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author markus schnalke <meillo@marmaro.de>
date Tue, 10 Jul 2012 23:13:45 +0200
parents 520b3c7abba1
children 731e747a805b
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meillo@58 1 .H0 "Discussion
meillo@0 2 .P
meillo@169 3 This main chapter discusses the practical work accomplished in the
meillo@169 4 mmh project.
meillo@169 5 It is structured along the goals set for the project.
meillo@169 6 The concrete work undertaken
meillo@58 7 is described in the examples of how the general goals were achieved.
meillo@87 8 The discussion compares the current version of mmh with the state of
meillo@171 9 nmh just before the mmh project started, i.e. fall 2011.
meillo@87 10 Current changes of nmh will be mentioned only as side notes.
meillo@87 11 .\" XXX where do I discuss the parallel development of nmh?
meillo@58 12
meillo@58 13
meillo@58 14
meillo@133 15 .\" --------------------------------------------------------------
meillo@125 16 .H1 "Streamlining
meillo@58 17
meillo@0 18 .P
meillo@169 19 MH once provided anything necessary for email handling.
meillo@169 20 The community around nmh has the similar understanding that nmh should
meillo@169 21 provide a complete email system.
meillo@178 22 In fundamental contrast, mmh shall be an MUA only.
meillo@87 23 I believe that the development of all-in-one mail systems is obsolete.
meillo@173 24 Today, email is too complex to be fully covered by a single project.
meillo@173 25 Such a project will not be able to excel in all aspects.
meillo@159 26 Instead, the aspects of email should be covered by multiple projects,
meillo@87 27 which then can be combined to form a complete system.
meillo@169 28 Excellent implementations for the various aspects of email already exist.
meillo@87 29 Just to name three examples: Postfix is a specialized MTA,
meillo@159 30 .\" XXX homepages verlinken
meillo@87 31 Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89 32 I believe that it is best to use such specialized tools instead of
meillo@87 33 providing the same function again as a side-component in the project.
meillo@164 34 .\" XXX mail agent picture here
meillo@58 35 .P
meillo@169 36 Doing something well requires focusing on a small set of specific aspects.
meillo@169 37 Under the assumption that development focussed on a particular area
meillo@169 38 produces better results there, specialized projects will be superior
meillo@87 39 in their field of focus.
meillo@87 40 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87 41 or modular \(en will never be the best choice in any of the fields.
meillo@169 42 Even in providing the best consistent all-in-one system, they are likely
meillo@87 43 to be beaten by projects that focus only on integrating existing mail
meillo@169 44 components to create a homogeneous system.
meillo@87 45 .P
meillo@173 46 The limiting resource in the community development of free software
meillo@87 47 is usually man power.
meillo@171 48 .\" XXX FIXME ref!
meillo@87 49 If the development power is spread over a large development area,
meillo@87 50 it becomes even more difficult to compete with the specialists in the
meillo@87 51 various fields.
meillo@87 52 The concrete situation for MH-based mail systems is even tougher,
meillo@169 53 given their small and aged community, concerning both developers and users.
meillo@87 54 .P
meillo@87 55 In consequence, I believe that the available development resources
meillo@100 56 should focus on the point where MH is most unique.
meillo@87 57 This is clearly the user interface \(en the MUA.
meillo@125 58 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60 59
meillo@60 60
meillo@100 61 .H2 "Mail Transfer Facilities
meillo@154 62 .Id mail-transfer-facilities
meillo@60 63 .P
meillo@60 64 In contrast to nmh, which also provides mail submission and mail retrieval
meillo@178 65 agents, mmh is an MUA only.
meillo@100 66 This general difference initiated the development of mmh.
meillo@169 67 The removal of the mail transfer facilities was the first work task
meillo@76 68 in the mmh project.
meillo@60 69 .P
meillo@169 70 Focusing on one mail agent role only, is motivated by Eric Allman's
meillo@105 71 experience with Sendmail.
meillo@159 72 He identified the limitation of Sendmail to the MTA task as one reason for
meillo@105 73 its success:
meillo@105 74 .[ [
meillo@105 75 costales sendmail
meillo@105 76 .], p. xviii]
meillo@105 77 .QS
meillo@105 78 Second, I limited myself to the routing function \(en
meillo@110 79 I wouldn't write user agents or delivery back-ends.
meillo@105 80 This was a departure of the dominant through of the time,
meillo@105 81 in which routing logic, local delivery, and often the network code
meillo@105 82 were incorporated directly into the user agents.
meillo@105 83 .QE
meillo@105 84 .P
meillo@159 85 In nmh, the Mail Submission Agent (MSA) is called
meillo@105 86 \fIMessage Transfer Service\fP (MTS).
meillo@105 87 This facility, implemented by the
meillo@105 88 .Pn post
meillo@105 89 command, established network connections and spoke SMTP to submit
meillo@159 90 messages to be relayed to the outside world.
meillo@169 91 The changes in email demanded changes in this part of nmh as well.
meillo@89 92 Encryption and authentication for network connections
meillo@87 93 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87 94 This added complexity to nmh without improving it in its core functions.
meillo@87 95 Also, keeping up with recent developments in the field of
meillo@87 96 mail transfer requires development power and specialists.
meillo@169 97 In mmh, this whole facility was simply cut off.
meillo@76 98 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76 99 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76 100 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87 101 Instead, mmh depends on an external MSA.
meillo@60 102 The only outgoing interface available to mmh is the
meillo@60 103 .Pn sendmail
meillo@87 104 command, which almost any MSA provides.
meillo@87 105 If not, a wrapper program can be written.
meillo@87 106 It must read the message from the standard input, extract the
meillo@87 107 recipient addresses from the message header, and hand the message
meillo@87 108 over to the MSA.
meillo@87 109 For example, a wrapper script for qmail would be:
meillo@87 110 .VS
meillo@87 111 #!/bin/sh
meillo@138 112 exec qmail-inject # ignore command line arguments
meillo@87 113 VE
meillo@87 114 The requirement to parse the recipient addresses out of the message header
meillo@87 115 is likely to be removed in the future.
meillo@169 116 Then mmh would pass the recipient addresses as command line arguments.
meillo@100 117 This appears to be the better interface.
meillo@87 118 .\" XXX implement it
meillo@60 119 .P
meillo@60 120 To retrieve mail, the
meillo@60 121 .Pn inc
meillo@169 122 command acted as an Mail Retrieval Agent (MRA).
meillo@100 123 It established network connections
meillo@76 124 and spoke POP3 to retrieve mail from remote servers.
meillo@76 125 As with mail submission, the network connections required encryption and
meillo@87 126 authentication, thus TLS and SASL were added.
meillo@169 127 Support for message retrieval through IMAP will soon become necessary
meillo@169 128 additions, too, and likewise for any other changes in mail transfer.
meillo@100 129 Not so for mmh because it has dropped the support for retrieving mail
meillo@100 130 from remote locations.
meillo@76 131 .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76 132 Instead, it depends on an external tool to cover this task.
meillo@169 133 Mmh has two paths for messages to enter mmh's mail storage:
meillo@100 134 (1) Mail can be incorporated with
meillo@60 135 .Pn inc
meillo@87 136 from the system maildrop, or (2) with
meillo@60 137 .Pn rcvstore
meillo@87 138 by reading them, one at a time, from the standard input.
meillo@60 139 .P
meillo@60 140 With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@178 141 mail system to being an MUA only.
meillo@60 142 Now, of course, mmh depends on third-party software.
meillo@87 143 An external MSA is required to transfer mail to the outside world;
meillo@60 144 an external MRA is required to retrieve mail from remote machines.
meillo@169 145 Excellent implementations of such software exist,
meillo@159 146 which likely are superior than the internal version.
meillo@159 147 Additionally, the best suiting programs can be freely chosen.
meillo@60 148 .P
meillo@60 149 As it had already been possible to use an external MSA or MRA,
meillo@60 150 why not keep the internal version for convenience?
meillo@159 151 .\" XXX ueberleitung
meillo@76 152 The question whether there is sense in having a fall-back pager in all
meillo@76 153 the command line tools, for the cases when
meillo@60 154 .Pn more
meillo@60 155 or
meillo@60 156 .Pn less
meillo@173 157 are not available, appears to be ridiculous.
meillo@100 158 Of course, MSAs and MRAs are more complex than text pagers
meillo@87 159 and not necessarily available but still the concept of orthogonal
meillo@87 160 design holds: ``Write programs that do one thing and do it well.''
meillo@87 161 .[
meillo@87 162 mcilroy unix phil
meillo@87 163 p. 53
meillo@87 164 .]
meillo@87 165 .[
meillo@87 166 mcilroy bstj foreword
meillo@87 167 .]
meillo@87 168 Here, this part of the Unix philosophy was applied not only
meillo@87 169 to the programs but to the project itself.
meillo@87 170 In other words:
meillo@164 171 Develop projects that focus on one thing and do it well.
meillo@169 172 Projects which have grown complex should be split, for the same
meillo@169 173 reasons that programs which have grown complex should be split.
meillo@100 174 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87 175 separate projects then they should be separated.
meillo@169 176 In my opinion, this is the case here.
meillo@87 177 The RFCs propose this separation by clearly distinguishing the different
meillo@87 178 mail handling tasks.
meillo@87 179 .[
meillo@87 180 rfc 821
meillo@87 181 .]
meillo@87 182 The small interfaces between the mail agents support the separation.
meillo@76 183 .P
meillo@169 184 Email once had been small and simple.
meillo@100 185 At that time,
meillo@60 186 .Pn /bin/mail
meillo@169 187 had covered everything there was to email and still was small and simple.
meillo@100 188 Later, the essential complexity of email increased.
meillo@87 189 (Essential complexity is the complexity defined by the problem itself.\0
meillo@87 190 .[[
meillo@87 191 brooks no silver bullet
meillo@87 192 .]])
meillo@171 193 Email systems reacted to this change: they grew.
meillo@100 194 RFCs started to introduce the concept of mail agents to separate the
meillo@100 195 various tasks because they became more extensive and new tasks appeared.
meillo@100 196 As the mail systems grew even more, parts were split off.
meillo@169 197 For instance, a POP server was included in the original MH;
meillo@169 198 it was removed in nmh.
meillo@164 199 Now is the time to go one step further and split off the MSA and MRA, too.
meillo@87 200 Not only does this decrease the code size of the project,
meillo@169 201 more importantly, it unburdens mmh of the whole field of
meillo@87 202 message transfer with all its implications for the project.
meillo@169 203 There is no more need for concern with changes in network transfer.
meillo@169 204 This independence is gained by depending on an external program
meillo@76 205 that covers the field.
meillo@76 206 Today, this is a reasonable exchange.
meillo@60 207 .P
meillo@159 208 .\" XXX ueberleitung ???
meillo@100 209 Functionality can be added in three different ways:
meillo@171 210 .LI 1
meillo@169 211 Implementing the function in the project itself.
meillo@171 212 .LI 2
meillo@87 213 Depending on a library that provides the function.
meillo@171 214 .LI 3
meillo@87 215 Depending on a program that provides the function.
meillo@171 216 .LP
meillo@159 217 .\" XXX Rework sentence
meillo@169 218 While implementing the function in the project itself leads to the
meillo@169 219 largest increase in code size and requires the most maintenance
meillo@169 220 and development work,
meillo@169 221 it increases the project's independence of other software the most.
meillo@169 222 Using libraries or external programs requires less maintenance work
meillo@87 223 but introduces dependencies on external software.
meillo@169 224 Programs have the smallest interfaces and provide the best separation,
meillo@87 225 but possibly limit the information exchange.
meillo@169 226 External libraries are more strongly connected than external programs,
meillo@169 227 thus information can be exchanged in a more flexible manner.
meillo@87 228 Adding code to a project increases maintenance work.
meillo@87 229 .\" XXX ref
meillo@159 230 Implementing complex functions in the project itself adds
meillo@87 231 a lot of code.
meillo@87 232 This should be avoided if possible.
meillo@169 233 Hence, the dependencies only change in their character,
meillo@169 234 not in their existence.
meillo@66 235 In mmh, library dependencies on
meillo@66 236 .Pn libsasl2
meillo@66 237 and
meillo@66 238 .Pn libcrypto /\c
meillo@66 239 .Pn libssl
meillo@159 240 were traded against program dependencies on an MSA and an MRA.
meillo@159 241 This also meant trading build-time dependencies against run-time
meillo@87 242 dependencies.
meillo@169 243 Besides providing stronger separation and greater flexibility,
meillo@169 244 program dependencies also allowed
meillo@66 245 over 6\|000 lines of code to be removed from mmh.
meillo@66 246 This made mmh's code base about 12\|% smaller.
meillo@87 247 Reducing the project's code size by such an amount without actually
meillo@87 248 losing functionality is a convincing argument.
meillo@87 249 Actually, as external MSAs and MRAs are likely superior to the
meillo@87 250 project's internal versions, the common user even gains functionality.
meillo@66 251 .P
meillo@169 252 Users of MH should not have problems setting up an external MSA and MRA.
meillo@60 253 Also, the popular MSAs and MRAs have large communities and a lot
meillo@169 254 of available documentation.
meillo@169 255 Choices for MSAs range from full-featured MTAs such as
meillo@159 256 .\" XXX refs
meillo@169 257 .I Postfix ,
meillo@169 258 over mid-size MTAs such as
meillo@60 259 .I masqmail
meillo@60 260 and
meillo@169 261 .I dma ,
meillo@169 262 to small forwarders such as
meillo@60 263 .I ssmtp
meillo@60 264 and
meillo@60 265 .I nullmailer .
meillo@60 266 Choices for MRAs include
meillo@60 267 .I fetchmail ,
meillo@60 268 .I getmail ,
meillo@60 269 .I mpop
meillo@60 270 and
meillo@60 271 .I fdm .
meillo@60 272
meillo@60 273
meillo@100 274 .H2 "Non-MUA Tools
meillo@60 275 .P
meillo@87 276 One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@173 277 Further more, any tools that do not significantly improve the MUA's job
meillo@87 278 should be removed.
meillo@87 279 Loosely related and rarely used tools distract from the lean appearance.
meillo@87 280 They require maintenance work without adding much to the core task.
meillo@125 281 By removing these tools, the project shall become more streamlined
meillo@87 282 and focused.
meillo@169 283 In mmh, the following tools are not available anymore:
meillo@62 284 .BU
meillo@58 285 .Pn conflict
meillo@87 286 was removed
meillo@76 287 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87 288 because it is a mail system maintenance tool that is not MUA-related.
meillo@87 289 It even checked
meillo@58 290 .Fn /etc/passwd
meillo@58 291 and
meillo@58 292 .Fn /etc/group
meillo@87 293 for consistency, which is completely unrelated to email.
meillo@87 294 A tool like
meillo@87 295 .Pn conflict
meillo@87 296 is surely useful, but it should not be shipped with mmh.
meillo@76 297 .\" XXX historic reasons?
meillo@62 298 .BU
meillo@58 299 .Pn rcvtty
meillo@87 300 was removed
meillo@87 301 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89 302 because its use case of writing to the user's terminal
meillo@159 303 on receival of mail is obsolete.
meillo@87 304 If users like to be informed of new mail, the shell's
meillo@58 305 .Ev MAILPATH
meillo@87 306 variable or graphical notifications are technically more appealing.
meillo@169 307 Writing directly to terminals is hardly ever desired today.
meillo@169 308 If, though, one prefers this approach, the standard tool
meillo@58 309 .Pn write
meillo@58 310 can be used in a way similar to:
meillo@82 311 .VS
meillo@58 312 scan -file - | write `id -un`
meillo@82 313 VE
meillo@62 314 .BU
meillo@58 315 .Pn viamail
meillo@159 316 .\" XXX was macht viamail
meillo@87 317 was removed
meillo@87 318 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87 319 when the new attachment system was activated, because
meillo@58 320 .Pn forw
meillo@76 321 could then cover the task itself.
meillo@62 322 The program
meillo@58 323 .Pn sendfiles
meillo@62 324 was rewritten as a shell script wrapper around
meillo@58 325 .Pn forw .
meillo@76 326 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62 327 .BU
meillo@58 328 .Pn msgchk
meillo@159 329 .\" XXX was macht msgchk
meillo@87 330 was removed
meillo@87 331 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87 332 because it lost its use case when POP support was removed.
meillo@76 333 A call to
meillo@58 334 .Pn msgchk
meillo@87 335 provided hardly more information than:
meillo@82 336 .VS
meillo@58 337 ls -l /var/mail/meillo
meillo@82 338 VE
meillo@100 339 It did distinguish between old and new mail, but
meillo@169 340 these details can be retrieved with
meillo@76 341 .Pn stat (1),
meillo@62 342 too.
meillo@100 343 A small shell script could be written to print the information
meillo@76 344 in a similar way, if truly necessary.
meillo@76 345 As mmh's
meillo@76 346 .Pn inc
meillo@87 347 only incorporates mail from the user's local maildrop,
meillo@62 348 and thus no data transfers over slow networks are involved,
meillo@169 349 there is hardly any need to check for new mail before incorporating it.
meillo@62 350 .BU
meillo@58 351 .Pn msh
meillo@87 352 was removed
meillo@76 353 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87 354 because the tool was in conflict with the philosophy of MH.
meillo@76 355 It provided an interactive shell to access the features of MH,
meillo@173 356 but it was not just a shell tailored to the needs of mail handling.
meillo@169 357 Instead, it was one large program that had several MH tools built in.
meillo@76 358 This conflicts with the major feature of MH of being a tool chest.
meillo@76 359 .Pn msh 's
meillo@159 360 main use case had been accessing Bulletin Boards, which have ceased to
meillo@62 361 be popular.
meillo@62 362 .P
meillo@62 363 Removing
meillo@169 364 .Pn msh
meillo@76 365 together with the truly archaic code relicts
meillo@58 366 .Pn vmh
meillo@58 367 and
meillo@169 368 .Pn wmh
meillo@62 369 saved more than 7\|000 lines of C code \(en
meillo@66 370 about 15\|% of the project's original source code amount.
meillo@100 371 Having less code \(en with equal readability, of course \(en
meillo@76 372 for the same functionality is an advantage.
meillo@63 373 Less code means less bugs and less maintenance work.
meillo@76 374 As
meillo@63 375 .Pn rcvtty
meillo@63 376 and
meillo@63 377 .Pn msgchk
meillo@87 378 are assumed to be rarely used and can be implemented in different ways,
meillo@87 379 why should one keep them?
meillo@125 380 Removing them streamlines mmh.
meillo@63 381 .Pn viamail 's
meillo@63 382 use case is now partly obsolete and partly covered by
meillo@63 383 .Pn forw ,
meillo@76 384 hence there's no reason to still maintain it.
meillo@63 385 .Pn conflict
meillo@76 386 is not related to the mail client, and
meillo@63 387 .Pn msh
meillo@63 388 conflicts with the basic concept of MH.
meillo@169 389 These two tools might still be useful, but they should not be part of mmh.
meillo@63 390 .P
meillo@169 391 Finally, there is
meillo@76 392 .Pn slocal .
meillo@76 393 .Pn slocal
meillo@76 394 is an MDA and thus not directly MUA-related.
meillo@100 395 It should be removed from mmh, because including it conflicts with
meillo@178 396 the idea that mmh is an MUA only.
meillo@100 397 .Pn slocal
meillo@100 398 should rather become a separate project.
meillo@87 399 However,
meillo@76 400 .Pn slocal
meillo@76 401 provides rule-based processing of messages, like filing them into
meillo@76 402 different folders, which is otherwise not available in mmh.
meillo@87 403 Although
meillo@76 404 .Pn slocal
meillo@169 405 neither pulls in dependencies, nor does it include a separate
meillo@154 406 technical area (cf. Sec.
meillo@154 407 .Cf mail-transfer-facilities ),
meillo@169 408 it still accounts for about 1\|000 lines of code that need to be maintained.
meillo@76 409 As
meillo@76 410 .Pn slocal
meillo@76 411 is almost self-standing, it should be split off into a separate project.
meillo@76 412 This would cut the strong connection between the MUA mmh and the MDA
meillo@76 413 .Pn slocal .
meillo@87 414 For anyone not using MH,
meillo@87 415 .Pn slocal
meillo@87 416 would become yet another independent MDA, like
meillo@87 417 .I procmail .
meillo@100 418 Then
meillo@87 419 .Pn slocal
meillo@100 420 could be installed without the complete MH system.
meillo@76 421 Likewise, mmh users could decide to use
meillo@76 422 .I procmail
meillo@87 423 without having a second, unused MDA,
meillo@87 424 .Pn slocal ,
meillo@76 425 installed.
meillo@100 426 That appears to be conceptionally the best solution.
meillo@76 427 Yet,
meillo@76 428 .Pn slocal
meillo@87 429 is not split off.
meillo@100 430 I defer the decision over
meillo@78 431 .Pn slocal
meillo@169 432 out of a need for deeper investigation.
meillo@100 433 In the meanwhile, it remains part of mmh.
meillo@159 434 However, its continued existence is not significant because
meillo@100 435 .Pn slocal
meillo@100 436 is unrelated to the rest of the project.
meillo@0 437
meillo@58 438
meillo@133 439
meillo@134 440 .H2 "Displaying Messages
meillo@155 441 .Id mhshow
meillo@131 442 .P
meillo@133 443 Since the very beginning, already in the first concept paper,
meillo@159 444 .\" XXX ref!!!
meillo@58 445 .Pn show
meillo@62 446 had been MH's message display program.
meillo@58 447 .Pn show
meillo@76 448 mapped message numbers and sequences to files and invoked
meillo@58 449 .Pn mhl
meillo@89 450 to have the files formatted.
meillo@173 451 With MIME, this approach was not sufficient anymore.
meillo@100 452 MIME messages can consist of multiple parts. Some parts are not
meillo@100 453 directly displayable and text content might be encoded in
meillo@58 454 foreign charsets.
meillo@58 455 .Pn show 's
meillo@76 456 understanding of messages and
meillo@58 457 .Pn mhl 's
meillo@173 458 display capabilities could not cope with the task any longer.
meillo@62 459 .P
meillo@88 460 Instead of extending these tools, additional tools were written from
meillo@88 461 scratch and added to the MH tool chest.
meillo@88 462 Doing so is encouraged by the tool chest approach.
meillo@88 463 Modular design is a great advantage for extending a system,
meillo@88 464 as new tools can be added without interfering with existing ones.
meillo@62 465 First, the new MIME features were added in form of the single program
meillo@58 466 .Pn mhn .
meillo@58 467 The command
meillo@82 468 .Cl "mhn -show 42
meillo@58 469 would show the MIME message numbered 42.
meillo@58 470 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58 471 the split of
meillo@58 472 .Pn mhn
meillo@88 473 into a set of specialized tools, which together covered the
meillo@88 474 multiple aspects of MIME.
meillo@88 475 One of them was
meillo@69 476 .Pn mhshow ,
meillo@88 477 which replaced
meillo@88 478 .Cl "mhn -show" .
meillo@88 479 It was capable of displaying MIME messages appropriately.
meillo@62 480 .P
meillo@88 481 From then on, two message display tools were part of nmh,
meillo@76 482 .Pn show
meillo@76 483 and
meillo@76 484 .Pn mhshow .
meillo@88 485 To ease the life of users,
meillo@69 486 .Pn show
meillo@69 487 was extended to automatically hand the job over to
meillo@69 488 .Pn mhshow
meillo@69 489 if displaying the message would be beyond
meillo@69 490 .Pn show 's
meillo@69 491 abilities.
meillo@88 492 In consequence, the user would simply invoke
meillo@69 493 .Pn show
meillo@69 494 (possibly through
meillo@69 495 .Pn next
meillo@69 496 or
meillo@69 497 .Pn prev )
meillo@69 498 and get the message printed with either
meillo@69 499 .Pn show
meillo@69 500 or
meillo@69 501 .Pn mhshow ,
meillo@69 502 whatever was more appropriate.
meillo@69 503 .P
meillo@69 504 Having two similar tools for essentially the same task is redundant.
meillo@173 505 Usually, users would not distinguish between
meillo@88 506 .Pn show
meillo@88 507 and
meillo@88 508 .Pn mhshow
meillo@88 509 in their daily mail reading.
