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Added system for references within the document. Macros: .Id and .Cf. ``.Id foo'' places a marker at that place. ``.Cf foo'' puts the section number of the marked place there. ``.Cf foo.page'' puts the page number of the marked place there.
author markus schnalke <meillo@marmaro.de>
date Fri, 06 Jul 2012 14:59:08 +0200
parents b7b81ae9c9d8
children 63e885fb48ba
rev   line source
meillo@58 1 .H0 "Discussion
meillo@0 2 .P
meillo@58 3 This main chapter discusses the practical work done in the mmh project.
meillo@104 4 It is structured along the goals to achieve.
meillo@104 5 The concrete work done
meillo@58 6 is described in the examples of how the general goals were achieved.
meillo@87 7 The discussion compares the current version of mmh with the state of
meillo@87 8 nmh just before the mmh project started, i.e. Fall 2011.
meillo@87 9 Current changes of nmh will be mentioned only as side notes.
meillo@87 10 .\" XXX where do I discuss the parallel development of nmh?
meillo@58 11
meillo@58 12
meillo@58 13
meillo@133 14 .\" --------------------------------------------------------------
meillo@125 15 .H1 "Streamlining
meillo@58 16
meillo@0 17 .P
meillo@58 18 MH had been considered an all-in-one system for mail handling.
meillo@58 19 The community around nmh has a similar understanding.
meillo@87 20 In fundamental difference, mmh shall be a MUA only.
meillo@87 21 I believe that the development of all-in-one mail systems is obsolete.
meillo@87 22 Today, email is too complex to be fully covered by single projects.
meillo@87 23 Such a project won't be able to excel in all aspects.
meillo@87 24 Instead, the aspects of email should be covered my multiple projects,
meillo@87 25 which then can be combined to form a complete system.
meillo@87 26 Excellent implementations for the various aspects of email exist already.
meillo@87 27 Just to name three examples: Postfix is a specialized MTA,
meillo@87 28 Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89 29 I believe that it is best to use such specialized tools instead of
meillo@87 30 providing the same function again as a side-component in the project.
meillo@58 31 .P
meillo@87 32 Doing something well, requires to focus on a small set of specific aspects.
meillo@87 33 Under the assumption that focused development produces better results
meillo@100 34 in the particular area, specialized projects will be superior
meillo@87 35 in their field of focus.
meillo@87 36 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87 37 or modular \(en will never be the best choice in any of the fields.
meillo@87 38 Even in providing the best consistent all-in-one system they are likely
meillo@87 39 to be beaten by projects that focus only on integrating existing mail
meillo@89 40 components to a homogeneous system.
meillo@87 41 .P
meillo@87 42 The limiting resource in Free Software community development
meillo@87 43 is usually man power.
meillo@87 44 If the development power is spread over a large development area,
meillo@87 45 it becomes even more difficult to compete with the specialists in the
meillo@87 46 various fields.
meillo@87 47 The concrete situation for MH-based mail systems is even tougher,
meillo@87 48 given the small and aged community, including both developers and users,
meillo@87 49 it has.
meillo@87 50 .P
meillo@87 51 In consequence, I believe that the available development resources
meillo@100 52 should focus on the point where MH is most unique.
meillo@87 53 This is clearly the user interface \(en the MUA.
meillo@125 54 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60 55
meillo@60 56
meillo@100 57 .H2 "Mail Transfer Facilities
meillo@60 58 .P
meillo@60 59 In contrast to nmh, which also provides mail submission and mail retrieval
meillo@87 60 agents, mmh is a MUA only.
meillo@100 61 This general difference initiated the development of mmh.
meillo@66 62 Removing the mail transfer facilities had been the first work task
meillo@76 63 in the mmh project.
meillo@60 64 .P
meillo@105 65 Focusing on one mail agent role only is motivated by Eric Allman's
meillo@105 66 experience with Sendmail.
meillo@105 67 He identified limiting Sendmail the MTA task had be one reason for
meillo@105 68 its success:
meillo@105 69 .[ [
meillo@105 70 costales sendmail
meillo@105 71 .], p. xviii]
meillo@105 72 .QS
meillo@105 73 Second, I limited myself to the routing function \(en
meillo@110 74 I wouldn't write user agents or delivery back-ends.
meillo@105 75 This was a departure of the dominant through of the time,
meillo@105 76 in which routing logic, local delivery, and often the network code
meillo@105 77 were incorporated directly into the user agents.
meillo@105 78 .QE
meillo@105 79 .P
meillo@105 80 In mmh, the Mail Submission Agent (MSA) is called
meillo@105 81 \fIMessage Transfer Service\fP (MTS).
meillo@105 82 This facility, implemented by the
meillo@105 83 .Pn post
meillo@105 84 command, established network connections and spoke SMTP to submit
meillo@60 85 messages for relay to the outside world.
meillo@105 86 The changes in email demanded changes in this part of nmh too.
meillo@89 87 Encryption and authentication for network connections
meillo@87 88 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87 89 This added complexity to nmh without improving it in its core functions.
meillo@87 90 Also, keeping up with recent developments in the field of
meillo@87 91 mail transfer requires development power and specialists.
meillo@87 92 In mmh this whole facility was simply cut off.
meillo@76 93 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76 94 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76 95 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87 96 Instead, mmh depends on an external MSA.
meillo@60 97 The only outgoing interface available to mmh is the
meillo@60 98 .Pn sendmail
meillo@87 99 command, which almost any MSA provides.
meillo@87 100 If not, a wrapper program can be written.
meillo@87 101 It must read the message from the standard input, extract the
meillo@87 102 recipient addresses from the message header, and hand the message
meillo@87 103 over to the MSA.
meillo@87 104 For example, a wrapper script for qmail would be:
meillo@87 105 .VS
meillo@87 106 #!/bin/sh
meillo@138 107 exec qmail-inject # ignore command line arguments
meillo@87 108 VE
meillo@87 109 The requirement to parse the recipient addresses out of the message header
meillo@87 110 is likely to be removed in the future.
meillo@87 111 Then mmh would give the recipient addresses as command line arguments.
meillo@100 112 This appears to be the better interface.
meillo@87 113 .\" XXX implement it
meillo@60 114 .P
meillo@60 115 To retrieve mail, the
meillo@60 116 .Pn inc
meillo@100 117 command acted as Mail Retrieval Agent (MRA).
meillo@100 118 It established network connections
meillo@76 119 and spoke POP3 to retrieve mail from remote servers.
meillo@76 120 As with mail submission, the network connections required encryption and
meillo@87 121 authentication, thus TLS and SASL were added.
meillo@87 122 Support for message retrieval through IMAP will become necessary
meillo@100 123 to be added soon, too, and likewise for any other changes in mail transfer.
meillo@100 124 Not so for mmh because it has dropped the support for retrieving mail
meillo@100 125 from remote locations.
meillo@76 126 .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76 127 Instead, it depends on an external tool to cover this task.
meillo@100 128 In mmh exist two paths for messages to enter mmh's mail storage:
meillo@100 129 (1) Mail can be incorporated with
meillo@60 130 .Pn inc
meillo@87 131 from the system maildrop, or (2) with
meillo@60 132 .Pn rcvstore
meillo@87 133 by reading them, one at a time, from the standard input.
meillo@60 134 .P
meillo@60 135 With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@87 136 mail system to being a MUA only.
meillo@60 137 Now, of course, mmh depends on third-party software.
meillo@87 138 An external MSA is required to transfer mail to the outside world;
meillo@60 139 an external MRA is required to retrieve mail from remote machines.
meillo@60 140 There exist excellent implementations of such software,
meillo@76 141 which do this specific task likely better than the internal
meillo@87 142 versions had done it.
meillo@87 143 Also, the best suiting programs can be freely chosen.
meillo@60 144 .P
meillo@60 145 As it had already been possible to use an external MSA or MRA,
meillo@60 146 why not keep the internal version for convenience?
meillo@76 147 The question whether there is sense in having a fall-back pager in all
meillo@76 148 the command line tools, for the cases when
meillo@60 149 .Pn more
meillo@60 150 or
meillo@60 151 .Pn less
meillo@76 152 aren't available, appears to be ridiculous.
meillo@100 153 Of course, MSAs and MRAs are more complex than text pagers
meillo@87 154 and not necessarily available but still the concept of orthogonal
meillo@87 155 design holds: ``Write programs that do one thing and do it well.''
meillo@87 156 .[
meillo@87 157 mcilroy unix phil
meillo@87 158 p. 53
meillo@87 159 .]
meillo@87 160 .[
meillo@87 161 mcilroy bstj foreword
meillo@87 162 .]
meillo@87 163 Here, this part of the Unix philosophy was applied not only
meillo@87 164 to the programs but to the project itself.
meillo@87 165 In other words:
meillo@87 166 ``Develop projects that focus on one thing and do it well.''
meillo@87 167 Projects grown complex should be split for the same reasons programs grown
meillo@87 168 complex should be split.
meillo@100 169 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87 170 separate projects then they should be separated.
meillo@87 171 This is the case here, in my opinion.
meillo@87 172 The RFCs propose this separation by clearly distinguishing the different
meillo@87 173 mail handling tasks.
meillo@87 174 .[
meillo@87 175 rfc 821
meillo@87 176 .]
meillo@87 177 The small interfaces between the mail agents support the separation.
meillo@76 178 .P
meillo@87 179 In the beginning, email had been small and simple.
meillo@100 180 At that time,
meillo@60 181 .Pn /bin/mail
meillo@100 182 had covered anything there was to email and still had been small
meillo@100 183 and simple.
meillo@100 184 Later, the essential complexity of email increased.
meillo@87 185 (Essential complexity is the complexity defined by the problem itself.\0
meillo@87 186 .[[
meillo@87 187 brooks no silver bullet
meillo@87 188 .]])
meillo@87 189 Email systems reacted to this change: They grew.
meillo@100 190 RFCs started to introduce the concept of mail agents to separate the
meillo@100 191 various tasks because they became more extensive and new tasks appeared.
meillo@100 192 As the mail systems grew even more, parts were split off.
meillo@100 193 In nmh, for instance, the POP server, which was included in the original
meillo@100 194 MH, was removed.
meillo@100 195 Now is the time to go one step further and split the MSA and MRA off, too.
meillo@87 196 Not only does this decrease the code size of the project,
meillo@87 197 but, more important, it unburdens mmh of the whole field of
meillo@87 198 message transfer with all its implications for the project.
meillo@100 199 There is no more need to concern with changes in network transfer.
meillo@76 200 This independence is received by depending on an external program
meillo@76 201 that covers the field.
meillo@76 202 Today, this is a reasonable exchange.
meillo@60 203 .P
meillo@100 204 Functionality can be added in three different ways:
meillo@87 205 .BU
meillo@87 206 Implementing the function originally in the project.
meillo@87 207 .BU
meillo@87 208 Depending on a library that provides the function.
meillo@87 209 .BU
meillo@87 210 Depending on a program that provides the function.
meillo@87 211 .P
meillo@87 212 Whereas adding the function originally to the project increases the
meillo@76 213 code size most and requires most maintenance and development work,
meillo@87 214 it makes the project most independent of other software.
meillo@87 215 Using libraries or external programs require less maintenance work
meillo@87 216 but introduces dependencies on external software.
meillo@87 217 Programs have the smallest interfaces and provide the best separation
meillo@87 218 but possibly limit the information exchange.
meillo@87 219 External libraries are stronger connected than external programs,
meillo@87 220 thus information can be exchanged more flexible.
meillo@87 221 Adding code to a project increases maintenance work.
meillo@87 222 .\" XXX ref
meillo@100 223 Implementing complex functions originally in the project adds
meillo@87 224 a lot of code.
meillo@87 225 This should be avoided if possible.
meillo@66 226 Hence, the dependencies only change in kind, not in their existence.
meillo@66 227 In mmh, library dependencies on
meillo@66 228 .Pn libsasl2
meillo@66 229 and
meillo@66 230 .Pn libcrypto /\c
meillo@66 231 .Pn libssl
meillo@66 232 were treated against program dependencies on an MSA and an MRA.
meillo@87 233 This also meant treating build-time dependencies against run-time
meillo@87 234 dependencies.
meillo@66 235 Besides program dependencies providing the stronger separation
meillo@66 236 and being more flexible, they also allowed
meillo@66 237 over 6\|000 lines of code to be removed from mmh.
meillo@66 238 This made mmh's code base about 12\|% smaller.
meillo@87 239 Reducing the project's code size by such an amount without actually
meillo@87 240 losing functionality is a convincing argument.
meillo@87 241 Actually, as external MSAs and MRAs are likely superior to the
meillo@87 242 project's internal versions, the common user even gains functionality.
meillo@66 243 .P
meillo@76 244 Users of MH should not have problems to set up an external MSA and MRA.
meillo@60 245 Also, the popular MSAs and MRAs have large communities and a lot
meillo@60 246 of documentation available.
meillo@87 247 Choices for MSAs range from full-featured MTAs like
meillo@60 248 .I Postfix
meillo@87 249 over mid-size MTAs like
meillo@60 250 .I masqmail
meillo@60 251 and
meillo@60 252 .I dma
meillo@60 253 to small forwarders like
meillo@60 254 .I ssmtp
meillo@60 255 and
meillo@60 256 .I nullmailer .
meillo@60 257 Choices for MRAs include
meillo@60 258 .I fetchmail ,
meillo@60 259 .I getmail ,
meillo@60 260 .I mpop
meillo@60 261 and
meillo@60 262 .I fdm .
meillo@60 263
meillo@60 264
meillo@100 265 .H2 "Non-MUA Tools
meillo@60 266 .P
meillo@87 267 One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@89 268 Further more, any tools that don't improve the MUA's job significantly
meillo@87 269 should be removed.
meillo@87 270 Loosely related and rarely used tools distract from the lean appearance.
meillo@87 271 They require maintenance work without adding much to the core task.
meillo@125 272 By removing these tools, the project shall become more streamlined
meillo@87 273 and focused.
meillo@76 274 In mmh the following tools are not available anymore:
meillo@62 275 .BU
meillo@58 276 .Pn conflict
meillo@87 277 was removed
meillo@76 278 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87 279 because it is a mail system maintenance tool that is not MUA-related.
meillo@87 280 It even checked
meillo@58 281 .Fn /etc/passwd
meillo@58 282 and
meillo@58 283 .Fn /etc/group
meillo@87 284 for consistency, which is completely unrelated to email.
meillo@87 285 A tool like
meillo@87 286 .Pn conflict
meillo@87 287 is surely useful, but it should not be shipped with mmh.
meillo@76 288 .\" XXX historic reasons?
meillo@62 289 .BU
meillo@58 290 .Pn rcvtty
meillo@87 291 was removed
meillo@87 292 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89 293 because its use case of writing to the user's terminal
meillo@76 294 on receiving of mail is obsolete.
meillo@87 295 If users like to be informed of new mail, the shell's
meillo@58 296 .Ev MAILPATH
meillo@87 297 variable or graphical notifications are technically more appealing.
meillo@100 298 Writing directly to terminals is hardly ever wanted today.
meillo@62 299 If though one wants to have it this way, the standard tool
meillo@58 300 .Pn write
meillo@58 301 can be used in a way similar to:
meillo@82 302 .VS
meillo@58 303 scan -file - | write `id -un`
meillo@82 304 VE
meillo@62 305 .BU
meillo@58 306 .Pn viamail
meillo@87 307 was removed
meillo@87 308 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87 309 when the new attachment system was activated, because
meillo@58 310 .Pn forw
meillo@76 311 could then cover the task itself.
meillo@62 312 The program
meillo@58 313 .Pn sendfiles
meillo@62 314 was rewritten as a shell script wrapper around
meillo@58 315 .Pn forw .
meillo@76 316 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62 317 .BU
meillo@58 318 .Pn msgchk
meillo@87 319 was removed
meillo@87 320 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87 321 because it lost its use case when POP support was removed.
meillo@76 322 A call to
meillo@58 323 .Pn msgchk
meillo@87 324 provided hardly more information than:
meillo@82 325 .VS
meillo@58 326 ls -l /var/mail/meillo
meillo@82 327 VE
meillo@100 328 It did distinguish between old and new mail, but
meillo@100 329 this detail information can be retrieved with
meillo@76 330 .Pn stat (1),
meillo@62 331 too.
meillo@100 332 A small shell script could be written to print the information
meillo@76 333 in a similar way, if truly necessary.
meillo@76 334 As mmh's
meillo@76 335 .Pn inc
meillo@87 336 only incorporates mail from the user's local maildrop,
meillo@62 337 and thus no data transfers over slow networks are involved,
meillo@76 338 there's hardly any need to check for new mail before incorporating it.
meillo@62 339 .BU
meillo@58 340 .Pn msh
meillo@87 341 was removed
meillo@76 342 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87 343 because the tool was in conflict with the philosophy of MH.
meillo@76 344 It provided an interactive shell to access the features of MH,
meillo@76 345 but it wasn't just a shell, tailored to the needs of mail handling.
meillo@76 346 Instead it was one large program that had several MH tools built in.
meillo@76 347 This conflicts with the major feature of MH of being a tool chest.
meillo@76 348 .Pn msh 's
meillo@76 349 main use case had been accessing Bulletin Boards, which have seized to
meillo@62 350 be popular.
meillo@62 351 .P
meillo@62 352 Removing
meillo@58 353 .Pn msh ,
meillo@76 354 together with the truly archaic code relicts
meillo@58 355 .Pn vmh
meillo@58 356 and
meillo@58 357 .Pn wmh ,
meillo@62 358 saved more than 7\|000 lines of C code \(en
meillo@66 359 about 15\|% of the project's original source code amount.
meillo@100 360 Having less code \(en with equal readability, of course \(en
meillo@76 361 for the same functionality is an advantage.
meillo@63 362 Less code means less bugs and less maintenance work.
meillo@76 363 As
meillo@63 364 .Pn rcvtty
meillo@63 365 and
meillo@63 366 .Pn msgchk
meillo@87 367 are assumed to be rarely used and can be implemented in different ways,
meillo@87 368 why should one keep them?
meillo@125 369 Removing them streamlines mmh.
meillo@63 370 .Pn viamail 's
meillo@63 371 use case is now partly obsolete and partly covered by
meillo@63 372 .Pn forw ,
meillo@76 373 hence there's no reason to still maintain it.
meillo@63 374 .Pn conflict
meillo@76 375 is not related to the mail client, and
meillo@63 376 .Pn msh
meillo@63 377 conflicts with the basic concept of MH.
meillo@76 378 Theses two tools might still be useful, but they should not be part of mmh.
meillo@63 379 .P
meillo@76 380 Finally, there's
meillo@76 381 .Pn slocal .
meillo@76 382 .Pn slocal
meillo@76 383 is an MDA and thus not directly MUA-related.
meillo@100 384 It should be removed from mmh, because including it conflicts with
meillo@100 385 the idea that mmh is a MUA only.
meillo@100 386 .Pn slocal
meillo@100 387 should rather become a separate project.
meillo@87 388 However,
meillo@76 389 .Pn slocal
meillo@76 390 provides rule-based processing of messages, like filing them into
meillo@76 391 different folders, which is otherwise not available in mmh.
meillo@87 392 Although
meillo@76 393 .Pn slocal
meillo@87 394 does neither pull in dependencies nor does it include a separate
meillo@100 395 technical area (cf. Sec. XXX), still,
meillo@100 396 it accounts for about 1\|000 lines of code that need to be maintained.
meillo@76 397 As
meillo@76 398 .Pn slocal
meillo@76 399 is almost self-standing, it should be split off into a separate project.
meillo@76 400 This would cut the strong connection between the MUA mmh and the MDA
meillo@76 401 .Pn slocal .
meillo@87 402 For anyone not using MH,
meillo@87 403 .Pn slocal
meillo@87 404 would become yet another independent MDA, like
meillo@87 405 .I procmail .
meillo@100 406 Then
meillo@87 407 .Pn slocal
meillo@100 408 could be installed without the complete MH system.
meillo@76 409 Likewise, mmh users could decide to use
meillo@76 410 .I procmail
meillo@87 411 without having a second, unused MDA,
meillo@87 412 .Pn slocal ,
meillo@76 413 installed.
meillo@100 414 That appears to be conceptionally the best solution.
meillo@76 415 Yet,
meillo@76 416 .Pn slocal
meillo@87 417 is not split off.
meillo@100 418 I defer the decision over
meillo@78 419 .Pn slocal
meillo@100 420 in need for deeper investigation.
meillo@100 421 In the meanwhile, it remains part of mmh.
meillo@100 422 That does not hurt because
meillo@100 423 .Pn slocal
meillo@100 424 is unrelated to the rest of the project.
meillo@0 425
meillo@58 426
meillo@133 427
meillo@134 428 .H2 "Displaying Messages
meillo@131 429 .P
meillo@133 430 Since the very beginning, already in the first concept paper,
meillo@58 431 .Pn show
meillo@62 432 had been MH's message display program.
meillo@58 433 .Pn show
meillo@76 434 mapped message numbers and sequences to files and invoked
meillo@58 435 .Pn mhl
meillo@89 436 to have the files formatted.
meillo@88 437 With MIME, this approach wasn't sufficient anymore.
meillo@100 438 MIME messages can consist of multiple parts. Some parts are not
meillo@100 439 directly displayable and text content might be encoded in
meillo@58 440 foreign charsets.
meillo@58 441 .Pn show 's
meillo@76 442 understanding of messages and
meillo@58 443 .Pn mhl 's
meillo@88 444 display capabilities couldn't cope with the task any longer.
meillo@62 445 .P
meillo@88 446 Instead of extending these tools, additional tools were written from
meillo@88 447 scratch and added to the MH tool chest.
meillo@88 448 Doing so is encouraged by the tool chest approach.
meillo@88 449 Modular design is a great advantage for extending a system,
meillo@88 450 as new tools can be added without interfering with existing ones.
meillo@62 451 First, the new MIME features were added in form of the single program
meillo@58 452 .Pn mhn .
meillo@58 453 The command
meillo@82 454 .Cl "mhn -show 42
meillo@58 455 would show the MIME message numbered 42.
meillo@58 456 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58 457 the split of
meillo@58 458 .Pn mhn
meillo@88 459 into a set of specialized tools, which together covered the
meillo@88 460 multiple aspects of MIME.
meillo@88 461 One of them was
meillo@69 462 .Pn mhshow ,
meillo@88 463 which replaced
meillo@88 464 .Cl "mhn -show" .
meillo@88 465 It was capable of displaying MIME messages appropriately.
meillo@62 466 .P
meillo@88 467 From then on, two message display tools were part of nmh,
meillo@76 468 .Pn show
meillo@76 469 and
meillo@76 470 .Pn mhshow .
meillo@88 471 To ease the life of users,
meillo@69 472 .Pn show
meillo@69 473 was extended to automatically hand the job over to
meillo@69 474 .Pn mhshow
meillo@69 475 if displaying the message would be beyond
meillo@69 476 .Pn show 's
meillo@69 477 abilities.
