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Further improvements in the discussion; added build dependency graphs.
author markus schnalke <meillo@marmaro.de>
date Sun, 15 Jul 2012 18:41:35 +0200
parents 8c537982d718
children 1fa5a74bf138
rev   line source
meillo@58 1 .H0 "Discussion
meillo@0 2 .P
meillo@169 3 This main chapter discusses the practical work accomplished in the
meillo@169 4 mmh project.
meillo@217 5 It is structured along the goals chosen for the project.
meillo@217 6 A selection of the work undertaken
meillo@217 7 is described.
meillo@217 8 .P
meillo@217 9 This discussion compares the present version of mmh with the state of
meillo@217 10 nmh at the time when the mmh project had started, i.e. fall 2011.
meillo@217 11 Recent changes in nmh are seldom part of the discussion.
meillo@217 12 Sometimes they are mentioned in side notes.
meillo@187 13 .P
meillo@187 14 For the reader's convenience, the structure of modern email systems
meillo@217 15 is depicted in the following figure.
meillo@187 16 It illustrates the path a message takes from sender to recipient.
meillo@217 17
meillo@217 18 .sp 1.5
meillo@187 19 .KS
meillo@187 20 .in 2c
meillo@187 21 .so input/mail-agents.pic
meillo@187 22 .KE
meillo@217 23 .sp 1.5
meillo@217 24
meillo@187 25 .LP
meillo@217 26 The ellipses denote mail agents, i.e. different jobs in email processing.
meillo@217 27 These are:
meillo@187 28 .IP "Mail User Agent (MUA)
meillo@217 29 The only program users directly interact with.
meillo@187 30 It includes functions to compose new mail, display received mail,
meillo@187 31 and to manage the mail storage.
meillo@217 32 It is called a \fImail client\fP as well.
meillo@187 33 .IP "Mail Submission Agent (MSA)
meillo@187 34 A special kind of Mail Transfer Agent, used to submit mail into the
meillo@187 35 mail transport system.
meillo@217 36 Often it is also called an MTA.
meillo@187 37 .IP "Mail Transfer Agent (MTA)
meillo@187 38 A node in the mail transport system.
meillo@217 39 It transfers incoming mail to a transport node nearer to the
meillo@217 40 final destination.
meillo@217 41 An MTA may be the final destination itself.
meillo@187 42 .IP "Mail Delivery Agent (MDA)
meillo@217 43 Delivers mail according to a set of rules.
meillo@217 44 Usually, the messages are stored to disk.
meillo@187 45 .IP "Mail Retrieval Agent (MRA)
meillo@217 46 Initiates the transfer of mail from a remote location to the local machine.
meillo@217 47 (The dashed arrow in the figure represents the pull request.)
meillo@217 48 .LP
meillo@217 49 The dashed boxes represent entities that usually reside on single machines.
meillo@217 50 The box on the lower left represents the sender's system.
meillo@187 51 The box on the upper left represents the first mail transfer node.
meillo@187 52 The box on the upper right represents the transfer node responsible for the
meillo@187 53 destination address.
meillo@217 54 The box on the lower right represents the recipient's system.
meillo@187 55 Often, the boxes above the dotted line are servers on the Internet.
meillo@217 56 Many mail clients, including nmh, include all of the components below
meillo@217 57 the dotted line.
meillo@217 58 This is not the case for mmh; it implements the MUA only.
meillo@187 59
meillo@187 60
meillo@187 61
meillo@58 62
meillo@58 63
meillo@58 64
meillo@133 65 .\" --------------------------------------------------------------
meillo@125 66 .H1 "Streamlining
meillo@58 67
meillo@0 68 .P
meillo@217 69 MH once provided a complete email system.
meillo@217 70 The community around nmh tries to keep nmh in similar shape.
meillo@178 71 In fundamental contrast, mmh shall be an MUA only.
meillo@87 72 I believe that the development of all-in-one mail systems is obsolete.
meillo@173 73 Today, email is too complex to be fully covered by a single project.
meillo@173 74 Such a project will not be able to excel in all aspects.
meillo@159 75 Instead, the aspects of email should be covered by multiple projects,
meillo@87 76 which then can be combined to form a complete system.
meillo@169 77 Excellent implementations for the various aspects of email already exist.
meillo@217 78 Just to name three examples: Postfix
meillo@217 79 .[
meillo@217 80 postfix website
meillo@217 81 .]
meillo@217 82 is a specialized MTA, Procmail
meillo@217 83 .[
meillo@217 84 procmail website
meillo@217 85 .]
meillo@217 86 is a specialized MDA, and Fetchmail
meillo@217 87 .[
meillo@217 88 fetchmail website
meillo@217 89 .]
meillo@217 90 is a specialized MRA.
meillo@89 91 I believe that it is best to use such specialized tools instead of
meillo@217 92 providing the same function once more as a side component.
meillo@58 93 .P
meillo@169 94 Doing something well requires focusing on a small set of specific aspects.
meillo@217 95 Under the assumption that development which is focussed on a particular
meillo@217 96 area produces better results there, specialized projects will be superior
meillo@87 97 in their field of focus.
meillo@87 98 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87 99 or modular \(en will never be the best choice in any of the fields.
meillo@217 100 Even in providing the most consistent all-in-one system, they are likely
meillo@217 101 to be beaten by projects that focus exclusively on the creation
meillo@217 102 of a homogeneous system by integrating existing mail components.
meillo@87 103 .P
meillo@217 104 Usually, the limiting resource in the community development of
meillo@217 105 free software is man power.
meillo@171 106 .\" XXX FIXME ref!
meillo@217 107 If the development effort is spread over a large development area,
meillo@217 108 it becomes more difficult to compete with the specialists in the
meillo@87 109 various fields.
meillo@87 110 The concrete situation for MH-based mail systems is even tougher,
meillo@169 111 given their small and aged community, concerning both developers and users.
meillo@87 112 .P
meillo@87 113 In consequence, I believe that the available development resources
meillo@100 114 should focus on the point where MH is most unique.
meillo@87 115 This is clearly the user interface \(en the MUA.
meillo@125 116 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60 117
meillo@60 118
meillo@100 119 .H2 "Mail Transfer Facilities
meillo@154 120 .Id mail-transfer-facilities
meillo@60 121 .P
meillo@217 122 The removal of the mail transfer facilities, effectively dropping the
meillo@217 123 MSA and MRA, had been the first work task in the mmh project.
meillo@217 124 The desire for this change initiated the creation of the mmh project.
meillo@60 125 .P
meillo@169 126 Focusing on one mail agent role only, is motivated by Eric Allman's
meillo@105 127 experience with Sendmail.
meillo@217 128 He identified the limitation of Sendmail
meillo@217 129 .[
meillo@217 130 sendmail website
meillo@217 131 .]