meillo@88 510 Having two separate display programs was therefore mainly unnecessary
meillo@88 511 from a user's point of view.
meillo@88 512 Besides, the development of both programs needed to be in sync,
meillo@76 513 to ensure that the programs behaved in a similar way,
meillo@76 514 because they were used like a single tool.
meillo@76 515 Different behavior would have surprised the user.
meillo@69 516 .P
meillo@69 517 Today, non-MIME messages are rather seen to be a special case of
meillo@100 518 MIME messages, although it is the other way round.
meillo@69 519 As
meillo@69 520 .Pn mhshow
meillo@159 521 had already been able to display non-MIME messages, it appeared natural
meillo@69 522 to drop
meillo@69 523 .Pn show
meillo@69 524 in favor of using
meillo@69 525 .Pn mhshow
meillo@69 526 exclusively.
meillo@88 527 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88 528 Removing
meillo@88 529 .Pn show
meillo@88 530 is no loss in function, because functionally
meillo@88 531 .Pn mhshow
meillo@88 532 covers it completely.
meillo@88 533 The old behavior of
meillo@88 534 .Pn show
meillo@88 535 can still be emulated with the simple command line:
meillo@88 536 .VS
meillo@88 537 mhl `mhpath c`
meillo@88 538 VE
meillo@88 539 .P
meillo@76 540 For convenience,
meillo@76 541 .Pn mhshow
meillo@88 542 was renamed to
meillo@88 543 .Pn show
meillo@88 544 after
meillo@88 545 .Pn show
meillo@88 546 was gone.
meillo@88 547 It is clear that such a rename may confuse future developers when
meillo@88 548 trying to understand the history.
meillo@88 549 Nevertheless, I consider the convenience on the user's side,
meillo@88 550 to call
meillo@88 551 .Pn show
meillo@88 552 when they want a message to be displayed, to outweigh the inconvenience
meillo@88 553 on the developer's side when understanding the project history.
meillo@69 554 .P
meillo@88 555 To prepare for the transition,
meillo@69 556 .Pn mhshow
meillo@69 557 was reworked to behave more like
meillo@69 558 .Pn show
meillo@69 559 first.
meillo@154 560 (cf. Sec.
meillo@154 561 .Cf mhshow )
meillo@164 562 .\" XXX code commits?
meillo@88 563 Once the tools behaved more alike, the replacing appeared to be
meillo@88 564 even more natural.
meillo@88 565 Today, mmh's new
meillo@69 566 .Pn show
meillo@159 567 has become the one single message display program once more,
meillo@159 568 with the difference
meillo@88 569 that today it handles MIME messages as well as non-MIME messages.
meillo@88 570 The outcome of the transition is one program less to maintain,
meillo@88 571 no second display program for users to deal with,
meillo@88 572 and less system complexity.
meillo@69 573 .P
meillo@88 574 Still, removing the old
meillo@69 575 .Pn show
meillo@88 576 hurts in one regard: It had been such a simple program.
meillo@159 577 Its lean elegance is missing from the new
meillo@159 578 .Pn show ,
meillo@159 579 .\" XXX
meillo@159 580 however there is no alternative;
meillo@159 581 supporting MIME demands higher essential complexity.
meillo@58 582
meillo@134 583 .ig
meillo@134 584 XXX
meillo@134 585 Consider including text on scan listings here
meillo@58 586
meillo@134 587 Scan listings shall not contain body content. Hence, removed this feature.
meillo@134 588 Scan listings shall operator on message headers and non-message information
meillo@134 589 only. Displaying the beginning of the body complicates everything too much.
meillo@134 590 That's no surprise, because it's something completely different. If you
meillo@134 591 want to examine the body, then use show(1)/mhshow(1).
meillo@134 592 Changed the default scan formats accordingly.
meillo@134 593 .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134 594 ..
meillo@131 595
meillo@131 596
meillo@131 597
meillo@133 598
meillo@100 599 .H2 "Configure Options
meillo@58 600 .P
meillo@76 601 Customization is a double-edged sword.
meillo@76 602 It allows better suiting setups, but not for free.
meillo@76 603 There is the cost of code complexity to be able to customize.
meillo@76 604 There is the cost of less tested setups, because there are
meillo@171 605 more possible setups and especially corner cases.
meillo@159 606 Additionally, there is the cost of choice itself.
meillo@76 607 The code complexity directly affects the developers.
meillo@173 608 Less tested code affects both users and developers.
meillo@159 609 The problem of choice affects the users, for once by having to choose,
meillo@159 610 but also by more complex interfaces that require more documentation.
meillo@159 611 Whenever options add few advantages but increase the complexity of the
meillo@159 612 system, they should be considered for removal.
meillo@72 613 I have reduced the number of project-specific configure options from
meillo@72 614 fifteen to three.
meillo@74 615
meillo@76 616 .U3 "Mail Transfer Facilities
meillo@74 617 .P
meillo@85 618 With the removal of the mail transfer facilities five configure
meillo@85 619 options vanished:
meillo@85 620 .P
meillo@85 621 The switches
meillo@85 622 .Sw --with-tls
meillo@85 623 and
meillo@85 624 .Sw --with-cyrus-sasl
meillo@89 625 had activated the support for transfer encryption and authentication.
meillo@159 626 .\" XXX cf
meillo@159 627 .\" XXX gruende kurz wiederholen
meillo@85 628 This is not needed anymore.
meillo@85 629 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85 630 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85 631 .P
meillo@159 632 .\" XXX cf
meillo@159 633 .\" XXX ``For the same reason ...''
meillo@85 634 The configure switch
meillo@85 635 .Sw --enable-pop
meillo@85 636 activated the message retrieval facility.
meillo@85 637 The code area that would be conditionally compiled in for TLS and SASL
meillo@85 638 support had been small.
meillo@85 639 The conditionally compiled code area for POP support had been much larger.
meillo@85 640 Whereas the code base changes would only slightly change on toggling
meillo@85 641 TLS or SASL support, it changed much on toggling POP support.
meillo@85 642 The changes in the code base could hardly be overviewed.
meillo@159 643 By having POP support togglable, a second code base had been created,
meillo@85 644 one that needed to be tested.
meillo@85 645 This situation is basically similar for the conditional TLS and SASL
meillo@85 646 code, but there the changes are minor and can yet be overviewed.
meillo@85 647 Still, conditional compilation of a code base creates variations
meillo@85 648 of the original program.
meillo@85 649 More variations require more testing and maintenance work.
meillo@85 650 .P
meillo@85 651 Two other options only specified default configuration values:
meillo@100 652 .Sw --with-mts
meillo@164 653 defined the default transport service.
meillo@85 654 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85 655 With
meillo@100 656 .Sw --with-smtpservers
meillo@164 657 default SMTP servers could be specified.
meillo@72 658 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@164 659 Both of them became irrelevant when the SMTP transport service was removed.
meillo@164 660 .\" XXX code ref
meillo@164 661 In mmh, all messages are handed over to
meillo@164 662 .Pn sendmail
meillo@164 663 for transportation.
meillo@164 664
meillo@72 665
meillo@74 666 .U3 "Backup Prefix
meillo@74 667 .P
meillo@76 668 The backup prefix is the string that was prepended to message
meillo@76 669 filenames to tag them as deleted.
meillo@173 670 By default it had been the comma character (`\fL,\fP').
meillo@159 671 .\" XXX Zeitlich ordnen
meillo@78 672 In July 2000, Kimmo Suominen introduced
meillo@78 673 the configure option
meillo@78 674 .Sw --with-hash-backup
meillo@173 675 to change the default to the hash character `\f(CW#\fP'.
meillo@78 676 The choice was probably personal preference, because first, the
meillo@78 677 option was named
meillo@78 678 .Sw --with-backup-prefix.
meillo@173 679 and had the prefix character as argument.
meillo@173 680 But giving the hash character as argument caused too many problems
meillo@100 681 for Autoconf,
meillo@173 682 thus the option was limited to use the hash character as the default prefix.
meillo@100 683 This supports the assumption, that the choice for the hash was
meillo@100 684 personal preference only.
meillo@173 685 Being related or not, words that start with the hash character
meillo@78 686 introduce a comment in the Unix shell.
meillo@72 687 Thus, the command line
meillo@72 688 .Cl "rm #13 #15
meillo@72 689 calls
meillo@72 690 .Pn rm
meillo@173 691 without arguments because the first hash character starts the comment
meillo@72 692 that reaches until the end of the line.
meillo@72 693 To delete the backup files,
meillo@72 694 .Cl "rm ./#13 ./#15"
meillo@72 695 needs to be used.
meillo@100 696 Using the hash as backup prefix can be seen as a precaution against
meillo@78 697 data loss.
meillo@78 698 .P
meillo@159 699 First, I removed the configure option but added the profile entry
meillo@72 700 .Pe backup-prefix ,
meillo@72 701 which allows to specify an arbitrary string as backup prefix.
meillo@72 702 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76 703 Profile entries are the common method to change mmh's behavior.
meillo@76 704 This change did not remove the choice but moved it to a location where
meillo@72 705 it suited better.
meillo@76 706 .P
meillo@78 707 Eventually, however, the new trash folder concept
meillo@154 708 (cf. Sec.
meillo@154 709 .Cf trash-folder )
meillo@164 710 removed the need for the backup prefix completely.
meillo@78 711 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133 712 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133 713
meillo@76 714
meillo@76 715 .U3 "Editor and Pager
meillo@74 716 .P
meillo@74 717 The two configure options
meillo@74 718 .CW --with-editor=EDITOR
meillo@74 719 .CW --with-pager=PAGER
meillo@74 720 were used to specify the default editor and pager at configure time.
meillo@109 721 Doing so at configure time made sense in the eighties,
meillo@76 722 when the set of available editors and pagers varied much across
meillo@76 723 different systems.
meillo@89 724 Today, the situation is more homogeneous.
meillo@74 725 The programs
meillo@74 726 .Pn vi
meillo@74 727 and
meillo@74 728 .Pn more
meillo@76 729 can be expected to be available on every Unix system,
meillo@74 730 as they are specified by POSIX since two decades.
meillo@74 731 (The specifications for
meillo@74 732 .Pn vi
meillo@74 733 and
meillo@74 734 .Pn more
meillo@74 735 appeared in
meillo@74 736 .[
meillo@74 737 posix 1987
meillo@74 738 .]
meillo@74 739 and,
meillo@74 740 .[
meillo@74 741 posix 1992
meillo@74 742 .]
meillo@74 743 respectively.)
meillo@74 744 As a first step, these two tools were hard-coded as defaults.
meillo@74 745 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74 746 Not changed were the
meillo@74 747 .Pe editor
meillo@74 748 and
meillo@74 749 .Pe moreproc
meillo@76 750 profile entries, which allowed the user to override the system defaults.
meillo@74 751 Later, the concept was reworked to respect the standard environment
meillo@74 752 variables
meillo@74 753 .Ev VISUAL
meillo@74 754 and
meillo@74 755 .Ev PAGER
meillo@76 756 if they are set.
meillo@74 757 Today, mmh determines the editor to use in the following order,
meillo@74 758 taking the first available and non-empty item:
meillo@171 759 .LI 1
meillo@74 760 Environment variable
meillo@74 761 .Ev MMHEDITOR
meillo@171 762 .LI 2
meillo@74 763 Profile entry
meillo@74 764 .Pe Editor
meillo@171 765 .LI 3
meillo@74 766 Environment variable
meillo@74 767 .Ev VISUAL
meillo@171 768 .LI 4
meillo@74 769 Environment variable
meillo@74 770 .Ev EDITOR
meillo@171 771 .LI 5
meillo@74 772 Command
meillo@74 773 .Pn vi .
meillo@171 774 .LP
meillo@76 775 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76 776 .P
meillo@89 777 The pager to use is determined in a similar order,
meillo@74 778 also taking the first available and non-empty item:
meillo@171 779 .LI 1
meillo@74 780 Environment variable
meillo@74 781 .Ev MMHPAGER
meillo@171 782 .LI 2
meillo@74 783 Profile entry
meillo@74 784 .Pe Pager
meillo@74 785 (replaces
meillo@74 786 .Pe moreproc )
meillo@171 787 .LI 3
meillo@74 788 Environment variable
meillo@74 789 .Ev PAGER
meillo@171 790 .LI 4
meillo@74 791 Command
meillo@74 792 .Pn more .
meillo@171 793 .LP
meillo@74 794 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74 795 .P
meillo@76 796 By respecting the
meillo@74 797 .Ev VISUAL /\c
meillo@74 798 .Ev EDITOR
meillo@74 799 and
meillo@74 800 .Ev PAGER
meillo@76 801 environment variables,
meillo@76 802 the new behavior confirms better to the common style on Unix systems.
meillo@76 803 Additionally, the new approach is more uniform and clearer to users.
meillo@72 804
meillo@72 805
meillo@76 806 .U3 "ndbm
meillo@72 807 .P
meillo@74 808 .Pn slocal
meillo@78 809 used to depend on
meillo@74 810 .I ndbm ,
meillo@74 811 a database library.
meillo@76 812 The database is used to store the `\fLMessage-ID\fP's of all
meillo@76 813 messages delivered.
meillo@74 814 This enables
meillo@74 815 .Pn slocal
meillo@74 816 to suppress delivering the same message to the same user twice.
meillo@74 817 (This features was enabled by the
meillo@74 818 .Sw -suppressdup
meillo@74 819 switch.)
meillo@74 820 .P
meillo@100 821 A variety of versions of the database library exist.
meillo@78 822 .[
meillo@78 823 wolter unix incompat notes dbm
meillo@78 824 .]
meillo@74 825 Complicated autoconf code was needed to detect them correctly.
meillo@74 826 Further more, the configure switches
meillo@74 827 .Sw --with-ndbm=ARG
meillo@74 828 and
meillo@74 829 .Sw --with-ndbmheader=ARG
meillo@74 830 were added to help with difficult setups that would
meillo@78 831 not be detected automatically or correctly.
meillo@74 832 .P
meillo@74 833 By removing the suppress duplicates feature of
meillo@74 834 .Pn slocal ,
meillo@74 835 the dependency on
meillo@74 836 .I ndbm
meillo@78 837 vanished and 120 lines of complex autoconf code could be saved.
meillo@74 838 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@89 839 The change removed functionality too, but that is minor to the
meillo@78 840 improvement by dropping the dependency and the complex autoconf code.
meillo@159 841 .\" XXX argument: slocal ist sowieso nicht teil vom mmh kern
meillo@72 842
meillo@74 843 .U3 "mh-e Support
meillo@72 844 .P
meillo@74 845 The configure option
meillo@74 846 .Sw --disable-mhe
meillo@74 847 was removed when the mh-e support was reworked.
meillo@74 848 Mh-e is the Emacs front-end to MH.
meillo@76 849 It requires MH to provide minor additional functions.
meillo@76 850 The
meillo@76 851 .Sw --disable-mhe
meillo@76 852 configure option could switch these extensions off.
meillo@76 853 After removing the support for old versions of mh-e,
meillo@74 854 only the
meillo@74 855 .Sw -build
meillo@76 856 switches of
meillo@74 857 .Pn forw
meillo@74 858 and
meillo@74 859 .Pn repl
meillo@76 860 are left to be mh-e extensions.
meillo@76 861 They are now always built in because they add little code and complexity.
meillo@76 862 In consequence, the
meillo@74 863 .Sw --disable-mhe
meillo@76 864 configure option was removed
meillo@72 865 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74 866 Removing the option removed a second code setup that would have
meillo@74 867 needed to be tested.
meillo@159 868 .\" XXX datum?
meillo@169 869 This change was first accomplished in nmh and thereafter merged into mmh.
meillo@76 870 .P
meillo@76 871 The interface changes in mmh require mh-e to be adjusted in order
meillo@76 872 to be able to use mmh as back-end.
meillo@76 873 This will require minor changes to mh-e, but removing the
meillo@76 874 .Sw -build
meillo@76 875 switches would require more rework.
meillo@72 876
meillo@74 877 .U3 "Masquerading
meillo@72 878 .P
meillo@74 879 The configure option
meillo@74 880 .Sw --enable-masquerade
meillo@76 881 could take up to three arguments:
meillo@76 882 `draft_from', `mmailid', and `username_extension'.
meillo@74 883 They activated different types of address masquerading.
meillo@74 884 All of them were implemented in the SMTP-speaking
meillo@74 885 .Pn post
meillo@76 886 command, which provided an MSA.
meillo@76 887 Address masquerading is an MTA's task and mmh does not cover
meillo@76 888 this field anymore.
meillo@76 889 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74 890 .P
meillo@74 891 The
meillo@74 892 .I mmailid
meillo@74 893 masquerading type is the oldest one of the three and the only one
meillo@74 894 available in the original MH.
meillo@74 895 It provided a
meillo@74 896 .I username
meillo@74 897 to
meillo@74 898 .I fakeusername
meillo@76 899 mapping, based on the password file's GECOS field.
meillo@74 900 The man page
meillo@74 901 .Mp mh-tailor(5)
meillo@74 902 described the use case as being the following:
meillo@98 903 .QS
meillo@74 904 This is useful if you want the messages you send to always
meillo@74 905 appear to come from the name of an MTA alias rather than your
meillo@74 906 actual account name. For instance, many organizations set up
meillo@74 907 `First.Last' sendmail aliases for all users. If this is
meillo@74 908 the case, the GECOS field for each user should look like:
meillo@74 909 ``First [Middle] Last <First.Last>''
meillo@98 910 .QE
meillo@74 911 .P
meillo@74 912 As mmh sends outgoing mail via the local MTA only,
meillo@76 913 the best location to do such global rewrites is there.
meillo@74 914 Besides, the MTA is conceptionally the right location because it
meillo@74 915 does the reverse mapping for incoming mail (aliasing), too.
meillo@76 916 Further more, masquerading set up there is readily available for all
meillo@74 917 mail software on the system.
meillo@76 918 Hence, mmailid masquerading was removed.
meillo@74 919 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74 920 .P
meillo@74 921 The
meillo@74 922 .I username_extension
meillo@76 923 masquerading type did not replace the username but would append a suffix,
meillo@76 924 specified by the
meillo@74 925 .Ev USERNAME_EXTENSION
meillo@76 926 environment variable, to it.
meillo@76 927 This provided support for the
meillo@74 928 .I user-extension
meillo@74 929 feature of qmail and the similar
meillo@74 930 .I "plussed user
meillo@74 931 processing of sendmail.
meillo@74 932 The decision to remove this username_extension masquerading was
meillo@74 933 motivated by the fact that
meillo@74 934 .Pn spost
meillo@173 935 had not supported it already.
meillo@76 936 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76 937 Username extensions are possible in mmh, but less convenient to use.
meillo@159 938 .\" XXX covered by next paragraph
meillo@76 939 .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74 940 .P
meillo@74 941 The
meillo@74 942 .I draft_from
meillo@74 943 masquerading type instructed
meillo@74 944 .Pn post
meillo@84 945 to use the value of the
meillo@84 946 .Hd From
meillo@84 947 header field as SMTP envelope sender.
meillo@76 948 Sender addresses could be replaced completely.
meillo@74 949 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76 950 Mmh offers a kind of masquerading similar in effect, but
meillo@74 951 with technical differences.
meillo@76 952 As mmh does not transfer messages itself, the local MTA has final control
meillo@76 953 over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76 954 by the MTA.
meillo@76 955 In times of pedantic spam checking, an MTA will take care to use
meillo@76 956 sensible envelope sender addresses to keep its own reputation up.
meillo@84 957 Nonetheless, the MUA can set the
meillo@84 958 .Hd From
meillo@84 959 header field and thereby propose
meillo@76 960 a sender address to the MTA.
meillo@74 961 The MTA may then decide to take that one or generate the canonical sender
meillo@74 962 address for use as envelope sender address.
meillo@74 963 .P
meillo@74 964 In mmh, the MTA will always extract the recipient and sender from the
meillo@84 965 message header (\c
meillo@74 966 .Pn sendmail 's
meillo@74 967 .Sw -t
meillo@74 968 switch).
meillo@84 969 The
meillo@84 970 .Hd From
meillo@84 971 header field of the draft may be set arbitrary by the user.
meillo@74 972 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74 973
meillo@74 974 .U3 "Remaining Options
meillo@74 975 .P
meillo@74 976 Two configure options remain in mmh.
meillo@74 977 One is the locking method to use:
meillo@74 978 .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@76 979 The idea of removing all methods except the portable dot locking
meillo@76 980 and having that one as the default is appealing, but this change
meillo@76 981 requires deeper technical investigation into the topic.
meillo@76 982 The other option,
meillo@74 983 .Sw --enable-debug ,
meillo@74 984 compiles the programs with debugging symbols and does not strip them.
meillo@74 985 This option is likely to stay.
meillo@72 986
meillo@72 987
meillo@58 988
meillo@63 989
meillo@100 990 .H2 "Command Line Switches
meillo@58 991 .P
meillo@171 992 The command line switches of MH tools is similar to the X Window style.
meillo@171 993 .\" XXX ref
meillo@93 994 They are words, introduced by a single dash.
meillo@93 995 For example:
meillo@93 996 .Cl "-truncate" .
meillo@93 997 Every program in mmh has two generic switches:
meillo@93 998 .Sw -help ,
meillo@93 999 to print a short message on how to use the program, and
meillo@159 1000 .Sw -Version
meillo@164 1001 (with capital `V'), to tell what version of mmh the program belongs to.
meillo@93 1002 .P
meillo@93 1003 Switches change the behavior of programs.
meillo@93 1004 Programs that do one thing in one way require no switches.
meillo@93 1005 In most cases, doing something in exactly one way is too limiting.
meillo@97 1006 If there is basically one task to accomplish, but it should be done
meillo@93 1007 in various ways, switches are a good approach to alter the behavior
meillo@93 1008 of a program.
meillo@93 1009 Changing the behavior of programs provides flexibility and customization
meillo@97 1010 to users, but at the same time it complicates the code, documentation and
meillo@93 1011 usage of the program.
meillo@97 1012 .\" XXX: Ref
meillo@93 1013 Therefore, the number of switches should be kept small.
meillo@93 1014 A small set of well-chosen switches does no harm.
meillo@93 1015 But usually, the number of switches increases over time.
meillo@93 1016 Already in 1985, Rose and Romine have identified this as a major
meillo@93 1017 problem of MH:
meillo@93 1018 .[ [
meillo@93 1019 rose romine real work
meillo@93 1020 .], p. 12]
meillo@98 1021 .QS
meillo@93 1022 A complaint often heard about systems which undergo substantial development
meillo@93 1023 by many people over a number of years, is that more and more options are
meillo@93 1024 introduced which add little to the functionality but greatly increase the
meillo@93 1025 amount of information a user needs to know in order to get useful work done.
meillo@93 1026 This is usually referred to as creeping featurism.
meillo@93 1027 .QP
meillo@93 1028 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93 1029 ten or so well-meaning programmers (the present authors included),
meillo@93 1030 suffers mightily from this.
meillo@98 1031 .QE
meillo@93 1032 .P
meillo@97 1033 Being reluctant to adding new switches \(en or `options',
meillo@97 1034 as Rose and Romine call them \(en is one part of a counter-action,
meillo@97 1035 the other part is removing hardly used switches.
meillo@97 1036 Nmh's tools had lots of switches already implemented,
meillo@97 1037 hence, cleaning up by removing some of them was the more important part
meillo@97 1038 of the counter-action.
meillo@93 1039 Removing existing functionality is always difficult because it
meillo@93 1040 breaks programs that use these functions.
meillo@93 1041 Also, for every obsolete feature, there'll always be someone who still
meillo@93 1042 uses it and thus opposes its removal.
meillo@93 1043 This puts the developer into the position,
meillo@93 1044 where sensible improvements to style are regarded as destructive acts.
meillo@97 1045 Yet, living with the featurism is far worse, in my eyes, because
meillo@97 1046 future needs will demand adding further features,
meillo@93 1047 worsening the situation more and more.
meillo@93 1048 Rose and Romine added in a footnote,
meillo@93 1049 ``[...]
meillo@93 1050 .Pn send
meillo@93 1051 will no doubt acquire an endless number of switches in the years to come.''
meillo@97 1052 Although clearly humorous, the comment points to the nature of the problem.