meillo@88 478 In consequence, the user would simply invoke
meillo@69 479 .Pn show
meillo@69 480 (possibly through
meillo@69 481 .Pn next
meillo@69 482 or
meillo@69 483 .Pn prev )
meillo@69 484 and get the message printed with either
meillo@69 485 .Pn show
meillo@69 486 or
meillo@69 487 .Pn mhshow ,
meillo@69 488 whatever was more appropriate.
meillo@69 489 .P
meillo@69 490 Having two similar tools for essentially the same task is redundant.
meillo@88 491 Usually,
meillo@88 492 users wouldn't distinguish between
meillo@88 493 .Pn show
meillo@88 494 and
meillo@88 495 .Pn mhshow
meillo@88 496 in their daily mail reading.
meillo@88 497 Having two separate display programs was therefore mainly unnecessary
meillo@88 498 from a user's point of view.
meillo@88 499 Besides, the development of both programs needed to be in sync,
meillo@76 500 to ensure that the programs behaved in a similar way,
meillo@76 501 because they were used like a single tool.
meillo@76 502 Different behavior would have surprised the user.
meillo@69 503 .P
meillo@69 504 Today, non-MIME messages are rather seen to be a special case of
meillo@100 505 MIME messages, although it is the other way round.
meillo@69 506 As
meillo@69 507 .Pn mhshow
meillo@88 508 had already be able to display non-MIME messages, it appeared natural
meillo@69 509 to drop
meillo@69 510 .Pn show
meillo@69 511 in favor of using
meillo@69 512 .Pn mhshow
meillo@69 513 exclusively.
meillo@88 514 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88 515 Removing
meillo@88 516 .Pn show
meillo@88 517 is no loss in function, because functionally
meillo@88 518 .Pn mhshow
meillo@88 519 covers it completely.
meillo@88 520 The old behavior of
meillo@88 521 .Pn show
meillo@88 522 can still be emulated with the simple command line:
meillo@88 523 .VS
meillo@88 524 mhl `mhpath c`
meillo@88 525 VE
meillo@88 526 .P
meillo@76 527 For convenience,
meillo@76 528 .Pn mhshow
meillo@88 529 was renamed to
meillo@88 530 .Pn show
meillo@88 531 after
meillo@88 532 .Pn show
meillo@88 533 was gone.
meillo@88 534 It is clear that such a rename may confuse future developers when
meillo@88 535 trying to understand the history.
meillo@88 536 Nevertheless, I consider the convenience on the user's side,
meillo@88 537 to call
meillo@88 538 .Pn show
meillo@88 539 when they want a message to be displayed, to outweigh the inconvenience
meillo@88 540 on the developer's side when understanding the project history.
meillo@69 541 .P
meillo@88 542 To prepare for the transition,
meillo@69 543 .Pn mhshow
meillo@69 544 was reworked to behave more like
meillo@69 545 .Pn show
meillo@69 546 first.
meillo@88 547 (cf. Sec. XXX)
meillo@88 548 Once the tools behaved more alike, the replacing appeared to be
meillo@88 549 even more natural.
meillo@88 550 Today, mmh's new
meillo@69 551 .Pn show
meillo@88 552 became the one single message display program again, with the difference
meillo@88 553 that today it handles MIME messages as well as non-MIME messages.
meillo@88 554 The outcome of the transition is one program less to maintain,
meillo@88 555 no second display program for users to deal with,
meillo@88 556 and less system complexity.
meillo@69 557 .P
meillo@88 558 Still, removing the old
meillo@69 559 .Pn show
meillo@88 560 hurts in one regard: It had been such a simple program.
meillo@88 561 Its lean elegance is missing to the new
meillo@69 562 .Pn show .
meillo@88 563 But there is no chance;
meillo@88 564 supporting MIME demands for higher essential complexity.
meillo@58 565
meillo@134 566 .ig
meillo@134 567 XXX
meillo@134 568 Consider including text on scan listings here
meillo@58 569
meillo@134 570 Scan listings shall not contain body content. Hence, removed this feature.
meillo@134 571 Scan listings shall operator on message headers and non-message information
meillo@134 572 only. Displaying the beginning of the body complicates everything too much.
meillo@134 573 That's no surprise, because it's something completely different. If you
meillo@134 574 want to examine the body, then use show(1)/mhshow(1).
meillo@134 575 Changed the default scan formats accordingly.
meillo@134 576 .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134 577 ..
meillo@131 578
meillo@131 579
meillo@131 580
meillo@133 581
meillo@100 582 .H2 "Configure Options
meillo@58 583 .P
meillo@76 584 Customization is a double-edged sword.
meillo@76 585 It allows better suiting setups, but not for free.
meillo@76 586 There is the cost of code complexity to be able to customize.
meillo@76 587 There is the cost of less tested setups, because there are
meillo@72 588 more possible setups and especially corner-cases.
meillo@76 589 And, there is the cost of choice itself.
meillo@76 590 The code complexity directly affects the developers.
meillo@72 591 Less tested code affects both, users and developers.
meillo@76 592 The problem of choice affects the users, for once by having to
meillo@100 593 choose, but also by more complex interfaces that require more documentation.
meillo@72 594 Whenever options add little advantages, they should be considered for
meillo@72 595 removal.
meillo@72 596 I have reduced the number of project-specific configure options from
meillo@72 597 fifteen to three.
meillo@74 598
meillo@76 599 .U3 "Mail Transfer Facilities
meillo@74 600 .P
meillo@85 601 With the removal of the mail transfer facilities five configure
meillo@85 602 options vanished:
meillo@85 603 .P
meillo@85 604 The switches
meillo@85 605 .Sw --with-tls
meillo@85 606 and
meillo@85 607 .Sw --with-cyrus-sasl
meillo@89 608 had activated the support for transfer encryption and authentication.
meillo@85 609 This is not needed anymore.
meillo@85 610 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85 611 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85 612 .P
meillo@85 613 The configure switch
meillo@85 614 .Sw --enable-pop
meillo@85 615 activated the message retrieval facility.
meillo@85 616 The code area that would be conditionally compiled in for TLS and SASL
meillo@85 617 support had been small.
meillo@85 618 The conditionally compiled code area for POP support had been much larger.
meillo@85 619 Whereas the code base changes would only slightly change on toggling
meillo@85 620 TLS or SASL support, it changed much on toggling POP support.
meillo@85 621 The changes in the code base could hardly be overviewed.
meillo@85 622 By having POP support togglable a second code base had been created,
meillo@85 623 one that needed to be tested.
meillo@85 624 This situation is basically similar for the conditional TLS and SASL
meillo@85 625 code, but there the changes are minor and can yet be overviewed.
meillo@85 626 Still, conditional compilation of a code base creates variations
meillo@85 627 of the original program.
meillo@85 628 More variations require more testing and maintenance work.
meillo@85 629 .P
meillo@85 630 Two other options only specified default configuration values:
meillo@100 631 .Sw --with-mts
meillo@100 632 defined the default transport service, either
meillo@100 633 .Ar smtp
meillo@100 634 or
meillo@100 635 .Ar sendmail .
meillo@85 636 In mmh this fixed to
meillo@85 637 .Ar sendmail .
meillo@85 638 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85 639 With
meillo@100 640 .Sw --with-smtpservers
meillo@85 641 default SMTP servers for the
meillo@85 642 .Ar smtp
meillo@85 643 transport service could be specified.
meillo@72 644 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@85 645 Both of them became irrelevant.
meillo@72 646
meillo@74 647 .U3 "Backup Prefix
meillo@74 648 .P
meillo@76 649 The backup prefix is the string that was prepended to message
meillo@76 650 filenames to tag them as deleted.
meillo@76 651 By default it had been the comma character `\f(CW,\fP'.
meillo@78 652 In July 2000, Kimmo Suominen introduced
meillo@78 653 the configure option
meillo@78 654 .Sw --with-hash-backup
meillo@78 655 to change the default to the hash symbol `\f(CW#\fP'.
meillo@78 656 The choice was probably personal preference, because first, the
meillo@78 657 option was named
meillo@78 658 .Sw --with-backup-prefix.
meillo@78 659 and had the prefix symbol as argument.
meillo@100 660 But giving the hash symbol as argument caused too many problems
meillo@100 661 for Autoconf,
meillo@100 662 thus the option was limited to use the hash symbol as the default prefix.
meillo@100 663 This supports the assumption, that the choice for the hash was
meillo@100 664 personal preference only.
meillo@100 665 Being related or not, words that start with the hash symbol
meillo@78 666 introduce a comment in the Unix shell.
meillo@72 667 Thus, the command line
meillo@72 668 .Cl "rm #13 #15
meillo@72 669 calls
meillo@72 670 .Pn rm
meillo@72 671 without arguments because the first hash symbol starts the comment
meillo@72 672 that reaches until the end of the line.
meillo@72 673 To delete the backup files,
meillo@72 674 .Cl "rm ./#13 ./#15"
meillo@72 675 needs to be used.
meillo@100 676 Using the hash as backup prefix can be seen as a precaution against
meillo@78 677 data loss.
meillo@78 678 .P
meillo@72 679 I removed the configure option but added the profile entry
meillo@72 680 .Pe backup-prefix ,
meillo@72 681 which allows to specify an arbitrary string as backup prefix.
meillo@72 682 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76 683 Profile entries are the common method to change mmh's behavior.
meillo@76 684 This change did not remove the choice but moved it to a location where
meillo@72 685 it suited better.
meillo@76 686 .P
meillo@78 687 Eventually, however, the new trash folder concept
meillo@78 688 .Cf "Sec. XXX
meillo@78 689 obsoleted the concept of the backup prefix completely.
meillo@78 690 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133 691 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133 692
meillo@76 693
meillo@76 694 .U3 "Editor and Pager
meillo@74 695 .P
meillo@74 696 The two configure options
meillo@74 697 .CW --with-editor=EDITOR
meillo@74 698 .CW --with-pager=PAGER
meillo@74 699 were used to specify the default editor and pager at configure time.
meillo@109 700 Doing so at configure time made sense in the eighties,
meillo@76 701 when the set of available editors and pagers varied much across
meillo@76 702 different systems.
meillo@89 703 Today, the situation is more homogeneous.
meillo@74 704 The programs
meillo@74 705 .Pn vi
meillo@74 706 and
meillo@74 707 .Pn more
meillo@76 708 can be expected to be available on every Unix system,
meillo@74 709 as they are specified by POSIX since two decades.
meillo@74 710 (The specifications for
meillo@74 711 .Pn vi
meillo@74 712 and
meillo@74 713 .Pn more
meillo@74 714 appeared in
meillo@74 715 .[
meillo@74 716 posix 1987
meillo@74 717 .]
meillo@74 718 and,
meillo@74 719 .[
meillo@74 720 posix 1992
meillo@74 721 .]
meillo@74 722 respectively.)
meillo@74 723 As a first step, these two tools were hard-coded as defaults.
meillo@74 724 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74 725 Not changed were the
meillo@74 726 .Pe editor
meillo@74 727 and
meillo@74 728 .Pe moreproc
meillo@76 729 profile entries, which allowed the user to override the system defaults.
meillo@74 730 Later, the concept was reworked to respect the standard environment
meillo@74 731 variables
meillo@74 732 .Ev VISUAL
meillo@74 733 and
meillo@74 734 .Ev PAGER
meillo@76 735 if they are set.
meillo@74 736 Today, mmh determines the editor to use in the following order,
meillo@74 737 taking the first available and non-empty item:
meillo@74 738 .IP (1)
meillo@74 739 Environment variable
meillo@74 740 .Ev MMHEDITOR
meillo@74 741 .IP (2)
meillo@74 742 Profile entry
meillo@74 743 .Pe Editor
meillo@74 744 .IP (3)
meillo@74 745 Environment variable
meillo@74 746 .Ev VISUAL
meillo@74 747 .IP (4)
meillo@74 748 Environment variable
meillo@74 749 .Ev EDITOR
meillo@74 750 .IP (5)
meillo@74 751 Command
meillo@74 752 .Pn vi .
meillo@74 753 .P
meillo@76 754 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76 755 .P
meillo@89 756 The pager to use is determined in a similar order,
meillo@74 757 also taking the first available and non-empty item:
meillo@74 758 .IP (1)
meillo@74 759 Environment variable
meillo@74 760 .Ev MMHPAGER
meillo@74 761 .IP (2)
meillo@74 762 Profile entry
meillo@74 763 .Pe Pager
meillo@74 764 (replaces
meillo@74 765 .Pe moreproc )
meillo@74 766 .IP (3)
meillo@74 767 Environment variable
meillo@74 768 .Ev PAGER
meillo@74 769 .IP (4)
meillo@74 770 Command
meillo@74 771 .Pn more .
meillo@74 772 .P
meillo@74 773 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74 774 .P
meillo@76 775 By respecting the
meillo@74 776 .Ev VISUAL /\c
meillo@74 777 .Ev EDITOR
meillo@74 778 and
meillo@74 779 .Ev PAGER
meillo@76 780 environment variables,
meillo@76 781 the new behavior confirms better to the common style on Unix systems.
meillo@76 782 Additionally, the new approach is more uniform and clearer to users.
meillo@72 783
meillo@72 784
meillo@76 785 .U3 "ndbm
meillo@72 786 .P
meillo@74 787 .Pn slocal
meillo@78 788 used to depend on
meillo@74 789 .I ndbm ,
meillo@74 790 a database library.
meillo@76 791 The database is used to store the `\fLMessage-ID\fP's of all
meillo@76 792 messages delivered.
meillo@74 793 This enables
meillo@74 794 .Pn slocal
meillo@74 795 to suppress delivering the same message to the same user twice.
meillo@74 796 (This features was enabled by the
meillo@74 797 .Sw -suppressdup
meillo@74 798 switch.)
meillo@74 799 .P
meillo@100 800 A variety of versions of the database library exist.
meillo@78 801 .[
meillo@78 802 wolter unix incompat notes dbm
meillo@78 803 .]
meillo@74 804 Complicated autoconf code was needed to detect them correctly.
meillo@74 805 Further more, the configure switches
meillo@74 806 .Sw --with-ndbm=ARG
meillo@74 807 and
meillo@74 808 .Sw --with-ndbmheader=ARG
meillo@74 809 were added to help with difficult setups that would
meillo@78 810 not be detected automatically or correctly.
meillo@74 811 .P
meillo@74 812 By removing the suppress duplicates feature of
meillo@74 813 .Pn slocal ,
meillo@74 814 the dependency on
meillo@74 815 .I ndbm
meillo@78 816 vanished and 120 lines of complex autoconf code could be saved.
meillo@74 817 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@89 818 The change removed functionality too, but that is minor to the
meillo@78 819 improvement by dropping the dependency and the complex autoconf code.
meillo@72 820
meillo@74 821 .U3 "mh-e Support
meillo@72 822 .P
meillo@74 823 The configure option
meillo@74 824 .Sw --disable-mhe
meillo@74 825 was removed when the mh-e support was reworked.
meillo@74 826 Mh-e is the Emacs front-end to MH.
meillo@76 827 It requires MH to provide minor additional functions.
meillo@76 828 The
meillo@76 829 .Sw --disable-mhe
meillo@76 830 configure option could switch these extensions off.
meillo@76 831 After removing the support for old versions of mh-e,
meillo@74 832 only the
meillo@74 833 .Sw -build
meillo@76 834 switches of
meillo@74 835 .Pn forw
meillo@74 836 and
meillo@74 837 .Pn repl
meillo@76 838 are left to be mh-e extensions.
meillo@76 839 They are now always built in because they add little code and complexity.
meillo@76 840 In consequence, the
meillo@74 841 .Sw --disable-mhe
meillo@76 842 configure option was removed
meillo@72 843 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74 844 Removing the option removed a second code setup that would have
meillo@74 845 needed to be tested.
meillo@76 846 This change was first done in nmh and thereafter merged into mmh.
meillo@76 847 .P
meillo@76 848 The interface changes in mmh require mh-e to be adjusted in order
meillo@76 849 to be able to use mmh as back-end.
meillo@76 850 This will require minor changes to mh-e, but removing the
meillo@76 851 .Sw -build
meillo@76 852 switches would require more rework.
meillo@72 853
meillo@74 854 .U3 "Masquerading
meillo@72 855 .P
meillo@74 856 The configure option
meillo@74 857 .Sw --enable-masquerade
meillo@76 858 could take up to three arguments:
meillo@76 859 `draft_from', `mmailid', and `username_extension'.
meillo@74 860 They activated different types of address masquerading.
meillo@74 861 All of them were implemented in the SMTP-speaking
meillo@74 862 .Pn post
meillo@76 863 command, which provided an MSA.
meillo@76 864 Address masquerading is an MTA's task and mmh does not cover
meillo@76 865 this field anymore.
meillo@76 866 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74 867 .P
meillo@74 868 The
meillo@74 869 .I mmailid
meillo@74 870 masquerading type is the oldest one of the three and the only one
meillo@74 871 available in the original MH.
meillo@74 872 It provided a
meillo@74 873 .I username
meillo@74 874 to
meillo@74 875 .I fakeusername
meillo@76 876 mapping, based on the password file's GECOS field.
meillo@74 877 The man page
meillo@74 878 .Mp mh-tailor(5)
meillo@74 879 described the use case as being the following:
meillo@98 880 .QS
meillo@74 881 This is useful if you want the messages you send to always
meillo@74 882 appear to come from the name of an MTA alias rather than your
meillo@74 883 actual account name. For instance, many organizations set up
meillo@74 884 `First.Last' sendmail aliases for all users. If this is
meillo@74 885 the case, the GECOS field for each user should look like:
meillo@74 886 ``First [Middle] Last <First.Last>''
meillo@98 887 .QE
meillo@74 888 .P
meillo@74 889 As mmh sends outgoing mail via the local MTA only,
meillo@76 890 the best location to do such global rewrites is there.
meillo@74 891 Besides, the MTA is conceptionally the right location because it
meillo@74 892 does the reverse mapping for incoming mail (aliasing), too.
meillo@76 893 Further more, masquerading set up there is readily available for all
meillo@74 894 mail software on the system.
meillo@76 895 Hence, mmailid masquerading was removed.
meillo@74 896 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74 897 .P
meillo@74 898 The
meillo@74 899 .I username_extension
meillo@76 900 masquerading type did not replace the username but would append a suffix,
meillo@76 901 specified by the
meillo@74 902 .Ev USERNAME_EXTENSION
meillo@76 903 environment variable, to it.
meillo@76 904 This provided support for the
meillo@74 905 .I user-extension
meillo@74 906 feature of qmail and the similar
meillo@74 907 .I "plussed user
meillo@74 908 processing of sendmail.
meillo@74 909 The decision to remove this username_extension masquerading was
meillo@74 910 motivated by the fact that
meillo@74 911 .Pn spost
meillo@76 912 hadn't supported it already.
meillo@76 913 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76 914 Username extensions are possible in mmh, but less convenient to use.
meillo@76 915 .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74 916 .P
meillo@74 917 The
meillo@74 918 .I draft_from
meillo@74 919 masquerading type instructed
meillo@74 920 .Pn post
meillo@84 921 to use the value of the
meillo@84 922 .Hd From
meillo@84 923 header field as SMTP envelope sender.
meillo@76 924 Sender addresses could be replaced completely.
meillo@74 925 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76 926 Mmh offers a kind of masquerading similar in effect, but
meillo@74 927 with technical differences.
meillo@76 928 As mmh does not transfer messages itself, the local MTA has final control
meillo@76 929 over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76 930 by the MTA.
meillo@76 931 In times of pedantic spam checking, an MTA will take care to use
meillo@76 932 sensible envelope sender addresses to keep its own reputation up.
meillo@84 933 Nonetheless, the MUA can set the
meillo@84 934 .Hd From
meillo@84 935 header field and thereby propose
meillo@76 936 a sender address to the MTA.
meillo@74 937 The MTA may then decide to take that one or generate the canonical sender
meillo@74 938 address for use as envelope sender address.
meillo@74 939 .P
meillo@74 940 In mmh, the MTA will always extract the recipient and sender from the
meillo@84 941 message header (\c
meillo@74 942 .Pn sendmail 's
meillo@74 943 .Sw -t
meillo@74 944 switch).
meillo@84 945 The
meillo@84 946 .Hd From
meillo@84 947 header field of the draft may be set arbitrary by the user.
meillo@74 948 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74 949
meillo@74 950 .U3 "Remaining Options
meillo@74 951 .P
meillo@74 952 Two configure options remain in mmh.
meillo@74 953 One is the locking method to use:
meillo@74 954 .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@76 955 The idea of removing all methods except the portable dot locking
meillo@76 956 and having that one as the default is appealing, but this change
meillo@76 957 requires deeper technical investigation into the topic.
meillo@76 958 The other option,
meillo@74 959 .Sw --enable-debug ,
meillo@74 960 compiles the programs with debugging symbols and does not strip them.
meillo@74 961 This option is likely to stay.
meillo@72 962
meillo@72 963
meillo@58 964
meillo@63 965
meillo@100 966 .H2 "Command Line Switches
meillo@58 967 .P
meillo@93 968 The command line switches of MH tools follow the X Window style.
meillo@93 969 They are words, introduced by a single dash.
meillo@93 970 For example:
meillo@93 971 .Cl "-truncate" .
meillo@93 972 Every program in mmh has two generic switches:
meillo@93 973 .Sw -help ,
meillo@93 974 to print a short message on how to use the program, and
meillo@93 975 .Sw -Version ,
meillo@93 976 to tell what version of mmh the program belongs to.
meillo@93 977 .P
meillo@93 978 Switches change the behavior of programs.
meillo@93 979 Programs that do one thing in one way require no switches.
meillo@93 980 In most cases, doing something in exactly one way is too limiting.
meillo@97 981 If there is basically one task to accomplish, but it should be done
meillo@93 982 in various ways, switches are a good approach to alter the behavior
meillo@93 983 of a program.
meillo@93 984 Changing the behavior of programs provides flexibility and customization
meillo@97 985 to users, but at the same time it complicates the code, documentation and
meillo@93 986 usage of the program.
meillo@97 987 .\" XXX: Ref
meillo@93 988 Therefore, the number of switches should be kept small.
meillo@93 989 A small set of well-chosen switches does no harm.
meillo@93 990 But usually, the number of switches increases over time.
meillo@93 991 Already in 1985, Rose and Romine have identified this as a major
meillo@93 992 problem of MH:
meillo@93 993 .[ [
meillo@93 994 rose romine real work
meillo@93 995 .], p. 12]
meillo@98 996 .QS
meillo@93 997 A complaint often heard about systems which undergo substantial development
meillo@93 998 by many people over a number of years, is that more and more options are
meillo@93 999 introduced which add little to the functionality but greatly increase the
meillo@93 1000 amount of information a user needs to know in order to get useful work done.
meillo@93 1001 This is usually referred to as creeping featurism.
meillo@93 1002 .QP
meillo@93 1003 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93 1004 ten or so well-meaning programmers (the present authors included),
meillo@93 1005 suffers mightily from this.
meillo@98 1006 .QE
meillo@93 1007 .P
meillo@97 1008 Being reluctant to adding new switches \(en or `options',
meillo@97 1009 as Rose and Romine call them \(en is one part of a counter-action,
meillo@97 1010 the other part is removing hardly used switches.