meillo@217 132 to the MTA task as one reason for its success:
meillo@105 133 .[ [
meillo@105 134 costales sendmail
meillo@105 135 .], p. xviii]
meillo@105 136 .QS
meillo@105 137 Second, I limited myself to the routing function \(en
meillo@110 138 I wouldn't write user agents or delivery back-ends.
meillo@217 139 This was a departure of the dominant thought of the time,
meillo@105 140 in which routing logic, local delivery, and often the network code
meillo@105 141 were incorporated directly into the user agents.
meillo@105 142 .QE
meillo@105 143 .P
meillo@187 144 In nmh, the MSA is called \fIMessage Transfer Service\fP (MTS).
meillo@105 145 This facility, implemented by the
meillo@105 146 .Pn post
meillo@217 147 command, establishes network connections and spoke SMTP to submit
meillo@159 148 messages to be relayed to the outside world.
meillo@217 149 When email transfer changed, this part needed to be changed as well.
meillo@89 150 Encryption and authentication for network connections
meillo@87 151 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@217 152 This added complexity without improving the core functions.
meillo@217 153 Furthermore, keeping up with recent developments in the field of
meillo@87 154 mail transfer requires development power and specialists.
meillo@217 155 In mmh, this whole facility was simply cut off
meillo@76 156 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76 157 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@217 158 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b .
meillo@87 159 Instead, mmh depends on an external MSA.
meillo@217 160 All outgoing mail in mmh goes through the
meillo@60 161 .Pn sendmail
meillo@87 162 command, which almost any MSA provides.
meillo@87 163 If not, a wrapper program can be written.
meillo@87 164 It must read the message from the standard input, extract the
meillo@87 165 recipient addresses from the message header, and hand the message
meillo@87 166 over to the MSA.
meillo@217 167 For example, a wrapper script for qmail
meillo@217 168 .[
meillo@217 169 qmail website
meillo@217 170 .]
meillo@217 171 would be:
meillo@87 172 .VS
meillo@87 173 #!/bin/sh
meillo@138 174 exec qmail-inject # ignore command line arguments
meillo@87 175 VE
meillo@87 176 The requirement to parse the recipient addresses out of the message header
meillo@217 177 may be removed in the future.
meillo@217 178 Mmh could pass the recipient addresses as command line arguments.
meillo@100 179 This appears to be the better interface.
meillo@60 180 .P
meillo@60 181 To retrieve mail, the
meillo@60 182 .Pn inc
meillo@217 183 command in nmh acts as MRA.
meillo@217 184 It establishes network connections
meillo@217 185 and speaks POP3 to retrieve mail from remote servers.
meillo@76 186 As with mail submission, the network connections required encryption and
meillo@217 187 authentication, thus TLS and SASL were added to nmh.
meillo@169 188 Support for message retrieval through IMAP will soon become necessary
meillo@169 189 additions, too, and likewise for any other changes in mail transfer.
meillo@217 190 But not in mmh because it has dropped the support for retrieving mail
meillo@217 191 from remote locations
meillo@217 192 .Ci ab7b48411962d26439f92f35ed084d3d6275459c .
meillo@76 193 Instead, it depends on an external tool to cover this task.
meillo@169 194 Mmh has two paths for messages to enter mmh's mail storage:
meillo@100 195 (1) Mail can be incorporated with
meillo@60 196 .Pn inc
meillo@87 197 from the system maildrop, or (2) with
meillo@60 198 .Pn rcvstore
meillo@87 199 by reading them, one at a time, from the standard input.
meillo@60 200 .P
meillo@217 201 With the removal of the MSA and MRA, mmh converted from a complete
meillo@217 202 mail system to only an MUA.
meillo@60 203 Now, of course, mmh depends on third-party software.
meillo@87 204 An external MSA is required to transfer mail to the outside world;
meillo@60 205 an external MRA is required to retrieve mail from remote machines.
meillo@217 206 Excellent implementations of such software exist.
meillo@217 207 They likely are superior to the internal versions that were removed.
meillo@217 208 Additionally, the best suiting programs can be chosen freely.
meillo@60 209 .P
meillo@217 210 As it had already been possible to use an external MSA and MRA,
meillo@217 211 why should the internal version not be kept for convenience?
meillo@217 212 .\" XXX commas correct?
meillo@217 213 Transfered to a different area,
meillo@217 214 the question whether there is sense in having a fall-back pager in all
meillo@76 215 the command line tools, for the cases when
meillo@60 216 .Pn more
meillo@60 217 or
meillo@60 218 .Pn less
meillo@173 219 are not available, appears to be ridiculous.
meillo@100 220 Of course, MSAs and MRAs are more complex than text pagers
meillo@87 221 and not necessarily available but still the concept of orthogonal
meillo@217 222 design holds: ``Write programs that do one thing and do it well''.
meillo@87 223 .[
meillo@87 224 mcilroy unix phil
meillo@87 225 p. 53
meillo@87 226 .]
meillo@87 227 .[
meillo@87 228 mcilroy bstj foreword
meillo@87 229 .]
meillo@87 230 Here, this part of the Unix philosophy was applied not only
meillo@87 231 to the programs but to the project itself.
meillo@87 232 In other words:
meillo@164 233 Develop projects that focus on one thing and do it well.
meillo@169 234 Projects which have grown complex should be split, for the same
meillo@169 235 reasons that programs which have grown complex should be split.
meillo@100 236 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87 237 separate projects then they should be separated.
meillo@217 238 In my opinion, this is the case.
meillo@217 239 The RFCs suggest this separation by clearly distinguishing the
meillo@217 240 different mail handling tasks [RFC\|821].
meillo@217 241 The small interfaces between the mail agents support the
meillo@217 242 separation as well.
meillo@76 243 .P
meillo@217 244 Once, email had been small and simple.
meillo@100 245 At that time,
meillo@60 246 .Pn /bin/mail
meillo@169 247 had covered everything there was to email and still was small and simple.
meillo@100 248 Later, the essential complexity of email increased.
meillo@217 249 (Essential complexity is the complexity defined by the problem itself.\&
meillo@217 250 .[ [
meillo@87 251 brooks no silver bullet
meillo@87 252 .]])
meillo@217 253 Consequently, email systems grew.
meillo@100 254 RFCs started to introduce the concept of mail agents to separate the
meillo@217 255 various roles because they became more extensive and because
meillo@217 256 new roles appeared.
meillo@217 257 As mail system implementations grew, parts of them were split off.
meillo@169 258 For instance, a POP server was included in the original MH;
meillo@169 259 it was removed in nmh.
meillo@217 260 Now is the time to go one step further and split off the MSA and MRA,
meillo@217 261 as well.
meillo@87 262 Not only does this decrease the code size of the project,
meillo@169 263 more importantly, it unburdens mmh of the whole field of
meillo@217 264 message transfer, with all its implications for the project.