meillo@97 1053 Refusing to add any new switches would encounter the problem at its root,
meillo@97 1054 but this is not practical.
meillo@97 1055 New needs will require new switches and it would be unwise to block
meillo@97 1056 them strictly.
meillo@97 1057 Nevertheless, removing obsolete switches still is an effective approach
meillo@97 1058 to deal with the problem.
meillo@97 1059 Working on an experimental branch without an established user base,
meillo@97 1060 eased my work because I did not offend users when I removed existing
meillo@110 1061 functions.
meillo@93 1062 .P
meillo@93 1063 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93 1064 .Pn send .
meillo@97 1065 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@97 1066 At the time of writing, no more than 7 visible switches and 1 hidden switch
meillo@97 1067 have remained in mmh's
meillo@97 1068 .Pn send .
meillo@97 1069 (These numbers include two generic switches, help and version.)
meillo@93 1070 .P
meillo@154 1071 The figure displays the number of switches for each of the tools
meillo@159 1072 that is available in both nmh and mmh.
meillo@100 1073 The tools are sorted by the number of switches they had in nmh.
meillo@100 1074 Visible and hidden switches were counted,
meillo@97 1075 but not the generic help and version switches.
meillo@93 1076 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93 1077 now it has no more than 5 \(en only half as many.
meillo@93 1078 If the `no' switches and similar inverse variant are folded onto
meillo@100 1079 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100 1080 has 4 now.
meillo@93 1081 The total number of functional switches in mmh dropped from 465
meillo@93 1082 to 234.
meillo@58 1083
meillo@93 1084 .KS
meillo@93 1085 .in 1c
meillo@93 1086 .so input/switches.grap
meillo@93 1087 .KE
meillo@58 1088
meillo@93 1089 .P
meillo@93 1090 A part of the switches vanished after functions were removed.
meillo@93 1091 This was the case for network mail transfer, for instance.
meillo@97 1092 Sometimes, however, the work flow was the other way:
meillo@97 1093 I looked through the
meillo@97 1094 .Mp mh-chart (7)
meillo@97 1095 man page to identify the tools with apparently too many switches.
meillo@97 1096 Then considering the value of each of the switches by examining
meillo@97 1097 the tool's man page and source code, aided by recherche and testing.
meillo@97 1098 This way, the removal of functions was suggested by the aim to reduce
meillo@97 1099 the number of switches per command.
meillo@97 1100
meillo@58 1101
meillo@93 1102 .U3 "Draft Folder Facility
meillo@93 1103 .P
meillo@100 1104 A change early in the project was the complete transition from
meillo@93 1105 the single draft message to the draft folder facility.
meillo@97 1106 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@164 1107 .\" XXX ref to section ...
meillo@109 1108 The draft folder facility was introduced in the mid-eighties, when
meillo@100 1109 Rose and Romine called it a ``relatively new feature''.
meillo@93 1110 .[
meillo@93 1111 rose romine real work
meillo@93 1112 .]
meillo@110 1113 Since then, the facility had existed but was inactive by default.
meillo@93 1114 The default activation and the related rework of the tools made it
meillo@93 1115 possible to remove the
meillo@93 1116 .Sw -[no]draftfolder ,
meillo@93 1117 and
meillo@93 1118 .Sw -draftmessage
meillo@93 1119 switches from
meillo@93 1120 .Pn comp ,
meillo@93 1121 .Pn repl ,
meillo@93 1122 .Pn forw ,
meillo@93 1123 .Pn dist ,
meillo@93 1124 .Pn whatnow ,
meillo@93 1125 and
meillo@93 1126 .Pn send .
meillo@97 1127 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@97 1128 The only flexibility removed with this change is having multiple
meillo@97 1129 draft folders within one profile.
meillo@97 1130 I consider this a theoretical problem only.
meillo@159 1131 At the same time, the
meillo@93 1132 .Sw -draft
meillo@93 1133 switch of
meillo@93 1134 .Pn anno ,
meillo@93 1135 .Pn refile ,
meillo@93 1136 and
meillo@93 1137 .Pn send
meillo@93 1138 was removed.
meillo@159 1139 The special treatment of \fIthe\fP draft message became irrelevant after
meillo@93 1140 the rework of the draft system.
meillo@159 1141 (cf. Sec.
meillo@154 1142 .Cf draft-folder )
meillo@164 1143 Furthermore,
meillo@95 1144 .Pn comp
meillo@164 1145 no longer needs a
meillo@95 1146 .Sw -file
meillo@164 1147 switch as the draft folder facility together with the
meillo@95 1148 .Sw -form
meillo@164 1149 switch are sufficient.
meillo@93 1150
meillo@95 1151
meillo@102 1152 .U3 "In Place Editing
meillo@93 1153 .P
meillo@93 1154 .Pn anno
meillo@93 1155 had the switches
meillo@93 1156 .Sw -[no]inplace
meillo@100 1157 to either annotate the message in place and thus preserve hard links,
meillo@93 1158 or annotate a copy to replace the original message, breaking hard links.
meillo@97 1159 Following the assumption that linked messages should truly be the
meillo@97 1160 same message, and annotating it should not break the link, the
meillo@93 1161 .Sw -[no]inplace
meillo@93 1162 switches were removed and the previous default
meillo@93 1163 .Sw -inplace
meillo@93 1164 was made the only behavior.
meillo@97 1165 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0
meillo@93 1166 The
meillo@93 1167 .Sw -[no]inplace
meillo@93 1168 switches of
meillo@93 1169 .Pn repl ,
meillo@93 1170 .Pn forw ,
meillo@93 1171 and
meillo@93 1172 .Pn dist
meillo@93 1173 could be removed, too, as they were simply passed through to
meillo@93 1174 .Pn anno .
meillo@93 1175 .P
meillo@93 1176 .Pn burst
meillo@93 1177 also had
meillo@93 1178 .Sw -[no]inplace
meillo@95 1179 switches, but with different meaning.
meillo@95 1180 With
meillo@95 1181 .Sw -inplace ,
meillo@95 1182 the digest had been replaced by the table of contents (i.e. the
meillo@110 1183 introduction text) and the burst messages were placed right
meillo@95 1184 after this message, renumbering all following messages.
meillo@95 1185 Also, any trailing text of the digest was lost, though,
meillo@95 1186 in practice, it usually consists of an end-of-digest marker only.
meillo@95 1187 Nontheless, this behavior appeared less elegant than the
meillo@95 1188 .Sw -noinplace
meillo@95 1189 behavior, which already had been the default.
meillo@95 1190 Nmh's
meillo@95 1191 .Mp burst (1)
meillo@95 1192 man page reads:
meillo@98 1193 .QS
meillo@164 1194 If
meillo@164 1195 .Sw -noinplace
meillo@164 1196 is given, each digest is preserved, no table
meillo@93 1197 of contents is produced, and the messages contained within
meillo@93 1198 the digest are placed at the end of the folder. Other messages
meillo@93 1199 are not tampered with in any way.
meillo@98 1200 .QE
meillo@95 1201 .LP
meillo@93 1202 The decision to drop the
meillo@93 1203 .Sw -inplace
meillo@95 1204 behavior was supported by the code complexity and the possible data loss
meillo@95 1205 it caused.
meillo@93 1206 .Sw -noinplace
meillo@95 1207 was chosen to be the definitive behavior.
meillo@97 1208 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93 1209
meillo@95 1210
meillo@95 1211 .U3 "Forms and Format Strings
meillo@93 1212 .P
meillo@95 1213 Historically, the tools that had
meillo@95 1214 .Sw -form
meillo@95 1215 switches to supply a form file had
meillo@95 1216 .Sw -format
meillo@95 1217 switches as well to supply the contents of a form file as a string
meillo@95 1218 on the command line directly.
meillo@95 1219 In consequence, the following two lines equaled:
meillo@95 1220 .VS
meillo@95 1221 scan -form scan.mailx
meillo@95 1222 scan -format "`cat .../scan.mailx`"
meillo@95 1223 VE
meillo@95 1224 The
meillo@95 1225 .Sw -format
meillo@95 1226 switches were dropped in favor for extending the
meillo@95 1227 .Sw -form
meillo@95 1228 switches.
meillo@97 1229 .Ci f51956be123db66b00138f80464d06f030dbb88d
meillo@95 1230 If their argument starts with an equal sign (`='),
meillo@95 1231 then the rest of the argument is taken as a format string,
meillo@95 1232 otherwise the arguments is treated as the name of a format file.
meillo@95 1233 Thus, now the following two lines equal:
meillo@95 1234 .VS
meillo@95 1235 scan -form scan.mailx
meillo@95 1236 scan -form "=`cat .../scan.mailx`"
meillo@95 1237 VE
meillo@95 1238 This rework removed the prefix collision between
meillo@95 1239 .Sw -form
meillo@95 1240 and
meillo@95 1241 .Sw -format .
meillo@95 1242 Now, typing
meillo@95 1243 .Sw -fo
meillo@95 1244 suffices to specify form or format string.
meillo@95 1245 .P
meillo@95 1246 The different meaning of
meillo@95 1247 .Sw -format
meillo@95 1248 for
meillo@95 1249 .Pn repl
meillo@95 1250 and
meillo@95 1251 .Pn forw
meillo@95 1252 was removed in mmh.
meillo@95 1253 .Pn forw
meillo@95 1254 was completely switched to MIME-type forwarding, thus removing the
meillo@95 1255 .Sw -[no]format .
meillo@97 1256 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@95 1257 For
meillo@95 1258 .Pn repl ,
meillo@95 1259 the
meillo@95 1260 .Sw -[no]format
meillo@95 1261 switches were reworked to
meillo@95 1262 .Sw -[no]filter
meillo@95 1263 switches.
meillo@97 1264 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@95 1265 The
meillo@95 1266 .Sw -format
meillo@95 1267 switches of
meillo@95 1268 .Pn send
meillo@95 1269 and
meillo@95 1270 .Pn post ,
meillo@95 1271 which had a third meaning,
meillo@95 1272 were removed likewise.
meillo@97 1273 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9
meillo@95 1274 Eventually, the ambiguity of the
meillo@95 1275 .Sw -format
meillo@95 1276 switches was resolved by not anymore having any such switch in mmh.
meillo@95 1277
meillo@95 1278
meillo@95 1279 .U3 "MIME Tools
meillo@95 1280 .P
meillo@95 1281 The MIME tools, which were once part of
meillo@100 1282 .Pn mhn
meillo@164 1283 .\" XXX
meillo@164 1284 (whatever that stood for),
meillo@95 1285 had several switches that added little practical value to the programs.
meillo@95 1286 The
meillo@95 1287 .Sw -[no]realsize
meillo@95 1288 switches of
meillo@95 1289 .Pn mhbuild
meillo@95 1290 and
meillo@95 1291 .Pn mhlist
meillo@97 1292 were removed, doing real size calculations always now
meillo@97 1293 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c ,
meillo@159 1294 as nmh's
meillo@159 1295 .Mp mhbuild (1)
meillo@159 1296 man page states
meillo@95 1297 ``This provides an accurate count at the expense of a small delay.''
meillo@95 1298 This small delay is not noticable on modern systems.
meillo@95 1299 .P
meillo@95 1300 The
meillo@95 1301 .Sw -[no]check
meillo@95 1302 switches were removed together with the support for
meillo@95 1303 .Hd Content-MD5
meillo@95 1304 header fields.
meillo@95 1305 .[
meillo@95 1306 rfc 1864
meillo@95 1307 .]
meillo@97 1308 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@154 1309 (cf. Sec.
meillo@154 1310 .Cf content-md5 )
meillo@95 1311 .P
meillo@95 1312 The
meillo@95 1313 .Sw -[no]ebcdicsafe
meillo@95 1314 and
meillo@95 1315 .Sw -[no]rfc934mode
meillo@95 1316 switches of
meillo@95 1317 .Pn mhbuild
meillo@95 1318 were removed because they are considered obsolete.
meillo@97 1319 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@97 1320 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88
meillo@95 1321 .P
meillo@95 1322 Content caching of external MIME parts, activated with the
meillo@95 1323 .Sw -rcache
meillo@95 1324 and
meillo@95 1325 .Sw -wcache
meillo@95 1326 switches was completely removed.
meillo@97 1327 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269
meillo@97 1328 External MIME parts are rare today, having a caching facility
meillo@159 1329 for them appears to be unnecessary.
meillo@95 1330 .P
meillo@95 1331 In pre-MIME times,
meillo@95 1332 .Pn mhl
meillo@95 1333 had covered many tasks that are part of MIME handling today.
meillo@95 1334 Therefore,
meillo@95 1335 .Pn mhl
meillo@95 1336 could be simplified to a large extend, reducing the number of its
meillo@95 1337 switches from 21 to 6.
meillo@97 1338 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@97 1339 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@95 1340
meillo@95 1341
meillo@95 1342
meillo@95 1343
meillo@95 1344 .U3 "Header Printing
meillo@95 1345 .P
meillo@95 1346 .Pn folder 's
meillo@95 1347 data output is self-explaining enough that
meillo@159 1348 displaying the header line makes little sense.
meillo@95 1349 Hence, the
meillo@95 1350 .Sw -[no]header
meillo@95 1351 switch was removed and headers are never printed.
meillo@97 1352 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7
meillo@95 1353 .P
meillo@95 1354 In
meillo@95 1355 .Pn mhlist ,
meillo@95 1356 the
meillo@95 1357 .Sw -[no]header
meillo@95 1358 switches were removed, too.
meillo@97 1359 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f
meillo@95 1360 But in this case headers are always printed,
meillo@95 1361 because the output is not self-explaining.
meillo@95 1362 .P
meillo@95 1363 .Pn scan
meillo@95 1364 also had
meillo@95 1365 .Sw -[no]header
meillo@95 1366 switches.
meillo@95 1367 Printing the header had been sensible until the introduction of
meillo@95 1368 format strings made it impossible to display the column headings.
meillo@95 1369 Only the folder name and the current date remained to be printed.
meillo@95 1370 As this information can be perfectly retrieved by
meillo@95 1371 .Pn folder
meillo@95 1372 and
meillo@95 1373 .Pn date ,
meillo@95 1374 consequently, the switches were removed.
meillo@97 1375 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e
meillo@95 1376 .P
meillo@95 1377 By removing all
meillo@95 1378 .Sw -header
meillo@95 1379 switches, the collision with
meillo@95 1380 .Sw -help
meillo@95 1381 on the first two letters was resolved.
meillo@95 1382 Currently,
meillo@95 1383 .Sw -h
meillo@95 1384 evaluates to
meillo@95 1385 .Sw -help
meillo@95 1386 for all tools of mmh.
meillo@95 1387
meillo@95 1388
meillo@139 1389 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95 1390 .P
meillo@95 1391 The
meillo@95 1392 .Sw -noedit
meillo@100 1393 switch of
meillo@95 1394 .Pn comp ,
meillo@95 1395 .Pn repl ,
meillo@95 1396 .Pn forw ,
meillo@95 1397 .Pn dist ,
meillo@95 1398 and
meillo@95 1399 .Pn whatnow
meillo@95 1400 was removed, but it can now be replaced by specifying
meillo@95 1401 .Sw -editor
meillo@95 1402 with an empty argument.
meillo@97 1403 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9
meillo@95 1404 (Specifying
meillo@159 1405 .Cl "-editor /bin/true
meillo@95 1406 is nearly the same, only differing by the previous editor being set.)
meillo@95 1407 .P
meillo@95 1408 The more important change is the removal of the
meillo@95 1409 .Sw -nowhatnowproc
meillo@95 1410 switch.
meillo@97 1411 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622
meillo@95 1412 This switch had introduced an awkward behavior, as explained in nmh's
meillo@95 1413 man page for
meillo@95 1414 .Mp comp (1):
meillo@98 1415 .QS
meillo@164 1416 The
meillo@164 1417 .Sw -editor
meillo@164 1418 .Ar editor
meillo@164 1419 switch indicates the editor to use for
meillo@164 1420 the initial edit. Upon exiting from the editor,
meillo@164 1421 .Pn comp
meillo@164 1422 will invoke the
meillo@164 1423 .Pn whatnow
meillo@164 1424 program. See
meillo@164 1425 .Mp whatnow (1)
meillo@164 1426 for a discussion of available options.
meillo@164 1427 The invocation of this program can be
meillo@164 1428 inhibited by using the
meillo@164 1429 .Sw -nowhatnowproc
meillo@164 1430 switch. (In truth of fact, it is the
meillo@164 1431 .Pn whatnow
meillo@164 1432 program which starts the initial edit.
meillo@164 1433 Hence,
meillo@164 1434 .Sw -nowhatnowproc
meillo@164 1435 will prevent any edit from occurring.)
meillo@98 1436 .QE
meillo@95 1437 .P
meillo@95 1438 Effectively, the
meillo@95 1439 .Sw -nowhatnowproc
meillo@100 1440 switch creates only a draft message.
meillo@95 1441 As
meillo@159 1442 .Cl "-whatnowproc /bin/true
meillo@95 1443 causes the same behavior, the
meillo@95 1444 .Sw -nowhatnowproc
meillo@95 1445 switch was removed for being redundant.
meillo@100 1446 Likely, the
meillo@95 1447 .Sw -nowhatnowproc
meillo@100 1448 switch was intended to be used by front-ends.
meillo@95 1449
meillo@95 1450
meillo@95 1451
meillo@95 1452 .U3 "Various
meillo@95 1453 .BU
meillo@139 1454 With the removal of MMDF maildrop format support,
meillo@139 1455 .Pn packf
meillo@139 1456 and
meillo@139 1457 .Pn rcvpack
meillo@139 1458 no longer needed their
meillo@139 1459 .Sw -mbox
meillo@139 1460 and
meillo@139 1461 .Sw -mmdf
meillo@139 1462 switches.
meillo@139 1463 .Sw -mbox
meillo@154 1464 is the sole behavior now.
meillo@139 1465 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@171 1466 Further rework in both tools made the
meillo@139 1467 .Sw -file
meillo@171 1468 switch unnecessary.
meillo@139 1469 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e
meillo@139 1470
meillo@139 1471 .BU
meillo@139 1472 Mmh's tools will no longer clear the screen (\c
meillo@139 1473 .Pn scan 's
meillo@139 1474 and
meillo@139 1475 .Pn mhl 's
meillo@139 1476 .Sw -[no]clear
meillo@139 1477 switches
meillo@139 1478 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139 1479 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@139 1480 Neither will
meillo@139 1481 .Pn mhl
meillo@139 1482 ring the bell (\c
meillo@139 1483 .Sw -[no]bell
meillo@139 1484 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@139 1485 nor page the output itself (\c
meillo@139 1486 .Sw -length
meillo@139 1487 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@159 1488 .\" XXX Ref
meillo@139 1489 Generally, the pager to use is no longer specified with the
meillo@139 1490 .Sw -[no]moreproc
meillo@139 1491 command line switches for
meillo@139 1492 .Pn mhl
meillo@139 1493 and
meillo@139 1494 .Pn show /\c
meillo@139 1495 .Pn mhshow .
meillo@139 1496 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a
meillo@139 1497
meillo@139 1498 .BU
meillo@96 1499 In order to avoid prefix collisions among switch names, the
meillo@95 1500 .Sw -version
meillo@95 1501 switch was renamed to
meillo@95 1502 .Sw -Version
meillo@95 1503 (with capital `V').
meillo@97 1504 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a
meillo@95 1505 Every program has the
meillo@95 1506 .Sw -version
meillo@95 1507 switch but its first three letters collided with the
meillo@95 1508 .Sw -verbose
meillo@95 1509 switch, present in many programs.
meillo@95 1510 The rename solved this problem once for all.
meillo@95 1511 Although this rename breaks a basic interface, having the
meillo@95 1512 .Sw -V
meillo@95 1513 abbreviation to display the version information, isn't all too bad.
meillo@139 1514
meillo@95 1515 .BU
meillo@95 1516 .Sw -[no]preserve
meillo@95 1517 of
meillo@95 1518 .Pn refile
meillo@168 1519 was removed
meillo@168 1520 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 1521 because what use was it anyway?
meillo@168 1522 Quoting nmh's man page
meillo@165 1523 .Mp refile (1):
meillo@98 1524 .QS
meillo@95 1525 Normally when a message is refiled, for each destination
meillo@95 1526 folder it is assigned the number which is one above the current
meillo@95 1527 highest message number in that folder. Use of the
meillo@164 1528 .Sw -preserv
meillo@164 1529 [sic!] switch will override this message renaming, and try
meillo@95 1530 to preserve the number of the message. If a conflict for a
meillo@164 1531 particular folder occurs when using the
meillo@164 1532 .Sw -preserve
meillo@164 1533 switch, then
meillo@164 1534 .Pn refile
meillo@164 1535 will use the next available message number which
meillo@95 1536 is above the message number you wish to preserve.
meillo@98 1537 .QE
meillo@139 1538
meillo@95 1539 .BU
meillo@95 1540 The removal of the
meillo@95 1541 .Sw -[no]reverse
meillo@95 1542 switches of
meillo@95 1543 .Pn scan
meillo@97 1544 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@95 1545 is a bug fix, supported by the comments
meillo@95 1546 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95 1547 by Rose and
meillo@95 1548 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@95 1549 This should be considered a bug.'' by Romine in the documentation.
meillo@159 1550 .\" XXX Ref: welche datei genau.
meillo@97 1551 The question remains why neither Rose and Romine had fixed this
meillo@109 1552 bug in the eighties when they wrote these comments nor has anyone
meillo@95 1553 thereafter.
meillo@93 1554
meillo@93 1555
meillo@93 1556 .ig
meillo@93 1557
meillo@95 1558 forw: [no]dashstuffing(mhl)
meillo@93 1559
meillo@95 1560 mhshow: [no]pause [no]serialonly
meillo@93 1561
meillo@93 1562 mhmail: resent queued
meillo@93 1563 inc: snoop, (pop)
meillo@93 1564
meillo@95 1565 mhl: [no]faceproc folder sleep
meillo@95 1566 [no]dashstuffing(forw) digest list volume number issue number
meillo@93 1567
meillo@95 1568 prompter: [no]doteof
meillo@93 1569
meillo@93 1570 refile: [no]preserve [no]unlink [no]rmmproc
meillo@93 1571
meillo@95 1572 send: [no]forward [no]mime [no]msgid
meillo@93 1573 [no]push split [no]unique (sasl) width snoop [no]dashstuffing
meillo@93 1574 attach attachformat
meillo@93 1575 whatnow: (noedit) attach
meillo@93 1576
meillo@93 1577 slocal: [no]suppressdups
meillo@93 1578
meillo@95 1579 spost: [no]filter [no]backup width [no]push idanno
meillo@93 1580 [no]check(whom) whom(whom)
meillo@93 1581
meillo@93 1582 whom: ???
meillo@93 1583
meillo@95 1584 ..
meillo@93 1585
meillo@93 1586
meillo@93 1587 .ig
meillo@93 1588
meillo@93 1589 .P
meillo@93 1590 In the best case, all switches are unambiguous on the first character,
meillo@93 1591 or on the three-letter prefix for the `no' variants.
meillo@96 1592 Reducing switch prefix collisions, shortens the necessary prefix length
meillo@93 1593 the user must type.
meillo@93 1594 Having less switches helps best.
meillo@93 1595
meillo@93 1596 ..
meillo@58 1597
meillo@95 1598
meillo@102 1599 .\" XXX: whatnow prompt commands
meillo@102 1600
meillo@102 1601
meillo@95 1602
meillo@95 1603
meillo@133 1604 .\" --------------------------------------------------------------
meillo@74 1605 .H1 "Modernizing
meillo@102 1606 .P
meillo@164 1607 In the more than thirty years of MH's existence, its code base was
meillo@159 1608 increasingly extended.
meillo@118 1609 New features entered the project and became alternatives to the
meillo@118 1610 existing behavior.
meillo@118 1611 Relicts from several decades have gathered in the code base,
meillo@118 1612 but seldom obsolete features were dropped.
meillo@118 1613 This section describes the removing of old code
meillo@118 1614 and the modernizing of the default setup.
meillo@118 1615 It focuses on the functional aspect only;
meillo@154 1616 the non-functional aspects of code style are discussed in Sec.
