
meillo@220 4091 .EP
meillo@145 4092
meillo@226 4093 The figures display all program to source file relationships where
meillo@226 4094 programs (ellipses) are built from multiple source files (rectangles).
meillo@220 4095 The primary source file of each program is omited from the graph.