meillo@169 265 There is no more need for concern with changes in network transfer.
meillo@217 266 This independence is gained by depending on external components
meillo@217 267 that cover the field.
meillo@60 268 .P
meillo@217 269 In general, functionality can be added in three different ways:
meillo@171 270 .LI 1
meillo@217 271 By implementing the function in the project itself.
meillo@171 272 .LI 2
meillo@217 273 By depending on a library that provides the function.
meillo@171 274 .LI 3
meillo@217 275 By depending on a program that provides the function.
meillo@171 276 .LP
meillo@159 277 .\" XXX Rework sentence
meillo@169 278 While implementing the function in the project itself leads to the
meillo@169 279 largest increase in code size and requires the most maintenance
meillo@169 280 and development work,
meillo@217 281 it keeps the project's dependence on other software lowest.
meillo@169 282 Using libraries or external programs requires less maintenance work
meillo@217 283 but introduces dependencies on external projects.
meillo@169 284 Programs have the smallest interfaces and provide the best separation,
meillo@87 285 but possibly limit the information exchange.
meillo@169 286 External libraries are more strongly connected than external programs,
meillo@169 287 thus information can be exchanged in a more flexible manner.
meillo@87 288 Adding code to a project increases maintenance work.
meillo@87 289 .\" XXX ref
meillo@217 290 As implementing complex functions in the project itself adds
meillo@217 291 a lot of code, this should be avoided if possible.
meillo@217 292 Thus, the dependencies only change in their character,
meillo@169 293 not in their existence.
meillo@66 294 In mmh, library dependencies on
meillo@66 295 .Pn libsasl2
meillo@66 296 and
meillo@66 297 .Pn libcrypto /\c
meillo@66 298 .Pn libssl
meillo@159 299 were traded against program dependencies on an MSA and an MRA.
meillo@159 300 This also meant trading build-time dependencies against run-time
meillo@87 301 dependencies.
meillo@169 302 Besides providing stronger separation and greater flexibility,
meillo@169 303 program dependencies also allowed
meillo@66 304 over 6\|000 lines of code to be removed from mmh.
meillo@66 305 This made mmh's code base about 12\|% smaller.
meillo@87 306 Reducing the project's code size by such an amount without actually
meillo@87 307 losing functionality is a convincing argument.
meillo@87 308 Actually, as external MSAs and MRAs are likely superior to the
meillo@87 309 project's internal versions, the common user even gains functionality.
meillo@66 310 .P
meillo@169 311 Users of MH should not have problems setting up an external MSA and MRA.
meillo@60 312 Also, the popular MSAs and MRAs have large communities and a lot
meillo@169 313 of available documentation.
meillo@217 314
meillo@217 315 Choices for MSAs range from small forwarders such as
meillo@217 316 .[
meillo@217 317 ssmtp website
meillo@217 318 .]
meillo@217 319 and,
meillo@217 320 .[
meillo@217 321 nullmailer website
meillo@217 322 .]
meillo@217 323 over mid-size MTAs including
meillo@217 324 .[
meillo@217 325 masqmail website
meillo@217 326 .]
meillo@217 327 and,
meillo@217 328 .[
meillo@217 329 dma dragonfly mail agent website
meillo@217 330 .]
meillo@217 331 up to full-featured MTAs as for instance.
meillo@217 332 .[
meillo@217 333 postfix website
meillo@217 334 .]
meillo@217 335 MRAs are provided for example by
meillo@217 336 .[ [
meillo@217 337 fetchmail website
meillo@217 338 .]
meillo@217 339 .[
meillo@217 340 getmail website
meillo@217 341 .]
meillo@217 342 .[
meillo@217 343 mpop website
meillo@217 344 .]
meillo@217 345 .[
meillo@217 346 fdm website
meillo@217 347 .]].
meillo@60 348
meillo@60 349
meillo@100 350 .H2 "Non-MUA Tools
meillo@60 351 .P
meillo@217 352 One goal of mmh is to remove the tools that do not significantly
meillo@217 353 contribute to the MUA's job.
meillo@217 354 Loosely related and rarely used tools distract from a lean appearance,
meillo@217 355 and require maintenance work without adding much to the core task.
meillo@217 356 By removing these tools, mmh became more streamlined and focused.
meillo@62 357 .BU
meillo@58 358 .Pn conflict
meillo@87 359 was removed
meillo@76 360 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@217 361 because it is a mail system maintenance tool and not MUA-related.
meillo@87 362 It even checked
meillo@58 363 .Fn /etc/passwd
meillo@58 364 and
meillo@58 365 .Fn /etc/group
meillo@87 366 for consistency, which is completely unrelated to email.
meillo@87 367 A tool like
meillo@87 368 .Pn conflict
meillo@87 369 is surely useful, but it should not be shipped with mmh.
meillo@76 370 .\" XXX historic reasons?
meillo@62 371 .BU
meillo@58 372 .Pn rcvtty
meillo@87 373 was removed
meillo@87 374 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89 375 because its use case of writing to the user's terminal
meillo@200 376 on reception of mail is obsolete.
meillo@87 377 If users like to be informed of new mail, the shell's
meillo@58 378 .Ev MAILPATH
meillo@87 379 variable or graphical notifications are technically more appealing.
meillo@217 380 Writing to terminals directly is hardly ever desired today.
meillo@169 381 If, though, one prefers this approach, the standard tool
meillo@58 382 .Pn write
meillo@58 383 can be used in a way similar to:
meillo@82 384 .VS
meillo@58 385 scan -file - | write `id -un`
meillo@82 386 VE
meillo@62 387 .BU
meillo@58 388 .Pn viamail
meillo@159 389 .\" XXX was macht viamail
meillo@87 390 was removed
meillo@87 391 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87 392 when the new attachment system was activated, because
meillo@58 393 .Pn forw
meillo@76 394 could then cover the task itself.
meillo@62 395 The program
meillo@58 396 .Pn sendfiles
meillo@62 397 was rewritten as a shell script wrapper around
meillo@58 398 .Pn forw .
meillo@76 399 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62 400 .BU
meillo@58 401 .Pn msgchk
meillo@159 402 .\" XXX was macht msgchk
meillo@87 403 was removed
meillo@87 404 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87 405 because it lost its use case when POP support was removed.
meillo@76 406 A call to
meillo@58 407 .Pn msgchk
meillo@87 408 provided hardly more information than:
meillo@82 409 .VS
meillo@58 410 ls -l /var/mail/meillo
meillo@82 411 VE
meillo@217 412 Yet, it distinguished between old and new mail, but
meillo@169 413 these details can be retrieved with
meillo@76 414 .Pn stat (1),
meillo@62 415 too.
meillo@100 416 A small shell script could be written to print the information
meillo@76 417 in a similar way, if truly necessary.