meillo@154 1617 .Cf code-style .
meillo@58 1618
meillo@58 1619
meillo@100 1620 .H2 "Code Relicts
meillo@0 1621 .P
meillo@159 1622 My position regarding the removal of obsolete functions of mmh,
meillo@159 1623 .\" XXX ``in order to remove old code,''
meillo@159 1624 is much more revolutional than the nmh community appreciates.
meillo@159 1625 Working on an experimental version, I was quickly able to drop
meillo@104 1626 functionality I considered ancient.
meillo@104 1627 The need for consensus with peers would have slowed this process down.
meillo@104 1628 Without the need to justify my decisions, I was able to rush forward.
meillo@110 1629 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@159 1630 .\" XXX ugs
meillo@104 1631 do the work:
meillo@104 1632 .[
meillo@104 1633 paul vixie edginess nmh-workers
meillo@104 1634 .]
meillo@104 1635 .QS
meillo@104 1636 let's stop walking on egg shells with this code base. there's no need to
meillo@104 1637 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104 1638 we don't need a separate branch for removing vmh
meillo@104 1639 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@164 1640 or depending on pure ansi/posix ``libc''.
meillo@104 1641 .QP
meillo@164 1642 these things should each be a day or two of work and the ``main branch''
meillo@104 1643 should just be modern. [...]
meillo@104 1644 let's push forward, aggressively.
meillo@104 1645 .QE
meillo@104 1646 .LP
meillo@104 1647 I did so already in the months before.
meillo@104 1648 I pushed forward.
meillo@159 1649 .\" XXX semicolon ?
meillo@104 1650 I simply dropped the cruft.
meillo@104 1651 .P
meillo@104 1652 The decision to drop a feature was based on literature research and
meillo@159 1653 careful thinking, but whether having had contact with this particular
meillo@104 1654 feature within my own computer life served as a rule of thumb.
meillo@159 1655 I explained my reasons in the commit messages
meillo@109 1656 in the version control system.
meillo@104 1657 Hence, others can comprehend my view and argue for undoing the change
meillo@104 1658 if I have missed an important aspect.
meillo@109 1659 I was quick in dropping parts.
meillo@179 1660 I rather include falsely dropped parts again, than going at a slower pace.
meillo@179 1661 Mmh is experimental work; it requires tough decisions.
meillo@159 1662 .\" XXX ``exp. work'' schon oft gesagt
meillo@12 1663
meillo@102 1664
meillo@104 1665 .U3 "Forking
meillo@12 1666 .P
meillo@109 1667 Being a tool chest, MH creates many processes.
meillo@104 1668 In earlier times
meillo@104 1669 .Fu fork()
meillo@104 1670 had been an expensive system call, because the process's image needed
meillo@159 1671 to be completely duplicated at once.
meillo@159 1672 This expensive work was especially unnecessary in the commonly occuring
meillo@159 1673 case wherein the image is replaced by a call to
meillo@104 1674 .Fu exec()
meillo@104 1675 right after having forked the child process.
meillo@104 1676 The
meillo@104 1677 .Fu vfork()
meillo@104 1678 system call was invented to speed up this particular case.
meillo@104 1679 It completely omits the duplication of the image.
meillo@104 1680 On old systems this resulted in significant speed ups.
meillo@104 1681 Therefore MH used
meillo@104 1682 .Fu vfork()
meillo@104 1683 whenever possible.
meillo@12 1684 .P
meillo@104 1685 Modern memory management units support copy-on-write semantics, which make
meillo@104 1686 .Fu fork()
meillo@104 1687 almost as fast as
meillo@104 1688 .Fu vfork() .
meillo@104 1689 The man page of
meillo@104 1690 .Mp vfork (2)
meillo@104 1691 in FreeBSD 8.0 states:
meillo@104 1692 .QS
meillo@104 1693 This system call will be eliminated when proper system sharing mechanisms
meillo@104 1694 are implemented. Users should not depend on the memory sharing semantics
meillo@104 1695 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104 1696 .QE
meillo@104 1697 .LP
meillo@104 1698 Vixie supports the removal with the note that ``the last
meillo@104 1699 system on which fork was so slow that an mh user would notice it, was
meillo@104 1700 Eunice. that was 1987''.
meillo@104 1701 .[
meillo@104 1702 nmh-workers vixie edginess
meillo@104 1703 .]
meillo@104 1704 I replaced all calls to
meillo@104 1705 .Fu vfork()
meillo@104 1706 with calls to
meillo@104 1707 .Fu fork() .
meillo@109 1708 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104 1709 .P
meillo@104 1710 Related to the costs of
meillo@104 1711 .Fu fork()
meillo@104 1712 is the probability of its success.
meillo@109 1713 In the eighties, on heavy loaded systems, calls to
meillo@104 1714 .Fu fork()
meillo@104 1715 were prone to failure.
meillo@104 1716 Hence, many of the
meillo@104 1717 .Fu fork()
meillo@104 1718 calls in the code were wrapped into loops to retry the
meillo@104 1719 .Fu fork()
meillo@159 1720 several times, to increase the chances to succeed, eventually.
meillo@109 1721 On modern systems, a failing
meillo@104 1722 .Fu fork()
meillo@109 1723 call is unusual.
meillo@104 1724 Hence, in the rare case when
meillo@104 1725 .Fu fork()
meillo@104 1726 fails, mmh programs simply abort.
meillo@109 1727 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12 1728
meillo@12 1729
meillo@109 1730 .U3 "Header Fields
meillo@104 1731 .BU
meillo@84 1732 The
meillo@84 1733 .Hd Encrypted
meillo@104 1734 header field was introduced by RFC\|822,
meillo@109 1735 but already marked as legacy in RFC\|2822.
meillo@109 1736 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104 1737 messages [RFC\|4880, RFC\|3156].
meillo@109 1738 Hence, the support for
meillo@104 1739 .Hd Encrypted
meillo@104 1740 header fields is removed in mmh.
meillo@109 1741 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104 1742 .BU
meillo@159 1743 The native support for
meillo@84 1744 .Hd Face
meillo@104 1745 header fields has been removed, as well.
meillo@109 1746 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104 1747 This feature is similar to the
meillo@84 1748 .Hd X-Face
meillo@84 1749 header field in its intent,
meillo@21 1750 but takes a different approach to store the image.
meillo@84 1751 Instead of encoding the image data directly into the header field,
meillo@109 1752 it contains the hostname and UDP port where the image
meillo@109 1753 date can be retrieved.
meillo@159 1754 There is even a third Face system,
meillo@109 1755 which is the successor of
meillo@109 1756 .Hd X-Face ,
meillo@109 1757 although it re-uses the
meillo@104 1758 .Hd Face
meillo@109 1759 header field.
meillo@109 1760 It was invented in 2005 and supports colored PNG images.
meillo@104 1761 None of the Face systems described here is popular today.
meillo@104 1762 Hence, mmh has no direct support for them.
meillo@104 1763 .BU
meillo@154 1764 .Id content-md5
meillo@104 1765 The
meillo@104 1766 .Hd Content-MD5
meillo@104 1767 header field was introduced by RFC\|1864.
meillo@104 1768 It provides detection of data corruption during the transfer.
meillo@104 1769 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104 1770 [RFC\|1864].
meillo@104 1771 The proper approach to verify content integrity in an
meillo@166 1772 end-to-end relationship is the use of digital signatures.
meillo@104 1773 .\" XXX (RFCs FIXME).
meillo@104 1774 On the other hand, transfer protocols should detect corruption during
meillo@109 1775 the transmission.
meillo@109 1776 The TCP includes a checksum field therefore.
meillo@104 1777 These two approaches in combinations render the
meillo@104 1778 .Hd Content-MD5
meillo@104 1779 header field superfluous.
meillo@109 1780 Not a single one out of 4\|200 messages from two decades
meillo@109 1781 in an nmh-workers mailing list archive contains a
meillo@104 1782 .Hd Content-MD5
meillo@104 1783 header field.
meillo@104 1784 Neither did any of the 60\|000 messages in my personal mail storage.
meillo@104 1785 Removing the support for this header field,
meillo@104 1786 removed the last place where MD5 computation was needed.
meillo@109 1787 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104 1788 Hence, the MD5 code could be removed as well.
meillo@104 1789 Over 500 lines of code vanished by this one change.
meillo@104 1790
meillo@104 1791
meillo@104 1792 .U3 "MMDF maildrop support
meillo@21 1793 .P
meillo@104 1794 This type of format is conceptionally similar to the mbox format,
meillo@139 1795 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139 1796 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104 1797 Mbox is the de-facto standard maildrop format on Unix,
meillo@159 1798 whereas the MMDF maildrop format is now forgotten.
meillo@159 1799 By dropping the MMDF maildrop format support,
meillo@159 1800 mbox became the only packed mailbox format supported in mmh.
meillo@104 1801 .P
meillo@109 1802 The simplifications within the code were moderate.
meillo@109 1803 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109 1804 But also, switches of
meillo@109 1805 .Pn packf
meillo@104 1806 and
meillo@109 1807 .Pn rcvpack
meillo@109 1808 could be removed.
meillo@109 1809 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109 1810 In the message parsing function
meillo@109 1811 .Fn sbr/m_getfld.c ,
meillo@109 1812 knowledge of MMDF packed mail boxes was removed.
meillo@109 1813 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109 1814 Further code structure simplifications may be possible there,
meillo@109 1815 because only one single packed mailbox format is left to be supported.
meillo@104 1816 I have not worked on them yet because
meillo@104 1817 .Fu m_getfld()
meillo@104 1818 is heavily optimized and thus dangerous to touch.
meillo@104 1819 The risk of damaging the intricate workings of the optimized code is
meillo@104 1820 too high.
meillo@104 1821
meillo@12 1822
meillo@101 1823 .U3 "Prompter's Control Keys
meillo@20 1824 .P
meillo@20 1825 The program
meillo@20 1826 .Pn prompter
meillo@104 1827 queries the user to fill in a message form.
meillo@104 1828 When used by
meillo@20 1829 .Pn comp
meillo@104 1830 as
meillo@104 1831 .Cl "comp -editor prompter" ,
meillo@20 1832 the resulting behavior is similar to
meillo@20 1833 .Pn mailx .
meillo@51 1834 Apparently,
meillo@20 1835 .Pn prompter
meillo@173 1836 had not been touched lately.
meillo@104 1837 Otherwise it's hardly explainable why it
meillo@20 1838 still offered the switches
meillo@84 1839 .Sw -erase
meillo@84 1840 .Ar chr
meillo@20 1841 and
meillo@84 1842 .Sw -kill
meillo@84 1843 .Ar chr
meillo@20 1844 to name the characters for command line editing.
meillo@21 1845 The times when this had been necessary are long time gone.
meillo@20 1846 Today these things work out-of-the-box, and if not, are configured
meillo@20 1847 with the standard tool
meillo@20 1848 .Pn stty .
meillo@104 1849 The switches are removed now
meillo@104 1850 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20 1851
meillo@104 1852
meillo@109 1853 .U3 "Hardcopy Terminal Support
meillo@21 1854 .P
meillo@109 1855 More of a funny anecdote is a check for being connected to a
meillo@109 1856 hardcopy terminal.
meillo@159 1857 It remained in the code until spring 2012, when I finally removed it
meillo@104 1858 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@21 1859 .P
meillo@109 1860 The check only prevented a pager to be placed between the printing
meillo@104 1861 program (\c
meillo@104 1862 .Pn mhl )
meillo@104 1863 and the terminal.
meillo@109 1864 In nmh, this could have been ensured statically with the
meillo@104 1865 .Sw -nomoreproc
meillo@109 1866 at the command line, too.
meillo@121 1867 In mmh, setting the profile entry
meillo@104 1868 .Pe Pager
meillo@104 1869 or the environment variable
meillo@104 1870 .Ev PAGER
meillo@104 1871 to
meillo@109 1872 .Pn cat
meillo@159 1873 is sufficient.
meillo@104 1874
meillo@104 1875
meillo@21 1876
meillo@12 1877
meillo@58 1878 .H2 "Attachments
meillo@22 1879 .P
meillo@101 1880 The mind model of email attachments is unrelated to MIME.
meillo@101 1881 Although the MIME RFCs (2045 through 2049) define the technical
meillo@109 1882 requirements for having attachments, they do not mention the word
meillo@101 1883 ``attachment''.
meillo@101 1884 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101 1885 [RFC\|2045], a more general concept.
meillo@101 1886 Multi-part messages are messages
meillo@101 1887 ``in which one or more different
meillo@101 1888 sets of data are combined in a single body''
meillo@101 1889 [RFC\|2046].
meillo@101 1890 MIME keeps its descriptions generic;
meillo@101 1891 it does not imply specific usage models.
meillo@109 1892 One usage model became prevalent: attachments.
meillo@101 1893 The idea is having a main text document with files of arbitrary kind
meillo@101 1894 attached to it.
meillo@101 1895 In MIME terms, this is a multi-part message having a text part first
meillo@110 1896 and parts of arbitrary type following.
meillo@101 1897 .P
meillo@101 1898 MH's MIME support is a direct implementation of the RFCs.
meillo@101 1899 The perception of the topic described in the RFCs is clearly visible
meillo@101 1900 in MH's implementation.
meillo@159 1901 .\" XXX rewrite ``no idea''.
meillo@159 1902 As a result,
meillo@159 1903 MH had all the MIME features but no idea of attachments.
meillo@173 1904 But users do not need all the MIME features,
meillo@109 1905 they want convenient attachment handling.
meillo@109 1906
meillo@102 1907
meillo@102 1908 .U3 "Composing MIME Messages
meillo@102 1909 .P
meillo@102 1910 In order to improve the situation on the message composing side,
meillo@102 1911 Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101 1912 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102 1913 In the file
meillo@102 1914 .Fn docs/README-ATTACHMENTS ,
meillo@102 1915 he described his motivation to do so as such:
meillo@101 1916 .QS
meillo@159 1917 Although nmh contains the necessary functionality for MIME message
meillo@159 1918 handing [sic!], the interface to this functionality is pretty obtuse.
meillo@101 1919 There's no way that I'm ever going to convince my partner to write
meillo@101 1920 .Pn mhbuild
meillo@101 1921 composition files!
meillo@101 1922 .QE
meillo@102 1923 .LP
meillo@102 1924 With this change, the mind model of attachments entered nmh.
meillo@102 1925 In the same document:
meillo@101 1926 .QS
meillo@101 1927 These changes simplify the task of managing attachments on draft files.
meillo@101 1928 They allow attachments to be added, listed, and deleted.
meillo@101 1929 MIME messages are automatically created when drafts with attachments
meillo@101 1930 are sent.
meillo@101 1931 .QE
meillo@102 1932 .LP
meillo@102 1933 Unfortunately, the attachment system,
meillo@102 1934 like any new facilities in nmh,
meillo@110 1935 was inactive by default.
meillo@101 1936 .P
meillo@101 1937 During my work in Argentina, I tried to improve the attachment system.
meillo@102 1938 But, because of great opposition in the nmh community,
meillo@102 1939 my patch died as a proposal on the mailing list, after long discussions.
meillo@101 1940 .[
meillo@101 1941 nmh-workers attachment proposal
meillo@101 1942 .]
meillo@110 1943 In January 2012, I extended the patch and applied it to mmh.
meillo@101 1944 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102 1945 In mmh, the attachment system is active by default.
meillo@102 1946 Instead of command line switches, the
meillo@102 1947 .Pe Attachment-Header
meillo@102 1948 profile entry is used to specify
meillo@102 1949 the name of the attachment header field.
meillo@102 1950 It is pre-defined to
meillo@102 1951 .Hd Attach .
meillo@101 1952 .P
meillo@159 1953 To add an attachment to a draft, a header line needs to be added:
meillo@101 1954 .VS
meillo@101 1955 To: bob
meillo@101 1956 Subject: The file you wanted
meillo@101 1957 Attach: /path/to/the/file-bob-wanted
meillo@101 1958 --------
meillo@101 1959 Here it is.
meillo@101 1960 VE
meillo@101 1961 The header field can be added to the draft manually in the editor,
meillo@102 1962 or by using the `attach' command at the WhatNow prompt, or
meillo@102 1963 non-interactively with
meillo@101 1964 .Pn anno :
meillo@101 1965 .VS
meillo@102 1966 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101 1967 VE
meillo@102 1968 Drafts with attachment headers are converted to MIME automatically by
meillo@102 1969 .Pn send .
meillo@102 1970 The conversion to MIME is invisible to the user.
meillo@159 1971 The draft stored in the draft folder is always in source form with
meillo@101 1972 attachment headers.
meillo@179 1973 If the MIMEification fails (e.g. because the file to attach
meillo@179 1974 is not accessible) the original draft is not changed.
meillo@101 1975 .P
meillo@102 1976 The attachment system handles the forwarding of messages, too.
meillo@173 1977 If the attachment header value starts with a plus character (`\fL+\fP'),
meillo@101 1978 like in
meillo@101 1979 .Cl "Attach: +bob 30 42" ,
meillo@159 1980 the given messages in the specified folder will be attached.
meillo@101 1981 This allowed to simplify
meillo@101 1982 .Pn forw .
meillo@101 1983 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101 1984 .P
meillo@101 1985 Closely related to attachments is non-ASCII text content,
meillo@101 1986 because it requires MIME too.
meillo@102 1987 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101 1988 to have the draft converted to MIME.
meillo@102 1989 This was necessary whenever the draft contained non-ASCII characters.
meillo@101 1990 If the user did not call `mime', a broken message would be sent.
meillo@101 1991 Therefore, the
meillo@101 1992 .Pe automimeproc
meillo@101 1993 profile entry could be specified to have the `mime' command invoked
meillo@102 1994 automatically each time.
meillo@179 1995 Unfortunately, this approach conflicted with the attachment system
meillo@101 1996 because the draft would already be in MIME format at the time
meillo@101 1997 when the attachment system wanted to MIMEify it.
meillo@102 1998 To use nmh's attachment system, `mime' must not be called at the
meillo@102 1999 WhatNow prompt and
meillo@101 2000 .Pe automimeproc
meillo@102 2001 must not be set in the profile.
meillo@101 2002 But then the case of non-ASCII text without attachment headers was
meillo@101 2003 not caught.
meillo@102 2004 All in all, the solution was complex and irritating.
meillo@168 2005 My patch from December 2010
meillo@168 2006 .[
meillo@168 2007 nmh-workers attachment proposal
meillo@168 2008 .]
meillo@168 2009 would have simplified the situation.
meillo@102 2010 .P
meillo@101 2011 Mmh's current solution is even more elaborate.
meillo@101 2012 Any necessary MIMEification is done automatically.
meillo@101 2013 There is no `mime' command at the WhatNow prompt anymore.
meillo@102 2014 The draft will be converted automatically to MIME when either an
meillo@102 2015 attachment header or non-ASCII text is present.
meillo@173 2016 Furthermore, the hash character (`\fL#\fP') is not special any more
meillo@159 2017 at line beginnings in the draft message.
meillo@159 2018 .\" XXX REF ?
meillo@159 2019 Users need not concern themselves with the whole topic at all.
meillo@101 2020 .P
meillo@102 2021 Although the new approach does not anymore support arbitrary MIME
meillo@102 2022 compositions directly, the full power of
meillo@101 2023 .Pn mhbuild
meillo@101 2024 can still be accessed.
meillo@102 2025 Given no attachment headers are included, the user can create
meillo@101 2026 .Pn mhbuild
meillo@102 2027 composition drafts like in nmh.
meillo@101 2028 Then, at the WhatNow prompt, he needs to invoke
meillo@101 2029 .Cl "edit mhbuild
meillo@101 2030 to convert it to MIME.
meillo@110 2031 Because the resulting draft does neither contain non-ASCII characters
meillo@102 2032 nor has it attachment headers, the attachment system will not touch it.
meillo@101 2033 .P
meillo@159 2034 The approach taken in mmh is tailored towards today's most common case:
meillo@159 2035 a text part, possibly with attachments.
meillo@159 2036 This case was simplified.
meillo@102 2037
meillo@112 2038
meillo@102 2039 .U3 "MIME Type Guessing
meillo@102 2040 .P
meillo@159 2041 From the programmer's point of view, the use of
meillo@101 2042 .Pn mhbuild
meillo@159 2043 composition drafts had one notable advantage over attachment headers:
meillo@159 2044 The user provides the appropriate MIME types for files to include.
meillo@102 2045 The attachment system needs to find out the correct MIME type itself.
meillo@102 2046 This is a difficult task, yet it spares the user irritating work.
meillo@102 2047 Determining the correct MIME type of content is partly mechanical,
meillo@102 2048 partly intelligent work.
meillo@102 2049 Forcing the user to find out the correct MIME type,
meillo@102 2050 forces him to do partly mechanical work.
meillo@179 2051 Letting the computer do the work can lead to bad choices for difficult
meillo@102 2052 content.
meillo@102 2053 For mmh, the latter option was chosen.
meillo@102 2054 .P
meillo@102 2055 Determining the MIME type by the suffix of the file name is a dumb
meillo@102 2056 approach, yet it is simple to implement and provides good results
meillo@102 2057 for the common cases.
meillo@102 2058 Mmh implements this approach in the
meillo@102 2059 .Pn print-mimetype
meillo@102 2060 script.
meillo@112 2061 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44
meillo@102 2062 Using it is the default choice.
meillo@102 2063 .P
meillo@112 2064 A far better, though less portable, approach is the use of
meillo@102 2065 .Pn file .
meillo@102 2066 This standard tool tries to determine the type of files.
meillo@102 2067 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102 2068 Additionally, its output was only intended for human beings,
meillo@102 2069 but not to be used by programs.
meillo@102 2070 It varies much.
meillo@102 2071 Nevertheless, modern versions of GNU
meillo@102 2072 .Pn file ,
meillo@102 2073 which is prevalent on the popular GNU/Linux systems,
meillo@159 2074 provide MIME type output in machine-readable form.
meillo@102 2075 Although this solution is highly system-dependent,
meillo@102 2076 it solves the difficult problem well.
meillo@102 2077 On systems where GNU
meillo@102 2078 .Pn file ,
meillo@102 2079 version 5.04 or higher, is available it should be used.
meillo@102 2080 One needs to specify the following profile entry to do so:
meillo@112 2081 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6
meillo@102 2082 .VS
meillo@102 2083 Mime-Type-Query: file -b --mime
meillo@102 2084 VE
meillo@102 2085 .LP
meillo@102 2086 Other versions of
meillo@102 2087 .Pn file
meillo@102 2088 might possibly be usable with wrapper scripts to reformat the output.
meillo@102 2089 The diversity among
meillo@102 2090 .Pn file
meillo@102 2091 implementations is great; one needs to check the local variant.
meillo@102 2092 .P
meillo@102 2093 If no MIME type can be determined, text content gets sent as
meillo@102 2094 `text/plain' and anything else under the generic fall-back type
meillo@102 2095 `application/octet-stream'.
meillo@102 2096 It is not possible in mmh to override the automatic MIME type guessing
meillo@102 2097 for a specific file.
meillo@159 2098 To do so, either the user would need to know in advance for which file
meillo@159 2099 the automatic guessing fails, or the system would require interaction.
meillo@102 2100 I consider both cases impractical.
meillo@102 2101 The existing solution should be sufficient.
meillo@102 2102 If not, the user may always fall back to
meillo@102 2103 .Pn mhbuild
meillo@102 2104 composition drafts and ignore the attachment system.
meillo@101 2105
meillo@102 2106
meillo@102 2107 .U3 "Storing Attachments
meillo@102 2108 .P
meillo@169 2109 Extracting MIME parts of a message and storing them to disk is performed by
meillo@108 2110 .Pn mhstore .
meillo@108 2111 The program has two operation modes,
meillo@108 2112 .Sw -auto
meillo@108 2113 and
meillo@108 2114 .Sw -noauto .
meillo@108 2115 With the former one, each part is stored under the filename given in the
meillo@108 2116 MIME part's meta information, if available.
meillo@108 2117 This naming information is usually available for modern attachments.
meillo@108 2118 If no filename is available, this MIME part is stored as if
meillo@108 2119 .Sw -noauto
meillo@108 2120 would have been specified.