meillo@97 1011 Nmh's tools had lots of switches already implemented,
meillo@97 1012 hence, cleaning up by removing some of them was the more important part
meillo@97 1013 of the counter-action.
meillo@93 1014 Removing existing functionality is always difficult because it
meillo@93 1015 breaks programs that use these functions.
meillo@93 1016 Also, for every obsolete feature, there'll always be someone who still
meillo@93 1017 uses it and thus opposes its removal.
meillo@93 1018 This puts the developer into the position,
meillo@93 1019 where sensible improvements to style are regarded as destructive acts.
meillo@97 1020 Yet, living with the featurism is far worse, in my eyes, because
meillo@97 1021 future needs will demand adding further features,
meillo@93 1022 worsening the situation more and more.
meillo@93 1023 Rose and Romine added in a footnote,
meillo@93 1024 ``[...]
meillo@93 1025 .Pn send
meillo@93 1026 will no doubt acquire an endless number of switches in the years to come.''
meillo@97 1027 Although clearly humorous, the comment points to the nature of the problem.
meillo@97 1028 Refusing to add any new switches would encounter the problem at its root,
meillo@97 1029 but this is not practical.
meillo@97 1030 New needs will require new switches and it would be unwise to block
meillo@97 1031 them strictly.
meillo@97 1032 Nevertheless, removing obsolete switches still is an effective approach
meillo@97 1033 to deal with the problem.
meillo@97 1034 Working on an experimental branch without an established user base,
meillo@97 1035 eased my work because I did not offend users when I removed existing
meillo@110 1036 functions.
meillo@93 1037 .P
meillo@93 1038 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93 1039 .Pn send .
meillo@97 1040 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@97 1041 At the time of writing, no more than 7 visible switches and 1 hidden switch
meillo@97 1042 have remained in mmh's
meillo@97 1043 .Pn send .
meillo@97 1044 (These numbers include two generic switches, help and version.)
meillo@93 1045 .P
meillo@97 1046 Fig. XXX
meillo@93 1047 .\" XXX Ref
meillo@97 1048 displays the number of switches for each of the tools that is available
meillo@97 1049 in both, nmh and mmh.
meillo@100 1050 The tools are sorted by the number of switches they had in nmh.
meillo@100 1051 Visible and hidden switches were counted,
meillo@97 1052 but not the generic help and version switches.
meillo@93 1053 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93 1054 now it has no more than 5 \(en only half as many.
meillo@93 1055 If the `no' switches and similar inverse variant are folded onto
meillo@100 1056 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100 1057 has 4 now.
meillo@93 1058 The total number of functional switches in mmh dropped from 465
meillo@93 1059 to 234.
meillo@58 1060
meillo@93 1061 .KS
meillo@93 1062 .in 1c
meillo@93 1063 .so input/switches.grap
meillo@93 1064 .KE
meillo@58 1065
meillo@93 1066 .P
meillo@93 1067 A part of the switches vanished after functions were removed.
meillo@93 1068 This was the case for network mail transfer, for instance.
meillo@97 1069 Sometimes, however, the work flow was the other way:
meillo@97 1070 I looked through the
meillo@97 1071 .Mp mh-chart (7)
meillo@97 1072 man page to identify the tools with apparently too many switches.
meillo@97 1073 Then considering the value of each of the switches by examining
meillo@97 1074 the tool's man page and source code, aided by recherche and testing.
meillo@97 1075 This way, the removal of functions was suggested by the aim to reduce
meillo@97 1076 the number of switches per command.
meillo@97 1077
meillo@58 1078
meillo@93 1079 .U3 "Draft Folder Facility
meillo@93 1080 .P
meillo@100 1081 A change early in the project was the complete transition from
meillo@93 1082 the single draft message to the draft folder facility.
meillo@97 1083 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@109 1084 The draft folder facility was introduced in the mid-eighties, when
meillo@100 1085 Rose and Romine called it a ``relatively new feature''.
meillo@93 1086 .[
meillo@93 1087 rose romine real work
meillo@93 1088 .]
meillo@110 1089 Since then, the facility had existed but was inactive by default.
meillo@93 1090 The default activation and the related rework of the tools made it
meillo@93 1091 possible to remove the
meillo@93 1092 .Sw -[no]draftfolder ,
meillo@93 1093 and
meillo@93 1094 .Sw -draftmessage
meillo@93 1095 switches from
meillo@93 1096 .Pn comp ,
meillo@93 1097 .Pn repl ,
meillo@93 1098 .Pn forw ,
meillo@93 1099 .Pn dist ,
meillo@93 1100 .Pn whatnow ,
meillo@93 1101 and
meillo@93 1102 .Pn send .
meillo@97 1103 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@97 1104 The only flexibility removed with this change is having multiple
meillo@97 1105 draft folders within one profile.
meillo@97 1106 I consider this a theoretical problem only.
meillo@93 1107 In the same go, the
meillo@93 1108 .Sw -draft
meillo@93 1109 switch of
meillo@93 1110 .Pn anno ,
meillo@93 1111 .Pn refile ,
meillo@93 1112 and
meillo@93 1113 .Pn send
meillo@93 1114 was removed.
meillo@93 1115 The special-casing of `the' draft message became irrelevant after
meillo@93 1116 the rework of the draft system.
meillo@93 1117 (See Sec. XXX.)
meillo@95 1118 Equally,
meillo@95 1119 .Pn comp
meillo@95 1120 lost its
meillo@95 1121 .Sw -file
meillo@95 1122 switch.
meillo@95 1123 The draft folder facility, together with the
meillo@95 1124 .Sw -form
meillo@95 1125 switch, are sufficient.
meillo@93 1126
meillo@95 1127
meillo@102 1128 .U3 "In Place Editing
meillo@93 1129 .P
meillo@93 1130 .Pn anno
meillo@93 1131 had the switches
meillo@93 1132 .Sw -[no]inplace
meillo@100 1133 to either annotate the message in place and thus preserve hard links,
meillo@93 1134 or annotate a copy to replace the original message, breaking hard links.
meillo@97 1135 Following the assumption that linked messages should truly be the
meillo@97 1136 same message, and annotating it should not break the link, the
meillo@93 1137 .Sw -[no]inplace
meillo@93 1138 switches were removed and the previous default
meillo@93 1139 .Sw -inplace
meillo@93 1140 was made the only behavior.
meillo@97 1141 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0
meillo@93 1142 The
meillo@93 1143 .Sw -[no]inplace
meillo@93 1144 switches of
meillo@93 1145 .Pn repl ,
meillo@93 1146 .Pn forw ,
meillo@93 1147 and
meillo@93 1148 .Pn dist
meillo@93 1149 could be removed, too, as they were simply passed through to
meillo@93 1150 .Pn anno .
meillo@93 1151 .P
meillo@93 1152 .Pn burst
meillo@93 1153 also had
meillo@93 1154 .Sw -[no]inplace
meillo@95 1155 switches, but with different meaning.
meillo@95 1156 With
meillo@95 1157 .Sw -inplace ,
meillo@95 1158 the digest had been replaced by the table of contents (i.e. the
meillo@110 1159 introduction text) and the burst messages were placed right
meillo@95 1160 after this message, renumbering all following messages.
meillo@95 1161 Also, any trailing text of the digest was lost, though,
meillo@95 1162 in practice, it usually consists of an end-of-digest marker only.
meillo@95 1163 Nontheless, this behavior appeared less elegant than the
meillo@95 1164 .Sw -noinplace
meillo@95 1165 behavior, which already had been the default.
meillo@95 1166 Nmh's
meillo@95 1167 .Mp burst (1)
meillo@95 1168 man page reads:
meillo@95 1169 .sp \n(PDu
meillo@98 1170 .QS
meillo@93 1171 If -noinplace is given, each digest is preserved, no table
meillo@93 1172 of contents is produced, and the messages contained within
meillo@93 1173 the digest are placed at the end of the folder. Other messages
meillo@93 1174 are not tampered with in any way.
meillo@98 1175 .QE
meillo@95 1176 .LP
meillo@93 1177 The decision to drop the
meillo@93 1178 .Sw -inplace
meillo@95 1179 behavior was supported by the code complexity and the possible data loss
meillo@95 1180 it caused.
meillo@93 1181 .Sw -noinplace
meillo@95 1182 was chosen to be the definitive behavior.
meillo@97 1183 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93 1184
meillo@95 1185
meillo@95 1186 .U3 "Forms and Format Strings
meillo@93 1187 .P
meillo@95 1188 Historically, the tools that had
meillo@95 1189 .Sw -form
meillo@95 1190 switches to supply a form file had
meillo@95 1191 .Sw -format
meillo@95 1192 switches as well to supply the contents of a form file as a string
meillo@95 1193 on the command line directly.
meillo@95 1194 In consequence, the following two lines equaled:
meillo@95 1195 .VS
meillo@95 1196 scan -form scan.mailx
meillo@95 1197 scan -format "`cat .../scan.mailx`"
meillo@95 1198 VE
meillo@95 1199 The
meillo@95 1200 .Sw -format
meillo@95 1201 switches were dropped in favor for extending the
meillo@95 1202 .Sw -form
meillo@95 1203 switches.
meillo@97 1204 .Ci f51956be123db66b00138f80464d06f030dbb88d
meillo@95 1205 If their argument starts with an equal sign (`='),
meillo@95 1206 then the rest of the argument is taken as a format string,
meillo@95 1207 otherwise the arguments is treated as the name of a format file.
meillo@95 1208 Thus, now the following two lines equal:
meillo@95 1209 .VS
meillo@95 1210 scan -form scan.mailx
meillo@95 1211 scan -form "=`cat .../scan.mailx`"
meillo@95 1212 VE
meillo@95 1213 This rework removed the prefix collision between
meillo@95 1214 .Sw -form
meillo@95 1215 and
meillo@95 1216 .Sw -format .
meillo@95 1217 Now, typing
meillo@95 1218 .Sw -fo
meillo@95 1219 suffices to specify form or format string.
meillo@95 1220 .P
meillo@95 1221 The different meaning of
meillo@95 1222 .Sw -format
meillo@95 1223 for
meillo@95 1224 .Pn repl
meillo@95 1225 and
meillo@95 1226 .Pn forw
meillo@95 1227 was removed in mmh.
meillo@95 1228 .Pn forw
meillo@95 1229 was completely switched to MIME-type forwarding, thus removing the
meillo@95 1230 .Sw -[no]format .
meillo@97 1231 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@95 1232 For
meillo@95 1233 .Pn repl ,
meillo@95 1234 the
meillo@95 1235 .Sw -[no]format
meillo@95 1236 switches were reworked to
meillo@95 1237 .Sw -[no]filter
meillo@95 1238 switches.
meillo@97 1239 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@95 1240 The
meillo@95 1241 .Sw -format
meillo@95 1242 switches of
meillo@95 1243 .Pn send
meillo@95 1244 and
meillo@95 1245 .Pn post ,
meillo@95 1246 which had a third meaning,
meillo@95 1247 were removed likewise.
meillo@97 1248 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9
meillo@95 1249 Eventually, the ambiguity of the
meillo@95 1250 .Sw -format
meillo@95 1251 switches was resolved by not anymore having any such switch in mmh.
meillo@95 1252
meillo@95 1253
meillo@95 1254 .U3 "MIME Tools
meillo@95 1255 .P
meillo@95 1256 The MIME tools, which were once part of
meillo@100 1257 .Pn mhn
meillo@100 1258 [sic!],
meillo@95 1259 had several switches that added little practical value to the programs.
meillo@95 1260 The
meillo@95 1261 .Sw -[no]realsize
meillo@95 1262 switches of
meillo@95 1263 .Pn mhbuild
meillo@95 1264 and
meillo@95 1265 .Pn mhlist
meillo@97 1266 were removed, doing real size calculations always now
meillo@97 1267 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c ,
meillo@97 1268 as
meillo@95 1269 ``This provides an accurate count at the expense of a small delay.''
meillo@95 1270 This small delay is not noticable on modern systems.
meillo@95 1271 .P
meillo@95 1272 The
meillo@95 1273 .Sw -[no]check
meillo@95 1274 switches were removed together with the support for
meillo@95 1275 .Hd Content-MD5
meillo@95 1276 header fields.
meillo@95 1277 .[
meillo@95 1278 rfc 1864
meillo@95 1279 .]
meillo@97 1280 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@95 1281 (See Sec. XXX)
meillo@95 1282 .P
meillo@95 1283 The
meillo@95 1284 .Sw -[no]ebcdicsafe
meillo@95 1285 and
meillo@95 1286 .Sw -[no]rfc934mode
meillo@95 1287 switches of
meillo@95 1288 .Pn mhbuild
meillo@95 1289 were removed because they are considered obsolete.
meillo@97 1290 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@97 1291 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88
meillo@95 1292 .P
meillo@95 1293 Content caching of external MIME parts, activated with the
meillo@95 1294 .Sw -rcache
meillo@95 1295 and
meillo@95 1296 .Sw -wcache
meillo@95 1297 switches was completely removed.
meillo@97 1298 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269
meillo@97 1299 External MIME parts are rare today, having a caching facility
meillo@96 1300 for them is appears to be unnecessary.
meillo@95 1301 .P
meillo@95 1302 In pre-MIME times,
meillo@95 1303 .Pn mhl
meillo@95 1304 had covered many tasks that are part of MIME handling today.
meillo@95 1305 Therefore,
meillo@95 1306 .Pn mhl
meillo@95 1307 could be simplified to a large extend, reducing the number of its
meillo@95 1308 switches from 21 to 6.
meillo@97 1309 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@97 1310 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@95 1311
meillo@95 1312
meillo@95 1313
meillo@95 1314
meillo@95 1315 .U3 "Header Printing
meillo@95 1316 .P
meillo@95 1317 .Pn folder 's
meillo@95 1318 data output is self-explaining enough that
meillo@95 1319 displaying the header line makes few sense.
meillo@95 1320 Hence, the
meillo@95 1321 .Sw -[no]header
meillo@95 1322 switch was removed and headers are never printed.
meillo@97 1323 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7
meillo@95 1324 .P
meillo@95 1325 In
meillo@95 1326 .Pn mhlist ,
meillo@95 1327 the
meillo@95 1328 .Sw -[no]header
meillo@95 1329 switches were removed, too.
meillo@97 1330 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f
meillo@95 1331 But in this case headers are always printed,
meillo@95 1332 because the output is not self-explaining.
meillo@95 1333 .P
meillo@95 1334 .Pn scan
meillo@95 1335 also had
meillo@95 1336 .Sw -[no]header
meillo@95 1337 switches.
meillo@95 1338 Printing the header had been sensible until the introduction of
meillo@95 1339 format strings made it impossible to display the column headings.
meillo@95 1340 Only the folder name and the current date remained to be printed.
meillo@95 1341 As this information can be perfectly retrieved by
meillo@95 1342 .Pn folder
meillo@95 1343 and
meillo@95 1344 .Pn date ,
meillo@95 1345 consequently, the switches were removed.
meillo@97 1346 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e
meillo@95 1347 .P
meillo@95 1348 By removing all
meillo@95 1349 .Sw -header
meillo@95 1350 switches, the collision with
meillo@95 1351 .Sw -help
meillo@95 1352 on the first two letters was resolved.
meillo@95 1353 Currently,
meillo@95 1354 .Sw -h
meillo@95 1355 evaluates to
meillo@95 1356 .Sw -help
meillo@95 1357 for all tools of mmh.
meillo@95 1358
meillo@95 1359
meillo@139 1360 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95 1361 .P
meillo@95 1362 The
meillo@95 1363 .Sw -noedit
meillo@100 1364 switch of
meillo@95 1365 .Pn comp ,
meillo@95 1366 .Pn repl ,
meillo@95 1367 .Pn forw ,
meillo@95 1368 .Pn dist ,
meillo@95 1369 and
meillo@95 1370 .Pn whatnow
meillo@95 1371 was removed, but it can now be replaced by specifying
meillo@95 1372 .Sw -editor
meillo@95 1373 with an empty argument.
meillo@97 1374 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9
meillo@95 1375 (Specifying
meillo@95 1376 .Cl "-editor true
meillo@95 1377 is nearly the same, only differing by the previous editor being set.)
meillo@95 1378 .P
meillo@95 1379 The more important change is the removal of the
meillo@95 1380 .Sw -nowhatnowproc
meillo@95 1381 switch.
meillo@97 1382 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622
meillo@95 1383 This switch had introduced an awkward behavior, as explained in nmh's
meillo@95 1384 man page for
meillo@95 1385 .Mp comp (1):
meillo@98 1386 .QS
meillo@98 1387 The \-editor editor switch indicates the editor to use for
meillo@98 1388 the initial edit. Upon exiting from the editor, comp will
meillo@98 1389 invoke the whatnow program. See whatnow(1) for a discussion
meillo@98 1390 of available options. The invocation of this program can be
meillo@98 1391 inhibited by using the \-nowhatnowproc switch. (In truth of
meillo@98 1392 fact, it is the whatnow program which starts the initial
meillo@98 1393 edit. Hence, \-nowhatnowproc will prevent any edit from
meillo@95 1394 occurring.)
meillo@98 1395 .QE
meillo@95 1396 .P
meillo@95 1397 Effectively, the
meillo@95 1398 .Sw -nowhatnowproc
meillo@100 1399 switch creates only a draft message.
meillo@95 1400 As
meillo@95 1401 .Cl "-whatnowproc true
meillo@95 1402 causes the same behavior, the
meillo@95 1403 .Sw -nowhatnowproc
meillo@95 1404 switch was removed for being redundant.
meillo@100 1405 Likely, the
meillo@95 1406 .Sw -nowhatnowproc
meillo@100 1407 switch was intended to be used by front-ends.
meillo@95 1408
meillo@95 1409
meillo@95 1410
meillo@95 1411 .U3 "Various
meillo@95 1412 .BU
meillo@139 1413 With the removal of MMDF maildrop format support,
meillo@139 1414 .Pn packf
meillo@139 1415 and
meillo@139 1416 .Pn rcvpack
meillo@139 1417 no longer needed their
meillo@139 1418 .Sw -mbox
meillo@139 1419 and
meillo@139 1420 .Sw -mmdf
meillo@139 1421 switches.
meillo@139 1422 .Sw -mbox
meillo@139 1423 is the sole behavior now.
meillo@139 1424 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@139 1425 In the same go,
meillo@139 1426 .Pn packf
meillo@139 1427 and
meillo@139 1428 .Pn rcvpack
meillo@139 1429 were reworked (see Sec. XXX) and their
meillo@139 1430 .Sw -file
meillo@139 1431 switch became unnecessary.
meillo@139 1432 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e
meillo@139 1433
meillo@139 1434 .BU
meillo@139 1435 Mmh's tools will no longer clear the screen (\c
meillo@139 1436 .Pn scan 's
meillo@139 1437 and
meillo@139 1438 .Pn mhl 's
meillo@139 1439 .Sw -[no]clear
meillo@139 1440 switches
meillo@139 1441 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139 1442 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@139 1443 Neither will
meillo@139 1444 .Pn mhl
meillo@139 1445 ring the bell (\c
meillo@139 1446 .Sw -[no]bell
meillo@139 1447 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@139 1448 nor page the output itself (\c
meillo@139 1449 .Sw -length
meillo@139 1450 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@139 1451 Generally, the pager to use is no longer specified with the
meillo@139 1452 .Sw -[no]moreproc
meillo@139 1453 command line switches for
meillo@139 1454 .Pn mhl
meillo@139 1455 and
meillo@139 1456 .Pn show /\c
meillo@139 1457 .Pn mhshow .
meillo@139 1458 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a
meillo@139 1459
meillo@139 1460 .BU
meillo@96 1461 In order to avoid prefix collisions among switch names, the
meillo@95 1462 .Sw -version
meillo@95 1463 switch was renamed to
meillo@95 1464 .Sw -Version
meillo@95 1465 (with capital `V').
meillo@97 1466 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a
meillo@95 1467 Every program has the
meillo@95 1468 .Sw -version
meillo@95 1469 switch but its first three letters collided with the
meillo@95 1470 .Sw -verbose
meillo@95 1471 switch, present in many programs.
meillo@95 1472 The rename solved this problem once for all.
meillo@95 1473 Although this rename breaks a basic interface, having the
meillo@95 1474 .Sw -V
meillo@95 1475 abbreviation to display the version information, isn't all too bad.
meillo@139 1476
meillo@95 1477 .BU
meillo@95 1478 .Sw -[no]preserve
meillo@95 1479 of
meillo@95 1480 .Pn refile
meillo@95 1481 was removed because what use was it anyway?
meillo@98 1482 .QS
meillo@95 1483 Normally when a message is refiled, for each destination
meillo@95 1484 folder it is assigned the number which is one above the current
meillo@95 1485 highest message number in that folder. Use of the
meillo@95 1486 \-preserv [sic!] switch will override this message renaming, and try
meillo@95 1487 to preserve the number of the message. If a conflict for a
meillo@95 1488 particular folder occurs when using the \-preserve switch,
meillo@95 1489 then refile will use the next available message number which
meillo@95 1490 is above the message number you wish to preserve.
meillo@98 1491 .QE
meillo@139 1492
meillo@95 1493 .BU
meillo@95 1494 The removal of the
meillo@95 1495 .Sw -[no]reverse
meillo@95 1496 switches of
meillo@95 1497 .Pn scan
meillo@97 1498 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@95 1499 is a bug fix, supported by the comments
meillo@95 1500 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95 1501 by Rose and
meillo@95 1502 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@95 1503 This should be considered a bug.'' by Romine in the documentation.
meillo@97 1504 The question remains why neither Rose and Romine had fixed this
meillo@109 1505 bug in the eighties when they wrote these comments nor has anyone
meillo@95 1506 thereafter.
meillo@93 1507
meillo@93 1508
meillo@93 1509 .ig
meillo@93 1510
meillo@95 1511 forw: [no]dashstuffing(mhl)
meillo@93 1512
meillo@95 1513 mhshow: [no]pause [no]serialonly
meillo@93 1514
meillo@93 1515 mhmail: resent queued
meillo@93 1516 inc: snoop, (pop)
meillo@93 1517
meillo@95 1518 mhl: [no]faceproc folder sleep
meillo@95 1519 [no]dashstuffing(forw) digest list volume number issue number
meillo@93 1520
meillo@95 1521 prompter: [no]doteof
meillo@93 1522
meillo@93 1523 refile: [no]preserve [no]unlink [no]rmmproc
meillo@93 1524
meillo@95 1525 send: [no]forward [no]mime [no]msgid
meillo@93 1526 [no]push split [no]unique (sasl) width snoop [no]dashstuffing
meillo@93 1527 attach attachformat
meillo@93 1528 whatnow: (noedit) attach
meillo@93 1529
meillo@93 1530 slocal: [no]suppressdups
meillo@93 1531
meillo@95 1532 spost: [no]filter [no]backup width [no]push idanno
meillo@93 1533 [no]check(whom) whom(whom)
meillo@93 1534
meillo@93 1535 whom: ???