meillo@76 418 As mmh's
meillo@76 419 .Pn inc
meillo@87 420 only incorporates mail from the user's local maildrop,
meillo@62 421 and thus no data transfers over slow networks are involved,
meillo@169 422 there is hardly any need to check for new mail before incorporating it.
meillo@62 423 .BU
meillo@58 424 .Pn msh
meillo@87 425 was removed
meillo@76 426 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87 427 because the tool was in conflict with the philosophy of MH.
meillo@217 428 It provided an interactive shell to access the features of MH.
meillo@217 429 However, it was not just a shell tailored to the needs of mail handling,
meillo@217 430 but one large program that had several MH tools built in.
meillo@217 431 This conflicted with the major feature of MH of being a tool chest.
meillo@76 432 .Pn msh 's
meillo@159 433 main use case had been accessing Bulletin Boards, which have ceased to
meillo@62 434 be popular.
meillo@62 435 .P
meillo@62 436 Removing
meillo@169 437 .Pn msh
meillo@212 438 together with the truly archaic code relics
meillo@58 439 .Pn vmh
meillo@58 440 and
meillo@169 441 .Pn wmh
meillo@62 442 saved more than 7\|000 lines of C code \(en
meillo@66 443 about 15\|% of the project's original source code amount.
meillo@100 444 Having less code \(en with equal readability, of course \(en
meillo@76 445 for the same functionality is an advantage.
meillo@63 446 Less code means less bugs and less maintenance work.
meillo@76 447 As
meillo@63 448 .Pn rcvtty
meillo@63 449 and
meillo@63 450 .Pn msgchk
meillo@87 451 are assumed to be rarely used and can be implemented in different ways,
meillo@87 452 why should one keep them?
meillo@217 453 Removing them streamlined mmh.
meillo@63 454 .Pn viamail 's
meillo@63 455 use case is now partly obsolete and partly covered by
meillo@63 456 .Pn forw ,
meillo@217 457 hence there is no reason to still maintain it.
meillo@63 458 .Pn conflict
meillo@76 459 is not related to the mail client, and
meillo@63 460 .Pn msh
meillo@63 461 conflicts with the basic concept of MH.
meillo@169 462 These two tools might still be useful, but they should not be part of mmh.
meillo@63 463 .P
meillo@220 464 .Id slocal
meillo@169 465 Finally, there is
meillo@217 466 .Pn slocal ,
meillo@217 467 which is an MDA and thus not directly MUA-related.
meillo@217 468 It should be removed from mmh because including it conflicts with
meillo@178 469 the idea that mmh is an MUA only.
meillo@87 470 However,
meillo@76 471 .Pn slocal
meillo@76 472 provides rule-based processing of messages, like filing them into
meillo@76 473 different folders, which is otherwise not available in mmh.
meillo@87 474 Although
meillo@76 475 .Pn slocal
meillo@169 476 neither pulls in dependencies, nor does it include a separate
meillo@154 477 technical area (cf. Sec.
meillo@154 478 .Cf mail-transfer-facilities ),
meillo@169 479 it still accounts for about 1\|000 lines of code that need to be maintained.
meillo@76 480 As
meillo@76 481 .Pn slocal
meillo@76 482 is almost self-standing, it should be split off into a separate project.
meillo@76 483 This would cut the strong connection between the MUA mmh and the MDA
meillo@76 484 .Pn slocal .
meillo@87 485 For anyone not using MH,
meillo@87 486 .Pn slocal
meillo@87 487 would become yet another independent MDA, like
meillo@87 488 .I procmail .
meillo@100 489 Then
meillo@87 490 .Pn slocal
meillo@217 491 could be installed without a complete MH system.
meillo@76 492 Likewise, mmh users could decide to use
meillo@76 493 .I procmail
meillo@217 494 without having a second, unused MDA, i.e.
meillo@87 495 .Pn slocal ,
meillo@76 496 installed.
meillo@100 497 That appears to be conceptionally the best solution.
meillo@76 498 Yet,
meillo@76 499 .Pn slocal
meillo@87 500 is not split off.
meillo@100 501 I defer the decision over
meillo@78 502 .Pn slocal
meillo@169 503 out of a need for deeper investigation.
meillo@217 504 In the meanwhile, it remains part of mmh
meillo@217 505 as its continued existence is not significant;
meillo@100 506 .Pn slocal
meillo@100 507 is unrelated to the rest of the project.
meillo@0 508
meillo@58 509
meillo@133 510
meillo@134 511 .H2 "Displaying Messages
meillo@155 512 .Id mhshow
meillo@131 513 .P
meillo@133 514 Since the very beginning, already in the first concept paper,
meillo@159 515 .\" XXX ref!!!
meillo@58 516 .Pn show
meillo@62 517 had been MH's message display program.
meillo@58 518 .Pn show
meillo@76 519 mapped message numbers and sequences to files and invoked
meillo@58 520 .Pn mhl
meillo@89 521 to have the files formatted.
meillo@173 522 With MIME, this approach was not sufficient anymore.
meillo@217 523 MIME messages can consist of multiple parts.
meillo@217 524 Some parts, like binary attachments or text content in foreign charsets,
meillo@217 525 are not directly displayable.
meillo@58 526 .Pn show 's
meillo@76 527 understanding of messages and
meillo@58 528 .Pn mhl 's
meillo@173 529 display capabilities could not cope with the task any longer.
meillo@62 530 .P
meillo@88 531 Instead of extending these tools, additional tools were written from
meillo@217 532 scratch and were added to the MH tool chest.
meillo@88 533 Doing so is encouraged by the tool chest approach.
meillo@88 534 Modular design is a great advantage for extending a system,
meillo@88 535 as new tools can be added without interfering with existing ones.
meillo@62 536 First, the new MIME features were added in form of the single program
meillo@58 537 .Pn mhn .
meillo@58 538 The command
meillo@82 539 .Cl "mhn -show 42
meillo@217 540 had then shown the message number
meillo@217 541 .Fn 42 ,
meillo@217 542 interpreting MIME.
meillo@58 543 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58 544 the split of
meillo@58 545 .Pn mhn
meillo@88 546 into a set of specialized tools, which together covered the
meillo@88 547 multiple aspects of MIME.
meillo@88 548 One of them was
meillo@69 549 .Pn mhshow ,
meillo@88 550 which replaced
meillo@88 551 .Cl "mhn -show" .
meillo@88 552 It was capable of displaying MIME messages appropriately.
meillo@62 553 .P
meillo@88 554 From then on, two message display tools were part of nmh,
meillo@76 555 .Pn show
meillo@76 556 and
meillo@76 557 .Pn mhshow .
meillo@88 558 To ease the life of users,
meillo@69 559 .Pn show
meillo@69 560 was extended to automatically hand the job over to
meillo@69 561 .Pn mhshow
meillo@69 562 if displaying the message would be beyond
meillo@69 563 .Pn show 's
meillo@69 564 abilities.