meillo@108 2121 In the
meillo@108 2122 .Sw -noauto
meillo@108 2123 mode, the parts are processed according to rules, defined by
meillo@108 2124 .Pe mhstore-store-*
meillo@108 2125 profile entries.
meillo@108 2126 These rules define generic filename templates for storing
meillo@108 2127 or commands to post-process the contents in arbitrary ways.
meillo@108 2128 If no matching rule is available the part is stored under a generic
meillo@108 2129 filename, built from message number, MIME part number, and MIME type.
meillo@108 2130 .P
meillo@108 2131 The
meillo@108 2132 .Sw -noauto
meillo@108 2133 mode had been the default in nmh because it was considered safe,
meillo@108 2134 in contrast to the
meillo@108 2135 .Sw -auto
meillo@108 2136 mode.
meillo@108 2137 In mmh,
meillo@108 2138 .Sw -auto
meillo@108 2139 is not dangerous anymore.
meillo@108 2140 Two changes were necessary:
meillo@171 2141 .LI 1
meillo@108 2142 Any directory path is removed from the proposed filename.
meillo@108 2143 Thus, the files are always stored in the expected directory.
meillo@108 2144 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@171 2145 .LI 2
meillo@108 2146 Tar files are not extracted automatically any more.
meillo@108 2147 Thus, the rest of the file system will not be touched.
meillo@108 2148 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108 2149 .LP
meillo@108 2150 Now, the outcome of mmh's
meillo@108 2151 .Cl "mhstore -auto
meillo@110 2152 can be foreseen from the output of
meillo@108 2153 .Cl "mhlist -verbose" .
meillo@108 2154 .P
meillo@108 2155 The
meillo@108 2156 .Sw -noauto
meillo@108 2157 mode is seen to be more powerful but less convenient.
meillo@108 2158 On the other hand,
meillo@108 2159 .Sw -auto
meillo@108 2160 is safe now and
meillo@108 2161 storing attachments under their original name is intuitive.
meillo@108 2162 Hence,
meillo@108 2163 .Sw -auto
meillo@108 2164 serves better as the default option.
meillo@108 2165 .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108 2166 .P
meillo@108 2167 Files are stored into the directory given by the
meillo@108 2168 .Pe Nmh-Storage
meillo@108 2169 profile entry, if set, or
meillo@108 2170 into the current working directory, otherwise.
meillo@108 2171 Storing to different directories is only possible with
meillo@108 2172 .Pe mhstore-store-*
meillo@108 2173 profile entries.
meillo@108 2174 .P
meillo@108 2175 Still, in both modes, existing files get overwritten silently.
meillo@108 2176 This can be considered a bug.
meillo@108 2177 Yet, each other behavior has its draw-backs, too.
meillo@108 2178 Refusing to replace files requires adding a
meillo@108 2179 .Sw -force
meillo@108 2180 option.
meillo@108 2181 Users will likely need to invoke
meillo@108 2182 .Pn mhstore
meillo@108 2183 a second time with
meillo@159 2184 .Sw -force .
meillo@159 2185 Eventually, only the user can decide in the specific case.
meillo@108 2186 This requires interaction, which I like to avoid if possible.
meillo@108 2187 Appending a unique suffix to the filename is another bad option.
meillo@108 2188 For now, the behavior remains as it is.
meillo@108 2189 .P
meillo@108 2190 In mmh, only MIME parts of type message are special in
meillo@108 2191 .Pn mhstore 's
meillo@108 2192 .Sw -auto
meillo@108 2193 mode.
meillo@108 2194 Instead of storing message/rfc822 parts as files to disk,
meillo@108 2195 they are stored as messages into the current mail folder.
meillo@159 2196 The same applies to message/partial, although the parts are
meillo@159 2197 automatically reassembled beforehand.
meillo@159 2198 MIME parts of type message/external-body are not automatically retrieved
meillo@159 2199 anymore.
meillo@159 2200 Instead, information on how to retrieve them is output.
meillo@108 2201 Not supporting this rare case saved nearly one thousand lines of code.
meillo@108 2202 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108 2203 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108 2204 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@159 2205 `application/octet-stream; type=tar' is not special anymore.
meillo@108 2206 Automatically extracting such MIME parts had been the dangerous part
meillo@108 2207 of the
meillo@108 2208 .Sw -auto
meillo@108 2209 mode.
meillo@108 2210 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108 2211
meillo@102 2212
meillo@102 2213
meillo@102 2214 .U3 "Showing MIME Messages
meillo@102 2215 .P
meillo@114 2216 The program
meillo@114 2217 .Pn mhshow
meillo@114 2218 had been written to display MIME messages.
meillo@114 2219 It implemented the conceptional view of the MIME RFCs.
meillo@114 2220 Nmh's
meillo@114 2221 .Pn mhshow
meillo@114 2222 handled each MIME part independently, presenting them separately
meillo@114 2223 to the user.
meillo@114 2224 This does not match today's understanding of email attachments,
meillo@114 2225 where displaying a message is seen to be a single, integrated operation.
meillo@114 2226 Today, email messages are expected to consist of a main text part
meillo@114 2227 plus possibly attachments.
meillo@114 2228 They are not any more seen to be arbitrary MIME hierarchies with
meillo@114 2229 information on how to display the individual parts.
meillo@114 2230 I adjusted
meillo@114 2231 .Pn mhshow 's
meillo@114 2232 behavior to the modern view on the topic.
meillo@114 2233 .P
meillo@159 2234 One should note that this section completely ignores the original
meillo@114 2235 .Pn show
meillo@114 2236 program, because it was not capable to display MIME messages
meillo@114 2237 and is no longer part of mmh.
meillo@179 2238 .\" XXX ref to other section
meillo@114 2239 Although
meillo@114 2240 .Pn mhshow
meillo@114 2241 was renamed to
meillo@114 2242 .Pn show
meillo@114 2243 in mmh, this section uses the name
meillo@114 2244 .Pn mhshow ,
meillo@114 2245 in order to avoid confusion.
meillo@114 2246 .P
meillo@114 2247 In mmh, the basic idea is that
meillo@114 2248 .Pn mhshow
meillo@114 2249 should display a message in one single pager session.
meillo@114 2250 Therefore,
meillo@114 2251 .Pn mhshow
meillo@114 2252 invokes a pager session for all its output,
meillo@114 2253 whenever it prints to a terminal.
meillo@114 2254 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e
meillo@114 2255 In consequence,
meillo@114 2256 .Pn mhl
meillo@114 2257 does no more invoke a pager.
meillo@114 2258 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@114 2259 With
meillo@114 2260 .Pn mhshow
meillo@114 2261 replacing the original
meillo@114 2262 .Pn show ,
meillo@114 2263 output from
meillo@114 2264 .Pn mhl
meillo@114 2265 does not go to the terminal directly, but through
meillo@114 2266 .Pn mhshow .
meillo@114 2267 Hence,
meillo@114 2268 .Pn mhl
meillo@114 2269 does not need to invoke a pager.
meillo@114 2270 The one and only job of
meillo@114 2271 .Pn mhl
meillo@114 2272 is to format messages or parts of them.
meillo@114 2273 The only place in mmh, where a pager is invoked is
meillo@114 2274 .Pn mhshow .
meillo@114 2275 .P
meillo@114 2276 .Pe mhshow-show-*
meillo@114 2277 profile entries can be used to display MIME parts in a specific way.
meillo@114 2278 For instance, PDF and Postscript files could be converted to plain text
meillo@114 2279 to display them in the terminal.
meillo@169 2280 In mmh, MIME parts will always be displayed serially.
meillo@114 2281 The request to display the MIME type `multipart/parallel' in parallel
meillo@114 2282 is ignored.
meillo@114 2283 It is simply treated as `multipart/mixed'.
meillo@114 2284 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6
meillo@114 2285 This could already be requested with the, now removed,
meillo@114 2286 .Sw -serialonly
meillo@114 2287 switch of
meillo@114 2288 .Pn mhshow .
meillo@179 2289 As MIME parts are always processed exclusively, i.e. serially,
meillo@114 2290 the `%e' escape in
meillo@114 2291 .Pe mhshow-show-*
meillo@114 2292 profile entries became useless and was thus removed.
meillo@114 2293 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae
meillo@114 2294 .P
meillo@114 2295 In the intended setup, only text content would be displayed.
meillo@114 2296 Non-text content would be converted to text by appropriate
meillo@114 2297 .Pe mhshow-show-*
meillo@114 2298 profile entries before, if possible and wanted.
meillo@114 2299 All output would be displayed in a single pager session.
meillo@114 2300 Other kinds of attachments are ignored.
meillo@114 2301 With
meillo@114 2302 .Pe mhshow-show-*
meillo@114 2303 profile entries for them, they can be displayed serially along
meillo@114 2304 the message.
meillo@114 2305 For parallel display, the attachments need to be stored to disk first.
meillo@114 2306 .P
meillo@114 2307 To display text content in foreign charsets, they need to be converted
meillo@114 2308 to the native charset.
meillo@114 2309 Therefore,
meillo@114 2310 .Pe mhshow-charset-*
meillo@114 2311 profile entries used to be needed.
meillo@169 2312 In mmh, the conversion is performed automatically by piping the
meillo@169 2313 text through the
meillo@114 2314 .Pn iconv
meillo@114 2315 command, if necessary.
meillo@114 2316 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60
meillo@114 2317 Custom
meillo@114 2318 .Pe mhshow-show-*
meillo@114 2319 rules for textual content might need a
meillo@114 2320 .Cl "iconv -f %c %f |
meillo@114 2321 prefix to have the text converted to the native charset.
meillo@114 2322 .P
meillo@121 2323 Although the conversion of foreign charsets to the native one
meillo@114 2324 has improved, it is not consistent enough.
meillo@114 2325 Further work needs to be done and
meillo@114 2326 the basic concepts in this field need to be re-thought.
meillo@114 2327 Though, the default setup of mmh displays message in foreign charsets
meillo@114 2328 correctly without the need to configure anything.
meillo@114 2329
meillo@114 2330
meillo@114 2331 .ig
meillo@114 2332
meillo@114 2333 .P
meillo@114 2334 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@173 2335 These tools will not download the contents automatically anymore. Instead,
meillo@114 2336 they print the information needed to get the contents. If someone should
meillo@114 2337 really receive one of those rare message/external-body messages, he can
meillo@114 2338 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114 2339 it!
meillo@114 2340 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114 2341 ~/.netrc are gone now.)
meillo@114 2342 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114 2343
meillo@114 2344 ..
meillo@102 2345
meillo@58 2346
meillo@58 2347
meillo@166 2348 .H2 "Signing and Encrypting
meillo@22 2349 .P
meillo@166 2350 Nmh offers no direct support for digital signatures and message encryption.
meillo@157 2351 This functionality needed to be added through third-party software.
meillo@166 2352 In mmh, the functionality should be included because it
meillo@166 2353 is a part of modern email and likely wanted by users of mmh.
meillo@157 2354 A fresh mmh installation should support signing and encrypting
meillo@157 2355 out-of-the-box.
meillo@157 2356 Therefore, Neil Rickert's
meillo@157 2357 .Pn mhsign
meillo@157 2358 and
meillo@157 2359 .Pn mhpgp
meillo@157 2360 scripts
meillo@157 2361 .[
meillo@157 2362 neil rickert mhsign mhpgp
meillo@157 2363 .]
meillo@177 2364 were included into mmh
meillo@177 2365 .Ci f45cdc98117a84f071759462c7ae212f4bc5ab2e
meillo@177 2366 .Ci 58cf09aa36e9f7f352a127158bbf1c5678bc6ed8 .
meillo@177 2367 The scripts fit well because they are lightweight and
meillo@177 2368 similar of style to the existing tools.
meillo@157 2369 Additionally, no licensing difficulties appeared,
meillo@157 2370 as they are part of the public domain.
meillo@112 2371 .P
meillo@157 2372 .Pn mhsign
meillo@157 2373 handles the signing and encrypting part.
meillo@157 2374 It comprises about 250 lines of shell code and interfaces between
meillo@157 2375 .Pn gnupg
meillo@157 2376 and
meillo@157 2377 the MH system.
meillo@177 2378 It was meant to be invoked manually at the WhatNow prompt, but in mmh,
meillo@157 2379 .Pn send
meillo@177 2380 invokes
meillo@177 2381 .pn mhsign
meillo@177 2382 automatically
meillo@177 2383 .Ci c7b5e1df086bcc37ff40163ee67571f076cf6683 .
meillo@177 2384 Special header fields were introduced to request this action.
meillo@157 2385 If a draft contains the
meillo@157 2386 .Hd Sign
meillo@157 2387 header field,
meillo@157 2388 .Pn send
meillo@177 2389 will initiate the signing.
meillo@177 2390 The signing key is either chosen automatically or specified by the
meillo@157 2391 .Pe Pgpkey
meillo@157 2392 profile entry.
meillo@157 2393 .Pn send
meillo@177 2394 always create signatures using the PGP/MIME standard, \" REF XXX
meillo@157 2395 but by manually invoking
meillo@157 2396 .Pn mhsign ,
meillo@157 2397 old-style non-MIME signatures can be created as well.
meillo@177 2398 To encrypt an outgoing message, the draft needs to contain an
meillo@157 2399 .Hd Enc
meillo@157 2400 header field.
meillo@177 2401 Public keys of all recipients are searched for in the gnupg keyring and
meillo@177 2402 in a file called
meillo@177 2403 .Fn pgpkeys ,
meillo@177 2404 which contains exceptions and overrides.
meillo@157 2405 Unless public keys are found for all recipients,
meillo@177 2406 .Pn mhsign
meillo@177 2407 will refuse to encrypt it.
meillo@157 2408 Currently, messages with hidden (BCC) recipients can not be encrypted.
meillo@171 2409 This work is pending because it requires a structurally more complex
meillo@171 2410 approach.
meillo@157 2411 .P
meillo@177 2412 .Pn mhpgp
meillo@177 2413 is the companion to
meillo@177 2414 .Pn mhsign .
meillo@177 2415 It verifies signatures and decrypts messages.
meillo@177 2416 Encrypted messages can either be temporarily decrypted for display
meillo@177 2417 or permanently decrypted and stored into the current folder.
meillo@177 2418 Currently,
meillo@177 2419 .Pn mhpgp
meillo@177 2420 needs to be invoked manually.
meillo@177 2421 The integration into
meillo@177 2422 .Pn show
meillo@177 2423 and
meillo@177 2424 .Pn mhstore
meillo@177 2425 to verify signatures and decrypt messages as needs
meillo@177 2426 is planned but not realized yet.
meillo@177 2427 .P
meillo@177 2428 Both scripts were written for nmh, hence they needed to be adjust
meillo@177 2429 according to the differences between nmh and mmh.
meillo@177 2430 For instance, they use the backup prefix no longer.
meillo@177 2431 Further more, compatibility support for old PGP features was dropped.
meillo@177 2432 .P
meillo@157 2433 The integrated message signing and encrypting support is one of the
meillo@157 2434 most recent features in mmh.
meillo@177 2435 It has not yet had the time to mature.
meillo@177 2436 User feedback and personal experience need to be accumulated to
meillo@177 2437 direct the further development of the facility.
meillo@177 2438 Although the feedback and experience is still missing,
meillo@177 2439 it seems to be worthwhile to consider adding
meillo@157 2440 .Sw -[no]sign
meillo@157 2441 and
meillo@157 2442 .Sw -[no]enc
meillo@157 2443 switches to
meillo@157 2444 .Pn send ,
meillo@177 2445 to be able to override the corresponding header fields.
meillo@177 2446 A profile entry:
meillo@157 2447 .VS
meillo@157 2448 send: -sign
meillo@157 2449 VE
meillo@177 2450 would then activate signing for all outgoing messages.
meillo@177 2451 With the present approach, a
meillo@177 2452 .Hd Send
meillo@177 2453 header component needs to be added to each draft template
meillo@177 2454 to achieve the same result.
meillo@177 2455 Adding the switches would ease the work greatly and keep the
meillo@177 2456 template files clean.
meillo@157 2457
meillo@58 2458
meillo@58 2459
meillo@102 2460
meillo@133 2461 .H2 "Draft and Trash Folder
meillo@131 2462 .P
meillo@58 2463
meillo@131 2464 .U3 "Draft Folder
meillo@154 2465 .Id draft-folder
meillo@131 2466 .P
meillo@131 2467 In the beginning, MH had the concept of a draft message.
meillo@131 2468 This is the file
meillo@131 2469 .Fn draft
meillo@131 2470 in the MH directory, which is treated special.
meillo@131 2471 On composing a message, this draft file was used.
meillo@131 2472 When starting to compose another message before the former one was sent,
meillo@131 2473 the user had to decide among:
meillo@171 2474 .LI 1
meillo@168 2475 Using the old draft to finish and send it before starting with a new one.
meillo@171 2476 .LI 2
meillo@168 2477 Discarding the old draft and replacing it with a new one.
meillo@171 2478 .LI 3
meillo@168 2479 Preserving the old draft by refiling it to a folder.
meillo@171 2480 .LP
meillo@168 2481 It was only possible to work in alternation on multiple drafts.
meillo@131 2482 Therefore, the current draft needed to be refiled to a folder and
meillo@168 2483 another one re-used for editing.
meillo@131 2484 Working on multiple drafts at the same time was impossible.
meillo@131 2485 The usual approach of switching to a different MH context did not
meillo@168 2486 help anything.
meillo@131 2487 .P
meillo@131 2488 The draft folder facility exists to
meillo@131 2489 allow true parallel editing of drafts, in a straight forward way.
meillo@131 2490 It was introduced by Marshall T. Rose, already in 1984.
meillo@131 2491 Similar to other new features, the draft folder was inactive by default.
meillo@131 2492 Even in nmh, the highly useful draft folder was not available
meillo@131 2493 out-of-the-box.
meillo@131 2494 At least, Richard Coleman added the man page
meillo@131 2495 .Mp mh-draft (5)
meillo@131 2496 to better document the feature.
meillo@131 2497 .P
meillo@131 2498 Not using the draft folder facility has the single advantage of having
meillo@131 2499 the draft file at a static location.
meillo@131 2500 This is simple in simple cases but the concept does not scale for more
meillo@131 2501 complex cases.
meillo@131 2502 The concept of the draft message is too limited for the problem.
meillo@131 2503 Therefore the draft folder was introduced.
meillo@131 2504 It is the more powerful and more natural concept.
meillo@131 2505 The draft folder is a folder like any other folder in MH.
meillo@131 2506 Its messages can be listed like any other messages.
meillo@131 2507 A draft message is no longer a special case.
meillo@131 2508 Tools do not need special switches to work on the draft message.
meillo@171 2509 Hence corner cases were removed.
meillo@131 2510 .P
meillo@131 2511 The trivial part of the work was activating the draft folder with a
meillo@131 2512 default name.
meillo@131 2513 I chose the name
meillo@131 2514 .Fn +drafts
meillo@131 2515 for obvious reasons.
meillo@131 2516 In consequence, the command line switches
meillo@131 2517 .Sw -draftfolder
meillo@131 2518 and
meillo@131 2519 .Sw -draftmessage
meillo@131 2520 could be removed.
meillo@131 2521 More difficult but also more improving was updating the tools to the
meillo@131 2522 new concept.
meillo@131 2523 For nearly three decades, the tools needed to support two draft handling
meillo@131 2524 approaches.
meillo@131 2525 By fully switching to the draft folder, the tools could be simplified
meillo@131 2526 by dropping the awkward draft message handling code.
meillo@131 2527 .Sw -draft
meillo@131 2528 switches were removed because operating on a draft message is no longer
meillo@131 2529 special.
meillo@131 2530 It became indistinguishable to operating on any other message.
meillo@168 2531 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@168 2532 .P
meillo@168 2533 There is no more need to query the user for draft handling
meillo@168 2534 .Ci 2d48b455c303a807041c35e4248955f8bec59eeb .
meillo@131 2535 It is always possible to add another new draft.
meillo@131 2536 Refiling drafts is without difference to refiling other messages.
meillo@168 2537 All of these special cases are gone.
meillo@131 2538 Yet, one draft-related switch remained.
meillo@131 2539 .Pn comp
meillo@131 2540 still has
meillo@131 2541 .Sw -[no]use
meillo@131 2542 for switching between two modes:
meillo@171 2543 .LI 1
meillo@168 2544 .Sw -use
meillo@168 2545 to modify an existing draft.
meillo@171 2546 .LI 2
meillo@168 2547 .Sw -nouse
meillo@168 2548 to compose a new draft, possibly taking some existing message as template.
meillo@171 2549 .LP
meillo@131 2550 In either case, the behavior of
meillo@131 2551 .Pn comp
meillo@131 2552 is deterministic.
meillo@131 2553 .P
meillo@131 2554 .Pn send
meillo@131 2555 now operates on the current message in the draft folder by default.
meillo@131 2556 As message and folder can both be overridden by specifying them on
meillo@131 2557 the command line, it is possible to send any message in the mail storage
meillo@131 2558 by simply specifying its number and folder.
meillo@131 2559 In contrast to the other tools,
meillo@131 2560 .Pn send
meillo@131 2561 takes the draft folder as its default folder.
meillo@131 2562 .P
meillo@131 2563 Dropping the draft message concept in favor for the draft folder concept,
meillo@131 2564 removed special cases with regular cases.
meillo@131 2565 This simplified the source code of the tools, as well as the concepts.
meillo@131 2566 In mmh, draft management does not break with the MH concepts
meillo@131 2567 but applies them.
meillo@133 2568 .Cl "scan +drafts" ,
meillo@133 2569 for instance, is a truly natural request.
meillo@169 2570 Most of the work was already performed by Rose in the eighties.
meillo@133 2571 The original improvement of mmh is dropping the old draft message approach
meillo@133 2572 and thus simplifying the tools, the documentation and the system as a whole.
meillo@131 2573 Although my part in the draft handling improvement was small,
meillo@133 2574 it was an important one.
meillo@131 2575
meillo@131 2576
meillo@131 2577 .U3 "Trash Folder
meillo@154 2578 .Id trash-folder
meillo@131 2579 .P
meillo@131 2580 Similar to the situation for drafts is the situation for removed messages.
meillo@131 2581 Historically, a message was ``deleted'' by prepending a specific
meillo@173 2582 \fIbackup prefix\fP, usually the comma character,
meillo@173 2583 to the file name.
meillo@164 2584 The specific file would then be ignored by MH because only files with
meillo@164 2585 names consisting of digits only are treated as messages.
meillo@131 2586 Although files remained in the file system,
meillo@168 2587 the messages were no longer visible in MH.
meillo@168 2588 To truly delete them, a maintenance job was needed.
meillo@168 2589 Usually a cron job was installed to delete them after a grace time.
meillo@131 2590 For instance:
meillo@131 2591 .VS
meillo@131 2592 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131 2593 VE
meillo@168 2594 In such a setup, the original message could be restored
meillo@131 2595 within the grace time interval by stripping the
meillo@164 2596 backup prefix from the file name.
meillo@168 2597 But the user could not rely on this statement.
meillo@168 2598 If the last message of a folder with six messages (\fL1-6\fP) was removed,
meillo@131 2599 message
meillo@131 2600 .Fn 6 ,
meillo@168 2601 became file
meillo@131 2602 .Fn ,6 .
meillo@168 2603 If then a new message entered the same folder, it would be named with
meillo@168 2604 the number one above the highest existing message number.
meillo@168 2605 In this case the message would be named
meillo@131 2606 .Fn 6
meillo@131 2607 then.
meillo@168 2608 If this new message would be removed as well,
meillo@168 2609 then the backup of the former message is overwritten.
meillo@168 2610 Hence, the ability to restore removed messages did not only depend on
meillo@131 2611 the ``sweeping cron job'' but also on the removing of further messages.
meillo@131 2612 It is undesirable to have such obscure and complex mechanisms.
meillo@168 2613 The user should be given a small set of clear assertions, such as
meillo@131 2614 ``Removed files are restorable within a seven-day grace time.''
meillo@131 2615 With the addition ``... unless a message with the same name in the
meillo@131 2616 same folder is removed before.'' the statement becomes complex.
meillo@131 2617 A user will hardly be able to keep track of any removal to know
meillo@131 2618 if the assertion still holds true for a specific file.