meillo@93 1536
meillo@95 1537 ..
meillo@93 1538
meillo@93 1539
meillo@93 1540 .ig
meillo@93 1541
meillo@93 1542 .P
meillo@93 1543 In the best case, all switches are unambiguous on the first character,
meillo@93 1544 or on the three-letter prefix for the `no' variants.
meillo@96 1545 Reducing switch prefix collisions, shortens the necessary prefix length
meillo@93 1546 the user must type.
meillo@93 1547 Having less switches helps best.
meillo@93 1548
meillo@93 1549 ..
meillo@58 1550
meillo@95 1551
meillo@102 1552 .\" XXX: whatnow prompt commands
meillo@102 1553
meillo@102 1554
meillo@95 1555
meillo@95 1556
meillo@133 1557 .\" --------------------------------------------------------------
meillo@74 1558 .H1 "Modernizing
meillo@102 1559 .P
meillo@118 1560 In the over thirty years of MH's existence, its code base was
meillo@118 1561 extended more and more.
meillo@118 1562 New features entered the project and became alternatives to the
meillo@118 1563 existing behavior.
meillo@118 1564 Relicts from several decades have gathered in the code base,
meillo@118 1565 but seldom obsolete features were dropped.
meillo@118 1566 This section describes the removing of old code
meillo@118 1567 and the modernizing of the default setup.
meillo@118 1568 It focuses on the functional aspect only;
meillo@118 1569 the non-functional aspects of code style are discussed in
meillo@118 1570 .\" FIXME REF
meillo@118 1571 Sec. XXX.
meillo@58 1572
meillo@58 1573
meillo@100 1574 .H2 "Code Relicts
meillo@0 1575 .P
meillo@109 1576 My position to drop obsolete functions of mmh, in order to remove old code,
meillo@104 1577 is much more revolutional than the nmh community likes to have it.
meillo@104 1578 Working on an experimental version, I was able to quickly drop
meillo@104 1579 functionality I considered ancient.
meillo@104 1580 The need for consensus with peers would have slowed this process down.
meillo@104 1581 Without the need to justify my decisions, I was able to rush forward.
meillo@110 1582 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104 1583 do the work:
meillo@104 1584 .[
meillo@104 1585 paul vixie edginess nmh-workers
meillo@104 1586 .]
meillo@104 1587 .QS
meillo@104 1588 let's stop walking on egg shells with this code base. there's no need to
meillo@104 1589 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104 1590 we don't need a separate branch for removing vmh
meillo@104 1591 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@104 1592 or depending on pure ansi/posix "libc".
meillo@104 1593 .QP
meillo@104 1594 these things should each be a day or two of work and the "main branch"
meillo@104 1595 should just be modern. [...]
meillo@104 1596 let's push forward, aggressively.
meillo@104 1597 .QE
meillo@104 1598 .LP
meillo@104 1599 I did so already in the months before.
meillo@104 1600 I pushed forward.
meillo@104 1601 I simply dropped the cruft.
meillo@104 1602 .P
meillo@104 1603 The decision to drop a feature was based on literature research and
meillo@104 1604 careful thinking, but whether having had contact to this particular
meillo@104 1605 feature within my own computer life served as a rule of thumb.
meillo@109 1606 Always, I explained my reasons in the commit messages
meillo@109 1607 in the version control system.
meillo@104 1608 Hence, others can comprehend my view and argue for undoing the change
meillo@104 1609 if I have missed an important aspect.
meillo@109 1610 I was quick in dropping parts.
meillo@109 1611 I rather re-included falsely dropped parts than going a slower pace.
meillo@109 1612 Mmh is experimental work; it required tough decisions.
meillo@12 1613
meillo@102 1614
meillo@104 1615 .U3 "Forking
meillo@12 1616 .P
meillo@109 1617 Being a tool chest, MH creates many processes.
meillo@104 1618 In earlier times
meillo@104 1619 .Fu fork()
meillo@104 1620 had been an expensive system call, because the process's image needed
meillo@104 1621 to be duplicated completely at once.
meillo@109 1622 This was especially painful in the common case when the image gets
meillo@104 1623 replaced by a call to
meillo@104 1624 .Fu exec()
meillo@104 1625 right after having forked the child process.
meillo@104 1626 The
meillo@104 1627 .Fu vfork()
meillo@104 1628 system call was invented to speed up this particular case.
meillo@104 1629 It completely omits the duplication of the image.
meillo@104 1630 On old systems this resulted in significant speed ups.
meillo@104 1631 Therefore MH used
meillo@104 1632 .Fu vfork()
meillo@104 1633 whenever possible.
meillo@12 1634 .P
meillo@104 1635 Modern memory management units support copy-on-write semantics, which make
meillo@104 1636 .Fu fork()
meillo@104 1637 almost as fast as
meillo@104 1638 .Fu vfork() .
meillo@104 1639 The man page of
meillo@104 1640 .Mp vfork (2)
meillo@104 1641 in FreeBSD 8.0 states:
meillo@104 1642 .QS
meillo@104 1643 This system call will be eliminated when proper system sharing mechanisms
meillo@104 1644 are implemented. Users should not depend on the memory sharing semantics
meillo@104 1645 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104 1646 .QE
meillo@104 1647 .LP
meillo@104 1648 Vixie supports the removal with the note that ``the last
meillo@104 1649 system on which fork was so slow that an mh user would notice it, was
meillo@104 1650 Eunice. that was 1987''.
meillo@104 1651 .[
meillo@104 1652 nmh-workers vixie edginess
meillo@104 1653 .]
meillo@104 1654 I replaced all calls to
meillo@104 1655 .Fu vfork()
meillo@104 1656 with calls to
meillo@104 1657 .Fu fork() .
meillo@109 1658 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104 1659 .P
meillo@104 1660 Related to the costs of
meillo@104 1661 .Fu fork()
meillo@104 1662 is the probability of its success.
meillo@109 1663 In the eighties, on heavy loaded systems, calls to
meillo@104 1664 .Fu fork()
meillo@104 1665 were prone to failure.
meillo@104 1666 Hence, many of the
meillo@104 1667 .Fu fork()
meillo@104 1668 calls in the code were wrapped into loops to retry the
meillo@104 1669 .Fu fork()
meillo@109 1670 several times, to increase the changes to succeed, eventually.
meillo@109 1671 On modern systems, a failing
meillo@104 1672 .Fu fork()
meillo@109 1673 call is unusual.
meillo@104 1674 Hence, in the rare case when
meillo@104 1675 .Fu fork()
meillo@104 1676 fails, mmh programs simply abort.
meillo@109 1677 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12 1678
meillo@12 1679
meillo@109 1680 .U3 "Header Fields
meillo@104 1681 .BU
meillo@84 1682 The
meillo@84 1683 .Hd Encrypted
meillo@104 1684 header field was introduced by RFC\|822,
meillo@109 1685 but already marked as legacy in RFC\|2822.
meillo@109 1686 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104 1687 messages [RFC\|4880, RFC\|3156].
meillo@109 1688 Hence, the support for
meillo@104 1689 .Hd Encrypted
meillo@104 1690 header fields is removed in mmh.
meillo@109 1691 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104 1692 .BU
meillo@84 1693 Native support for
meillo@84 1694 .Hd Face
meillo@104 1695 header fields has been removed, as well.
meillo@109 1696 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104 1697 This feature is similar to the
meillo@84 1698 .Hd X-Face
meillo@84 1699 header field in its intent,
meillo@21 1700 but takes a different approach to store the image.
meillo@84 1701 Instead of encoding the image data directly into the header field,
meillo@109 1702 it contains the hostname and UDP port where the image
meillo@109 1703 date can be retrieved.
meillo@109 1704 There exists even a third Face system,
meillo@109 1705 which is the successor of
meillo@109 1706 .Hd X-Face ,
meillo@109 1707 although it re-uses the
meillo@104 1708 .Hd Face
meillo@109 1709 header field.
meillo@109 1710 It was invented in 2005 and supports colored PNG images.
meillo@104 1711 None of the Face systems described here is popular today.
meillo@104 1712 Hence, mmh has no direct support for them.
meillo@104 1713 .BU
meillo@104 1714 The
meillo@104 1715 .Hd Content-MD5
meillo@104 1716 header field was introduced by RFC\|1864.
meillo@104 1717 It provides detection of data corruption during the transfer.
meillo@104 1718 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104 1719 [RFC\|1864].
meillo@104 1720 The proper approach to verify content integrity in an
meillo@104 1721 end-to-end relationship is the use of digital cryptography.
meillo@104 1722 .\" XXX (RFCs FIXME).
meillo@104 1723 On the other hand, transfer protocols should detect corruption during
meillo@109 1724 the transmission.
meillo@109 1725 The TCP includes a checksum field therefore.
meillo@104 1726 These two approaches in combinations render the
meillo@104 1727 .Hd Content-MD5
meillo@104 1728 header field superfluous.
meillo@109 1729 Not a single one out of 4\|200 messages from two decades
meillo@109 1730 in an nmh-workers mailing list archive contains a
meillo@104 1731 .Hd Content-MD5
meillo@104 1732 header field.
meillo@104 1733 Neither did any of the 60\|000 messages in my personal mail storage.
meillo@104 1734 Removing the support for this header field,
meillo@104 1735 removed the last place where MD5 computation was needed.
meillo@109 1736 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104 1737 Hence, the MD5 code could be removed as well.
meillo@104 1738 Over 500 lines of code vanished by this one change.
meillo@104 1739
meillo@104 1740
meillo@104 1741 .U3 "MMDF maildrop support
meillo@21 1742 .P
meillo@104 1743 This type of format is conceptionally similar to the mbox format,
meillo@139 1744 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139 1745 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104 1746 Mbox is the de-facto standard maildrop format on Unix,
meillo@109 1747 whereas the MMDF maildrop format became forgotten.
meillo@104 1748 I did drop MMDF maildrop format support.
meillo@109 1749 Mbox is the only packed mailbox format supported in mmh.
meillo@104 1750 .P
meillo@109 1751 The simplifications within the code were moderate.
meillo@109 1752 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109 1753 But also, switches of
meillo@109 1754 .Pn packf
meillo@104 1755 and
meillo@109 1756 .Pn rcvpack
meillo@109 1757 could be removed.
meillo@109 1758 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109 1759 In the message parsing function
meillo@109 1760 .Fn sbr/m_getfld.c ,
meillo@109 1761 knowledge of MMDF packed mail boxes was removed.
meillo@109 1762 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109 1763 Further code structure simplifications may be possible there,
meillo@109 1764 because only one single packed mailbox format is left to be supported.
meillo@104 1765 I have not worked on them yet because
meillo@104 1766 .Fu m_getfld()
meillo@104 1767 is heavily optimized and thus dangerous to touch.
meillo@104 1768 The risk of damaging the intricate workings of the optimized code is
meillo@104 1769 too high.
meillo@104 1770 .\" XXX: move somewhere else
meillo@104 1771 This problem is know to the developers of nmh, too.
meillo@109 1772 They also avoid touching this minefield.
meillo@104 1773
meillo@12 1774
meillo@101 1775 .U3 "Prompter's Control Keys
meillo@20 1776 .P
meillo@20 1777 The program
meillo@20 1778 .Pn prompter
meillo@104 1779 queries the user to fill in a message form.
meillo@104 1780 When used by
meillo@20 1781 .Pn comp
meillo@104 1782 as
meillo@104 1783 .Cl "comp -editor prompter" ,
meillo@20 1784 the resulting behavior is similar to
meillo@20 1785 .Pn mailx .
meillo@51 1786 Apparently,
meillo@20 1787 .Pn prompter
meillo@104 1788 hadn't been touched lately.
meillo@104 1789 Otherwise it's hardly explainable why it
meillo@20 1790 still offered the switches
meillo@84 1791 .Sw -erase
meillo@84 1792 .Ar chr
meillo@20 1793 and
meillo@84 1794 .Sw -kill
meillo@84 1795 .Ar chr
meillo@20 1796 to name the characters for command line editing.
meillo@21 1797 The times when this had been necessary are long time gone.
meillo@20 1798 Today these things work out-of-the-box, and if not, are configured
meillo@20 1799 with the standard tool
meillo@20 1800 .Pn stty .
meillo@104 1801 The switches are removed now
meillo@104 1802 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20 1803
meillo@104 1804
meillo@109 1805 .U3 "Hardcopy Terminal Support
meillo@21 1806 .P
meillo@109 1807 More of a funny anecdote is a check for being connected to a
meillo@109 1808 hardcopy terminal.
meillo@109 1809 It remained in the code until Spring 2012, when I finally removed it
meillo@104 1810 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@109 1811 I would be truly happy to see such a terminal in action today,
meillo@109 1812 maybe even being able to work on it.
meillo@109 1813 But I fear my chances are null.
meillo@21 1814 .P
meillo@109 1815 The check only prevented a pager to be placed between the printing
meillo@104 1816 program (\c
meillo@104 1817 .Pn mhl )
meillo@104 1818 and the terminal.
meillo@109 1819 In nmh, this could have been ensured statically with the
meillo@104 1820 .Sw -nomoreproc
meillo@109 1821 at the command line, too.
meillo@121 1822 In mmh, setting the profile entry
meillo@104 1823 .Pe Pager
meillo@104 1824 or the environment variable
meillo@104 1825 .Ev PAGER
meillo@104 1826 to
meillo@109 1827 .Pn cat
meillo@109 1828 does the job.
meillo@104 1829
meillo@104 1830
meillo@21 1831
meillo@12 1832
meillo@58 1833 .H2 "Attachments
meillo@22 1834 .P
meillo@101 1835 The mind model of email attachments is unrelated to MIME.
meillo@101 1836 Although the MIME RFCs (2045 through 2049) define the technical
meillo@109 1837 requirements for having attachments, they do not mention the word
meillo@101 1838 ``attachment''.
meillo@101 1839 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101 1840 [RFC\|2045], a more general concept.
meillo@101 1841 Multi-part messages are messages
meillo@101 1842 ``in which one or more different
meillo@101 1843 sets of data are combined in a single body''
meillo@101 1844 [RFC\|2046].
meillo@101 1845 MIME keeps its descriptions generic;
meillo@101 1846 it does not imply specific usage models.
meillo@109 1847 One usage model became prevalent: attachments.
meillo@101 1848 The idea is having a main text document with files of arbitrary kind
meillo@101 1849 attached to it.
meillo@101 1850 In MIME terms, this is a multi-part message having a text part first
meillo@110 1851 and parts of arbitrary type following.
meillo@101 1852 .P
meillo@101 1853 MH's MIME support is a direct implementation of the RFCs.
meillo@101 1854 The perception of the topic described in the RFCs is clearly visible
meillo@101 1855 in MH's implementation.
meillo@109 1856 In result, MH had all the MIME features but no idea of attachments.
meillo@109 1857 But users don't need all the MIME features,
meillo@109 1858 they want convenient attachment handling.
meillo@109 1859
meillo@102 1860
meillo@102 1861 .U3 "Composing MIME Messages
meillo@102 1862 .P
meillo@102 1863 In order to improve the situation on the message composing side,
meillo@102 1864 Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101 1865 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102 1866 In the file
meillo@102 1867 .Fn docs/README-ATTACHMENTS ,
meillo@102 1868 he described his motivation to do so as such:
meillo@101 1869 .QS
meillo@101 1870 Although nmh contains the necessary functionality for MIME message handing,
meillo@101 1871 the interface to this functionality is pretty obtuse.
meillo@101 1872 There's no way that I'm ever going to convince my partner to write
meillo@101 1873 .Pn mhbuild
meillo@101 1874 composition files!
meillo@101 1875 .QE
meillo@102 1876 .LP
meillo@102 1877 With this change, the mind model of attachments entered nmh.
meillo@102 1878 In the same document:
meillo@101 1879 .QS
meillo@101 1880 These changes simplify the task of managing attachments on draft files.
meillo@101 1881 They allow attachments to be added, listed, and deleted.
meillo@101 1882 MIME messages are automatically created when drafts with attachments
meillo@101 1883 are sent.
meillo@101 1884 .QE
meillo@102 1885 .LP
meillo@102 1886 Unfortunately, the attachment system,
meillo@102 1887 like any new facilities in nmh,
meillo@110 1888 was inactive by default.
meillo@101 1889 .P
meillo@101 1890 During my work in Argentina, I tried to improve the attachment system.
meillo@102 1891 But, because of great opposition in the nmh community,
meillo@102 1892 my patch died as a proposal on the mailing list, after long discussions.
meillo@101 1893 .[
meillo@101 1894 nmh-workers attachment proposal
meillo@101 1895 .]
meillo@110 1896 In January 2012, I extended the patch and applied it to mmh.
meillo@101 1897 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102 1898 In mmh, the attachment system is active by default.
meillo@102 1899 Instead of command line switches, the
meillo@102 1900 .Pe Attachment-Header
meillo@102 1901 profile entry is used to specify
meillo@102 1902 the name of the attachment header field.
meillo@102 1903 It is pre-defined to
meillo@102 1904 .Hd Attach .
meillo@101 1905 .P
meillo@101 1906 To add an attachment to a draft, simply add an attachment header:
meillo@101 1907 .VS
meillo@101 1908 To: bob
meillo@101 1909 Subject: The file you wanted
meillo@101 1910 Attach: /path/to/the/file-bob-wanted
meillo@101 1911 --------
meillo@101 1912 Here it is.
meillo@101 1913 VE
meillo@101 1914 The header field can be added to the draft manually in the editor,
meillo@102 1915 or by using the `attach' command at the WhatNow prompt, or
meillo@102 1916 non-interactively with
meillo@101 1917 .Pn anno :
meillo@101 1918 .VS
meillo@102 1919 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101 1920 VE
meillo@102 1921 Drafts with attachment headers are converted to MIME automatically by
meillo@102 1922 .Pn send .
meillo@102 1923 The conversion to MIME is invisible to the user.
meillo@102 1924 The draft stored in the draft folder is always in source form, with
meillo@101 1925 attachment headers.
meillo@101 1926 If the MIMEification fails, for instance because the file to attach
meillo@101 1927 is not accessible, the original draft is not changed.
meillo@101 1928 .P
meillo@102 1929 The attachment system handles the forwarding of messages, too.
meillo@101 1930 If the attachment header value starts with a plus character (`+'),
meillo@101 1931 like in
meillo@101 1932 .Cl "Attach: +bob 30 42" ,
meillo@101 1933 The given messages in the specified folder will be attached.
meillo@101 1934 This allowed to simplify
meillo@101 1935 .Pn forw .
meillo@101 1936 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101 1937 .P
meillo@101 1938 Closely related to attachments is non-ASCII text content,
meillo@101 1939 because it requires MIME too.
meillo@102 1940 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101 1941 to have the draft converted to MIME.
meillo@102 1942 This was necessary whenever the draft contained non-ASCII characters.
meillo@101 1943 If the user did not call `mime', a broken message would be sent.
meillo@101 1944 Therefore, the
meillo@101 1945 .Pe automimeproc
meillo@101 1946 profile entry could be specified to have the `mime' command invoked
meillo@102 1947 automatically each time.
meillo@101 1948 Unfortunately, this approach conflicted with with attachment system
meillo@101 1949 because the draft would already be in MIME format at the time
meillo@101 1950 when the attachment system wanted to MIMEify it.
meillo@102 1951 To use nmh's attachment system, `mime' must not be called at the
meillo@102 1952 WhatNow prompt and
meillo@101 1953 .Pe automimeproc
meillo@102 1954 must not be set in the profile.
meillo@101 1955 But then the case of non-ASCII text without attachment headers was
meillo@101 1956 not caught.
meillo@102 1957 All in all, the solution was complex and irritating.
meillo@102 1958 My patch from December 2010 would have simplified the situation.
meillo@102 1959 .P
meillo@101 1960 Mmh's current solution is even more elaborate.
meillo@101 1961 Any necessary MIMEification is done automatically.
meillo@101 1962 There is no `mime' command at the WhatNow prompt anymore.
meillo@102 1963 The draft will be converted automatically to MIME when either an
meillo@102 1964 attachment header or non-ASCII text is present.
meillo@101 1965 Further more, the special meaning of the hash character (`#')
meillo@102 1966 at line beginnings in the draft message is removed.
meillo@102 1967 Users need not at all deal with the whole topic.
meillo@101 1968 .P
meillo@102 1969 Although the new approach does not anymore support arbitrary MIME
meillo@102 1970 compositions directly, the full power of
meillo@101 1971 .Pn mhbuild
meillo@101 1972 can still be accessed.
meillo@102 1973 Given no attachment headers are included, the user can create
meillo@101 1974 .Pn mhbuild
meillo@102 1975 composition drafts like in nmh.
meillo@101 1976 Then, at the WhatNow prompt, he needs to invoke
meillo@101 1977 .Cl "edit mhbuild
meillo@101 1978 to convert it to MIME.
meillo@110 1979 Because the resulting draft does neither contain non-ASCII characters
meillo@102 1980 nor has it attachment headers, the attachment system will not touch it.
meillo@101 1981 .P
meillo@121 1982 The approach taken in mmh is tailored towards todays most common case:
meillo@101 1983 a text part with possibly attachments.
meillo@102 1984 This case is simplified a lot for users.
meillo@102 1985
meillo@112 1986
meillo@102 1987 .U3 "MIME Type Guessing
meillo@102 1988 .P
meillo@102 1989 The use of
meillo@101 1990 .Pn mhbuild
meillo@102 1991 composition drafts had one notable advantage over attachment headers
meillo@102 1992 from the programmer's point of view: The user provides the appropriate
meillo@102 1993 MIME types for files to include.
meillo@102 1994 The attachment system needs to find out the correct MIME type itself.
meillo@102 1995 This is a difficult task, yet it spares the user irritating work.
meillo@102 1996 Determining the correct MIME type of content is partly mechanical,
meillo@102 1997 partly intelligent work.
meillo@102 1998 Forcing the user to find out the correct MIME type,
meillo@102 1999 forces him to do partly mechanical work.
meillo@102 2000 Letting the computer do the work, can lead to bad choices for difficult
meillo@102 2001 content.
meillo@102 2002 For mmh, the latter option was chosen.
meillo@102 2003 .P
meillo@102 2004 Determining the MIME type by the suffix of the file name is a dumb
meillo@102 2005 approach, yet it is simple to implement and provides good results
meillo@102 2006 for the common cases.
meillo@102 2007 Mmh implements this approach in the
meillo@102 2008 .Pn print-mimetype
meillo@102 2009 script.
meillo@112 2010 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44
meillo@102 2011 Using it is the default choice.
meillo@102 2012 .P
meillo@112 2013 A far better, though less portable, approach is the use of
meillo@102 2014 .Pn file .
meillo@102 2015 This standard tool tries to determine the type of files.
meillo@102 2016 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102 2017 Additionally, its output was only intended for human beings,
meillo@102 2018 but not to be used by programs.
meillo@102 2019 It varies much.
meillo@102 2020 Nevertheless, modern versions of GNU
meillo@102 2021 .Pn file ,
meillo@102 2022 which is prevalent on the popular GNU/Linux systems,
meillo@102 2023 provides MIME type output in machine-readable form.