meillo@88 565 In consequence, the user would simply invoke
meillo@69 566 .Pn show
meillo@69 567 (possibly through
meillo@69 568 .Pn next
meillo@69 569 or
meillo@69 570 .Pn prev )
meillo@69 571 and get the message printed with either
meillo@69 572 .Pn show
meillo@69 573 or
meillo@69 574 .Pn mhshow ,
meillo@69 575 whatever was more appropriate.
meillo@69 576 .P
meillo@217 577 Having two similar tools for basically the same task is redundancy.
meillo@217 578 Usually, users do not distinguish between
meillo@88 579 .Pn show
meillo@88 580 and
meillo@88 581 .Pn mhshow
meillo@88 582 in their daily mail reading.
meillo@217 583 Having two separate display programs was therefore unnecessary
meillo@88 584 from a user's point of view.
meillo@88 585 Besides, the development of both programs needed to be in sync,
meillo@76 586 to ensure that the programs behaved in a similar way,
meillo@76 587 because they were used like a single tool.
meillo@76 588 Different behavior would have surprised the user.
meillo@69 589 .P
meillo@69 590 Today, non-MIME messages are rather seen to be a special case of
meillo@100 591 MIME messages, although it is the other way round.
meillo@69 592 As
meillo@69 593 .Pn mhshow
meillo@217 594 already had been able to display non-MIME messages, it appeared natural
meillo@69 595 to drop
meillo@69 596 .Pn show
meillo@69 597 in favor of using
meillo@69 598 .Pn mhshow
meillo@217 599 exclusively
meillo@217 600 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853 .
meillo@88 601 Removing
meillo@88 602 .Pn show
meillo@217 603 is no loss in function, because
meillo@88 604 .Pn mhshow
meillo@88 605 covers it completely.
meillo@217 606 Yet, the old behavior of
meillo@88 607 .Pn show
meillo@88 608 can still be emulated with the simple command line:
meillo@88 609 .VS
meillo@88 610 mhl `mhpath c`
meillo@88 611 VE
meillo@88 612 .P
meillo@76 613 For convenience,
meillo@76 614 .Pn mhshow
meillo@88 615 was renamed to
meillo@88 616 .Pn show
meillo@88 617 after
meillo@88 618 .Pn show
meillo@88 619 was gone.
meillo@88 620 It is clear that such a rename may confuse future developers when
meillo@88 621 trying to understand the history.
meillo@88 622 Nevertheless, I consider the convenience on the user's side,
meillo@217 623 to outweigh the inconvenience for understanding the evolution
meillo@217 624 of the tools.
meillo@69 625 .P
meillo@88 626 To prepare for the transition,
meillo@69 627 .Pn mhshow
meillo@69 628 was reworked to behave more like
meillo@69 629 .Pn show
meillo@217 630 first (cf. Sec.
meillo@217 631 .Cf mhshow ).
meillo@164 632 .\" XXX code commits?
meillo@88 633 Once the tools behaved more alike, the replacing appeared to be
meillo@88 634 even more natural.
meillo@88 635 Today, mmh's new
meillo@69 636 .Pn show
meillo@217 637 has become the one single message display program once again,
meillo@159 638 with the difference
meillo@88 639 that today it handles MIME messages as well as non-MIME messages.
meillo@217 640 The outcomes of the transition are one program less to maintain,
meillo@88 641 no second display program for users to deal with,
meillo@88 642 and less system complexity.
meillo@69 643 .P
meillo@88 644 Still, removing the old
meillo@69 645 .Pn show
meillo@88 646 hurts in one regard: It had been such a simple program.
meillo@159 647 Its lean elegance is missing from the new
meillo@159 648 .Pn show ,
meillo@159 649 .\" XXX
meillo@159 650 however there is no alternative;
meillo@159 651 supporting MIME demands higher essential complexity.
meillo@58 652
meillo@134 653 .ig
meillo@134 654 XXX
meillo@134 655 Consider including text on scan listings here
meillo@58 656
meillo@134 657 Scan listings shall not contain body content. Hence, removed this feature.
meillo@134 658 Scan listings shall operator on message headers and non-message information
meillo@134 659 only. Displaying the beginning of the body complicates everything too much.
meillo@134 660 That's no surprise, because it's something completely different. If you
meillo@134 661 want to examine the body, then use show(1)/mhshow(1).
meillo@134 662 Changed the default scan formats accordingly.
meillo@134 663 .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134 664 ..
meillo@131 665
meillo@131 666
meillo@131 667
meillo@133 668
meillo@100 669 .H2 "Configure Options
meillo@58 670 .P
meillo@76 671 Customization is a double-edged sword.
meillo@76 672 It allows better suiting setups, but not for free.
meillo@76 673 There is the cost of code complexity to be able to customize.
meillo@76 674 There is the cost of less tested setups, because there are
meillo@171 675 more possible setups and especially corner cases.
meillo@159 676 Additionally, there is the cost of choice itself.
meillo@76 677 The code complexity directly affects the developers.
meillo@173 678 Less tested code affects both users and developers.
meillo@217 679 The problem of choice affects the users, for once by having to choose
meillo@159 680 but also by more complex interfaces that require more documentation.
meillo@159 681 Whenever options add few advantages but increase the complexity of the
meillo@159 682 system, they should be considered for removal.
meillo@72 683 I have reduced the number of project-specific configure options from
meillo@217 684 15 to 3.
meillo@74 685
meillo@76 686 .U3 "Mail Transfer Facilities
meillo@74 687 .P
meillo@217 688 With the removal of the mail transfer facilities 5 configure
meillo@85 689 options vanished:
meillo@85 690 .P
meillo@85 691 The switches
meillo@85 692 .Sw --with-tls
meillo@85 693 and
meillo@85 694 .Sw --with-cyrus-sasl
meillo@89 695 had activated the support for transfer encryption and authentication.
meillo@159 696 .\" XXX cf
meillo@159 697 .\" XXX gruende kurz wiederholen
meillo@217 698 They are not needed anymore.
meillo@85 699 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85 700 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85 701 .P
meillo@159 702 .\" XXX cf
meillo@159 703 .\" XXX ``For the same reason ...''
meillo@85 704 The configure switch
meillo@85 705 .Sw --enable-pop
meillo@85 706 activated the message retrieval facility.
meillo@217 707 Whereas the code area that had been conditionally compiled in
meillo@217 708 for TLS and SASL support was small,
meillo@217 709 the conditionally compiled code area for POP support was much larger.
meillo@217 710 The code base had only changed slightly on toggling TLS or SASL
meillo@217 711 support but it had changed much on toggling POP support.
meillo@85 712 The changes in the code base could hardly be overviewed.