meillo@164 2619 In practice, the real mechanism is unclear to the user.
meillo@131 2620 The consequences of further removals are not obvious.
meillo@131 2621 .P
meillo@131 2622 Further more, the backup files are scattered within the whole mail storage.
meillo@131 2623 This complicates managing them.
meillo@164 2624 It is possible with the help of
meillo@131 2625 .Pn find ,
meillo@131 2626 but everything would be more convenient
meillo@131 2627 if the deleted messages would be collected in one place.
meillo@131 2628 .P
meillo@131 2629 The profile entry
meillo@131 2630 .Pe rmmproc
meillo@131 2631 (previously named
meillo@131 2632 .Pe Delete-Prog )
meillo@131 2633 was introduced very early to improve the situation.
meillo@164 2634 It could be set to any command, which would be executed to remove
meillo@131 2635 the specified messages.
meillo@168 2636 This would override the default action described above.
meillo@168 2637 Refiling the to-be-removed files to a trash folder is the usual example.
meillo@131 2638 Nmh's man page
meillo@131 2639 .Mp rmm (1)
meillo@131 2640 proposes to set the
meillo@131 2641 .Pe rmmproc
meillo@131 2642 to
meillo@131 2643 .Cl "refile +d
meillo@168 2644 to move messages to the trash folder,
meillo@131 2645 .Fn +d ,
meillo@131 2646 instead of renaming them with the backup prefix.
meillo@131 2647 The man page proposes additionally the expunge command
meillo@131 2648 .Cl "rm `mhpath +d all`
meillo@168 2649 to empty the trash folder.
meillo@131 2650 .P
meillo@131 2651 Removing messages in such a way has advantages.
meillo@131 2652 The mail storage is prevented from being cluttered with removed messages
meillo@131 2653 because they are all collected in one place.
meillo@131 2654 Existing and removed messages are thus separated more strictly.
meillo@131 2655 No backup files are silently overwritten.
meillo@164 2656 But most important is the ability to keep removed messages in the MH domain.
meillo@131 2657 Messages in the trash folder can be listed like those in any other folder.
meillo@131 2658 Deleted messages can be displayed like any other messages.
meillo@169 2659 .Pn refile
meillo@169 2660 can restore deleted messages.
meillo@131 2661 All operations on deleted files are still covered by the MH tools.
meillo@131 2662 The trash folder is just like any other folder in the mail storage.
meillo@131 2663 .P
meillo@131 2664 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131 2665 in favor for replacing it by the better suiting trash folder system.
meillo@131 2666 Hence,
meillo@131 2667 .Pn rmm
meillo@131 2668 calls
meillo@131 2669 .Pn refile
meillo@131 2670 to move the to-be-removed message to the trash folder,
meillo@131 2671 .Fn +trash
meillo@131 2672 by default.
meillo@164 2673 To sweep it clean, the user can use
meillo@131 2674 .Cl "rmm -unlink +trash a" ,
meillo@131 2675 where the
meillo@131 2676 .Sw -unlink
meillo@131 2677 switch causes the files to be unlinked.
meillo@168 2678 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 2679 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@131 2680 .P
meillo@168 2681 Dropping the legacy approach and converting to the new approach completely
meillo@131 2682 simplified the code base.
meillo@131 2683 The relationship between
meillo@131 2684 .Pn rmm
meillo@131 2685 and
meillo@131 2686 .Pn refile
meillo@131 2687 was inverted.
meillo@131 2688 In mmh,
meillo@131 2689 .Pn rmm
meillo@131 2690 invokes
meillo@131 2691 .Pn refile ,
meillo@131 2692 which used to be the other way round.
meillo@131 2693 Yet, the relationship is simpler now.
meillo@164 2694 Loops, like described in nmh's man page for
meillo@131 2695 .Mp refile (1),
meillo@164 2696 can no longer occur:
meillo@131 2697 .QS
meillo@131 2698 Since
meillo@131 2699 .Pn refile
meillo@131 2700 uses your
meillo@131 2701 .Pe rmmproc
meillo@131 2702 to delete the message, the
meillo@131 2703 .Pe rmmproc
meillo@131 2704 must NOT call
meillo@131 2705 .Pn refile
meillo@131 2706 without specifying
meillo@131 2707 .Sw -normmproc
meillo@131 2708 or you will create an infinite loop.
meillo@131 2709 .QE
meillo@131 2710 .LP
meillo@131 2711 .Pn rmm
meillo@131 2712 either unlinks a message with
meillo@131 2713 .Fu unlink()
meillo@131 2714 or invokes
meillo@131 2715 .Pn refile
meillo@131 2716 to move it to the trash folder.
meillo@131 2717 .Pn refile
meillo@131 2718 does not invoke any tools.
meillo@131 2719 .P
meillo@136 2720 By generalizing the message removal in the way that it became covered
meillo@136 2721 by the MH concepts made the whole system more powerful.
meillo@131 2722
meillo@131 2723
meillo@131 2724
meillo@131 2725
meillo@131 2726
meillo@133 2727 .H2 "Modern Defaults
meillo@133 2728 .P
meillo@133 2729 Nmh has a bunch of convenience-improving features inactive by default,
meillo@133 2730 although one can expect every new user wanting to have them active.
meillo@133 2731 The reason they are inactive by default is the wish to stay compatible
meillo@133 2732 with old versions.
meillo@136 2733 But what is the definition for old versions?
meillo@136 2734 Still, the highly useful draft folder facility has not been activated
meillo@136 2735 by default although it was introduced over twenty-five years ago.
meillo@133 2736 .[
meillo@133 2737 rose romine real work
meillo@133 2738 .]
meillo@136 2739 The community seems not to care.
meillo@136 2740 This is one of several examples that require new users to first build up
meillo@136 2741 a profile before they can access the modern features of nmh.
meillo@136 2742 Without an extensive profile, the setup is hardly usable
meillo@133 2743 for modern emailing.
meillo@133 2744 The point is not the customization of the setup,
meillo@136 2745 but the need to activate generally useful facilities.
meillo@133 2746 .P
meillo@133 2747 Yet, the real problem lies less in enabling the features, as this is
meillo@133 2748 straight forward as soon as one knows what he wants.
meillo@168 2749 The real problem is that new users need deep insight into the project
meillo@168 2750 to find out about inactive features nmh already provides.
meillo@133 2751 To give an example, I needed one year of using nmh
meillo@133 2752 before I became aware of the existence of the attachment system.
meillo@133 2753 One could argue that this fact disqualifies my reading of the
meillo@133 2754 documentation.
meillo@133 2755 If I would have installed nmh from source back then, I could agree.
meillo@133 2756 Yet, I had used a prepackaged version and had expected that it would
meillo@133 2757 just work.
meillo@133 2758 Nevertheless, I had been convinced by the concepts of MH already
meillo@133 2759 and I am a software developer,
meillo@133 2760 still I required a lot of time to discover the cool features.
meillo@133 2761 How can we expect users to be even more advanced than me,
meillo@133 2762 just to allow them use MH in a convenient and modern way?
meillo@133 2763 Unless they are strongly convinced of the concepts, they will fail.
meillo@133 2764 I have seen friends of me giving up disappointed
meillo@133 2765 before they truly used the system,
meillo@133 2766 although they had been motivated in the beginning.
meillo@173 2767 They suffer hard enough to get used to the tool chest approach,
meillo@179 2768 we developers should spare them further inconveniences.
meillo@133 2769 .P
meillo@136 2770 Maintaining compatibility for its own sake is bad,
meillo@136 2771 because the code base collects more and more compatibility code.
meillo@136 2772 Sticking to the compatiblity code means remaining limited;
meillo@168 2773 whereas adjusting to the changes renders the compatibility unnecessary.
meillo@168 2774 Keeping unused alternatives in the code is a bad choice as they likely
meillo@136 2775 gather bugs, by not being well tested.
meillo@136 2776 Also, the increased code size and the greater number of conditions
meillo@136 2777 increase the maintenance costs.
meillo@133 2778 If any MH implementation would be the back-end of widespread
meillo@133 2779 email clients with large user bases, compatibility would be more
meillo@133 2780 important.
meillo@133 2781 Yet, it appears as if this is not the case.
meillo@133 2782 Hence, compatibility is hardly important for technical reasons.
meillo@133 2783 Its importance originates rather from personal reasons.
meillo@133 2784 Nmh's user base is small and old.
meillo@133 2785 Changing the interfaces would cause inconvenience to long-term users of MH.
meillo@133 2786 It would force them to change their many years old MH configurations.
meillo@168 2787 I do understand this aspect, but by sticking to the old users,
meillo@168 2788 new users are kept away.
meillo@133 2789 Yet, the future lies in new users.
meillo@168 2790 In consequence, mmh invites new users by providing a convenient
meillo@168 2791 and modern setup, readily usable out-of-the-box.
meillo@133 2792 .P
meillo@136 2793 In mmh, all modern features are active by default and many previous
meillo@136 2794 approaches are removed or only accessible in manual ways.
meillo@136 2795 New default features include:
meillo@133 2796 .BU
meillo@133 2797 The attachment system (\c
meillo@133 2798 .Hd Attach ).
meillo@133 2799 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@133 2800 .BU
meillo@133 2801 The draft folder facility (\c
meillo@133 2802 .Fn +drafts ).
meillo@133 2803 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@133 2804 .BU
meillo@133 2805 The unseen sequence (`u')
meillo@133 2806 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@133 2807 and the sequence negation prefix (`!').
meillo@133 2808 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc
meillo@133 2809 .BU
meillo@133 2810 Quoting the original message in the reply.
meillo@133 2811 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@133 2812 .BU
meillo@133 2813 Forwarding messages using MIME.
meillo@133 2814 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@171 2815 .LP
meillo@136 2816 In consequence, a setup with a profile that defines only the path to the
meillo@136 2817 mail storage, is already convenient to use.
meillo@168 2818 Again, Paul Vixie's ``edginess'' call supports the direction I took:
meillo@136 2819 ``the `main branch' should just be modern''.
meillo@136 2820 .[
meillo@136 2821 paul vixie edginess nmh-workers
meillo@136 2822 .]
meillo@131 2823
meillo@133 2824
meillo@133 2825
meillo@133 2826
meillo@133 2827
meillo@133 2828 .\" --------------------------------------------------------------
meillo@131 2829 .H1 "Styling
meillo@22 2830 .P
meillo@118 2831 Kernighan and Pike have emphasized the importance of style in the
meillo@118 2832 preface of their book:
meillo@118 2833 .[ [
meillo@118 2834 kernighan pike practice of programming
meillo@118 2835 .], p. x]
meillo@118 2836 .QS
meillo@118 2837 Chapter 1 discusses programming style.
meillo@118 2838 Good style is so important to good programming that we have chose
meillo@118 2839 to cover it first.
meillo@118 2840 .QE
meillo@168 2841 This section covers changes in mmh that were guided by the desire
meillo@118 2842 to improve on style.
meillo@118 2843 Many of them follow the rules given in the quoted book.
meillo@118 2844 .[
meillo@118 2845 kernighan pike practice of programming
meillo@118 2846 .]
meillo@118 2847
meillo@118 2848
meillo@127 2849
meillo@127 2850
meillo@127 2851 .H2 "Code Style
meillo@154 2852 .Id code-style
meillo@118 2853 .P
meillo@118 2854 .U3 "Indentation Style
meillo@118 2855 .P
meillo@118 2856 Indentation styles are the holy cow of programmers.
meillo@168 2857 Kernighan and Pike
meillo@118 2858 .[ [
meillo@118 2859 kernighan pike practice of programming
meillo@118 2860 .], p. 10]
meillo@168 2861 wrote:
meillo@118 2862 .QS
meillo@118 2863 Programmers have always argued about the layout of programs,
meillo@118 2864 but the specific style is much less important than its consistent
meillo@118 2865 application.
meillo@121 2866 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118 2867 time arguing.
meillo@118 2868 .QE
meillo@118 2869 .P
meillo@118 2870 I agree that the constant application is most important,
meillo@118 2871 but I believe that some styles have advantages over others.
meillo@118 2872 For instance the indentation with tab characters only.
meillo@118 2873 Tab characters directly map to the nesting level \(en
meillo@118 2874 one tab, one level.
meillo@118 2875 Tab characters are flexible because developers can adjust them to
meillo@118 2876 whatever width they like to have.
meillo@118 2877 There is no more need to run
meillo@118 2878 .Pn unexpand
meillo@118 2879 or
meillo@118 2880 .Pn entab
meillo@118 2881 programs to ensure the correct mixture of leading tabs and spaces.
meillo@118 2882 The simple rules are: (1) Leading whitespace must consist of tabs only.
meillo@118 2883 (2) Any other whitespace should consist of spaces.
meillo@121 2884 These two rules ensure the integrity of the visual appearance.
meillo@121 2885 Although reformatting existing code should be avoided, I did it.
meillo@136 2886 I did not waste time arguing; I just reformated the code.
meillo@118 2887 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118 2888
meillo@118 2889 .U3 "Comments
meillo@118 2890 .P
meillo@118 2891 Section 1.6 of
meillo@118 2892 .[ [
meillo@118 2893 kernighan pike practice of programming
meillo@118 2894 .], p. 23]
meillo@118 2895 demands: ``Don't belabor the obvious.''
meillo@122 2896 Hence, I simply removed all the comments in the following code excerpt:
meillo@118 2897 .VS
meillo@120 2898 context_replace(curfolder, folder); /* update current folder */
meillo@120 2899 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120 2900 seq_save(mp); /* synchronize message sequences */
meillo@120 2901 folder_free(mp); /* free folder/message structure */
meillo@120 2902 context_save(); /* save the context file */
meillo@120 2903
meillo@120 2904 [...]
meillo@120 2905
meillo@120 2906 int c; /* current character */
meillo@120 2907 char *cp; /* miscellaneous character pointer */
meillo@120 2908
meillo@120 2909 [...]
meillo@120 2910
meillo@120 2911 /* NUL-terminate the field */
meillo@120 2912 *cp = '\0';
meillo@118 2913 VE
meillo@120 2914 .Ci 426543622b377fc5d091455cba685e114b6df674
meillo@118 2915 .P
meillo@136 2916 The program code explains enough itself, already.
meillo@136 2917
meillo@118 2918
meillo@118 2919 .U3 "Names
meillo@118 2920 .P
meillo@118 2921 Kernighan and Pike suggest:
meillo@118 2922 ``Use active names for functions''.
meillo@118 2923 .[ [
meillo@118 2924 kernighan pike practice of programming
meillo@118 2925 .], p. 4]
meillo@118 2926 One application of this rule was the rename of
meillo@118 2927 .Fu check_charset()
meillo@118 2928 to
meillo@118 2929 .Fu is_native_charset() .
meillo@118 2930 .Ci 8d77b48284c58c135a6b2787e721597346ab056d
meillo@118 2931 The same change fixed a violation of ``Be accurate'' as well.
meillo@118 2932 The code did not match the expectation the function suggested,
meillo@118 2933 as it, for whatever reason, only compared the first ten characters
meillo@118 2934 of the charset name.
meillo@118 2935 .P
meillo@118 2936 More important than using active names is using descriptive names.
meillo@145 2937 .VS
meillo@145 2938 m_unknown(in); /* the MAGIC invocation... */
meillo@145 2939 VE
meillo@145 2940 Renaming the obscure
meillo@118 2941 .Fu m_unknown()
meillo@145 2942 function was a delightful event, although it made the code less funny.
meillo@118 2943 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846
meillo@118 2944 .P
meillo@118 2945 Magic numbers are generally considered bad style.
meillo@118 2946 Obviously, Kernighan and Pike agree:
meillo@118 2947 ``Give names to magic numbers''.
meillo@118 2948 .[ [
meillo@118 2949 kernighan pike practice of programming
meillo@118 2950 .], p. 19]
meillo@118 2951 One such change was naming the type of input \(en mbox or mail folder \(en
meillo@118 2952 to be scanned:
meillo@118 2953 .VS
meillo@118 2954 #define SCN_MBOX (-1)
meillo@118 2955 #define SCN_FOLD 0
meillo@118 2956 VE
meillo@118 2957 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@118 2958 .P
meillo@118 2959 The argument
meillo@118 2960 .Ar outnum
meillo@118 2961 of the function
meillo@118 2962 .Fu scan()
meillo@118 2963 in
meillo@118 2964 .Fn uip/scansbr.c
meillo@118 2965 defines the number of the message to be created.
meillo@118 2966 If no message is to be created, the argument is misused to transport
meillo@118 2967 program logic.
meillo@118 2968 This lead to obscure code.
meillo@118 2969 I improved the clarity of the code by introducing two variables:
meillo@118 2970 .VS
meillo@118 2971 int incing = (outnum > 0);
meillo@118 2972 int ismbox = (outnum != 0);
meillo@118 2973 VE
meillo@118 2974 They cover the magic values and are used for conditions.
meillo@118 2975 The variable
meillo@118 2976 .Ar outnum
meillo@118 2977 is only used when it holds an ordinary message number.
meillo@118 2978 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f
meillo@118 2979 The clarity improvement of the change showed detours in the program logic
meillo@118 2980 of related code parts.
meillo@118 2981 Having the new variables with descriptive names, a more
meillo@121 2982 straight forward implementation became apparent.
meillo@169 2983 Before the code was clarified, the possibility to improve had not be seen.
meillo@118 2984 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723
meillo@118 2985
meillo@133 2986
meillo@133 2987
meillo@133 2988 .H2 "Structural Rework
meillo@133 2989 .P
meillo@136 2990 Although the stylistic changes described up to here improve the
meillo@136 2991 readability of the source code, all of them are changes ``in the small''.
meillo@136 2992 Structural changes affect a much larger area.
meillo@136 2993 They are more difficult to do but lead to larger improvements,
meillo@136 2994 especially as they influence the outer shape of the tools as well.
meillo@118 2995 .P
meillo@118 2996 At the end of their chapter on style,
meillo@118 2997 Kernighan and Pike ask: ``But why worry about style?''
meillo@136 2998 Following are two examples of structural rework that show
meillo@136 2999 why style is important in the first place.
meillo@136 3000
meillo@136 3001
meillo@136 3002 .U3 "Rework of \f(CWanno\fP
meillo@118 3003 .P
meillo@120 3004 Until 2002,
meillo@120 3005 .Pn anno
meillo@120 3006 had six functional command line switches,
meillo@120 3007 .Sw -component
meillo@120 3008 and
meillo@120 3009 .Sw -text ,
meillo@168 3010 which have an argument each,
meillo@120 3011 and the two pairs of flags,
meillo@120 3012 .Sw -[no]date
meillo@120 3013 and
meillo@120 3014 .Sw -[no]inplace .
meillo@120 3015 Then Jon Steinhart introduced his attachment system.
meillo@120 3016 In need for more advanced annotation handling, he extended
meillo@120 3017 .Pn anno .
meillo@120 3018 He added five more switches:
meillo@120 3019 .Sw -draft ,
meillo@120 3020 .Sw -list ,
meillo@120 3021 .Sw -delete ,
meillo@120 3022 .Sw -append ,
meillo@120 3023 and
meillo@120 3024 .Sw -number ,
meillo@120 3025 the last one taking an argument.
meillo@121 3026 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@120 3027 Later,
meillo@120 3028 .Sw -[no]preserve
meillo@120 3029 was added.
meillo@121 3030 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@120 3031 Then, the Synopsis section of the man page
meillo@120 3032 .Mp anno (1)
meillo@120 3033 read:
meillo@120 3034 .VS
meillo@120 3035 anno [+folder] [msgs] [-component field] [-inplace | -noinplace]
meillo@120 3036 [-date | -nodate] [-draft] [-append] [-list] [-delete]
meillo@120 3037 [-number [num|all]] [-preserve | -nopreserve] [-version]
meillo@120 3038 [-help] [-text body]
meillo@120 3039 VE
meillo@120 3040 .LP
meillo@120 3041 The implementation followed the same structure.
meillo@120 3042 Problems became visible when
meillo@120 3043 .Cl "anno -list -number 42
meillo@120 3044 worked on the current message instead on message number 42,
meillo@120 3045 and
meillo@120 3046 .Cl "anno -list -number l:5
meillo@124 3047 did not work on the last five messages but failed with the mysterious
meillo@120 3048 error message: ``anno: missing argument to -list''.
meillo@121 3049 Yet, the invocation matched the specification in the man page.
meillo@120 3050 There, the correct use of
meillo@120 3051 .Sw -number
meillo@120 3052 was defined as being
meillo@120 3053 .Cl "[-number [num|all]]
meillo@120 3054 and the textual description for the combination with
meillo@120 3055 .Sw -list
meillo@120 3056 read:
meillo@120 3057 .QS
meillo@164 3058 The
meillo@164 3059 .Sw -list
meillo@164 3060 option produces a listing of the field bodies for
meillo@120 3061 header fields with names matching the specified component,
meillo@164 3062 one per line. The listing is numbered, starting at 1, if the
meillo@164 3063 .Sw -number
meillo@164 3064 option is also used.
meillo@120 3065 .QE
meillo@120 3066 .LP
meillo@120 3067 The problem was manifold.
meillo@120 3068 The code required a numeric argument to the
meillo@120 3069 .Sw -number
meillo@120 3070 switch.
meillo@120 3071 If it was missing or non-numeric,
meillo@120 3072 .Pn anno
meillo@120 3073 aborted with an error message that had an off-by-one error,
meillo@120 3074 printing the switch one before the failing one.
meillo@120 3075 Semantically, the argument to the
meillo@120 3076 .Sw -number
meillo@120 3077 switch is only necessary in combination with
meillo@120 3078 .Sw -delete ,
meillo@120 3079 but not with
meillo@120 3080 .Sw -list .
meillo@120 3081 .P
meillo@171 3082 Trying to fix these problems on the surface would not have solved
meillo@171 3083 them truly, as they originate from a discrepance between the semantic
meillo@120 3084 structure of the problem and the structure implemented in the program.
meillo@120 3085 Such structural differences can not be cured on the surface.
meillo@120 3086 They need to be solved by adjusting the structure of the implementation
meillo@120 3087 to the structure of the problem.
meillo@120 3088 .P
meillo@120 3089 In 2002, the new switches
meillo@120 3090 .Sw -list
meillo@120 3091 and
meillo@120 3092 .Sw -delete
meillo@120 3093 were added in the same way, the
meillo@120 3094 .Sw -number
meillo@120 3095 switch for instance had been added.
meillo@120 3096 Yet, they are of structural different type.
meillo@120 3097 Semantically,
meillo@120 3098 .Sw -list
meillo@120 3099 and
meillo@120 3100 .Sw -delete
meillo@120 3101 introduce modes of operation.
meillo@120 3102 Historically,
meillo@120 3103 .Pn anno
meillo@120 3104 had only one operation mode: adding header fields.
meillo@171 3105 With the extension, it got two more modes:
meillo@120 3106 listing and deleting header fields.
meillo@120 3107 The structure of the code changes did not pay respect to this
meillo@120 3108 fundamental change to
meillo@120 3109 .Pn anno 's
meillo@120 3110 behavior.
meillo@120 3111 Neither the implementation nor the documentation did clearly
meillo@120 3112 define them as being exclusive modes of operation.
meillo@120 3113 Having identified the problem, I solved it by putting structure into
meillo@120 3114 .Pn anno
meillo@120 3115 and its documentation.
meillo@120 3116 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11
meillo@120 3117 .P
meillo@173 3118 The difference is visible in both the code and the documentation.
meillo@121 3119 The following code excerpt:
meillo@120 3120 .VS
meillo@120 3121 int delete = -2; /* delete header element if set */
meillo@120 3122 int list = 0; /* list header elements if set */
meillo@120 3123 [...]
meillo@121 3124 case DELETESW: /* delete annotations */
meillo@121 3125 delete = 0;
meillo@121 3126 continue;
meillo@121 3127 case LISTSW: /* produce a listing */
meillo@121 3128 list = 1;
meillo@121 3129 continue;
meillo@120 3130 VE
meillo@121 3131 .LP
meillo@121 3132 was replaced by:
meillo@120 3133 .VS
meillo@120 3134 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120 3135 [...]