meillo@102 2024 Although this solution is highly system-dependent,
meillo@102 2025 it solves the difficult problem well.
meillo@102 2026 On systems where GNU
meillo@102 2027 .Pn file ,
meillo@102 2028 version 5.04 or higher, is available it should be used.
meillo@102 2029 One needs to specify the following profile entry to do so:
meillo@112 2030 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6
meillo@102 2031 .VS
meillo@102 2032 Mime-Type-Query: file -b --mime
meillo@102 2033 VE
meillo@102 2034 .LP
meillo@102 2035 Other versions of
meillo@102 2036 .Pn file
meillo@102 2037 might possibly be usable with wrapper scripts to reformat the output.
meillo@102 2038 The diversity among
meillo@102 2039 .Pn file
meillo@102 2040 implementations is great; one needs to check the local variant.
meillo@102 2041 .P
meillo@102 2042 If no MIME type can be determined, text content gets sent as
meillo@102 2043 `text/plain' and anything else under the generic fall-back type
meillo@102 2044 `application/octet-stream'.
meillo@102 2045 It is not possible in mmh to override the automatic MIME type guessing
meillo@102 2046 for a specific file.
meillo@102 2047 To do so, the user would need to know in advance for which file
meillo@102 2048 the automatic guessing does fail, or the system would require interaction.
meillo@102 2049 I consider both cases impractical.
meillo@102 2050 The existing solution should be sufficient.
meillo@102 2051 If not, the user may always fall back to
meillo@102 2052 .Pn mhbuild
meillo@102 2053 composition drafts and ignore the attachment system.
meillo@101 2054
meillo@102 2055
meillo@102 2056 .U3 "Storing Attachments
meillo@102 2057 .P
meillo@108 2058 Extracting MIME parts of a message and storing them to disk is done by
meillo@108 2059 .Pn mhstore .
meillo@108 2060 The program has two operation modes,
meillo@108 2061 .Sw -auto
meillo@108 2062 and
meillo@108 2063 .Sw -noauto .
meillo@108 2064 With the former one, each part is stored under the filename given in the
meillo@108 2065 MIME part's meta information, if available.
meillo@108 2066 This naming information is usually available for modern attachments.
meillo@108 2067 If no filename is available, this MIME part is stored as if
meillo@108 2068 .Sw -noauto
meillo@108 2069 would have been specified.
meillo@108 2070 In the
meillo@108 2071 .Sw -noauto
meillo@108 2072 mode, the parts are processed according to rules, defined by
meillo@108 2073 .Pe mhstore-store-*
meillo@108 2074 profile entries.
meillo@108 2075 These rules define generic filename templates for storing
meillo@108 2076 or commands to post-process the contents in arbitrary ways.
meillo@108 2077 If no matching rule is available the part is stored under a generic
meillo@108 2078 filename, built from message number, MIME part number, and MIME type.
meillo@108 2079 .P
meillo@108 2080 The
meillo@108 2081 .Sw -noauto
meillo@108 2082 mode had been the default in nmh because it was considered safe,
meillo@108 2083 in contrast to the
meillo@108 2084 .Sw -auto
meillo@108 2085 mode.
meillo@108 2086 In mmh,
meillo@108 2087 .Sw -auto
meillo@108 2088 is not dangerous anymore.
meillo@108 2089 Two changes were necessary:
meillo@108 2090 .BU
meillo@108 2091 Any directory path is removed from the proposed filename.
meillo@108 2092 Thus, the files are always stored in the expected directory.
meillo@108 2093 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@108 2094 .BU
meillo@108 2095 Tar files are not extracted automatically any more.
meillo@108 2096 Thus, the rest of the file system will not be touched.
meillo@108 2097 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108 2098 .LP
meillo@108 2099 Now, the outcome of mmh's
meillo@108 2100 .Cl "mhstore -auto
meillo@110 2101 can be foreseen from the output of
meillo@108 2102 .Cl "mhlist -verbose" .
meillo@108 2103 .P
meillo@108 2104 The
meillo@108 2105 .Sw -noauto
meillo@108 2106 mode is seen to be more powerful but less convenient.
meillo@108 2107 On the other hand,
meillo@108 2108 .Sw -auto
meillo@108 2109 is safe now and
meillo@108 2110 storing attachments under their original name is intuitive.
meillo@108 2111 Hence,
meillo@108 2112 .Sw -auto
meillo@108 2113 serves better as the default option.
meillo@108 2114 .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108 2115 .P
meillo@108 2116 Files are stored into the directory given by the
meillo@108 2117 .Pe Nmh-Storage
meillo@108 2118 profile entry, if set, or
meillo@108 2119 into the current working directory, otherwise.
meillo@108 2120 Storing to different directories is only possible with
meillo@108 2121 .Pe mhstore-store-*
meillo@108 2122 profile entries.
meillo@108 2123 .P
meillo@108 2124 Still, in both modes, existing files get overwritten silently.
meillo@108 2125 This can be considered a bug.
meillo@108 2126 Yet, each other behavior has its draw-backs, too.
meillo@108 2127 Refusing to replace files requires adding a
meillo@108 2128 .Sw -force
meillo@108 2129 option.
meillo@108 2130 Users will likely need to invoke
meillo@108 2131 .Pn mhstore
meillo@108 2132 a second time with
meillo@108 2133 .Sw -force
meillo@108 2134 then.
meillo@108 2135 Eventually, only the user can decide in the concrete case.
meillo@108 2136 This requires interaction, which I like to avoid if possible.
meillo@108 2137 Appending a unique suffix to the filename is another bad option.
meillo@108 2138 For now, the behavior remains as it is.
meillo@108 2139 .P
meillo@108 2140 In mmh, only MIME parts of type message are special in
meillo@108 2141 .Pn mhstore 's
meillo@108 2142 .Sw -auto
meillo@108 2143 mode.
meillo@108 2144 Instead of storing message/rfc822 parts as files to disk,
meillo@108 2145 they are stored as messages into the current mail folder.
meillo@108 2146 The same applies to message/partial, only, the parts are reassembled
meillo@108 2147 automatically before.
meillo@108 2148 Parts of type message/external-body are not automatically retrieved
meillo@108 2149 anymore. Instead, Information on how to retrieve them is output.
meillo@108 2150 Not supporting this rare case saved nearly one thousand lines of code.
meillo@108 2151 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108 2152 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108 2153 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@108 2154 Not special anymore is `application/octet-stream; type=tar'.
meillo@108 2155 Automatically extracting such MIME parts had been the dangerous part
meillo@108 2156 of the
meillo@108 2157 .Sw -auto
meillo@108 2158 mode.
meillo@108 2159 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108 2160
meillo@102 2161
meillo@102 2162
meillo@102 2163 .U3 "Showing MIME Messages
meillo@102 2164 .P
meillo@114 2165 The program
meillo@114 2166 .Pn mhshow
meillo@114 2167 had been written to display MIME messages.
meillo@114 2168 It implemented the conceptional view of the MIME RFCs.
meillo@114 2169 Nmh's
meillo@114 2170 .Pn mhshow
meillo@114 2171 handled each MIME part independently, presenting them separately
meillo@114 2172 to the user.
meillo@114 2173 This does not match today's understanding of email attachments,
meillo@114 2174 where displaying a message is seen to be a single, integrated operation.
meillo@114 2175 Today, email messages are expected to consist of a main text part
meillo@114 2176 plus possibly attachments.
meillo@114 2177 They are not any more seen to be arbitrary MIME hierarchies with
meillo@114 2178 information on how to display the individual parts.
meillo@114 2179 I adjusted
meillo@114 2180 .Pn mhshow 's
meillo@114 2181 behavior to the modern view on the topic.
meillo@114 2182 .P
meillo@114 2183 Note that this section completely ignores the original
meillo@114 2184 .Pn show
meillo@114 2185 program, because it was not capable to display MIME messages
meillo@114 2186 and is no longer part of mmh.
meillo@114 2187 Although
meillo@114 2188 .Pn mhshow
meillo@114 2189 was renamed to
meillo@114 2190 .Pn show
meillo@114 2191 in mmh, this section uses the name
meillo@114 2192 .Pn mhshow ,
meillo@114 2193 in order to avoid confusion.
meillo@114 2194 .P
meillo@114 2195 In mmh, the basic idea is that
meillo@114 2196 .Pn mhshow
meillo@114 2197 should display a message in one single pager session.
meillo@114 2198 Therefore,
meillo@114 2199 .Pn mhshow
meillo@114 2200 invokes a pager session for all its output,
meillo@114 2201 whenever it prints to a terminal.
meillo@114 2202 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e
meillo@114 2203 In consequence,
meillo@114 2204 .Pn mhl
meillo@114 2205 does no more invoke a pager.
meillo@114 2206 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@114 2207 With
meillo@114 2208 .Pn mhshow
meillo@114 2209 replacing the original
meillo@114 2210 .Pn show ,
meillo@114 2211 output from
meillo@114 2212 .Pn mhl
meillo@114 2213 does not go to the terminal directly, but through
meillo@114 2214 .Pn mhshow .
meillo@114 2215 Hence,
meillo@114 2216 .Pn mhl
meillo@114 2217 does not need to invoke a pager.
meillo@114 2218 The one and only job of
meillo@114 2219 .Pn mhl
meillo@114 2220 is to format messages or parts of them.
meillo@114 2221 The only place in mmh, where a pager is invoked is
meillo@114 2222 .Pn mhshow .
meillo@114 2223 .P
meillo@114 2224 .Pe mhshow-show-*
meillo@114 2225 profile entries can be used to display MIME parts in a specific way.
meillo@114 2226 For instance, PDF and Postscript files could be converted to plain text
meillo@114 2227 to display them in the terminal.
meillo@114 2228 In mmh, the displaying of MIME parts will always be done serially.
meillo@114 2229 The request to display the MIME type `multipart/parallel' in parallel
meillo@114 2230 is ignored.
meillo@114 2231 It is simply treated as `multipart/mixed'.
meillo@114 2232 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6
meillo@114 2233 This could already be requested with the, now removed,
meillo@114 2234 .Sw -serialonly
meillo@114 2235 switch of
meillo@114 2236 .Pn mhshow .
meillo@114 2237 As MIME parts are always processed exclusively , i.e. serially,
meillo@114 2238 the `%e' escape in
meillo@114 2239 .Pe mhshow-show-*
meillo@114 2240 profile entries became useless and was thus removed.
meillo@114 2241 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae
meillo@114 2242 .P
meillo@114 2243 In the intended setup, only text content would be displayed.
meillo@114 2244 Non-text content would be converted to text by appropriate
meillo@114 2245 .Pe mhshow-show-*
meillo@114 2246 profile entries before, if possible and wanted.
meillo@114 2247 All output would be displayed in a single pager session.
meillo@114 2248 Other kinds of attachments are ignored.
meillo@114 2249 With
meillo@114 2250 .Pe mhshow-show-*
meillo@114 2251 profile entries for them, they can be displayed serially along
meillo@114 2252 the message.
meillo@114 2253 For parallel display, the attachments need to be stored to disk first.
meillo@114 2254 .P
meillo@114 2255 To display text content in foreign charsets, they need to be converted
meillo@114 2256 to the native charset.
meillo@114 2257 Therefore,
meillo@114 2258 .Pe mhshow-charset-*
meillo@114 2259 profile entries used to be needed.
meillo@121 2260 In mmh, the conversion is done automatically by piping the text through
meillo@114 2261 the
meillo@114 2262 .Pn iconv
meillo@114 2263 command, if necessary.
meillo@114 2264 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60
meillo@114 2265 Custom
meillo@114 2266 .Pe mhshow-show-*
meillo@114 2267 rules for textual content might need a
meillo@114 2268 .Cl "iconv -f %c %f |
meillo@114 2269 prefix to have the text converted to the native charset.
meillo@114 2270 .P
meillo@121 2271 Although the conversion of foreign charsets to the native one
meillo@114 2272 has improved, it is not consistent enough.
meillo@114 2273 Further work needs to be done and
meillo@114 2274 the basic concepts in this field need to be re-thought.
meillo@114 2275 Though, the default setup of mmh displays message in foreign charsets
meillo@114 2276 correctly without the need to configure anything.
meillo@114 2277
meillo@114 2278
meillo@114 2279 .ig
meillo@114 2280
meillo@114 2281 .P
meillo@114 2282 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@114 2283 These tools won't download the contents automatically anymore. Instead,
meillo@114 2284 they print the information needed to get the contents. If someone should
meillo@114 2285 really receive one of those rare message/external-body messages, he can
meillo@114 2286 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114 2287 it!
meillo@114 2288 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114 2289 ~/.netrc are gone now.)
meillo@114 2290 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114 2291
meillo@114 2292 ..
meillo@102 2293
meillo@58 2294
meillo@58 2295
meillo@58 2296 .H2 "Digital Cryptography
meillo@22 2297 .P
meillo@58 2298 Signing and encryption.
meillo@112 2299 .P
meillo@112 2300 FIXME
meillo@58 2301
meillo@58 2302
meillo@102 2303
meillo@133 2304 .H2 "Draft and Trash Folder
meillo@131 2305 .P
meillo@58 2306
meillo@131 2307 .U3 "Draft Folder
meillo@131 2308 .P
meillo@131 2309 In the beginning, MH had the concept of a draft message.
meillo@131 2310 This is the file
meillo@131 2311 .Fn draft
meillo@131 2312 in the MH directory, which is treated special.
meillo@131 2313 On composing a message, this draft file was used.
meillo@131 2314 As the draft file was one particular file, only one draft could be
meillo@131 2315 managed at any time.
meillo@131 2316 When starting to compose another message before the former one was sent,
meillo@131 2317 the user had to decide among:
meillo@131 2318 .BU
meillo@131 2319 Use the old draft to finish and send it before starting with a new one.
meillo@131 2320 .BU
meillo@131 2321 Discard the old draft, replacing it with the new one.
meillo@131 2322 .BU
meillo@131 2323 Preserve the old draft by refiling it to a folder.
meillo@131 2324 .P
meillo@131 2325 This was, it was only possible to work in alternation on multiple drafts.
meillo@131 2326 Therefore, the current draft needed to be refiled to a folder and
meillo@131 2327 another one re-using for editing.
meillo@131 2328 Working on multiple drafts at the same time was impossible.
meillo@131 2329 The usual approach of switching to a different MH context did not
meillo@131 2330 change anything.
meillo@131 2331 .P
meillo@131 2332 The draft folder facility exists to
meillo@131 2333 allow true parallel editing of drafts, in a straight forward way.
meillo@131 2334 It was introduced by Marshall T. Rose, already in 1984.
meillo@131 2335 Similar to other new features, the draft folder was inactive by default.
meillo@131 2336 Even in nmh, the highly useful draft folder was not available
meillo@131 2337 out-of-the-box.
meillo@131 2338 At least, Richard Coleman added the man page
meillo@131 2339 .Mp mh-draft (5)
meillo@131 2340 to better document the feature.
meillo@131 2341 .P
meillo@131 2342 Not using the draft folder facility has the single advantage of having
meillo@131 2343 the draft file at a static location.
meillo@131 2344 This is simple in simple cases but the concept does not scale for more
meillo@131 2345 complex cases.
meillo@131 2346 The concept of the draft message is too limited for the problem.
meillo@131 2347 Therefore the draft folder was introduced.
meillo@131 2348 It is the more powerful and more natural concept.
meillo@131 2349 The draft folder is a folder like any other folder in MH.
meillo@131 2350 Its messages can be listed like any other messages.
meillo@131 2351 A draft message is no longer a special case.
meillo@131 2352 Tools do not need special switches to work on the draft message.
meillo@131 2353 Hence corner-cases were removed.
meillo@131 2354 .P
meillo@131 2355 The trivial part of the work was activating the draft folder with a
meillo@131 2356 default name.
meillo@131 2357 I chose the name
meillo@131 2358 .Fn +drafts
meillo@131 2359 for obvious reasons.
meillo@131 2360 In consequence, the command line switches
meillo@131 2361 .Sw -draftfolder
meillo@131 2362 and
meillo@131 2363 .Sw -draftmessage
meillo@131 2364 could be removed.
meillo@131 2365 More difficult but also more improving was updating the tools to the
meillo@131 2366 new concept.
meillo@131 2367 For nearly three decades, the tools needed to support two draft handling
meillo@131 2368 approaches.
meillo@131 2369 By fully switching to the draft folder, the tools could be simplified
meillo@131 2370 by dropping the awkward draft message handling code.
meillo@131 2371 .Sw -draft
meillo@131 2372 switches were removed because operating on a draft message is no longer
meillo@131 2373 special.
meillo@131 2374 It became indistinguishable to operating on any other message.
meillo@131 2375 There is no more need to query the user for draft handling.
meillo@131 2376 It is always possible to add another new draft.
meillo@131 2377 Refiling drafts is without difference to refiling other messages.
meillo@131 2378 All these special cases are gone.
meillo@131 2379 Yet, one draft-related switch remained.
meillo@131 2380 .Pn comp
meillo@131 2381 still has
meillo@131 2382 .Sw -[no]use
meillo@131 2383 for switching between two modes:
meillo@131 2384 .BU
meillo@131 2385 .Sw -use :
meillo@131 2386 Modify an existing draft.
meillo@131 2387 .BU
meillo@131 2388 .Sw -nouse :
meillo@131 2389 Compose a new draft, possibly taking some existing message as a form.
meillo@131 2390 .P
meillo@131 2391 In either case, the behavior of
meillo@131 2392 .Pn comp
meillo@131 2393 is deterministic.
meillo@131 2394 .P
meillo@131 2395 .Pn send
meillo@131 2396 now operates on the current message in the draft folder by default.
meillo@131 2397 As message and folder can both be overridden by specifying them on
meillo@131 2398 the command line, it is possible to send any message in the mail storage
meillo@131 2399 by simply specifying its number and folder.
meillo@131 2400 In contrast to the other tools,
meillo@131 2401 .Pn send
meillo@131 2402 takes the draft folder as its default folder.
meillo@131 2403 .P
meillo@131 2404 Dropping the draft message concept in favor for the draft folder concept,
meillo@131 2405 removed special cases with regular cases.
meillo@131 2406 This simplified the source code of the tools, as well as the concepts.
meillo@131 2407 In mmh, draft management does not break with the MH concepts
meillo@131 2408 but applies them.
meillo@133 2409 .Cl "scan +drafts" ,
meillo@133 2410 for instance, is a truly natural request.
meillo@131 2411 Most of the work was already done by Rose in the eighties.
meillo@133 2412 The original improvement of mmh is dropping the old draft message approach
meillo@133 2413 and thus simplifying the tools, the documentation and the system as a whole.
meillo@131 2414 Although my part in the draft handling improvement was small,
meillo@133 2415 it was an important one.
meillo@131 2416
meillo@131 2417
meillo@131 2418 .U3 "Trash Folder
meillo@131 2419 .P
meillo@131 2420 Similar to the situation for drafts is the situation for removed messages.
meillo@131 2421 Historically, a message was ``deleted'' by prepending a specific
meillo@131 2422 \fIbackup prefix\fP, usually the comma character,
meillo@131 2423 to the file name.
meillo@131 2424 The specific message would vanish from MH because only files with
meillo@131 2425 non-digit characters in their name are not treated as messages.
meillo@131 2426 Although files remained in the file system,
meillo@131 2427 the messages were no more visible in MH.
meillo@131 2428 To truly delete them, a maintenance job is needed.
meillo@131 2429 Usually a cron job is installed to delete them after a grace time.
meillo@131 2430 For instance:
meillo@131 2431 .VS
meillo@131 2432 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131 2433 VE
meillo@131 2434 In such a setup, the original message can be restored
meillo@131 2435 within the grace time interval by stripping the
meillo@131 2436 the backup prefix from the file name.
meillo@131 2437 But one can not rely on this statement.
meillo@131 2438 If the last message of a folder with six messages (1-6) is removed,
meillo@131 2439 message
meillo@131 2440 .Fn 6 ,
meillo@131 2441 becomes file
meillo@131 2442 .Fn ,6 .
meillo@131 2443 If then a new message enters the same folder, it will be given
meillo@131 2444 the number one higher than the highest existing message.
meillo@131 2445 In this case the message is named
meillo@131 2446 .Fn 6
meillo@131 2447 then.
meillo@131 2448 If this message is removed as well,
meillo@131 2449 then the backup of the former message gets overwritten.
meillo@131 2450 Hence, the ability to restore removed messages does not only depend on
meillo@131 2451 the ``sweeping cron job'' but also on the removing of further messages.
meillo@131 2452 It is undesirable to have such obscure and complex mechanisms.
meillo@131 2453 The user should be given a small set of clear assertions.
meillo@131 2454 ``Removed files are restorable within a seven-day grace time.''
meillo@131 2455 is such a clear assertion.
meillo@131 2456 With the addition ``... unless a message with the same name in the
meillo@131 2457 same folder is removed before.'' the statement becomes complex.
meillo@131 2458 A user will hardly be able to keep track of any removal to know
meillo@131 2459 if the assertion still holds true for a specific file.
meillo@131 2460 The the real mechanism is practically obscure to the user.
meillo@131 2461 The consequences of further removals are not obvious.
meillo@131 2462 .P
meillo@131 2463 Further more, the backup files are scattered within the whole mail storage.
meillo@131 2464 This complicates managing them.
meillo@131 2465 It is possible, with help of
meillo@131 2466 .Pn find ,
meillo@131 2467 but everything would be more convenient
meillo@131 2468 if the deleted messages would be collected in one place.
meillo@131 2469 .P
meillo@131 2470 The profile entry
meillo@131 2471 .Pe rmmproc
meillo@131 2472 (previously named
meillo@131 2473 .Pe Delete-Prog )
meillo@131 2474 was introduced very early to improve the situation.
meillo@131 2475 It could be set to any command, which would be executed to removed
meillo@131 2476 the specified messages.
meillo@131 2477 This would override the default action, described above.
meillo@131 2478 Refiling the to-be-removed files to a garbage folder is the usual example.
meillo@131 2479 Nmh's man page
meillo@131 2480 .Mp rmm (1)
meillo@131 2481 proposes to set the
meillo@131 2482 .Pe rmmproc
meillo@131 2483 to
meillo@131 2484 .Cl "refile +d
meillo@131 2485 to move messages to the garbage folder,
meillo@131 2486 .Fn +d ,
meillo@131 2487 instead of renaming them with the backup prefix.
meillo@131 2488 The man page proposes additionally the expunge command
meillo@131 2489 .Cl "rm `mhpath +d all`
meillo@131 2490 to empty the garbage folder.
meillo@131 2491 .P
meillo@131 2492 Removing messages in such a way has advantages.
meillo@131 2493 The mail storage is prevented from being cluttered with removed messages
meillo@131 2494 because they are all collected in one place.
meillo@131 2495 Existing and removed messages are thus separated more strictly.
meillo@131 2496 No backup files are silently overwritten.
meillo@131 2497 Most important is the ability to keep removed messages in the MH domain.