meillo@159 713 By having POP support togglable, a second code base had been created,
meillo@85 714 one that needed to be tested.
meillo@85 715 This situation is basically similar for the conditional TLS and SASL
meillo@85 716 code, but there the changes are minor and can yet be overviewed.
meillo@85 717 Still, conditional compilation of a code base creates variations
meillo@85 718 of the original program.
meillo@85 719 More variations require more testing and maintenance work.
meillo@85 720 .P
meillo@85 721 Two other options only specified default configuration values:
meillo@100 722 .Sw --with-mts
meillo@217 723 defined the default transport service
meillo@217 724 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226 .
meillo@85 725 With
meillo@100 726 .Sw --with-smtpservers
meillo@217 727 default SMTP servers could be specified
meillo@217 728 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9 .
meillo@164 729 Both of them became irrelevant when the SMTP transport service was removed.
meillo@164 730 .\" XXX code ref
meillo@164 731 In mmh, all messages are handed over to
meillo@164 732 .Pn sendmail
meillo@164 733 for transportation.
meillo@164 734
meillo@72 735
meillo@74 736 .U3 "Backup Prefix
meillo@74 737 .P
meillo@76 738 The backup prefix is the string that was prepended to message
meillo@76 739 filenames to tag them as deleted.
meillo@173 740 By default it had been the comma character (`\fL,\fP').
meillo@159 741 .\" XXX Zeitlich ordnen
meillo@78 742 In July 2000, Kimmo Suominen introduced
meillo@78 743 the configure option
meillo@78 744 .Sw --with-hash-backup
meillo@173 745 to change the default to the hash character `\f(CW#\fP'.
meillo@217 746 This choice was probably personal preference, but,
meillo@217 747 being related or not, words that start with the hash character
meillo@78 748 introduce a comment in the Unix shell.
meillo@72 749 Thus, the command line
meillo@72 750 .Cl "rm #13 #15
meillo@72 751 calls
meillo@72 752 .Pn rm
meillo@217 753 without arguments because the first hash character starts a comment
meillo@72 754 that reaches until the end of the line.
meillo@72 755 To delete the backup files,
meillo@72 756 .Cl "rm ./#13 ./#15"
meillo@72 757 needs to be used.
meillo@217 758 Thus, using the hash as backup prefix may be seen as a precaution
meillo@217 759 against backup loss.
meillo@78 760 .P
meillo@159 761 First, I removed the configure option but added the profile entry
meillo@217 762 .Pe Backup-Prefix ,
meillo@217 763 which allowed to specify an arbitrary string as backup prefix
meillo@217 764 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086 .
meillo@76 765 This change did not remove the choice but moved it to a location where
meillo@217 766 it suited better, in my eyes.
meillo@76 767 .P
meillo@217 768 Eventually however, the new trash folder concept
meillo@154 769 (cf. Sec.
meillo@154 770 .Cf trash-folder )
meillo@164 771 removed the need for the backup prefix completely.
meillo@78 772 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133 773 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133 774
meillo@76 775
meillo@76 776 .U3 "Editor and Pager
meillo@74 777 .P
meillo@74 778 The two configure options
meillo@74 779 .CW --with-editor=EDITOR
meillo@74 780 .CW --with-pager=PAGER
meillo@74 781 were used to specify the default editor and pager at configure time.
meillo@109 782 Doing so at configure time made sense in the eighties,
meillo@76 783 when the set of available editors and pagers varied much across
meillo@76 784 different systems.
meillo@89 785 Today, the situation is more homogeneous.
meillo@74 786 The programs
meillo@74 787 .Pn vi
meillo@74 788 and
meillo@74 789 .Pn more
meillo@76 790 can be expected to be available on every Unix system,
meillo@74 791 as they are specified by POSIX since two decades.
meillo@74 792 (The specifications for
meillo@74 793 .Pn vi
meillo@74 794 and
meillo@74 795 .Pn more
meillo@74 796 appeared in
meillo@74 797 .[
meillo@74 798 posix 1987
meillo@74 799 .]
meillo@74 800 and,
meillo@74 801 .[
meillo@74 802 posix 1992
meillo@74 803 .]
meillo@74 804 respectively.)
meillo@217 805 As a first step, these two tools were hard-coded as defaults
meillo@217 806 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f .
meillo@74 807 Not changed were the
meillo@74 808 .Pe editor
meillo@74 809 and
meillo@74 810 .Pe moreproc
meillo@76 811 profile entries, which allowed the user to override the system defaults.
meillo@217 812 Later, the concept was reworked again to respect the standard
meillo@217 813 environment variables
meillo@74 814 .Ev VISUAL
meillo@74 815 and
meillo@74 816 .Ev PAGER
meillo@76 817 if they are set.
meillo@74 818 Today, mmh determines the editor to use in the following order,
meillo@217 819 taking the first available and non-empty item
meillo@217 820 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b :
meillo@171 821 .LI 1
meillo@74 822 Environment variable
meillo@74 823 .Ev MMHEDITOR
meillo@171 824 .LI 2
meillo@74 825 Profile entry
meillo@74 826 .Pe Editor
meillo@171 827 .LI 3
meillo@74 828 Environment variable
meillo@74 829 .Ev VISUAL
meillo@171 830 .LI 4
meillo@74 831 Environment variable
meillo@74 832 .Ev EDITOR
meillo@171 833 .LI 5
meillo@74 834 Command
meillo@74 835 .Pn vi .
meillo@171 836 .LP
meillo@217 837 The pager to use is determined in a similar order
meillo@217 838 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e :
meillo@171 839 .LI 1
meillo@74 840 Environment variable
meillo@74 841 .Ev MMHPAGER
meillo@171 842 .LI 2
meillo@74 843 Profile entry
meillo@74 844 .Pe Pager
meillo@74 845 (replaces
meillo@74 846 .Pe moreproc )
meillo@171 847 .LI 3
meillo@74 848 Environment variable
meillo@74 849 .Ev PAGER
meillo@171 850 .LI 4
meillo@74 851 Command
meillo@74 852 .Pn more .
meillo@171 853 .LP
meillo@76 854 By respecting the
meillo@74 855 .Ev VISUAL /\c
meillo@74 856 .Ev EDITOR
meillo@74 857 and
meillo@74 858 .Ev PAGER
meillo@76 859 environment variables,
meillo@217 860 the new behavior complies with the common style on Unix systems.
meillo@217 861 It is more uniform and clearer for users.
meillo@72 862
meillo@72 863
meillo@76 864 .U3 "ndbm
meillo@72 865 .P
meillo@74 866 .Pn slocal
meillo@217 867 used to depend on the database library
meillo@217 868 .I ndbm .
meillo@217 869 The database is used to store the
meillo@217 870 .Hd Message-ID
meillo@217 871 header field values of all messages delivered.