meillo@121 3136 case DELETESW: /* delete annotations */
meillo@121 3137 mode = MODE_DEL;
meillo@121 3138 continue;
meillo@121 3139 case LISTSW: /* produce a listing */
meillo@121 3140 mode = MODE_LIST;
meillo@121 3141 continue;
meillo@120 3142 VE
meillo@120 3143 .LP
meillo@121 3144 The replacement code does not only reflect the problem's structure better,
meillo@121 3145 it is easier to understand as well.
meillo@121 3146 The same applies to the documentation.
meillo@120 3147 The man page was completely reorganized to propagate the same structure.
meillo@121 3148 This is visible in the Synopsis section:
meillo@120 3149 .VS
meillo@120 3150 anno [+folder] [msgs] [-component field] [-text body]
meillo@120 3151 [-append] [-date | -nodate] [-preserve | -nopreserve]
meillo@120 3152 [-Version] [-help]
meillo@120 3153
meillo@120 3154 anno -delete [+folder] [msgs] [-component field] [-text
meillo@120 3155 body] [-number num | all ] [-preserve | -nopreserve]
meillo@120 3156 [-Version] [-help]
meillo@120 3157
meillo@120 3158 anno -list [+folder] [msgs] [-component field] [-number]
meillo@120 3159 [-Version] [-help]
meillo@120 3160 VE
meillo@121 3161 .\" XXX think about explaining the -preserve rework?
meillo@118 3162
meillo@58 3163
meillo@58 3164
meillo@133 3165 .U3 "Path Conversion
meillo@133 3166 .P
meillo@134 3167 Four kinds of path names can appear in MH:
meillo@171 3168 .LI 1
meillo@134 3169 Absolute Unix directory paths, like
meillo@134 3170 .Fn /etc/passwd .
meillo@171 3171 .LI 2
meillo@134 3172 Relative Unix directory paths, like
meillo@134 3173 .Fn ./foo/bar .
meillo@171 3174 .LI 3
meillo@134 3175 Absolute MH folder paths, like
meillo@134 3176 .Fn +friends/phil .
meillo@171 3177 .LI 4
meillo@134 3178 Relative MH folder paths, like
meillo@134 3179 .Fn @subfolder .
meillo@171 3180 .LP
meillo@134 3181 The last type, relative MH folder paths, are hardly documented.
meillo@134 3182 Nonetheless, they are useful for large mail storages.
meillo@134 3183 The current mail folder is specified as `\c
meillo@134 3184 .Fn @ ',
meillo@134 3185 just like the current directory is specified as `\c
meillo@134 3186 .Fn . '.
meillo@134 3187 .P
meillo@134 3188 To allow MH tools to understand all four notations,
meillo@134 3189 they need to convert between them.
meillo@134 3190 In nmh, these path name conversion functions were located in the files
meillo@134 3191 .Fn sbr/path.c
meillo@134 3192 (``return a pathname'') and
meillo@134 3193 .Fn sbr/m_maildir.c
meillo@134 3194 (``get the path for the mail directory'').
meillo@134 3195 The seven functions in the two files were documented with no more
meillo@134 3196 than two comments, which described obvious information.
meillo@134 3197 The function signatures were neither explaining:
meillo@134 3198 .VS
meillo@134 3199 char *path(char *, int);
meillo@134 3200 char *pluspath(char *);
meillo@134 3201 char *m_mailpath(char *);
meillo@134 3202 char *m_maildir(char *);
meillo@134 3203 VE
meillo@134 3204 .P
meillo@134 3205 My investigation provides the following description:
meillo@171 3206 .LI 1
meillo@134 3207 The second parameter of
meillo@134 3208 .Fu path()
meillo@134 3209 defines the type of path given as first parameter.
meillo@134 3210 Directory paths are converted to absolute directory paths.
meillo@134 3211 Folder paths are converted to absolute folder paths.
meillo@173 3212 Folder paths must not include a leading `\fL@\fP' character.
meillo@134 3213 Leading plus characters are preserved.
meillo@134 3214 The result is a pointer to newly allocated memory.
meillo@171 3215 .LI 2
meillo@134 3216 .Fu pluspath()
meillo@134 3217 is a convenience-wrapper to
meillo@134 3218 .Fu path() ,
meillo@134 3219 to convert folder paths only.
meillo@134 3220 This function can not be used for directory paths.
meillo@134 3221 An empty string parameter causes a buffer overflow.
meillo@171 3222 .LI 3
meillo@134 3223 .Fu m_mailpath()
meillo@134 3224 converts directory paths to absolute directory paths.
meillo@173 3225 The characters `\fL+\fP' or `\fL@\fP' at the beginning of the path name are
meillo@134 3226 treated literal, i.e. as the first character of a relative directory path.
meillo@134 3227 Hence, this function can not be used for folder paths.
meillo@134 3228 In any case, the result is an absolute directory path.
meillo@134 3229 The result is a pointer to newly allocated memory.
meillo@171 3230 .LI 4
meillo@134 3231 .Fu m_maildir()
meillo@134 3232 returns the parameter unchanged if it is an absolute directory path
meillo@173 3233 or begins with the entry `\fL.\fP' or `\fL..\fP'.
meillo@134 3234 All other strings are prepended with the current working directory.
meillo@134 3235 Hence, this functions can not be used for folder paths.
meillo@134 3236 The result is either an absolute directory path or a relative
meillo@134 3237 directory path, starting with a dot.
meillo@134 3238 In contrast to the other functions, the result is a pointer to
meillo@134 3239 static memory.
meillo@134 3240 .P
meillo@134 3241 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@134 3242 No clear terminology was used to name the different kinds of path names.
meillo@134 3243 The first argument of
meillo@134 3244 .Fu m_mailpath() ,
meillo@134 3245 for instance, was named
meillo@134 3246 .Ar folder ,
meillo@134 3247 though
meillo@134 3248 .Fu m_mailpath()
meillo@134 3249 can not be used for MH folders.
meillo@134 3250 .P
meillo@134 3251 I reworked the path name conversion completely, introducing clarity.
meillo@134 3252 First of all, the terminology needed to be defined.
meillo@134 3253 A path name is either in the Unix domain, then it is called
meillo@134 3254 \fIdirectory path\fP, `dirpath' for short, or it is in the MH domain,
meillo@134 3255 then it is called \fIfolder path\fP, `folpath' for short.
meillo@134 3256 The two terms need to be used with strict distinction.
meillo@134 3257 Having a clear terminology is often an indicator of having understood
meillo@134 3258 the problem itself.
meillo@134 3259 Second, I exploited the concept of path type indicators.
meillo@134 3260 By requesting every path name to start with a clear type identifier,
meillo@134 3261 conversion between the types can be fully automated.
meillo@134 3262 Thus the tools can accept paths of any type from the user.
meillo@134 3263 Therefore, it was necessary to require relative directory paths to be
meillo@134 3264 prefixed with a dot character.
meillo@134 3265 In consequence, the dot character could no longer be an alias for the
meillo@134 3266 current message.
meillo@134 3267 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134 3268 Third, I created three new functions to replace the previous mess:
meillo@171 3269 .LI 1
meillo@134 3270 .Fu expandfol()
meillo@134 3271 converts folder paths to absolute folder paths,
meillo@134 3272 without the leading plus character.
meillo@134 3273 Directory paths are simply passed through.
meillo@134 3274 This function is to be used for folder paths only, thus the name.
meillo@134 3275 The result is a pointer to static memory.
meillo@171 3276 .LI 2
meillo@134 3277 .Fu expanddir()
meillo@134 3278 converts directory paths to absolute directory paths.
meillo@134 3279 Folder paths are treated as relative directory paths.
meillo@134 3280 This function is to be used for directory paths only, thus the name.
meillo@134 3281 The result is a pointer to static memory.
meillo@171 3282 .LI 3
meillo@134 3283 .Fu toabsdir()
meillo@134 3284 converts any type of path to an absolute directory path.
meillo@134 3285 This is the function of choice for path conversion.
meillo@134 3286 Absolute directory paths are the most general representation of a
meillo@134 3287 path name.
meillo@134 3288 The result is a pointer to static memory.
meillo@134 3289 .P
meillo@134 3290 The new functions have names that indicate their use.
meillo@134 3291 Two of the functions convert relative to absolute path names of the
meillo@134 3292 same type.
meillo@134 3293 The third function converts any path name type to the most general one,
meillo@134 3294 the absolute directory path.
meillo@134 3295 All of the functions return pointers to static memory.
meillo@134 3296 All three functions are implemented in
meillo@134 3297 .Fn sbr/path.c .
meillo@134 3298 .Fn sbr/m_maildir.c
meillo@134 3299 is removed.
meillo@168 3300 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3301 .P
meillo@134 3302 Along with the path conversion rework, I also replaced
meillo@134 3303 .Fu getfolder(FDEF)
meillo@134 3304 with
meillo@134 3305 .Fu getdeffol()
meillo@134 3306 and
meillo@134 3307 .Fu getfolder(FCUR)
meillo@134 3308 with
meillo@134 3309 .Fu getcurfol() ,
meillo@134 3310 which is only a convenience wrapper for
meillo@134 3311 .Fu expandfol("@") .
meillo@134 3312 This code was moved from
meillo@134 3313 .Fn sbr/getfolder.c
meillo@134 3314 to
meillo@134 3315 .Fn sbr/path.c .
meillo@168 3316 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3317 .P
meillo@134 3318 The related function
meillo@134 3319 .Fu etcpath()
meillo@134 3320 was moved to
meillo@134 3321 .Fn sbr/path.c ,
meillo@168 3322 too
meillo@168 3323 .Ci b4c29794c12099556151d93a860ee51badae2e35 .
meillo@134 3324 Previously, it had been located in
meillo@134 3325 .Fn config/config.c ,
meillo@134 3326 for whatever reasons.
meillo@134 3327 .P
meillo@134 3328 .Fn sbr/path.c
meillo@134 3329 now contains all path handling code.
meillo@134 3330 Only 173 lines of code were needed to replace the previous 252 lines.
meillo@134 3331 The readability of the code is highly improved.
meillo@134 3332 Additionally, each of the six exported and one static functions
meillo@134 3333 is introduced by an explaining comment.
meillo@133 3334
meillo@133 3335
meillo@133 3336
meillo@133 3337
meillo@133 3338 .H2 "Profile Reading
meillo@133 3339 .P
meillo@138 3340 The MH profile contains the configuration for the user-specific MH setup.
meillo@138 3341 MH tools read the profile right after starting up,
meillo@138 3342 as it contains the location of the user's mail storage
meillo@138 3343 and similar settings that influence the whole setup.
meillo@138 3344 Further more, the profile contains the default switches for the tools,
meillo@138 3345 hence, it must be read before the command line switches are processed.
meillo@138 3346 .P
meillo@138 3347 For historic reasons, some MH tools did not read the profile and context.
meillo@138 3348 Among them were
meillo@138 3349 .Pn post /\c
meillo@138 3350 .Pn spost ,
meillo@138 3351 .Pn mhmail ,
meillo@138 3352 and
meillo@138 3353 .Pn slocal .
meillo@138 3354 The reason why these tools ignored the profile were not clearly stated.
meillo@138 3355 During the discussion on the nmh-workers mailing list,
meillo@138 3356 .[
meillo@138 3357 nmh-workers levine post profile
meillo@138 3358 .]
meillo@138 3359 David Levine posted an explanation, quoting John Romine:
meillo@138 3360 .QS
meillo@138 3361 I asked John Romine and here's what he had to say, which
meillo@138 3362 agrees and provides an example that convinces me:
meillo@138 3363 .QS
meillo@164 3364 My take on this is that
meillo@164 3365 .Pn post
meillo@164 3366 should not be called by users directly, and it doesn't read the
meillo@164 3367 .Fn .mh_profile
meillo@138 3368 (only front-end UI programs read the profile).
meillo@138 3369 .QP
meillo@164 3370 For example, there can be contexts where
meillo@164 3371 .Pn post
meillo@164 3372 is called by a helper program (like `\c
meillo@164 3373 .Pn mhmail ')
meillo@164 3374 which may be run by a non-MH user.
meillo@164 3375 We don't want this to prompt the user to create an MH profile, etc.
meillo@138 3376 .QP
meillo@164 3377 My suggestion would be to have
meillo@164 3378 .Pn send
meillo@164 3379 pass a (hidden) `\c
meillo@164 3380 .Sw -fileproc
meillo@164 3381 .Ar proc '
meillo@164 3382 option to
meillo@164 3383 .Pn post
meillo@164 3384 if needed.
meillo@164 3385 You could also
meillo@164 3386 use an environment variable (I think
meillo@164 3387 .Pn send /\c
meillo@164 3388 .Pn whatnow
meillo@164 3389 do this).
meillo@138 3390 .QE
meillo@164 3391 I think that's the way to go.
meillo@164 3392 My personal preference is to use a command line option,
meillo@164 3393 not an environment variable.
meillo@138 3394 .QE
meillo@138 3395 .P
meillo@138 3396 To solve the problem of
meillo@138 3397 .Pn post
meillo@138 3398 not honoring the
meillo@138 3399 .Pe fileproc
meillo@138 3400 profile entry,
meillo@138 3401 the community roughly agreed that a switch
meillo@138 3402 .Sw -fileproc
meillo@138 3403 should be added to
meillo@138 3404 .Pn post
meillo@138 3405 to be able to pass a different fileproc.
meillo@138 3406 I strongly disagree with this approach because it does not solve
meillo@138 3407 the problem; it only removes a single symptom.
meillo@138 3408 The problem is that
meillo@138 3409 .Pn post
meillo@138 3410 does not behave as expected.
meillo@138 3411 But all programs should behave as expected.
meillo@138 3412 Clear and simple concepts are a precondition for this.
meillo@138 3413 Hence, the real solution is having all MH tools read the profile.
meillo@138 3414 .P
meillo@138 3415 Yet, the problem has a further aspect.
meillo@138 3416 It mainly originates in
meillo@138 3417 .Pn mhmail .
meillo@138 3418 .Pn mhmail
meillo@138 3419 was intended to be a replacement for
meillo@138 3420 .Pn mailx
meillo@138 3421 on systems with MH installations.
meillo@138 3422 .Pn mhmail
meillo@138 3423 should have been able to use just like
meillo@138 3424 .Pn mailx ,
meillo@138 3425 but sending the message via MH's
meillo@138 3426 .Pn post
meillo@138 3427 instead of
meillo@138 3428 .Pn sendmail .
meillo@138 3429 Using
meillo@138 3430 .Pn mhmail
meillo@138 3431 should not be influenced by the question whether the user had
meillo@138 3432 MH set up for himself or not.
meillo@138 3433 .Pn mhmail
meillo@138 3434 did not read the profile as this requests the user to set up MH
meillo@138 3435 if not done yet.
meillo@138 3436 As
meillo@138 3437 .Pn mhmail
meillo@138 3438 used
meillo@138 3439 .Pn post ,
meillo@138 3440 .Pn post
meillo@138 3441 could not read the profile neither.
meillo@138 3442 This is the reason why
meillo@138 3443 .Pn post
meillo@138 3444 does not read the profile.
meillo@138 3445 This is the reason for the actual problem.
meillo@138 3446 It was not much of a problem because
meillo@138 3447 .Pn post
meillo@138 3448 was not intended to be used by users directly.
meillo@138 3449 .Pn send
meillo@138 3450 is the interactive front-end to
meillo@138 3451 .Pn post .
meillo@138 3452 .Pn send
meillo@138 3453 read the profile and passed all relevant values on the command line to
meillo@138 3454 .Pn post
meillo@138 3455 \(en an awkward solution.
meillo@138 3456 .P
meillo@138 3457 The important insight is that
meillo@138 3458 .Pn mhmail
meillo@138 3459 is no true MH tool.
meillo@138 3460 The concepts broke because this outlandish tool was treated as any other
meillo@138 3461 MH tool.
meillo@138 3462 Instead it should have been treated accordingly to its foreign style.
meillo@138 3463 The solution is not to prevent the tools reading the profile but
meillo@138 3464 to instruct them reading a different profile.
meillo@138 3465 .Pn mhmail
meillo@138 3466 could have set up a well-defined profile and caused all MH tools
meillo@138 3467 in the session use it by exporting an environment variable.
meillo@138 3468 With this approach, no special cases would have been introduced,
meillo@138 3469 no surprises would have been caused.
meillo@138 3470 By writing a clean-profile-wrapper, the concept could have been
meillo@173 3471 generalized orthogonally to the whole MH tool chest.
meillo@138 3472 Then Rose's motivation behind the decision that
meillo@138 3473 .Pn post
meillo@138 3474 ignores the profile, as quoted by Jeffrey Honig,
meillo@138 3475 .[
meillo@138 3476 nmh-workers post profile
meillo@138 3477 .]
meillo@138 3478 would have become possible:
meillo@138 3479 .QS
meillo@138 3480 when you run mh commands in a script, you want all the defaults to be
meillo@138 3481 what the man page says.
meillo@138 3482 when you run a command by hand, then you want your own defaults...
meillo@138 3483 .QE
meillo@138 3484 .LP
meillo@171 3485 Yet, I consider this explanation shortsighted.
meillo@138 3486 We should rather regard theses two cases as just two different MH setups,
meillo@138 3487 based on two different profiles.
meillo@138 3488 Mapping such problems on the concepts of switching between different
meillo@138 3489 profiles, solves them once for all.
meillo@138 3490 .P
meillo@138 3491 In mmh, the wish to have
meillo@138 3492 .Pn mhmail
meillo@173 3493 as a replacement for
meillo@138 3494 .Pn mailx
meillo@138 3495 is considered obsolete.
meillo@138 3496 Mmh's
meillo@138 3497 .Pn mhmail
meillo@138 3498 does no longer cover this use-case.
meillo@138 3499 Currently,
meillo@138 3500 .Pn mhmail
meillo@138 3501 is in a transition state.
meillo@138 3502 .Ci 32d4f9daaa70519be3072479232ff7be0500d009
meillo@138 3503 It may become a front-end to
meillo@138 3504 .Pn comp ,
meillo@138 3505 which provides an interface more convenient in some cases.
meillo@138 3506 In this case,
meillo@138 3507 .Pn mhmail
meillo@138 3508 will become an ordinary MH tool, reading the profile.
meillo@138 3509 If, however, this idea will not convince, then
meillo@138 3510 .Pn mhmail
meillo@138 3511 will be removed.
meillo@138 3512 .P
meillo@173 3513 Every program in the mmh tool chest reads the profile.
meillo@138 3514 The only exception is
meillo@138 3515 .Pn slocal ,
meillo@173 3516 which is not considered part of the mmh tool chest.
meillo@138 3517 This MDA is only distributed with mmh, currently.
meillo@138 3518 Mmh has no
meillo@138 3519 .Pn post
meillo@138 3520 program, but
meillo@138 3521 .Pn spost ,
meillo@138 3522 which now reads the profile.
meillo@138 3523 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8
meillo@138 3524 With this change,
meillo@138 3525 .Pn send
meillo@138 3526 and
meillo@138 3527 .Pn spost
meillo@138 3528 can be considered to be merged.
meillo@138 3529 .Pn spost
meillo@169 3530 is only invoked directly by the to-be-changed
meillo@138 3531 .Pn mhmail
meillo@138 3532 implementation and by
meillo@138 3533 .Pn rcvdist ,
meillo@138 3534 which will require rework.
meillo@138 3535 .P
meillo@138 3536 The
meillo@138 3537 .Fu context_foil()
meillo@138 3538 function to pretend to have read an empty profile was removed.
meillo@138 3539 .Ci 68af8da96bea87a5541988870130b6209ce396f6
meillo@138 3540 All mmh tools read the profile.
meillo@133 3541
meillo@133 3542
meillo@127 3543
meillo@121 3544 .H2 "Standard Libraries
meillo@22 3545 .P
meillo@121 3546 MH is one decade older than the POSIX and ANSI C standards.
meillo@121 3547 Hence, MH included own implementations of functions
meillo@121 3548 that are standardized and thus widely available today,
meillo@121 3549 but were not back then.
meillo@121 3550 Today, twenty years after the POSIX and ANSI C were published,
meillo@121 3551 developers can expect system to comply with these standards.
meillo@121 3552 In consequence, MH-specific replacements for standard functions
meillo@121 3553 can and should be dropped.
meillo@121 3554 Kernighan and Pike advise: ``Use standard libraries.''
meillo@121 3555 .[ [
meillo@121 3556 kernighan pike practice of programming
meillo@121 3557 .], p. 196]
meillo@121 3558 Actually, MH had followed this advice in history,
meillo@121 3559 but it had not adjusted to the changes in this field.
meillo@121 3560 The
meillo@121 3561 .Fu snprintf()
meillo@121 3562 function, for instance, was standardized with C99 and is available
meillo@121 3563 almost everywhere because of its high usefulness.
meillo@123 3564 In project's own implementation of
meillo@121 3565 .Fu snprintf()
meillo@123 3566 was dropped in March 2012 in favor for using the one of the
meillo@123 3567 standard library.
meillo@123 3568 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32
meillo@123 3569 Such decisions limit the portability of mmh
meillo@173 3570 if systems do not support these standardized and widespread functions.
meillo@123 3571 This compromise is made because mmh focuses on the future.
meillo@121 3572 .P
meillo@123 3573 I am not yet thirty years old and my C and Unix experience comprises
meillo@123 3574 only half a dozen years.
meillo@121 3575 Hence, I need to learn about the history in retrospective.
meillo@121 3576 I have not used those ancient constructs myself.
meillo@121 3577 I have not suffered from their incompatibilities.
meillo@121 3578 I have not longed for standardization.
meillo@121 3579 All my programming experience is from a time when ANSI C and POSIX
meillo@121 3580 were well established already.
meillo@121 3581 I have only read a lot of books about the (good) old times.
meillo@121 3582 This puts me in a difficult positions when working with old code.
meillo@123 3583 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123 3584 programming styles, whereas older programmers know these things by
meillo@123 3585 heart from their own experience.
meillo@121 3586 .P
meillo@123 3587 Being aware of the situation, I rather let people with more historic
meillo@123 3588 experience replace ancient code constructs with standardized ones.
meillo@121 3589 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121 3590 He converted project-specific functions to POSIX replacements,
meillo@121 3591 also removing the conditionals compilation of now standardized features.
meillo@123 3592 Ken Hornstein and David Levine had their part in the work, too.
meillo@121 3593 Often, I only needed to pull over changes from nmh into mmh.
meillo@121 3594 These changes include many commits; these are among them:
meillo@121 3595 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121 3596 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102 3597 .P
meillo@123 3598 During my own work, I tidied up the \fIMH standard library\fP,
meillo@123 3599 .Fn libmh.a ,
meillo@123 3600 which is located in the
meillo@123 3601 .Fn sbr
meillo@123 3602 (``subroutines'') directory in the source tree.
meillo@123 3603 The MH library includes functions that mmh tools usually need.
meillo@123 3604 Among them are MH-specific functions for profile, context, sequence,
meillo@123 3605 and folder handling, but as well
meillo@123 3606 MH-independent functions, such as auxiliary string functions,
meillo@123 3607 portability interfaces and error-checking wrappers for critical
meillo@123 3608 functions of the standard library.
meillo@123 3609 .P
meillo@123 3610 I have replaced the
meillo@121 3611 .Fu atooi()
meillo@121 3612 function with calls to
meillo@123 3613 .Fu strtoul()
meillo@139 3614 with the third parameter, the base, set to eight.
meillo@121 3615 .Fu strtoul()
meillo@123 3616 is part of C89 and thus considered safe to use.
meillo@121 3617 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74
meillo@102 3618 .P
meillo@121 3619 I did remove project-included fallback implementations of
meillo@121 3620 .Fu memmove()
meillo@121 3621 and
meillo@121 3622 .Fu strerror() ,
meillo@121 3623 although Peter Maydell had re-included them into nmh in 2008
meillo@121 3624 to support SunOS 4.
meillo@121 3625 Nevertheless, these functions are part of ANSI C.
meillo@121 3626 Systems that do not even provide full ANSI C support should not
meillo@121 3627 put a load on mmh.
meillo@121 3628 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215
meillo@121 3629 .P
meillo@121 3630 The
meillo@121 3631 .Fu copy()
meillo@121 3632 function copies the string in argument one to the location in two.