meillo@131 2498 Messages in the trash folder can be listed like those in any other folder.
meillo@131 2499 Deleted messages can be displayed like any other messages.
meillo@131 2500 Restoring a deleted messages can be done with
meillo@131 2501 .Pn refile .
meillo@131 2502 All operations on deleted files are still covered by the MH tools.
meillo@131 2503 The trash folder is just like any other folder in the mail storage.
meillo@131 2504 .P
meillo@131 2505 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131 2506 in favor for replacing it by the better suiting trash folder system.
meillo@131 2507 Hence,
meillo@131 2508 .Pn rmm
meillo@131 2509 calls
meillo@131 2510 .Pn refile
meillo@131 2511 to move the to-be-removed message to the trash folder,
meillo@131 2512 .Fn +trash
meillo@131 2513 by default.
meillo@131 2514 To sweep it clean, one can use
meillo@131 2515 .Cl "rmm -unlink +trash a" ,
meillo@131 2516 where the
meillo@131 2517 .Sw -unlink
meillo@131 2518 switch causes the files to be unlinked.
meillo@131 2519 .P
meillo@131 2520 Dropping the legacy approach and completely converting to the new approach
meillo@131 2521 simplified the code base.
meillo@131 2522 The relationship between
meillo@131 2523 .Pn rmm
meillo@131 2524 and
meillo@131 2525 .Pn refile
meillo@131 2526 was inverted.
meillo@131 2527 In mmh,
meillo@131 2528 .Pn rmm
meillo@131 2529 invokes
meillo@131 2530 .Pn refile ,
meillo@131 2531 which used to be the other way round.
meillo@131 2532 Yet, the relationship is simpler now.
meillo@131 2533 No more can loops, like described in nmh's man page for
meillo@131 2534 .Mp refile (1),
meillo@131 2535 occur:
meillo@131 2536 .QS
meillo@131 2537 Since
meillo@131 2538 .Pn refile
meillo@131 2539 uses your
meillo@131 2540 .Pe rmmproc
meillo@131 2541 to delete the message, the
meillo@131 2542 .Pe rmmproc
meillo@131 2543 must NOT call
meillo@131 2544 .Pn refile
meillo@131 2545 without specifying
meillo@131 2546 .Sw -normmproc
meillo@131 2547 or you will create an infinite loop.
meillo@131 2548 .QE
meillo@131 2549 .LP
meillo@131 2550 .Pn rmm
meillo@131 2551 either unlinks a message with
meillo@131 2552 .Fu unlink()
meillo@131 2553 or invokes
meillo@131 2554 .Pn refile
meillo@131 2555 to move it to the trash folder.
meillo@131 2556 .Pn refile
meillo@131 2557 does not invoke any tools.
meillo@131 2558 .P
meillo@136 2559 By generalizing the message removal in the way that it became covered
meillo@136 2560 by the MH concepts made the whole system more powerful.
meillo@131 2561
meillo@131 2562
meillo@131 2563
meillo@131 2564
meillo@131 2565
meillo@133 2566 .H2 "Modern Defaults
meillo@133 2567 .P
meillo@133 2568 Nmh has a bunch of convenience-improving features inactive by default,
meillo@133 2569 although one can expect every new user wanting to have them active.
meillo@133 2570 The reason they are inactive by default is the wish to stay compatible
meillo@133 2571 with old versions.
meillo@136 2572 But what is the definition for old versions?
meillo@136 2573 Still, the highly useful draft folder facility has not been activated
meillo@136 2574 by default although it was introduced over twenty-five years ago.
meillo@133 2575 .[
meillo@133 2576 rose romine real work
meillo@133 2577 .]
meillo@136 2578 The community seems not to care.
meillo@136 2579 This is one of several examples that require new users to first build up
meillo@136 2580 a profile before they can access the modern features of nmh.
meillo@136 2581 Without an extensive profile, the setup is hardly usable
meillo@133 2582 for modern emailing.
meillo@133 2583 The point is not the customization of the setup,
meillo@136 2584 but the need to activate generally useful facilities.
meillo@133 2585 .P
meillo@133 2586 Yet, the real problem lies less in enabling the features, as this is
meillo@133 2587 straight forward as soon as one knows what he wants.
meillo@133 2588 The real problem is that new users need deep insights into the project
meillo@133 2589 before they find out what they are missing and that nmh actually
meillo@133 2590 provides it already, it just was not activated.
meillo@133 2591 To give an example, I needed one year of using nmh
meillo@133 2592 before I became aware of the existence of the attachment system.
meillo@133 2593 One could argue that this fact disqualifies my reading of the
meillo@133 2594 documentation.
meillo@133 2595 If I would have installed nmh from source back then, I could agree.
meillo@133 2596 Yet, I had used a prepackaged version and had expected that it would
meillo@133 2597 just work.
meillo@133 2598 Nevertheless, I had been convinced by the concepts of MH already
meillo@133 2599 and I am a software developer,
meillo@133 2600 still I required a lot of time to discover the cool features.
meillo@133 2601 How can we expect users to be even more advanced than me,
meillo@133 2602 just to allow them use MH in a convenient and modern way?
meillo@133 2603 Unless they are strongly convinced of the concepts, they will fail.
meillo@133 2604 I have seen friends of me giving up disappointed
meillo@133 2605 before they truly used the system,
meillo@133 2606 although they had been motivated in the beginning.
meillo@133 2607 They suffer hard enough to get used to the toolchest approach,
meillo@133 2608 we should spare them further inconveniences.
meillo@133 2609 .P
meillo@136 2610 Maintaining compatibility for its own sake is bad,
meillo@136 2611 because the code base collects more and more compatibility code.
meillo@136 2612 Sticking to the compatiblity code means remaining limited;
meillo@136 2613 not using it renders it unnecessary.
meillo@136 2614 Keeping unused alternative in the code is a bad choice as they likely
meillo@136 2615 gather bugs, by not being well tested.
meillo@136 2616 Also, the increased code size and the greater number of conditions
meillo@136 2617 increase the maintenance costs.
meillo@133 2618 If any MH implementation would be the back-end of widespread
meillo@133 2619 email clients with large user bases, compatibility would be more
meillo@133 2620 important.
meillo@133 2621 Yet, it appears as if this is not the case.
meillo@133 2622 Hence, compatibility is hardly important for technical reasons.
meillo@133 2623 Its importance originates rather from personal reasons.
meillo@133 2624 Nmh's user base is small and old.
meillo@133 2625 Changing the interfaces would cause inconvenience to long-term users of MH.
meillo@133 2626 It would force them to change their many years old MH configurations.
meillo@133 2627 I do understand this aspect, but it keeps new users from using MH.
meillo@133 2628 By sticking to the old users, new users are kept away.
meillo@133 2629 Yet, the future lies in new users.
meillo@133 2630 Hence, mmh invites new users by providing a convenient and modern setup,
meillo@133 2631 readily usable out-of-the-box.
meillo@133 2632 .P
meillo@136 2633 In mmh, all modern features are active by default and many previous
meillo@136 2634 approaches are removed or only accessible in manual ways.
meillo@136 2635 New default features include:
meillo@133 2636 .BU
meillo@133 2637 The attachment system (\c
meillo@133 2638 .Hd Attach ).
meillo@133 2639 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@133 2640 .BU
meillo@133 2641 The draft folder facility (\c
meillo@133 2642 .Fn +drafts ).
meillo@133 2643 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@133 2644 .BU
meillo@133 2645 The unseen sequence (`u')
meillo@133 2646 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@133 2647 and the sequence negation prefix (`!').
meillo@133 2648 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc
meillo@133 2649 .BU
meillo@133 2650 Quoting the original message in the reply.
meillo@133 2651 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@133 2652 .BU
meillo@133 2653 Forwarding messages using MIME.
meillo@133 2654 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@136 2655 .P
meillo@136 2656 In consequence, a setup with a profile that defines only the path to the
meillo@136 2657 mail storage, is already convenient to use.
meillo@136 2658 Again, Paul Vixie's ``edginess'' appeal supports the direction I took:
meillo@136 2659 ``the `main branch' should just be modern''.
meillo@136 2660 .[
meillo@136 2661 paul vixie edginess nmh-workers
meillo@136 2662 .]
meillo@131 2663
meillo@133 2664
meillo@133 2665
meillo@133 2666
meillo@133 2667
meillo@133 2668 .\" --------------------------------------------------------------
meillo@131 2669 .H1 "Styling
meillo@22 2670 .P
meillo@118 2671 Kernighan and Pike have emphasized the importance of style in the
meillo@118 2672 preface of their book:
meillo@118 2673 .[ [
meillo@118 2674 kernighan pike practice of programming
meillo@118 2675 .], p. x]
meillo@118 2676 .QS
meillo@118 2677 Chapter 1 discusses programming style.
meillo@118 2678 Good style is so important to good programming that we have chose
meillo@118 2679 to cover it first.
meillo@118 2680 .QE
meillo@118 2681 This section covers changes in mmh that were motivated by the desire
meillo@118 2682 to improve on style.
meillo@118 2683 Many of them follow the rules given in the quoted book.
meillo@118 2684 .[
meillo@118 2685 kernighan pike practice of programming
meillo@118 2686 .]
meillo@118 2687
meillo@118 2688
meillo@127 2689
meillo@127 2690
meillo@127 2691 .H2 "Code Style
meillo@118 2692 .P
meillo@118 2693 .U3 "Indentation Style
meillo@118 2694 .P
meillo@118 2695 Indentation styles are the holy cow of programmers.
meillo@118 2696 Again Kernighan and Pike:
meillo@118 2697 .[ [
meillo@118 2698 kernighan pike practice of programming
meillo@118 2699 .], p. 10]
meillo@118 2700 .QS
meillo@118 2701 Programmers have always argued about the layout of programs,
meillo@118 2702 but the specific style is much less important than its consistent
meillo@118 2703 application.
meillo@121 2704 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118 2705 time arguing.
meillo@118 2706 .QE
meillo@118 2707 .P
meillo@118 2708 I agree that the constant application is most important,
meillo@118 2709 but I believe that some styles have advantages over others.
meillo@118 2710 For instance the indentation with tab characters only.
meillo@118 2711 Tab characters directly map to the nesting level \(en
meillo@118 2712 one tab, one level.
meillo@118 2713 Tab characters are flexible because developers can adjust them to
meillo@118 2714 whatever width they like to have.
meillo@118 2715 There is no more need to run
meillo@118 2716 .Pn unexpand
meillo@118 2717 or
meillo@118 2718 .Pn entab
meillo@118 2719 programs to ensure the correct mixture of leading tabs and spaces.
meillo@118 2720 The simple rules are: (1) Leading whitespace must consist of tabs only.
meillo@118 2721 (2) Any other whitespace should consist of spaces.
meillo@121 2722 These two rules ensure the integrity of the visual appearance.
meillo@121 2723 Although reformatting existing code should be avoided, I did it.
meillo@136 2724 I did not waste time arguing; I just reformated the code.
meillo@118 2725 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118 2726
meillo@118 2727 .U3 "Comments
meillo@118 2728 .P
meillo@118 2729 Section 1.6 of
meillo@118 2730 .[ [
meillo@118 2731 kernighan pike practice of programming
meillo@118 2732 .], p. 23]
meillo@118 2733 demands: ``Don't belabor the obvious.''
meillo@122 2734 Hence, I simply removed all the comments in the following code excerpt:
meillo@118 2735 .VS
meillo@120 2736 context_replace(curfolder, folder); /* update current folder */
meillo@120 2737 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120 2738 seq_save(mp); /* synchronize message sequences */
meillo@120 2739 folder_free(mp); /* free folder/message structure */
meillo@120 2740 context_save(); /* save the context file */
meillo@120 2741
meillo@120 2742 [...]
meillo@120 2743
meillo@120 2744 int c; /* current character */
meillo@120 2745 char *cp; /* miscellaneous character pointer */
meillo@120 2746
meillo@120 2747 [...]
meillo@120 2748
meillo@120 2749 /* NUL-terminate the field */
meillo@120 2750 *cp = '\0';
meillo@118 2751 VE
meillo@120 2752 .Ci 426543622b377fc5d091455cba685e114b6df674
meillo@118 2753 .P
meillo@136 2754 The program code explains enough itself, already.
meillo@136 2755
meillo@118 2756
meillo@118 2757 .U3 "Names
meillo@118 2758 .P
meillo@118 2759 Kernighan and Pike suggest:
meillo@118 2760 ``Use active names for functions''.
meillo@118 2761 .[ [
meillo@118 2762 kernighan pike practice of programming
meillo@118 2763 .], p. 4]
meillo@118 2764 One application of this rule was the rename of
meillo@118 2765 .Fu check_charset()
meillo@118 2766 to
meillo@118 2767 .Fu is_native_charset() .
meillo@118 2768 .Ci 8d77b48284c58c135a6b2787e721597346ab056d
meillo@118 2769 The same change fixed a violation of ``Be accurate'' as well.
meillo@118 2770 The code did not match the expectation the function suggested,
meillo@118 2771 as it, for whatever reason, only compared the first ten characters
meillo@118 2772 of the charset name.
meillo@118 2773 .P
meillo@118 2774 More important than using active names is using descriptive names.
meillo@145 2775 .VS
meillo@145 2776 m_unknown(in); /* the MAGIC invocation... */
meillo@145 2777 VE
meillo@145 2778 Renaming the obscure
meillo@118 2779 .Fu m_unknown()
meillo@145 2780 function was a delightful event, although it made the code less funny.
meillo@118 2781 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846
meillo@118 2782 .P
meillo@118 2783 Magic numbers are generally considered bad style.
meillo@118 2784 Obviously, Kernighan and Pike agree:
meillo@118 2785 ``Give names to magic numbers''.
meillo@118 2786 .[ [
meillo@118 2787 kernighan pike practice of programming
meillo@118 2788 .], p. 19]
meillo@118 2789 One such change was naming the type of input \(en mbox or mail folder \(en
meillo@118 2790 to be scanned:
meillo@118 2791 .VS
meillo@118 2792 #define SCN_MBOX (-1)
meillo@118 2793 #define SCN_FOLD 0
meillo@118 2794 VE
meillo@118 2795 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@118 2796 .P
meillo@118 2797 The argument
meillo@118 2798 .Ar outnum
meillo@118 2799 of the function
meillo@118 2800 .Fu scan()
meillo@118 2801 in
meillo@118 2802 .Fn uip/scansbr.c
meillo@118 2803 defines the number of the message to be created.
meillo@118 2804 If no message is to be created, the argument is misused to transport
meillo@118 2805 program logic.
meillo@118 2806 This lead to obscure code.
meillo@118 2807 I improved the clarity of the code by introducing two variables:
meillo@118 2808 .VS
meillo@118 2809 int incing = (outnum > 0);
meillo@118 2810 int ismbox = (outnum != 0);
meillo@118 2811 VE
meillo@118 2812 They cover the magic values and are used for conditions.
meillo@118 2813 The variable
meillo@118 2814 .Ar outnum
meillo@118 2815 is only used when it holds an ordinary message number.
meillo@118 2816 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f
meillo@118 2817 The clarity improvement of the change showed detours in the program logic
meillo@118 2818 of related code parts.
meillo@118 2819 Having the new variables with descriptive names, a more
meillo@121 2820 straight forward implementation became apparent.
meillo@118 2821 Before the clarification was done,
meillo@118 2822 the possibility to improve had not be seen.
meillo@118 2823 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723
meillo@118 2824
meillo@133 2825
meillo@133 2826
meillo@133 2827 .H2 "Structural Rework
meillo@133 2828 .P
meillo@136 2829 Although the stylistic changes described up to here improve the
meillo@136 2830 readability of the source code, all of them are changes ``in the small''.
meillo@136 2831 Structural changes affect a much larger area.
meillo@136 2832 They are more difficult to do but lead to larger improvements,
meillo@136 2833 especially as they influence the outer shape of the tools as well.
meillo@118 2834 .P
meillo@118 2835 At the end of their chapter on style,
meillo@118 2836 Kernighan and Pike ask: ``But why worry about style?''
meillo@136 2837 Following are two examples of structural rework that show
meillo@136 2838 why style is important in the first place.
meillo@136 2839
meillo@136 2840
meillo@136 2841 .U3 "Rework of \f(CWanno\fP
meillo@118 2842 .P
meillo@120 2843 Until 2002,
meillo@120 2844 .Pn anno
meillo@120 2845 had six functional command line switches,
meillo@120 2846 .Sw -component
meillo@120 2847 and
meillo@120 2848 .Sw -text ,
meillo@120 2849 which took an argument each,
meillo@120 2850 and the two pairs of flags,
meillo@120 2851 .Sw -[no]date
meillo@120 2852 and
meillo@120 2853 .Sw -[no]inplace.,
meillo@120 2854 .Sw -component
meillo@120 2855 and
meillo@120 2856 .Sw -text ,
meillo@120 2857 which took an argument each,
meillo@120 2858 and the two pairs of flags,
meillo@120 2859 .Sw -[no]date
meillo@120 2860 and
meillo@120 2861 .Sw -[no]inplace .
meillo@120 2862 Then Jon Steinhart introduced his attachment system.
meillo@120 2863 In need for more advanced annotation handling, he extended
meillo@120 2864 .Pn anno .
meillo@120 2865 He added five more switches:
meillo@120 2866 .Sw -draft ,
meillo@120 2867 .Sw -list ,
meillo@120 2868 .Sw -delete ,
meillo@120 2869 .Sw -append ,
meillo@120 2870 and
meillo@120 2871 .Sw -number ,
meillo@120 2872 the last one taking an argument.
meillo@121 2873 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@120 2874 Later,
meillo@120 2875 .Sw -[no]preserve
meillo@120 2876 was added.
meillo@121 2877 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@120 2878 Then, the Synopsis section of the man page
meillo@120 2879 .Mp anno (1)
meillo@120 2880 read:
meillo@120 2881 .VS
meillo@120 2882 anno [+folder] [msgs] [-component field] [-inplace | -noinplace]
meillo@120 2883 [-date | -nodate] [-draft] [-append] [-list] [-delete]
meillo@120 2884 [-number [num|all]] [-preserve | -nopreserve] [-version]
meillo@120 2885 [-help] [-text body]
meillo@120 2886 VE
meillo@120 2887 .LP
meillo@120 2888 The implementation followed the same structure.
meillo@120 2889 Problems became visible when
meillo@120 2890 .Cl "anno -list -number 42
meillo@120 2891 worked on the current message instead on message number 42,
meillo@120 2892 and
meillo@120 2893 .Cl "anno -list -number l:5
meillo@124 2894 did not work on the last five messages but failed with the mysterious
meillo@120 2895 error message: ``anno: missing argument to -list''.
meillo@121 2896 Yet, the invocation matched the specification in the man page.
meillo@120 2897 There, the correct use of
meillo@120 2898 .Sw -number
meillo@120 2899 was defined as being
meillo@120 2900 .Cl "[-number [num|all]]
meillo@120 2901 and the textual description for the combination with
meillo@120 2902 .Sw -list
meillo@120 2903 read:
meillo@120 2904 .QS
meillo@120 2905 The -list option produces a listing of the field bodies for
meillo@120 2906 header fields with names matching the specified component,
meillo@120 2907 one per line. The listing is numbered, starting at 1, if
meillo@120 2908 the -number option is also used.
meillo@120 2909 .QE
meillo@120 2910 .LP
meillo@120 2911 The problem was manifold.
meillo@120 2912 The code required a numeric argument to the
meillo@120 2913 .Sw -number
meillo@120 2914 switch.
meillo@120 2915 If it was missing or non-numeric,
meillo@120 2916 .Pn anno
meillo@120 2917 aborted with an error message that had an off-by-one error,
meillo@120 2918 printing the switch one before the failing one.
meillo@120 2919 Semantically, the argument to the
meillo@120 2920 .Sw -number
meillo@120 2921 switch is only necessary in combination with
meillo@120 2922 .Sw -delete ,
meillo@120 2923 but not with
meillo@120 2924 .Sw -list .
meillo@120 2925 In the former case it is even necessary.
meillo@120 2926 .P
meillo@120 2927 Trying to fix these problems on the surface would not have solved it truly.
meillo@120 2928 The problems discovered originate from a discrepance between the semantic
meillo@120 2929 structure of the problem and the structure implemented in the program.
meillo@120 2930 Such structural differences can not be cured on the surface.
meillo@120 2931 They need to be solved by adjusting the structure of the implementation
meillo@120 2932 to the structure of the problem.
meillo@120 2933 .P
meillo@120 2934 In 2002, the new switches
meillo@120 2935 .Sw -list
meillo@120 2936 and
meillo@120 2937 .Sw -delete
meillo@120 2938 were added in the same way, the
meillo@120 2939 .Sw -number
meillo@120 2940 switch for instance had been added.
meillo@120 2941 Yet, they are of structural different type.
meillo@120 2942 Semantically,
meillo@120 2943 .Sw -list
meillo@120 2944 and
meillo@120 2945 .Sw -delete
meillo@120 2946 introduce modes of operation.
meillo@120 2947 Historically,
meillo@120 2948 .Pn anno
meillo@120 2949 had only one operation mode: adding header fields.
meillo@120 2950 With the extension, it got two moder modes:
meillo@120 2951 listing and deleting header fields.
meillo@120 2952 The structure of the code changes did not pay respect to this
meillo@120 2953 fundamental change to
meillo@120 2954 .Pn anno 's
meillo@120 2955 behavior.
meillo@120 2956 Neither the implementation nor the documentation did clearly
meillo@120 2957 define them as being exclusive modes of operation.
meillo@120 2958 Having identified the problem, I solved it by putting structure into
meillo@120 2959 .Pn anno
meillo@120 2960 and its documentation.
meillo@120 2961 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11
meillo@120 2962 .P
meillo@120 2963 The difference is visible in both, the code and the documentation.
meillo@121 2964 The following code excerpt:
meillo@120 2965 .VS
meillo@120 2966 int delete = -2; /* delete header element if set */
meillo@120 2967 int list = 0; /* list header elements if set */
meillo@120 2968 [...]
meillo@121 2969 case DELETESW: /* delete annotations */
meillo@121 2970 delete = 0;
meillo@121 2971 continue;
meillo@121 2972 case LISTSW: /* produce a listing */
meillo@121 2973 list = 1;
meillo@121 2974 continue;
meillo@120 2975 VE
meillo@121 2976 .LP
meillo@121 2977 was replaced by:
meillo@120 2978 .VS
meillo@120 2979 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120 2980 [...]
meillo@121 2981 case DELETESW: /* delete annotations */
meillo@121 2982 mode = MODE_DEL;
meillo@121 2983 continue;
meillo@121 2984 case LISTSW: /* produce a listing */
meillo@121 2985 mode = MODE_LIST;
meillo@121 2986 continue;
meillo@120 2987 VE
meillo@120 2988 .LP
meillo@121 2989 The replacement code does not only reflect the problem's structure better,
meillo@121 2990 it is easier to understand as well.
meillo@121 2991 The same applies to the documentation.
meillo@120 2992 The man page was completely reorganized to propagate the same structure.