meillo@217 872 This enabled
meillo@74 873 .Pn slocal
meillo@74 874 to suppress delivering the same message to the same user twice.
meillo@217 875 This features was enabled by the
meillo@74 876 .Sw -suppressdup
meillo@217 877 switch.
meillo@74 878 .P
meillo@217 879 As a variety of versions of the database library exist,
meillo@78 880 .[
meillo@78 881 wolter unix incompat notes dbm
meillo@78 882 .]
meillo@217 883 complicated autoconf code was needed to detect them correctly.
meillo@181 884 Furthermore, the configure switches
meillo@74 885 .Sw --with-ndbm=ARG
meillo@74 886 and
meillo@74 887 .Sw --with-ndbmheader=ARG
meillo@74 888 were added to help with difficult setups that would
meillo@217 889 not be detected automatically or not correctly.
meillo@74 890 .P
meillo@74 891 By removing the suppress duplicates feature of
meillo@74 892 .Pn slocal ,
meillo@74 893 the dependency on
meillo@74 894 .I ndbm
meillo@217 895 vanished and 120 lines of complex autoconf code could be saved
meillo@217 896 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf .
meillo@217 897 The change removed functionality but that is considered minor to the
meillo@217 898 improvement of dropping the dependency and the complex autoconf code.
meillo@159 899 .\" XXX argument: slocal ist sowieso nicht teil vom mmh kern
meillo@72 900
meillo@217 901 .U3 "MH-E Support
meillo@72 902 .P
meillo@74 903 The configure option
meillo@74 904 .Sw --disable-mhe
meillo@217 905 was removed when the MH-E support was reworked.
meillo@217 906 MH-E is the Emacs front-end to MH.
meillo@217 907 .[
meillo@217 908 mh-e emacs website
meillo@217 909 .]
meillo@76 910 It requires MH to provide minor additional functions.
meillo@76 911 The
meillo@76 912 .Sw --disable-mhe
meillo@217 913 configure option had switched off these extensions.
meillo@217 914 After removing the support for old versions of MH-E,
meillo@74 915 only the
meillo@74 916 .Sw -build
meillo@76 917 switches of
meillo@74 918 .Pn forw
meillo@74 919 and
meillo@74 920 .Pn repl
meillo@217 921 are left to be MH-E extensions.
meillo@76 922 They are now always built in because they add little code and complexity.
meillo@76 923 In consequence, the
meillo@74 924 .Sw --disable-mhe
meillo@76 925 configure option was removed
meillo@217 926 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643 .
meillo@217 927 Dropping the option also removed a variant of the code base
meillo@217 928 that would have needed to be tested.
meillo@217 929 This change was undertaken in January 2012 in nmh and
meillo@217 930 thereafter merged into mmh.
meillo@217 931
meillo@72 932
meillo@74 933 .U3 "Masquerading
meillo@72 934 .P
meillo@74 935 The configure option
meillo@74 936 .Sw --enable-masquerade
meillo@76 937 could take up to three arguments:
meillo@217 938 .Ar draft_from ,
meillo@217 939 .Ar mmailid ,
meillo@217 940 and
meillo@217 941 .Ar username_extension .
meillo@74 942 They activated different types of address masquerading.
meillo@74 943 All of them were implemented in the SMTP-speaking
meillo@74 944 .Pn post
meillo@217 945 command.
meillo@76 946 Address masquerading is an MTA's task and mmh does not cover
meillo@76 947 this field anymore.
meillo@76 948 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74 949 .P
meillo@74 950 The
meillo@74 951 .I mmailid
meillo@74 952 masquerading type is the oldest one of the three and the only one
meillo@74 953 available in the original MH.
meillo@74 954 It provided a
meillo@74 955 .I username
meillo@74 956 to
meillo@74 957 .I fakeusername
meillo@217 958 mapping, based on the
meillo@217 959 .Fn passwd 's
meillo@217 960 GECOS field.
meillo@217 961 Nmh's man page
meillo@181 962 .Mp mh-tailor (5)
meillo@74 963 described the use case as being the following:
meillo@98 964 .QS
meillo@74 965 This is useful if you want the messages you send to always
meillo@74 966 appear to come from the name of an MTA alias rather than your
meillo@74 967 actual account name. For instance, many organizations set up
meillo@74 968 `First.Last' sendmail aliases for all users. If this is
meillo@74 969 the case, the GECOS field for each user should look like:
meillo@74 970 ``First [Middle] Last <First.Last>''
meillo@98 971 .QE
meillo@74 972 .P
meillo@74 973 As mmh sends outgoing mail via the local MTA only,
meillo@76 974 the best location to do such global rewrites is there.
meillo@74 975 Besides, the MTA is conceptionally the right location because it
meillo@74 976 does the reverse mapping for incoming mail (aliasing), too.
meillo@181 977 Furthermore, masquerading set up there is readily available for all
meillo@74 978 mail software on the system.
meillo@76 979 Hence, mmailid masquerading was removed.
meillo@74 980 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74 981 .P
meillo@74 982 The
meillo@74 983 .I username_extension
meillo@76 984 masquerading type did not replace the username but would append a suffix,
meillo@76 985 specified by the
meillo@74 986 .Ev USERNAME_EXTENSION
meillo@76 987 environment variable, to it.
meillo@76 988 This provided support for the
meillo@74 989 .I user-extension
meillo@217 990 feature of qmail
meillo@217 991 .[ [
meillo@217 992 sill qmail handbook
meillo@217 993 .], p. 141]
meillo@217 994 and the similar
meillo@74 995 .I "plussed user
meillo@217 996 processing of Sendmail.
meillo@217 997 .[ [
meillo@217 998 sendmail costales
meillo@217 999 .], p. 476]
meillo@217 1000 The decision to remove this username_extension masquerading
meillo@217 1001 was motivated by the fact that
meillo@74 1002 .Pn spost
meillo@217 1003 had not supported it yet.
meillo@217 1004 Username extensions can be used in mmh, but less convenient.
meillo@159 1005 .\" XXX covered by next paragraph
meillo@76 1006 .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@217 1007 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@74 1008 .P
meillo@74 1009 The
meillo@74 1010 .I draft_from
meillo@74 1011 masquerading type instructed
meillo@74 1012 .Pn post
meillo@84 1013 to use the value of the
meillo@84 1014 .Hd From
meillo@84 1015 header field as SMTP envelope sender.
meillo@76 1016 Sender addresses could be replaced completely.
meillo@76 1017 Mmh offers a kind of masquerading similar in effect, but
meillo@74 1018 with technical differences.
meillo@76 1019 As mmh does not transfer messages itself, the local MTA has final control
meillo@217 1020 over the sender's address.
meillo@217 1021 Any masquerading mmh introduces may be reverted by the MTA.
meillo@76 1022 In times of pedantic spam checking, an MTA will take care to use
meillo@76 1023 sensible envelope sender addresses to keep its own reputation up.