meillo@121 3633 In contrast to
meillo@121 3634 .Fu strcpy() ,
meillo@121 3635 it returns a pointer to the terminating null-byte in the destination area.
meillo@123 3636 The code was adjusted to replace
meillo@121 3637 .Fu copy()
meillo@123 3638 with
meillo@121 3639 .Fu strcpy() ,
meillo@121 3640 except within
meillo@121 3641 .Fu concat() ,
meillo@121 3642 where
meillo@121 3643 .Fu copy()
meillo@123 3644 was more convenient.
meillo@123 3645 Therefore, the definition of
meillo@121 3646 .Fu copy()
meillo@123 3647 was moved into the source file of
meillo@121 3648 .Fu concat()
meillo@123 3649 and its visibility is now limited to it.
meillo@121 3650 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb
meillo@121 3651 .P
meillo@121 3652 The function
meillo@121 3653 .Fu r1bindex()
meillo@121 3654 had been a generalized version of
meillo@121 3655 .Fu basename()
meillo@121 3656 with minor differences.
meillo@121 3657 As all calls to
meillo@121 3658 .Fu r1bindex()
meillo@121 3659 had the slash (`/') as delimiter anyway,
meillo@121 3660 replacing
meillo@121 3661 .Fu r1bindex()
meillo@121 3662 with the more specific and better-named function
meillo@121 3663 .Fu basename()
meillo@121 3664 became desirable.
meillo@121 3665 Unfortunately, many of the 54 calls to
meillo@121 3666 .Fu r1bindex()
meillo@123 3667 depended on a special behavior,
meillo@121 3668 which differed from the POSIX specification for
meillo@121 3669 .Fu basename() .
meillo@121 3670 Hence,
meillo@121 3671 .Fu r1bindex()
meillo@121 3672 was kept but renamed to
meillo@123 3673 .Fu mhbasename() ,
meillo@123 3674 fixing the delimiter to the slash.
meillo@121 3675 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60
meillo@121 3676 For possible uses of
meillo@121 3677 .Fu r1bindex()
meillo@121 3678 with a different delimiter,
meillo@121 3679 the ANSI C function
meillo@121 3680 .Fu strrchr()
meillo@121 3681 provides the core functionality.
meillo@121 3682 .P
meillo@121 3683 The
meillo@121 3684 .Fu ssequal()
meillo@121 3685 function \(en apparently for ``substring equal'' \(en
meillo@121 3686 was renamed to
meillo@121 3687 .Fu isprefix() ,
meillo@121 3688 because this is what it actually checks.
meillo@121 3689 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711
meillo@121 3690 Its source file had included the following comments, no joke.
meillo@121 3691 .VS
meillo@121 3692 /*
meillo@121 3693 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121 3694 * It is actually checking if s1 is a PREFIX of s2.
meillo@121 3695 * All calls to this function need to be checked to see
meillo@121 3696 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121 3697 * should be kept if it's sufficient.
meillo@121 3698 */
meillo@121 3699
meillo@121 3700 /*
meillo@121 3701 * Check if s1 is a substring of s2.
meillo@121 3702 * If yes, then return 1, else return 0.
meillo@121 3703 */
meillo@121 3704 VE
meillo@123 3705 Two months later, it was completely removed by replacing it with
meillo@123 3706 .Fu strncmp() .
meillo@123 3707 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb
meillo@121 3708
meillo@102 3709
meillo@102 3710
meillo@102 3711
meillo@133 3712
meillo@133 3713 .H2 "User Data Locations
meillo@133 3714 .P
meillo@133 3715 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133 3716 The profile is a file named
meillo@133 3717 .Fn \&.mh_profile
meillo@133 3718 in the user's home directory.
meillo@133 3719 It contains the static configuration.
meillo@133 3720 It also contains the location of the MH directory in the profile entry
meillo@133 3721 .Pe Path .
meillo@133 3722 The MH directory contains the mail storage and is the first
meillo@133 3723 place to search for personal forms, scan formats, and similar
meillo@133 3724 configuration files.
meillo@133 3725 The location of the MH directory can be chosen freely by the user.
meillo@133 3726 The default and usual name is a directory named
meillo@133 3727 .Fn Mail
meillo@133 3728 in the home directory.
meillo@133 3729 .P
meillo@133 3730 The way MH data is splitted between profile and MH directory is a legacy.
meillo@133 3731 It is only sensible in a situation where the profile is the only
meillo@133 3732 configuration file.
meillo@133 3733 Why else should the mail storage and the configuration files be intermixed?
meillo@133 3734 They are different kinds of data:
meillo@133 3735 The data to be operated on and the configuration to change how
meillo@133 3736 tools operate.
meillo@133 3737 Splitting the configuration between the profile and the MH directory
meillo@133 3738 is bad.
meillo@133 3739 Merging the mail storage and the configuration in one directory is bad
meillo@133 3740 as well.
meillo@133 3741 As the mail storage and the configuration were not separated sensibly
meillo@133 3742 in the first place, I did it now.
meillo@133 3743 .P
meillo@133 3744 Personal mmh data is grouped by type, resulting in two distinct parts:
meillo@171 3745 the mail storage and the configuration.
meillo@133 3746 In mmh, the mail storage directory still contains all the messages,
meillo@133 3747 but, in exception of public sequences files, nothing else.
meillo@133 3748 In difference to nmh, the auxiliary configuration files are no longer
meillo@133 3749 located there.
meillo@133 3750 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@133 3751 but his \fImail storage\fP.
meillo@133 3752 Its location is still user-chosen, with the default name
meillo@133 3753 .Fn Mail ,
meillo@133 3754 in the user's home directory.
meillo@133 3755 In mmh, the configuration is grouped together in
meillo@133 3756 the hidden directory
meillo@133 3757 .Fn \&.mmh
meillo@133 3758 in the user's home directory.
meillo@133 3759 This \fImmh directory\fP contains the context file, personal forms,
meillo@133 3760 scan formats, and the like, but also the user's profile, now named
meillo@133 3761 .Fn profile .
meillo@133 3762 The location of the profile is no longer fixed to
meillo@133 3763 .Fn $HOME/.mh_profile
meillo@133 3764 but to
meillo@133 3765 .Fn $HOME/.mmh/profile .
meillo@173 3766 Having both the file
meillo@133 3767 .Fn $HOME/.mh_profile
meillo@133 3768 and the configuration directory
meillo@133 3769 .Fn $HOME/.mmh
meillo@133 3770 appeared to be inconsistent.
meillo@133 3771 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133 3772 Unix users.
meillo@168 3773 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3774 .P
meillo@168 3775 MH allows users to have multiple MH setups.
meillo@133 3776 Therefore, it is necessary to select a different profile.
meillo@133 3777 The profile is the single entry point to access the rest of a
meillo@133 3778 personal MH setup.
meillo@133 3779 In nmh, the environment variable
meillo@133 3780 .Ev MH
meillo@133 3781 could be used to specifiy a different profile.
meillo@133 3782 To operate in the same MH setup with a separate context,
meillo@133 3783 the
meillo@133 3784 .Ev MHCONTEXT
meillo@133 3785 environment variable could be used.
meillo@133 3786 This allows having own current folders and current messages in
meillo@133 3787 each terminal, for instance.
meillo@133 3788 In mmh, three environment variables are used.
meillo@133 3789 .Ev MMH
meillo@133 3790 overrides the default location of the mmh directory (\c
meillo@133 3791 .Fn .mmh ).
meillo@133 3792 .Ev MMHP
meillo@133 3793 and
meillo@133 3794 .Ev MMHC
meillo@133 3795 override the paths to the profile and context files, respectively.
meillo@133 3796 This approach allows the set of personal configuration files to be chosen
meillo@133 3797 independently from the profile, context, and mail storage.
meillo@168 3798 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3799 .P
meillo@133 3800 The separation of the files by type is sensible and convenient.
meillo@133 3801 The new approach has no functional disadvantages,
meillo@133 3802 as every setup I can imagine can be implemented with both approaches,
meillo@133 3803 possibly even easier with the new approach.
meillo@133 3804 The main achievement of the change is the clear and sensible split
meillo@133 3805 between mail storage and configuration.
meillo@133 3806
meillo@133 3807
meillo@133 3808
meillo@133 3809
meillo@133 3810
meillo@118 3811 .H2 "Modularization
meillo@118 3812 .P
meillo@123 3813 The source code of the mmh tools is located in the
meillo@122 3814 .Fn uip
meillo@123 3815 (``user interface programs'') directory.
meillo@179 3816 Each tools has a source file with the name of the command.
meillo@122 3817 For example,
meillo@122 3818 .Pn rmm
meillo@122 3819 is built from
meillo@122 3820 .Fn uip/rmm.c .
meillo@123 3821 Some source files are used for multiple programs.
meillo@122 3822 For example
meillo@122 3823 .Fn uip/scansbr.c
meillo@173 3824 is used for both
meillo@122 3825 .Pn scan
meillo@122 3826 and
meillo@122 3827 .Pn inc .
meillo@122 3828 In nmh, 49 tools were built from 76 source files.
meillo@123 3829 This is a ratio of 1.6 source files per program.
meillo@123 3830 32 programs depended on multiple source files;
meillo@123 3831 17 programs depended on one source file only.
meillo@122 3832 In mmh, 39 tools are built from 51 source files.
meillo@123 3833 This is a ratio of 1.3 source files per program.
meillo@123 3834 18 programs depend on multiple source files;
meillo@123 3835 21 programs depend on one source file only.
meillo@123 3836 (These numbers and the ones in the following text ignore the MH library
meillo@123 3837 as well as shell scripts and multiple names for the same program.)
meillo@122 3838 .P
meillo@123 3839 Splitting the source code of a large program into multiple files can
meillo@122 3840 increase the readability of its source code.
meillo@124 3841 Most of the mmh tools, however, are simple and straight-forward programs.
meillo@122 3842 With the exception of the MIME handling tools,
meillo@122 3843 .Pn pick
meillo@179 3844 is the largest tool.
meillo@122 3845 It contains 1\|037 lines of source code (measured with
meillo@122 3846 .Pn sloccount ), excluding the MH library.
meillo@122 3847 Only the MIME handling tools (\c
meillo@122 3848 .Pn mhbuild ,
meillo@122 3849 .Pn mhstore ,
meillo@122 3850 .Pn show ,
meillo@122 3851 etc.)
meillo@122 3852 are larger.
meillo@122 3853 Splitting programs with less than 1\|000 lines of code into multiple
meillo@123 3854 source files seldom leads to better readability.
meillo@123 3855 For such tools, splitting makes sense
meillo@122 3856 when parts of the code are reused in other programs,
meillo@179 3857 and the reused code fragment is (1) not general enough
meillo@179 3858 for including it in the MH library
meillo@179 3859 or (2) has dependencies on a library that only few programs need.
meillo@122 3860 .Fn uip/packsbr.c ,
meillo@122 3861 for instance, provides the core program logic for the
meillo@122 3862 .Pn packf
meillo@122 3863 and
meillo@122 3864 .Pn rcvpack
meillo@122 3865 programs.
meillo@122 3866 .Fn uip/packf.c
meillo@122 3867 and
meillo@122 3868 .Fn uip/rcvpack.c
meillo@122 3869 mainly wrap the core function appropriately.
meillo@122 3870 No other tools use the folder packing functions.
meillo@123 3871 As another example,
meillo@123 3872 .Fn uip/termsbr.c
meillo@123 3873 provides termcap support, which requires linking with a termcap or
meillo@123 3874 curses library.
meillo@123 3875 Including
meillo@123 3876 .Fn uip/termsbr.c
meillo@123 3877 into the MH library would require every program to be linked with
meillo@123 3878 termcap or curses, although only few of the programs require it.
meillo@122 3879 .P
meillo@122 3880 The task of MIME handling is complex enough that splitting its code
meillo@122 3881 into multiple source files improves the readability.
meillo@122 3882 The program
meillo@122 3883 .Pn mhstore ,
meillo@122 3884 for instance, is compiled out of seven source files with 2\|500
meillo@122 3885 lines of code in summary.
meillo@122 3886 The main code file
meillo@122 3887 .Fn uip/mhstore.c
meillo@123 3888 consists of 800 lines; the other 1\|700 lines of code are reused in
meillo@123 3889 other MIME handling tools.
meillo@123 3890 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123 3891 a MH-MIME library, as a companion to the MH standard library.
meillo@122 3892 This is left open for the future.
meillo@122 3893 .P
meillo@169 3894 The work already accomplished focussed on the non-MIME tools.
meillo@122 3895 The amount of code compiled into each program was reduced.
meillo@123 3896 This eases the understanding of the code base.
meillo@122 3897 In nmh,
meillo@122 3898 .Pn comp
meillo@122 3899 was built from six source files:
meillo@122 3900 .Fn comp.c ,
meillo@122 3901 .Fn whatnowproc.c ,
meillo@122 3902 .Fn whatnowsbr.c ,
meillo@122 3903 .Fn sendsbr.c ,
meillo@122 3904 .Fn annosbr.c ,
meillo@122 3905 and
meillo@122 3906 .Fn distsbr.c .
meillo@122 3907 In mmh, it builds from only two:
meillo@122 3908 .Fn comp.c
meillo@122 3909 and
meillo@122 3910 .Fn whatnowproc.c .
meillo@123 3911 In nmh's
meillo@123 3912 .Pn comp ,
meillo@123 3913 the core function of
meillo@122 3914 .Pn whatnow ,
meillo@122 3915 .Pn send ,
meillo@122 3916 and
meillo@122 3917 .Pn anno
meillo@123 3918 were compiled into
meillo@122 3919 .Pn comp .
meillo@123 3920 This saved the need to execute these programs with
meillo@122 3921 .Fu fork()
meillo@122 3922 and
meillo@122 3923 .Fu exec() ,
meillo@122 3924 two expensive system calls.
meillo@171 3925 Whereas this approach improved the time performance,
meillo@171 3926 it interwove the source code.
meillo@122 3927 Core functionalities were not encapsulated into programs but into
meillo@122 3928 function, which were then wrapped by programs.
meillo@122 3929 For example,
meillo@122 3930 .Fn uip/annosbr.c
meillo@122 3931 included the function
meillo@122 3932 .Fu annotate() .
meillo@122 3933 Each program that wanted to annotate messages, included the source file
meillo@123 3934 .Fn uip/annosbr.c
meillo@123 3935 and called
meillo@123 3936 .Fu annotate() .
meillo@123 3937 Because the function
meillo@123 3938 .Fu annotate()
meillo@123 3939 was used like the tool
meillo@123 3940 .Pn anno ,
meillo@123 3941 it had seven parameters, reflecting the command line switches of the tool.
meillo@122 3942 When another pair of command line switches was added to
meillo@122 3943 .Pn anno ,
meillo@122 3944 a rather ugly hack was implemented to avoid adding another parameter
meillo@122 3945 to the function.
meillo@122 3946 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@122 3947 .P
meillo@122 3948 Separation simplifies the understanding of program code
meillo@122 3949 because the area influenced by any particular statement is smaller.
meillo@122 3950 The separating on the program-level is more strict than the separation
meillo@122 3951 on the function level.
meillo@122 3952 In mmh, the relevant code of
meillo@122 3953 .Pn comp
meillo@122 3954 comprises the two files
meillo@122 3955 .Fn uip/comp.c
meillo@122 3956 and
meillo@122 3957 .Fn uip/whatnowproc.c ,
meillo@123 3958 together 210 lines of code.
meillo@122 3959 In nmh,
meillo@122 3960 .Pn comp
meillo@122 3961 comprises six files with 2\|450 lines.
meillo@123 3962 Not all of the code in these six files was actually used by
meillo@122 3963 .Pn comp ,
meillo@123 3964 but the code reader needed to read all of the code first to know which
meillo@123 3965 parts were used.
meillo@122 3966 .P
meillo@123 3967 As I have read a lot in the code base during the last two years,
meillo@123 3968 I learned about the easy and the difficult parts.
meillo@171 3969 Code is easy to understand if the influenced code area is small
meillo@171 3970 and its boundaries are strictly defined.
meillo@171 3971 Further more, the code needs to solve the problem in a straight-forward way.
meillo@123 3972 .P
meillo@123 3973 .\" XXX move this paragraph somewhere else?
meillo@123 3974 Reading
meillo@122 3975 .Pn rmm 's
meillo@122 3976 source code in
meillo@122 3977 .Fn uip/rmm.c
meillo@122 3978 is my recommendation for a beginner's entry point into the code base of nmh.
meillo@122 3979 The reasons are that the task of
meillo@122 3980 .Pn rmm
meillo@122 3981 is straight forward and it consists of one small source code file only,
meillo@122 3982 yet its source includes code constructs typical for MH tools.
meillo@122 3983 With the introduction of the trash folder in mmh,
meillo@122 3984 .Pn rmm
meillo@122 3985 became a bit more complex, because it invokes
meillo@122 3986 .Pn refile .
meillo@122 3987 Still, it is a good example for a simple tool with clear sources.
meillo@122 3988 .P
meillo@122 3989 Understanding
meillo@122 3990 .Pn comp
meillo@122 3991 requires to read 210 lines of code in mmh, but ten times as much in nmh.
meillo@123 3992 Due to the aforementioned hack in
meillo@122 3993 .Pn anno
meillo@122 3994 to save the additional parameter, information passed through the program's
meillo@122 3995 source base in obscure ways.
meillo@123 3996 Thus, understanding
meillo@122 3997 .Pn comp ,
meillo@123 3998 required understanding the inner workings of
meillo@122 3999 .Fn uip/annosbr.c
meillo@122 4000 first.
meillo@123 4001 To be sure to fully understand a program, its whole source code needs
meillo@122 4002 to be examined.
meillo@123 4003 Not doing so is a leap of faith, assuming that the developers
meillo@122 4004 have avoided obscure programming techniques.
meillo@122 4005 By separating the tools on the program-level, the boundaries are
meillo@122 4006 clearly visible and technically enforced.
meillo@122 4007 The interfaces are calls to
meillo@122 4008 .Fu exec()
meillo@122 4009 rather than arbitrary function calls.
meillo@123 4010 .P
meillo@123 4011 But the real problem is another:
meillo@123 4012 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123 4013 Understanding
meillo@122 4014 .Pn comp
meillo@123 4015 requires understanding
meillo@123 4016 .Fn uip/annosbr.c
meillo@123 4017 and
meillo@123 4018 .Fn uip/sendsbr.c
meillo@123 4019 because
meillo@123 4020 .Pn comp
meillo@123 4021 does annotate and send messages.
meillo@123 4022 In nmh, there surely exists the tool
meillo@122 4023 .Pn send ,
meillo@179 4024 which does mainly send messages.
meillo@123 4025 But
meillo@122 4026 .Pn comp
meillo@123 4027 and
meillo@122 4028 .Pn repl
meillo@122 4029 and
meillo@122 4030 .Pn forw
meillo@122 4031 and
meillo@122 4032 .Pn dist
meillo@122 4033 and
meillo@122 4034 .Pn whatnow
meillo@122 4035 and
meillo@123 4036 .Pn viamail ,
meillo@179 4037 they all (!) have the same message sending function included, as well.
meillo@123 4038 In result,
meillo@123 4039 .Pn comp
meillo@123 4040 sends messages without using
meillo@123 4041 .Pn send .
meillo@123 4042 The situation is the same as if
meillo@123 4043 .Pn grep
meillo@123 4044 would page without
meillo@123 4045 .Pn more
meillo@123 4046 just because both programs are part of the same code base.
meillo@123 4047 .P
meillo@173 4048 The clear separation on the surface \(en the tool chest approach \(en
meillo@123 4049 is violated on the level below.
meillo@122 4050 This violation is for the sake of time performance.
meillo@122 4051 On systems where
meillo@122 4052 .Fu fork()
meillo@122 4053 and
meillo@122 4054 .Fu exec()
meillo@122 4055 are expensive, the quicker response might be noticable.
meillo@124 4056 In the old times, sacrificing readability and conceptional beauty for
meillo@124 4057 speed might even have been a must to prevent MH from being unusably slow.
meillo@122 4058 Whatever the reasons had been, today they are gone.
meillo@123 4059 No longer should we sacrifice readability or conceptional beauty.
meillo@122 4060 No longer should we violate the Unix philosophy's ``one tool, one job''
meillo@122 4061 guideline.
meillo@123 4062 No longer should we keep speed improvements that became unnecessary.
meillo@122 4063 .P
meillo@123 4064 Therefore, mmh's
meillo@123 4065 .Pn comp
meillo@123 4066 does no longer send messages.
meillo@123 4067 In mmh, different jobs are divided among separate programs that
meillo@122 4068 invoke each other as needed.
meillo@123 4069 In consequence,
meillo@123 4070 .Pn comp
meillo@123 4071 invokes
meillo@123 4072 .Pn whatnow
meillo@123 4073 which thereafter invokes
meillo@123 4074 .Pn send .
meillo@168 4075 .Ci 3df5ab3c116e6d4a2fb4bb5cc9dfc5f781825815
meillo@168 4076 .Ci c73c00bfccd22ec77e9593f47462aeca4a8cd9c0
meillo@123 4077 The clear separation on the surface is maintained on the level below.
meillo@123 4078 Human users and the tools use the same interface \(en
meillo@123 4079 annotations, for example, are made by invoking
meillo@123 4080 .Pn anno ,
meillo@123 4081 no matter if requested by programs or by human beings.
meillo@168 4082 .Ci 469a4163c2a1a43731d412eaa5d9cae7d670c48b
meillo@168 4083 .Ci aed384169af5204b8002d06e7a22f89197963d2d
meillo@168 4084 .Ci 3caf9e298a8861729ca8b8a84f57022b6f3ea742
meillo@123 4085 The decrease of tools built from multiple source files and thus
meillo@123 4086 the decrease of
meillo@123 4087 .Fn uip/*sbr.c
meillo@123 4088 files confirm the improvement.
meillo@168 4089 .Ci 9e6d91313f01c96b4058d6bf419a8ca9a207bc33
meillo@168 4090 .ci 81744a46ac9f845d6c2b9908074d269275178d2e
meillo@168 4091 .Ci f0f858069d21111f0dbea510044593f89c9b0829
meillo@168 4092 .Ci 0503a6e9be34f24858b55b555a5c948182b9f24b
meillo@168 4093 .Ci 27826f9353e0f0b04590b7d0f8f83e60462b90f0
meillo@168 4094 .Ci d1da1f94ce62160aebb30df4063ccbc53768656b
meillo@168 4095 .Ci c42222869e318fff5dec395eca3e776db3075455
meillo@123 4096 .P
meillo@145 4097 .\" XXX move this paragraph up somewhere
meillo@123 4098 One disadvantage needs to be taken with this change:
meillo@123 4099 The compiler can no longer check the integrity of the interfaces.
meillo@123 4100 By changing the command line interfaces of tools, it is
meillo@123 4101 the developer's job to adjust the invocations of these tools as well.
meillo@123 4102 As this is a manual task and regression tests, which could detect such
meillo@124 4103 problems, are not available yet, it is prone to errors.
meillo@123 4104 These errors will not be detected at compile time but at run time.
meillo@171 4105 Installing regression tests is a pending task.
meillo@123 4106 In the best case, a uniform way of invoking tools from other tools
meillo@123 4107 can be developed to allow automated testing at compile time.
meillo@145 4108
meillo@145 4109
meillo@145 4110 .ig
meillo@145 4111 XXX consider writing about mhl vs. mhlproc
meillo@145 4112
meillo@145 4113 sbr/showfile.c
meillo@145 4114
meillo@145 4115 23 /*
meillo@145 4116 24 ** If you have your lproc listed as "mhl",
meillo@145 4117 25 ** then really invoked the mhlproc instead
meillo@145 4118 26 ** (which is usually mhl anyway).
meillo@145 4119 27 */
meillo@145 4120
meillo@145 4121 Sat Nov 24 19:09:14 1984 /mtr (agent: Marshall Rose) <uci@udel-dewey>
meillo@145 4122
meillo@145 4123 sbr/showfile.c: if lproc is "mhl", use mhlproc for consistency
meillo@145 4124 (Actually, user should use "lproc: show", "showproc: mhl".)
meillo@145 4125 ..