meillo@121 2993 This is visible in the Synopsis section:
meillo@120 2994 .VS
meillo@120 2995 anno [+folder] [msgs] [-component field] [-text body]
meillo@120 2996 [-append] [-date | -nodate] [-preserve | -nopreserve]
meillo@120 2997 [-Version] [-help]
meillo@120 2998
meillo@120 2999 anno -delete [+folder] [msgs] [-component field] [-text
meillo@120 3000 body] [-number num | all ] [-preserve | -nopreserve]
meillo@120 3001 [-Version] [-help]
meillo@120 3002
meillo@120 3003 anno -list [+folder] [msgs] [-component field] [-number]
meillo@120 3004 [-Version] [-help]
meillo@120 3005 VE
meillo@121 3006 .\" XXX think about explaining the -preserve rework?
meillo@118 3007
meillo@58 3008
meillo@58 3009
meillo@133 3010 .U3 "Path Conversion
meillo@133 3011 .P
meillo@134 3012 Four kinds of path names can appear in MH:
meillo@134 3013 .IP (1)
meillo@134 3014 Absolute Unix directory paths, like
meillo@134 3015 .Fn /etc/passwd .
meillo@134 3016 .IP (2)
meillo@134 3017 Relative Unix directory paths, like
meillo@134 3018 .Fn ./foo/bar .
meillo@134 3019 .IP (3)
meillo@134 3020 Absolute MH folder paths, like
meillo@134 3021 .Fn +friends/phil .
meillo@134 3022 .IP (4)
meillo@134 3023 Relative MH folder paths, like
meillo@134 3024 .Fn @subfolder .
meillo@134 3025 .P
meillo@134 3026 The last type, relative MH folder paths, are hardly documented.
meillo@134 3027 Nonetheless, they are useful for large mail storages.
meillo@134 3028 The current mail folder is specified as `\c
meillo@134 3029 .Fn @ ',
meillo@134 3030 just like the current directory is specified as `\c
meillo@134 3031 .Fn . '.
meillo@134 3032 .P
meillo@134 3033 To allow MH tools to understand all four notations,
meillo@134 3034 they need to convert between them.
meillo@134 3035 In nmh, these path name conversion functions were located in the files
meillo@134 3036 .Fn sbr/path.c
meillo@134 3037 (``return a pathname'') and
meillo@134 3038 .Fn sbr/m_maildir.c
meillo@134 3039 (``get the path for the mail directory'').
meillo@134 3040 The seven functions in the two files were documented with no more
meillo@134 3041 than two comments, which described obvious information.
meillo@134 3042 The function signatures were neither explaining:
meillo@134 3043 .VS
meillo@134 3044 char *path(char *, int);
meillo@134 3045 char *pluspath(char *);
meillo@134 3046 char *m_mailpath(char *);
meillo@134 3047 char *m_maildir(char *);
meillo@134 3048 VE
meillo@134 3049 .P
meillo@134 3050 My investigation provides the following description:
meillo@134 3051 .BU
meillo@134 3052 The second parameter of
meillo@134 3053 .Fu path()
meillo@134 3054 defines the type of path given as first parameter.
meillo@134 3055 Directory paths are converted to absolute directory paths.
meillo@134 3056 Folder paths are converted to absolute folder paths.
meillo@134 3057 Folder paths must not include a leading `@' character.
meillo@134 3058 Leading plus characters are preserved.
meillo@134 3059 The result is a pointer to newly allocated memory.
meillo@134 3060 .BU
meillo@134 3061 .Fu pluspath()
meillo@134 3062 is a convenience-wrapper to
meillo@134 3063 .Fu path() ,
meillo@134 3064 to convert folder paths only.
meillo@134 3065 This function can not be used for directory paths.
meillo@134 3066 An empty string parameter causes a buffer overflow.
meillo@134 3067 .BU
meillo@134 3068 .Fu m_mailpath()
meillo@134 3069 converts directory paths to absolute directory paths.
meillo@134 3070 The characters `+' or `@' at the beginning of the path name are
meillo@134 3071 treated literal, i.e. as the first character of a relative directory path.
meillo@134 3072 Hence, this function can not be used for folder paths.
meillo@134 3073 In any case, the result is an absolute directory path.
meillo@134 3074 The result is a pointer to newly allocated memory.
meillo@134 3075 .BU
meillo@134 3076 .Fu m_maildir()
meillo@134 3077 returns the parameter unchanged if it is an absolute directory path
meillo@134 3078 or begins with the entry `.' or `..'.
meillo@134 3079 All other strings are prepended with the current working directory.
meillo@134 3080 Hence, this functions can not be used for folder paths.
meillo@134 3081 The result is either an absolute directory path or a relative
meillo@134 3082 directory path, starting with a dot.
meillo@134 3083 In contrast to the other functions, the result is a pointer to
meillo@134 3084 static memory.
meillo@134 3085 .P
meillo@134 3086 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@134 3087 No clear terminology was used to name the different kinds of path names.
meillo@134 3088 The first argument of
meillo@134 3089 .Fu m_mailpath() ,
meillo@134 3090 for instance, was named
meillo@134 3091 .Ar folder ,
meillo@134 3092 though
meillo@134 3093 .Fu m_mailpath()
meillo@134 3094 can not be used for MH folders.
meillo@134 3095 .P
meillo@134 3096 I reworked the path name conversion completely, introducing clarity.
meillo@134 3097 First of all, the terminology needed to be defined.
meillo@134 3098 A path name is either in the Unix domain, then it is called
meillo@134 3099 \fIdirectory path\fP, `dirpath' for short, or it is in the MH domain,
meillo@134 3100 then it is called \fIfolder path\fP, `folpath' for short.
meillo@134 3101 The two terms need to be used with strict distinction.
meillo@134 3102 Having a clear terminology is often an indicator of having understood
meillo@134 3103 the problem itself.
meillo@134 3104 Second, I exploited the concept of path type indicators.
meillo@134 3105 By requesting every path name to start with a clear type identifier,
meillo@134 3106 conversion between the types can be fully automated.
meillo@134 3107 Thus the tools can accept paths of any type from the user.
meillo@134 3108 Therefore, it was necessary to require relative directory paths to be
meillo@134 3109 prefixed with a dot character.
meillo@134 3110 In consequence, the dot character could no longer be an alias for the
meillo@134 3111 current message.
meillo@134 3112 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134 3113 Third, I created three new functions to replace the previous mess:
meillo@134 3114 .BU
meillo@134 3115 .Fu expandfol()
meillo@134 3116 converts folder paths to absolute folder paths,
meillo@134 3117 without the leading plus character.
meillo@134 3118 Directory paths are simply passed through.
meillo@134 3119 This function is to be used for folder paths only, thus the name.
meillo@134 3120 The result is a pointer to static memory.
meillo@134 3121 .BU
meillo@134 3122 .Fu expanddir()
meillo@134 3123 converts directory paths to absolute directory paths.
meillo@134 3124 Folder paths are treated as relative directory paths.
meillo@134 3125 This function is to be used for directory paths only, thus the name.
meillo@134 3126 The result is a pointer to static memory.
meillo@134 3127 .BU
meillo@134 3128 .Fu toabsdir()
meillo@134 3129 converts any type of path to an absolute directory path.
meillo@134 3130 This is the function of choice for path conversion.
meillo@134 3131 Absolute directory paths are the most general representation of a
meillo@134 3132 path name.
meillo@134 3133 The result is a pointer to static memory.
meillo@134 3134 .P
meillo@134 3135 The new functions have names that indicate their use.
meillo@134 3136 Two of the functions convert relative to absolute path names of the
meillo@134 3137 same type.
meillo@134 3138 The third function converts any path name type to the most general one,
meillo@134 3139 the absolute directory path.
meillo@134 3140 All of the functions return pointers to static memory.
meillo@134 3141 All three functions are implemented in
meillo@134 3142 .Fn sbr/path.c .
meillo@134 3143 .Fn sbr/m_maildir.c
meillo@134 3144 is removed.
meillo@134 3145 .P
meillo@134 3146 Along with the path conversion rework, I also replaced
meillo@134 3147 .Fu getfolder(FDEF)
meillo@134 3148 with
meillo@134 3149 .Fu getdeffol()
meillo@134 3150 and
meillo@134 3151 .Fu getfolder(FCUR)
meillo@134 3152 with
meillo@134 3153 .Fu getcurfol() ,
meillo@134 3154 which is only a convenience wrapper for
meillo@134 3155 .Fu expandfol("@") .
meillo@134 3156 This code was moved from
meillo@134 3157 .Fn sbr/getfolder.c
meillo@134 3158 to
meillo@134 3159 .Fn sbr/path.c .
meillo@134 3160 .P
meillo@134 3161 The related function
meillo@134 3162 .Fu etcpath()
meillo@134 3163 was moved to
meillo@134 3164 .Fn sbr/path.c ,
meillo@134 3165 too.
meillo@134 3166 Previously, it had been located in
meillo@134 3167 .Fn config/config.c ,
meillo@134 3168 for whatever reasons.
meillo@134 3169 .P
meillo@134 3170 .Fn sbr/path.c
meillo@134 3171 now contains all path handling code.
meillo@134 3172 Only 173 lines of code were needed to replace the previous 252 lines.
meillo@134 3173 The readability of the code is highly improved.
meillo@134 3174 Additionally, each of the six exported and one static functions
meillo@134 3175 is introduced by an explaining comment.
meillo@134 3176 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@133 3177
meillo@133 3178
meillo@133 3179
meillo@133 3180
meillo@133 3181 .H2 "Profile Reading
meillo@133 3182 .P
meillo@138 3183 The MH profile contains the configuration for the user-specific MH setup.
meillo@138 3184 MH tools read the profile right after starting up,
meillo@138 3185 as it contains the location of the user's mail storage
meillo@138 3186 and similar settings that influence the whole setup.
meillo@138 3187 Further more, the profile contains the default switches for the tools,
meillo@138 3188 hence, it must be read before the command line switches are processed.
meillo@138 3189 .P
meillo@138 3190 For historic reasons, some MH tools did not read the profile and context.
meillo@138 3191 Among them were
meillo@138 3192 .Pn post /\c
meillo@138 3193 .Pn spost ,
meillo@138 3194 .Pn mhmail ,
meillo@138 3195 and
meillo@138 3196 .Pn slocal .
meillo@138 3197 The reason why these tools ignored the profile were not clearly stated.
meillo@138 3198 During the discussion on the nmh-workers mailing list,
meillo@138 3199 .[
meillo@138 3200 nmh-workers levine post profile
meillo@138 3201 .]
meillo@138 3202 David Levine posted an explanation, quoting John Romine:
meillo@138 3203 .QS
meillo@138 3204 I asked John Romine and here's what he had to say, which
meillo@138 3205 agrees and provides an example that convinces me:
meillo@138 3206 .QS
meillo@138 3207 My take on this is that post should not be called by
meillo@138 3208 users directly, and it doesn't read the .mh_profile
meillo@138 3209 (only front-end UI programs read the profile).
meillo@138 3210 .QP
meillo@138 3211 For example, there can be contexts where post is called
meillo@138 3212 by a helper program (like 'mhmail') which may be run by
meillo@138 3213 a non-MH user. We don't want this to prompt the user
meillo@138 3214 to create an MH profile, etc.
meillo@138 3215 .QP
meillo@138 3216 My suggestion would be to have send pass a (hidden)
meillo@138 3217 `\-fileproc proc' option to post if needed. You could also
meillo@138 3218 use an environment variable (I think send/whatnow do
meillo@138 3219 this).
meillo@138 3220 .QE
meillo@138 3221 I think that's the way to go. My personal preference is to use a command line option, not an environment variable.
meillo@138 3222 .QE
meillo@138 3223 .P
meillo@138 3224 To solve the problem of
meillo@138 3225 .Pn post
meillo@138 3226 not honoring the
meillo@138 3227 .Pe fileproc
meillo@138 3228 profile entry,
meillo@138 3229 the community roughly agreed that a switch
meillo@138 3230 .Sw -fileproc
meillo@138 3231 should be added to
meillo@138 3232 .Pn post
meillo@138 3233 to be able to pass a different fileproc.
meillo@138 3234 I strongly disagree with this approach because it does not solve
meillo@138 3235 the problem; it only removes a single symptom.
meillo@138 3236 The problem is that
meillo@138 3237 .Pn post
meillo@138 3238 does not behave as expected.
meillo@138 3239 But all programs should behave as expected.
meillo@138 3240 Clear and simple concepts are a precondition for this.
meillo@138 3241 Hence, the real solution is having all MH tools read the profile.
meillo@138 3242 .P
meillo@138 3243 Yet, the problem has a further aspect.
meillo@138 3244 It mainly originates in
meillo@138 3245 .Pn mhmail .
meillo@138 3246 .Pn mhmail
meillo@138 3247 was intended to be a replacement for
meillo@138 3248 .Pn mailx
meillo@138 3249 on systems with MH installations.
meillo@138 3250 .Pn mhmail
meillo@138 3251 should have been able to use just like
meillo@138 3252 .Pn mailx ,
meillo@138 3253 but sending the message via MH's
meillo@138 3254 .Pn post
meillo@138 3255 instead of
meillo@138 3256 .Pn sendmail .
meillo@138 3257 Using
meillo@138 3258 .Pn mhmail
meillo@138 3259 should not be influenced by the question whether the user had
meillo@138 3260 MH set up for himself or not.
meillo@138 3261 .Pn mhmail
meillo@138 3262 did not read the profile as this requests the user to set up MH
meillo@138 3263 if not done yet.
meillo@138 3264 As
meillo@138 3265 .Pn mhmail
meillo@138 3266 used
meillo@138 3267 .Pn post ,
meillo@138 3268 .Pn post
meillo@138 3269 could not read the profile neither.
meillo@138 3270 This is the reason why
meillo@138 3271 .Pn post
meillo@138 3272 does not read the profile.
meillo@138 3273 This is the reason for the actual problem.
meillo@138 3274 It was not much of a problem because
meillo@138 3275 .Pn post
meillo@138 3276 was not intended to be used by users directly.
meillo@138 3277 .Pn send
meillo@138 3278 is the interactive front-end to
meillo@138 3279 .Pn post .
meillo@138 3280 .Pn send
meillo@138 3281 read the profile and passed all relevant values on the command line to
meillo@138 3282 .Pn post
meillo@138 3283 \(en an awkward solution.
meillo@138 3284 .P
meillo@138 3285 The important insight is that
meillo@138 3286 .Pn mhmail
meillo@138 3287 is no true MH tool.
meillo@138 3288 The concepts broke because this outlandish tool was treated as any other
meillo@138 3289 MH tool.
meillo@138 3290 Instead it should have been treated accordingly to its foreign style.
meillo@138 3291 The solution is not to prevent the tools reading the profile but
meillo@138 3292 to instruct them reading a different profile.
meillo@138 3293 .Pn mhmail
meillo@138 3294 could have set up a well-defined profile and caused all MH tools
meillo@138 3295 in the session use it by exporting an environment variable.
meillo@138 3296 With this approach, no special cases would have been introduced,
meillo@138 3297 no surprises would have been caused.
meillo@138 3298 By writing a clean-profile-wrapper, the concept could have been
meillo@138 3299 generalized orthogonally to the whole MH toolchest.
meillo@138 3300 Then Rose's motivation behind the decision that
meillo@138 3301 .Pn post
meillo@138 3302 ignores the profile, as quoted by Jeffrey Honig,
meillo@138 3303 .[
meillo@138 3304 nmh-workers post profile
meillo@138 3305 .]
meillo@138 3306 would have become possible:
meillo@138 3307 .QS
meillo@138 3308 when you run mh commands in a script, you want all the defaults to be
meillo@138 3309 what the man page says.
meillo@138 3310 when you run a command by hand, then you want your own defaults...
meillo@138 3311 .QE
meillo@138 3312 .LP
meillo@138 3313 Yet, I consider this explanation short-sighted.
meillo@138 3314 We should rather regard theses two cases as just two different MH setups,
meillo@138 3315 based on two different profiles.
meillo@138 3316 Mapping such problems on the concepts of switching between different
meillo@138 3317 profiles, solves them once for all.
meillo@138 3318 .P
meillo@138 3319 In mmh, the wish to have
meillo@138 3320 .Pn mhmail
meillo@138 3321 as as replacement for
meillo@138 3322 .Pn mailx
meillo@138 3323 is considered obsolete.
meillo@138 3324 Mmh's
meillo@138 3325 .Pn mhmail
meillo@138 3326 does no longer cover this use-case.
meillo@138 3327 Currently,
meillo@138 3328 .Pn mhmail
meillo@138 3329 is in a transition state.
meillo@138 3330 .Ci 32d4f9daaa70519be3072479232ff7be0500d009
meillo@138 3331 It may become a front-end to
meillo@138 3332 .Pn comp ,
meillo@138 3333 which provides an interface more convenient in some cases.
meillo@138 3334 In this case,
meillo@138 3335 .Pn mhmail
meillo@138 3336 will become an ordinary MH tool, reading the profile.
meillo@138 3337 If, however, this idea will not convince, then
meillo@138 3338 .Pn mhmail
meillo@138 3339 will be removed.
meillo@138 3340 .P
meillo@138 3341 Every program in the mmh toolchest reads the profile.
meillo@138 3342 The only exception is
meillo@138 3343 .Pn slocal ,
meillo@138 3344 which is not considered part of the mmh toolchest.
meillo@138 3345 This MDA is only distributed with mmh, currently.
meillo@138 3346 Mmh has no
meillo@138 3347 .Pn post
meillo@138 3348 program, but
meillo@138 3349 .Pn spost ,
meillo@138 3350 which now reads the profile.
meillo@138 3351 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8
meillo@138 3352 With this change,
meillo@138 3353 .Pn send
meillo@138 3354 and
meillo@138 3355 .Pn spost
meillo@138 3356 can be considered to be merged.
meillo@138 3357 Direct invocations of
meillo@138 3358 .Pn spost
meillo@138 3359 are only done by the to-be-changed
meillo@138 3360 .Pn mhmail
meillo@138 3361 implementation and by
meillo@138 3362 .Pn rcvdist ,
meillo@138 3363 which will require rework.
meillo@138 3364 .P
meillo@138 3365 The
meillo@138 3366 .Fu context_foil()
meillo@138 3367 function to pretend to have read an empty profile was removed.
meillo@138 3368 .Ci 68af8da96bea87a5541988870130b6209ce396f6
meillo@138 3369 All mmh tools read the profile.
meillo@133 3370
meillo@133 3371
meillo@127 3372
meillo@121 3373 .H2 "Standard Libraries
meillo@22 3374 .P
meillo@121 3375 MH is one decade older than the POSIX and ANSI C standards.
meillo@121 3376 Hence, MH included own implementations of functions
meillo@121 3377 that are standardized and thus widely available today,
meillo@121 3378 but were not back then.
meillo@121 3379 Today, twenty years after the POSIX and ANSI C were published,
meillo@121 3380 developers can expect system to comply with these standards.
meillo@121 3381 In consequence, MH-specific replacements for standard functions
meillo@121 3382 can and should be dropped.
meillo@121 3383 Kernighan and Pike advise: ``Use standard libraries.''
meillo@121 3384 .[ [
meillo@121 3385 kernighan pike practice of programming
meillo@121 3386 .], p. 196]
meillo@121 3387 Actually, MH had followed this advice in history,
meillo@121 3388 but it had not adjusted to the changes in this field.
meillo@121 3389 The
meillo@121 3390 .Fu snprintf()
meillo@121 3391 function, for instance, was standardized with C99 and is available
meillo@121 3392 almost everywhere because of its high usefulness.
meillo@123 3393 In project's own implementation of
meillo@121 3394 .Fu snprintf()
meillo@123 3395 was dropped in March 2012 in favor for using the one of the
meillo@123 3396 standard library.
meillo@123 3397 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32
meillo@123 3398 Such decisions limit the portability of mmh
meillo@121 3399 if systems don't support these standardized and widespread functions.
meillo@123 3400 This compromise is made because mmh focuses on the future.
meillo@121 3401 .P
meillo@123 3402 I am not yet thirty years old and my C and Unix experience comprises
meillo@123 3403 only half a dozen years.
meillo@121 3404 Hence, I need to learn about the history in retrospective.
meillo@121 3405 I have not used those ancient constructs myself.
meillo@121 3406 I have not suffered from their incompatibilities.
meillo@121 3407 I have not longed for standardization.
meillo@121 3408 All my programming experience is from a time when ANSI C and POSIX
meillo@121 3409 were well established already.
meillo@121 3410 I have only read a lot of books about the (good) old times.
meillo@121 3411 This puts me in a difficult positions when working with old code.
meillo@123 3412 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123 3413 programming styles, whereas older programmers know these things by
meillo@123 3414 heart from their own experience.
meillo@121 3415 .P
meillo@123 3416 Being aware of the situation, I rather let people with more historic
meillo@123 3417 experience replace ancient code constructs with standardized ones.
meillo@121 3418 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121 3419 He converted project-specific functions to POSIX replacements,
meillo@121 3420 also removing the conditionals compilation of now standardized features.
meillo@123 3421 Ken Hornstein and David Levine had their part in the work, too.
meillo@121 3422 Often, I only needed to pull over changes from nmh into mmh.
meillo@121 3423 These changes include many commits; these are among them:
meillo@121 3424 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121 3425 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102 3426 .P
meillo@123 3427 During my own work, I tidied up the \fIMH standard library\fP,
meillo@123 3428 .Fn libmh.a ,
meillo@123 3429 which is located in the
meillo@123 3430 .Fn sbr
meillo@123 3431 (``subroutines'') directory in the source tree.
meillo@123 3432 The MH library includes functions that mmh tools usually need.
meillo@123 3433 Among them are MH-specific functions for profile, context, sequence,
meillo@123 3434 and folder handling, but as well
meillo@123 3435 MH-independent functions, such as auxiliary string functions,
meillo@123 3436 portability interfaces and error-checking wrappers for critical
meillo@123 3437 functions of the standard library.
meillo@123 3438 .P
meillo@123 3439 I have replaced the
meillo@121 3440 .Fu atooi()
meillo@121 3441 function with calls to
meillo@123 3442 .Fu strtoul()
meillo@139 3443 with the third parameter, the base, set to eight.
meillo@121 3444 .Fu strtoul()
meillo@123 3445 is part of C89 and thus considered safe to use.
meillo@121 3446 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74
meillo@102 3447 .P
meillo@121 3448 I did remove project-included fallback implementations of
meillo@121 3449 .Fu memmove()
meillo@121 3450 and
meillo@121 3451 .Fu strerror() ,
meillo@121 3452 although Peter Maydell had re-included them into nmh in 2008
meillo@121 3453 to support SunOS 4.
meillo@121 3454 Nevertheless, these functions are part of ANSI C.
meillo@121 3455 Systems that do not even provide full ANSI C support should not
meillo@121 3456 put a load on mmh.
meillo@121 3457 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215
meillo@121 3458 .P
meillo@121 3459 The
meillo@121 3460 .Fu copy()
meillo@121 3461 function copies the string in argument one to the location in two.
meillo@121 3462 In contrast to
meillo@121 3463 .Fu strcpy() ,
meillo@121 3464 it returns a pointer to the terminating null-byte in the destination area.
meillo@123 3465 The code was adjusted to replace
meillo@121 3466 .Fu copy()
meillo@123 3467 with
meillo@121 3468 .Fu strcpy() ,
meillo@121 3469 except within
meillo@121 3470 .Fu concat() ,
meillo@121 3471 where
meillo@121 3472 .Fu copy()
meillo@123 3473 was more convenient.
meillo@123 3474 Therefore, the definition of
meillo@121 3475 .Fu copy()
meillo@123 3476 was moved into the source file of
meillo@121 3477 .Fu concat()
meillo@123 3478 and its visibility is now limited to it.
meillo@121 3479 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb
meillo@121 3480 .P
meillo@121 3481 The function
meillo@121 3482 .Fu r1bindex()
meillo@121 3483 had been a generalized version of
meillo@121 3484 .Fu basename()
meillo@121 3485 with minor differences.
meillo@121 3486 As all calls to
meillo@121 3487 .Fu r1bindex()
meillo@121 3488 had the slash (`/') as delimiter anyway,
meillo@121 3489 replacing
meillo@121 3490 .Fu r1bindex()
meillo@121 3491 with the more specific and better-named function
meillo@121 3492 .Fu basename()
meillo@121 3493 became desirable.
meillo@121 3494 Unfortunately, many of the 54 calls to
meillo@121 3495 .Fu r1bindex()
meillo@123 3496 depended on a special behavior,
meillo@121 3497 which differed from the POSIX specification for
meillo@121 3498 .Fu basename() .
meillo@121 3499 Hence,
meillo@121 3500 .Fu r1bindex()
meillo@121 3501 was kept but renamed to
meillo@123 3502 .Fu mhbasename() ,
meillo@123 3503 fixing the delimiter to the slash.
meillo@121 3504 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60
meillo@121 3505 For possible uses of
meillo@121 3506 .Fu r1bindex()
meillo@121 3507 with a different delimiter,
meillo@121 3508 the ANSI C function
meillo@121 3509 .Fu strrchr()
meillo@121 3510 provides the core functionality.
meillo@121 3511 .P
meillo@121 3512 The
meillo@121 3513 .Fu ssequal()
meillo@121 3514 function \(en apparently for ``substring equal'' \(en
meillo@121 3515 was renamed to
meillo@121 3516 .Fu isprefix() ,
meillo@121 3517 because this is what it actually checks.
meillo@121 3518 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711
meillo@121 3519 Its source file had included the following comments, no joke.
meillo@121 3520 .VS
meillo@121 3521 /*
meillo@121 3522 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121 3523 * It is actually checking if s1 is a PREFIX of s2.
meillo@121 3524 * All calls to this function need to be checked to see
meillo@121 3525 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121 3526 * should be kept if it's sufficient.
meillo@121 3527 */
meillo@121 3528
meillo@121 3529 /*
meillo@121 3530 * Check if s1 is a substring of s2.
meillo@121 3531 * If yes, then return 1, else return 0.
meillo@121 3532 */
meillo@121 3533 VE
meillo@123 3534 Two months later, it was completely removed by replacing it with
meillo@123 3535 .Fu strncmp() .
meillo@123 3536 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb
meillo@121 3537
meillo@102 3538
meillo@102 3539
meillo@102 3540
meillo@133 3541
meillo@133 3542 .H2 "User Data Locations
meillo@133 3543 .P
meillo@133 3544 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133 3545 The profile is a file named
meillo@133 3546 .Fn \&.mh_profile
meillo@133 3547 in the user's home directory.
meillo@133 3548 It contains the static configuration.
meillo@133 3549 It also contains the location of the MH directory in the profile entry
meillo@133 3550 .Pe Path .
meillo@133 3551 The MH directory contains the mail storage and is the first
meillo@133 3552 place to search for personal forms, scan formats, and similar
meillo@133 3553 configuration files.
meillo@133 3554 The location of the MH directory can be chosen freely by the user.
meillo@133 3555 The default and usual name is a directory named
meillo@133 3556 .Fn Mail
meillo@133 3557 in the home directory.
meillo@133 3558 .P
meillo@133 3559 The way MH data is splitted between profile and MH directory is a legacy.
meillo@133 3560 It is only sensible in a situation where the profile is the only
meillo@133 3561 configuration file.
meillo@133 3562 Why else should the mail storage and the configuration files be intermixed?
meillo@133 3563 They are different kinds of data:
meillo@133 3564 The data to be operated on and the configuration to change how
meillo@133 3565 tools operate.
meillo@133 3566 Splitting the configuration between the profile and the MH directory
meillo@133 3567 is bad.
meillo@133 3568 Merging the mail storage and the configuration in one directory is bad
meillo@133 3569 as well.
meillo@133 3570 As the mail storage and the configuration were not separated sensibly
meillo@133 3571 in the first place, I did it now.
meillo@133 3572 .P
meillo@133 3573 Personal mmh data is grouped by type, resulting in two distinct parts:
meillo@133 3574 The mail storage and the configuration.
meillo@133 3575 In mmh, the mail storage directory still contains all the messages,
meillo@133 3576 but, in exception of public sequences files, nothing else.
meillo@133 3577 In difference to nmh, the auxiliary configuration files are no longer
meillo@133 3578 located there.
meillo@133 3579 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@133 3580 but his \fImail storage\fP.
meillo@133 3581 Its location is still user-chosen, with the default name
meillo@133 3582 .Fn Mail ,
meillo@133 3583 in the user's home directory.
meillo@133 3584 In mmh, the configuration is grouped together in
meillo@133 3585 the hidden directory
meillo@133 3586 .Fn \&.mmh
meillo@133 3587 in the user's home directory.
meillo@133 3588 This \fImmh directory\fP contains the context file, personal forms,
meillo@133 3589 scan formats, and the like, but also the user's profile, now named
meillo@133 3590 .Fn profile .
meillo@133 3591 The location of the profile is no longer fixed to
meillo@133 3592 .Fn $HOME/.mh_profile
meillo@133 3593 but to
meillo@133 3594 .Fn $HOME/.mmh/profile .
meillo@133 3595 Having both, the file
meillo@133 3596 .Fn $HOME/.mh_profile
meillo@133 3597 and the configuration directory
meillo@133 3598 .Fn $HOME/.mmh
meillo@133 3599 appeared to be inconsistent.
meillo@133 3600 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133 3601 Unix users.
meillo@133 3602 .P
meillo@133 3603 MH allows users to have multiiple MH setups.
meillo@133 3604 Therefore, it is necessary to select a different profile.
meillo@133 3605 The profile is the single entry point to access the rest of a
meillo@133 3606 personal MH setup.
meillo@133 3607 In nmh, the environment variable
meillo@133 3608 .Ev MH
meillo@133 3609 could be used to specifiy a different profile.
meillo@133 3610 To operate in the same MH setup with a separate context,
meillo@133 3611 the
meillo@133 3612 .Ev MHCONTEXT
meillo@133 3613 environment variable could be used.
meillo@133 3614 This allows having own current folders and current messages in
meillo@133 3615 each terminal, for instance.
meillo@133 3616 In mmh, three environment variables are used.
meillo@133 3617 .Ev MMH
meillo@133 3618 overrides the default location of the mmh directory (\c
meillo@133 3619 .Fn .mmh ).
meillo@133 3620 .Ev MMHP
meillo@133 3621 and
meillo@133 3622 .Ev MMHC
meillo@133 3623 override the paths to the profile and context files, respectively.
meillo@133 3624 This approach allows the set of personal configuration files to be chosen
meillo@133 3625 independently from the profile, context, and mail storage.
meillo@133 3626 .P
meillo@133 3627 The separation of the files by type is sensible and convenient.
meillo@133 3628 The new approach has no functional disadvantages,
meillo@133 3629 as every setup I can imagine can be implemented with both approaches,
meillo@133 3630 possibly even easier with the new approach.
meillo@133 3631 The main achievement of the change is the clear and sensible split
meillo@133 3632 between mail storage and configuration.
meillo@133 3633
meillo@133 3634
meillo@133 3635
meillo@133 3636
meillo@133 3637
meillo@118 3638 .H2 "Modularization
meillo@118 3639 .P
meillo@123 3640 The source code of the mmh tools is located in the
meillo@122 3641 .Fn uip
meillo@123 3642 (``user interface programs'') directory.
meillo@123 3643 Each tools has a source file with the same name.
meillo@122 3644 For example,
meillo@122 3645 .Pn rmm
meillo@122 3646 is built from
meillo@122 3647 .Fn uip/rmm.c .
meillo@123 3648 Some source files are used for multiple programs.
meillo@122 3649 For example
meillo@122 3650 .Fn uip/scansbr.c
meillo@123 3651 is used for both,
meillo@122 3652 .Pn scan
meillo@122 3653 and
meillo@122 3654 .Pn inc .
meillo@122 3655 In nmh, 49 tools were built from 76 source files.
meillo@123 3656 This is a ratio of 1.6 source files per program.
meillo@123 3657 32 programs depended on multiple source files;
meillo@123 3658 17 programs depended on one source file only.
meillo@122 3659 In mmh, 39 tools are built from 51 source files.
meillo@123 3660 This is a ratio of 1.3 source files per program.
meillo@123 3661 18 programs depend on multiple source files;
meillo@123 3662 21 programs depend on one source file only.
meillo@123 3663 (These numbers and the ones in the following text ignore the MH library
meillo@123 3664 as well as shell scripts and multiple names for the same program.)
meillo@122 3665 .P
meillo@123 3666 Splitting the source code of a large program into multiple files can
meillo@122 3667 increase the readability of its source code.
meillo@124 3668 Most of the mmh tools, however, are simple and straight-forward programs.
meillo@122 3669 With the exception of the MIME handling tools,
meillo@122 3670 .Pn pick
meillo@122 3671 is the largest tools.
meillo@122 3672 It contains 1\|037 lines of source code (measured with
meillo@122 3673 .Pn sloccount ), excluding the MH library.
meillo@122 3674 Only the MIME handling tools (\c
meillo@122 3675 .Pn mhbuild ,
meillo@122 3676 .Pn mhstore ,
meillo@122 3677 .Pn show ,
meillo@122 3678 etc.)
meillo@122 3679 are larger.
meillo@122 3680 Splitting programs with less than 1\|000 lines of code into multiple
meillo@123 3681 source files seldom leads to better readability.
meillo@123 3682 For such tools, splitting makes sense
meillo@122 3683 when parts of the code are reused in other programs,
meillo@122 3684 and the reused code fragment is not general enough
meillo@122 3685 for including it in the MH library,
meillo@124 3686 or, if the code has dependencies on a library that only few programs need.
meillo@122 3687 .Fn uip/packsbr.c ,
meillo@122 3688 for instance, provides the core program logic for the
meillo@122 3689 .Pn packf
meillo@122 3690 and
meillo@122 3691 .Pn rcvpack
meillo@122 3692 programs.
meillo@122 3693 .Fn uip/packf.c
meillo@122 3694 and
meillo@122 3695 .Fn uip/rcvpack.c
meillo@122 3696 mainly wrap the core function appropriately.
meillo@122 3697 No other tools use the folder packing functions.
meillo@123 3698 As another example,
meillo@123 3699 .Fn uip/termsbr.c
meillo@123 3700 provides termcap support, which requires linking with a termcap or
meillo@123 3701 curses library.
meillo@123 3702 Including
meillo@123 3703 .Fn uip/termsbr.c
meillo@123 3704 into the MH library would require every program to be linked with
meillo@123 3705 termcap or curses, although only few of the programs require it.
meillo@122 3706 .P
meillo@122 3707 The task of MIME handling is complex enough that splitting its code
meillo@122 3708 into multiple source files improves the readability.
meillo@122 3709 The program
meillo@122 3710 .Pn mhstore ,
meillo@122 3711 for instance, is compiled out of seven source files with 2\|500
meillo@122 3712 lines of code in summary.
meillo@122 3713 The main code file
meillo@122 3714 .Fn uip/mhstore.c
meillo@123 3715 consists of 800 lines; the other 1\|700 lines of code are reused in
meillo@123 3716 other MIME handling tools.
meillo@123 3717 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123 3718 a MH-MIME library, as a companion to the MH standard library.
meillo@122 3719 This is left open for the future.
meillo@122 3720 .P
meillo@123 3721 The work already done, focussed on the non-MIME tools.
meillo@122 3722 The amount of code compiled into each program was reduced.
meillo@123 3723 This eases the understanding of the code base.
meillo@122 3724 In nmh,
meillo@122 3725 .Pn comp
meillo@122 3726 was built from six source files:
meillo@122 3727 .Fn comp.c ,
meillo@122 3728 .Fn whatnowproc.c ,
meillo@122 3729 .Fn whatnowsbr.c ,
meillo@122 3730 .Fn sendsbr.c ,
meillo@122 3731 .Fn annosbr.c ,
meillo@122 3732 and
meillo@122 3733 .Fn distsbr.c .
meillo@122 3734 In mmh, it builds from only two:
meillo@122 3735 .Fn comp.c
meillo@122 3736 and
meillo@122 3737 .Fn whatnowproc.c .
meillo@123 3738 In nmh's
meillo@123 3739 .Pn comp ,
meillo@123 3740 the core function of
meillo@122 3741 .Pn whatnow ,
meillo@122 3742 .Pn send ,
meillo@122 3743 and
meillo@122 3744 .Pn anno
meillo@123 3745 were compiled into
meillo@122 3746 .Pn comp .
meillo@123 3747 This saved the need to execute these programs with
meillo@122 3748 .Fu fork()
meillo@122 3749 and
meillo@122 3750 .Fu exec() ,
meillo@122 3751 two expensive system calls.
meillo@122 3752 Whereis this approach improved the time performance,
meillo@122 3753 it interweaved the source code.
meillo@122 3754 Core functionalities were not encapsulated into programs but into
meillo@122 3755 function, which were then wrapped by programs.
meillo@122 3756 For example,
meillo@122 3757 .Fn uip/annosbr.c
meillo@122 3758 included the function
meillo@122 3759 .Fu annotate() .
meillo@122 3760 Each program that wanted to annotate messages, included the source file
meillo@123 3761 .Fn uip/annosbr.c
meillo@123 3762 and called
meillo@123 3763 .Fu annotate() .
meillo@123 3764 Because the function
meillo@123 3765 .Fu annotate()
meillo@123 3766 was used like the tool
meillo@123 3767 .Pn anno ,
meillo@123 3768 it had seven parameters, reflecting the command line switches of the tool.
meillo@122 3769 When another pair of command line switches was added to
meillo@122 3770 .Pn anno ,
meillo@122 3771 a rather ugly hack was implemented to avoid adding another parameter
meillo@122 3772 to the function.
meillo@122 3773 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@122 3774 .P
meillo@122 3775 Separation simplifies the understanding of program code
meillo@122 3776 because the area influenced by any particular statement is smaller.
meillo@122 3777 The separating on the program-level is more strict than the separation
meillo@122 3778 on the function level.
meillo@122 3779 In mmh, the relevant code of
meillo@122 3780 .Pn comp
meillo@122 3781 comprises the two files
meillo@122 3782 .Fn uip/comp.c
meillo@122 3783 and
meillo@122 3784 .Fn uip/whatnowproc.c ,
meillo@123 3785 together 210 lines of code.
meillo@122 3786 In nmh,
meillo@122 3787 .Pn comp
meillo@122 3788 comprises six files with 2\|450 lines.
meillo@123 3789 Not all of the code in these six files was actually used by
meillo@122 3790 .Pn comp ,
meillo@123 3791 but the code reader needed to read all of the code first to know which
meillo@123 3792 parts were used.
meillo@122 3793 .P
meillo@123 3794 As I have read a lot in the code base during the last two years,
meillo@123 3795 I learned about the easy and the difficult parts.
meillo@123 3796 Code is easy to understand if:
meillo@123 3797 .BU
meillo@139 3798 The influenced code area is small.
meillo@123 3799 .BU
meillo@139 3800 The boundaries are strictly defined.
meillo@123 3801 .BU
meillo@139 3802 The code is written straight-forward.
meillo@123 3803 .P
meillo@123 3804 .\" XXX move this paragraph somewhere else?
meillo@123 3805 Reading
meillo@122 3806 .Pn rmm 's
meillo@122 3807 source code in
meillo@122 3808 .Fn uip/rmm.c
meillo@122 3809 is my recommendation for a beginner's entry point into the code base of nmh.
meillo@122 3810 The reasons are that the task of
meillo@122 3811 .Pn rmm
meillo@122 3812 is straight forward and it consists of one small source code file only,
meillo@122 3813 yet its source includes code constructs typical for MH tools.
meillo@122 3814 With the introduction of the trash folder in mmh,
meillo@122 3815 .Pn rmm
meillo@122 3816 became a bit more complex, because it invokes
meillo@122 3817 .Pn refile .
meillo@122 3818 Still, it is a good example for a simple tool with clear sources.
meillo@122 3819 .P
meillo@122 3820 Understanding
meillo@122 3821 .Pn comp
meillo@122 3822 requires to read 210 lines of code in mmh, but ten times as much in nmh.
meillo@123 3823 Due to the aforementioned hack in
meillo@122 3824 .Pn anno
meillo@122 3825 to save the additional parameter, information passed through the program's
meillo@122 3826 source base in obscure ways.
meillo@123 3827 Thus, understanding
meillo@122 3828 .Pn comp ,
meillo@123 3829 required understanding the inner workings of
meillo@122 3830 .Fn uip/annosbr.c
meillo@122 3831 first.
meillo@123 3832 To be sure to fully understand a program, its whole source code needs
meillo@122 3833 to be examined.
meillo@123 3834 Not doing so is a leap of faith, assuming that the developers
meillo@122 3835 have avoided obscure programming techniques.
meillo@122 3836 By separating the tools on the program-level, the boundaries are
meillo@122 3837 clearly visible and technically enforced.
meillo@122 3838 The interfaces are calls to
meillo@122 3839 .Fu exec()
meillo@122 3840 rather than arbitrary function calls.
meillo@123 3841 .P
meillo@123 3842 But the real problem is another:
meillo@123 3843 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123 3844 Understanding
meillo@122 3845 .Pn comp
meillo@123 3846 requires understanding
meillo@123 3847 .Fn uip/annosbr.c
meillo@123 3848 and
meillo@123 3849 .Fn uip/sendsbr.c
meillo@123 3850 because
meillo@123 3851 .Pn comp
meillo@123 3852 does annotate and send messages.
meillo@123 3853 In nmh, there surely exists the tool
meillo@122 3854 .Pn send ,
meillo@123 3855 which does (almost) only send messages.
meillo@123 3856 But
meillo@122 3857 .Pn comp
meillo@123 3858 and
meillo@122 3859 .Pn repl
meillo@122 3860 and
meillo@122 3861 .Pn forw
meillo@122 3862 and
meillo@122 3863 .Pn dist
meillo@122 3864 and
meillo@122 3865 .Pn whatnow
meillo@122 3866 and
meillo@123 3867 .Pn viamail ,
meillo@123 3868 they all (!) have the same message sending function included, too.
meillo@123 3869 In result,
meillo@123 3870 .Pn comp
meillo@123 3871 sends messages without using
meillo@123 3872 .Pn send .
meillo@123 3873 The situation is the same as if
meillo@123 3874 .Pn grep
meillo@123 3875 would page without
meillo@123 3876 .Pn more
meillo@123 3877 just because both programs are part of the same code base.
meillo@123 3878 .P
meillo@122 3879 The clear separation on the surface \(en the toolchest approach \(en
meillo@123 3880 is violated on the level below.
meillo@122 3881 This violation is for the sake of time performance.
meillo@122 3882 On systems where
meillo@122 3883 .Fu fork()
meillo@122 3884 and
meillo@122 3885 .Fu exec()
meillo@122 3886 are expensive, the quicker response might be noticable.
meillo@124 3887 In the old times, sacrificing readability and conceptional beauty for
meillo@124 3888 speed might even have been a must to prevent MH from being unusably slow.
meillo@122 3889 Whatever the reasons had been, today they are gone.
meillo@123 3890 No longer should we sacrifice readability or conceptional beauty.
meillo@122 3891 No longer should we violate the Unix philosophy's ``one tool, one job''
meillo@122 3892 guideline.
meillo@123 3893 No longer should we keep speed improvements that became unnecessary.
meillo@122 3894 .P
meillo@123 3895 Therefore, mmh's
meillo@123 3896 .Pn comp
meillo@123 3897 does no longer send messages.
meillo@123 3898 In mmh, different jobs are divided among separate programs that
meillo@122 3899 invoke each other as needed.
meillo@123 3900 In consequence,
meillo@123 3901 .Pn comp
meillo@123 3902 invokes
meillo@123 3903 .Pn whatnow
meillo@123 3904 which thereafter invokes
meillo@123 3905 .Pn send .
meillo@123 3906 The clear separation on the surface is maintained on the level below.
meillo@123 3907 Human users and the tools use the same interface \(en
meillo@123 3908 annotations, for example, are made by invoking
meillo@123 3909 .Pn anno ,
meillo@123 3910 no matter if requested by programs or by human beings.
meillo@123 3911 The decrease of tools built from multiple source files and thus
meillo@123 3912 the decrease of
meillo@123 3913 .Fn uip/*sbr.c
meillo@123 3914 files confirm the improvement.
meillo@123 3915 .P
meillo@145 3916 .\" XXX move this paragraph up somewhere
meillo@123 3917 One disadvantage needs to be taken with this change:
meillo@123 3918 The compiler can no longer check the integrity of the interfaces.
meillo@123 3919 By changing the command line interfaces of tools, it is
meillo@123 3920 the developer's job to adjust the invocations of these tools as well.
meillo@123 3921 As this is a manual task and regression tests, which could detect such
meillo@124 3922 problems, are not available yet, it is prone to errors.
meillo@123 3923 These errors will not be detected at compile time but at run time.
meillo@123 3924 Installing regression tests is a task left to do.
meillo@123 3925 In the best case, a uniform way of invoking tools from other tools
meillo@123 3926 can be developed to allow automated testing at compile time.
meillo@145 3927
meillo@145 3928
meillo@145 3929 .ig
meillo@145 3930 XXX consider writing about mhl vs. mhlproc
meillo@145 3931
meillo@145 3932 sbr/showfile.c
meillo@145 3933
meillo@145 3934 23 /*
meillo@145 3935 24 ** If you have your lproc listed as "mhl",
meillo@145 3936 25 ** then really invoked the mhlproc instead
meillo@145 3937 26 ** (which is usually mhl anyway).
meillo@145 3938 27 */
meillo@145 3939
meillo@145 3940 Sat Nov 24 19:09:14 1984 /mtr (agent: Marshall Rose) <uci@udel-dewey>
meillo@145 3941
meillo@145 3942 sbr/showfile.c: if lproc is "mhl", use mhlproc for consistency
meillo@145 3943 (Actually, user should use "lproc: show", "showproc: mhl".)
meillo@145 3944 ..