meillo@84 1024 Nonetheless, the MUA can set the
meillo@84 1025 .Hd From
meillo@217 1026 header field and thereby propose a sender address to the MTA.
meillo@74 1027 The MTA may then decide to take that one or generate the canonical sender
meillo@74 1028 address for use as envelope sender address.
meillo@217 1029 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@74 1030 .P
meillo@74 1031 In mmh, the MTA will always extract the recipient and sender from the
meillo@84 1032 message header (\c
meillo@74 1033 .Pn sendmail 's
meillo@74 1034 .Sw -t
meillo@74 1035 switch).
meillo@84 1036 The
meillo@84 1037 .Hd From
meillo@84 1038 header field of the draft may be set arbitrary by the user.
meillo@74 1039 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74 1040
meillo@74 1041 .U3 "Remaining Options
meillo@74 1042 .P
meillo@74 1043 Two configure options remain in mmh.
meillo@74 1044 One is the locking method to use:
meillo@74 1045 .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@217 1046 The idea of removing all methods except the portable
meillo@217 1047 .I "dot locking
meillo@76 1048 and having that one as the default is appealing, but this change
meillo@76 1049 requires deeper technical investigation into the topic.
meillo@76 1050 The other option,
meillo@74 1051 .Sw --enable-debug ,
meillo@217 1052 compiles the programs with debugging symbols.
meillo@74 1053 This option is likely to stay.
meillo@72 1054
meillo@72 1055
meillo@58 1056
meillo@63 1057
meillo@100 1058 .H2 "Command Line Switches
meillo@58 1059 .P
meillo@217 1060 The command line switches of MH tools follow a style similar to
meillo@217 1061 the X Window System style.
meillo@171 1062 .\" XXX ref
meillo@217 1063 The switches consist of a single dash (`\fL-\fP') followed by a word.
meillo@217 1064 For example
meillo@217 1065 .Cl -truncate .
meillo@212 1066 To ease typing, the word can be abbreviated, given the remaining
meillo@217 1067 prefix is unambiguous.
meillo@212 1068 If no other switch starts with the letter `t', then any of
meillo@212 1069 .Cl "-truncate" ,
meillo@212 1070 .Cl "-trunc" ,
meillo@212 1071 .Cl "-tr" ,
meillo@212 1072 and
meillo@212 1073 .Cl "-t
meillo@212 1074 is equal.
meillo@212 1075 As a result, switches can neither be grouped (as in
meillo@212 1076 .Cl "ls -ltr" )
meillo@212 1077 nor can switch arguments be appended directly to the switch (as in
meillo@212 1078 .Cl "sendmail -q30m" ).
meillo@212 1079 Many switches have negating counter-parts, which start with `no'.
meillo@212 1080 For example
meillo@212 1081 .Cl "-notruncate
meillo@212 1082 inverts the
meillo@212 1083 .Cl "-truncate
meillo@212 1084 switch.
meillo@212 1085 They exist to override the effect of default switches in the profile.
meillo@93 1086 Every program in mmh has two generic switches:
meillo@93 1087 .Sw -help ,
meillo@93 1088 to print a short message on how to use the program, and
meillo@159 1089 .Sw -Version
meillo@164 1090 (with capital `V'), to tell what version of mmh the program belongs to.
meillo@93 1091 .P
meillo@93 1092 Switches change the behavior of programs.
meillo@93 1093 Programs that do one thing in one way require no switches.
meillo@93 1094 In most cases, doing something in exactly one way is too limiting.
meillo@217 1095 If one task should be accomplished in various ways,
meillo@217 1096 switches are a good approach to alter the behavior of a program.
meillo@93 1097 Changing the behavior of programs provides flexibility and customization
meillo@217 1098 to users, but at the same time it complicates the code,
meillo@217 1099 the documentation, and the usage of the program.
meillo@97 1100 .\" XXX: Ref
meillo@93 1101 Therefore, the number of switches should be kept small.
meillo@217 1102 A small set of well-chosen switches is best.
meillo@217 1103 Usually, the number of switches increases over time.
meillo@93 1104 Already in 1985, Rose and Romine have identified this as a major
meillo@93 1105 problem of MH:
meillo@93 1106 .[ [
meillo@93 1107 rose romine real work
meillo@93 1108 .], p. 12]
meillo@98 1109 .QS
meillo@93 1110 A complaint often heard about systems which undergo substantial development
meillo@93 1111 by many people over a number of years, is that more and more options are
meillo@93 1112 introduced which add little to the functionality but greatly increase the
meillo@93 1113 amount of information a user needs to know in order to get useful work done.
meillo@93 1114 This is usually referred to as creeping featurism.
meillo@93 1115 .QP
meillo@93 1116 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93 1117 ten or so well-meaning programmers (the present authors included),
meillo@93 1118 suffers mightily from this.
meillo@98 1119 .QE
meillo@93 1120 .P
meillo@217 1121 Being reluctant to adding new switches (or \fIoptions\fP,
meillo@217 1122 as Rose and Romine call them) is one part of a counter-action,
meillo@97 1123 the other part is removing hardly used switches.
meillo@217 1124 Nmh's tools have lots of switches already implemented.
meillo@217 1125 Hence, cleaning up by removing some of them was the more important part
meillo@97 1126 of the counter-action.
meillo@93 1127 Removing existing functionality is always difficult because it
meillo@93 1128 breaks programs that use these functions.
meillo@93 1129 Also, for every obsolete feature, there'll always be someone who still
meillo@93 1130 uses it and thus opposes its removal.
meillo@93 1131 This puts the developer into the position,
meillo@93 1132 where sensible improvements to style are regarded as destructive acts.
meillo@97 1133 Yet, living with the featurism is far worse, in my eyes, because
meillo@97 1134 future needs will demand adding further features,
meillo@93 1135 worsening the situation more and more.
meillo@93 1136 Rose and Romine added in a footnote,
meillo@93 1137 ``[...]
meillo@93 1138 .Pn send
meillo@217 1139 will no doubt acquire an endless number of switches in the years to come''
meillo@217 1140 .[ [
meillo@217 1141 rose romine real work
meillo@217 1142 .], p. 12].
meillo@97 1143 Although clearly humorous, the comment points to the nature of the problem.
meillo@97 1144 Refusing to add any new switches would encounter the problem at its root,
meillo@97 1145 but this is not practical.
meillo@97 1146 New needs will require new switches and it would be unwise to block
meillo@97 1147 them strictly.
meillo@97 1148 Nevertheless, removing obsolete switches still is an effective approach
meillo@97 1149 to deal with the problem.
meillo@97 1150 Working on an experimental branch without an established user base,
meillo@97 1151 eased my work because I did not offend users when I removed existing
meillo@110 1152 functions.
meillo@93 1153 .P
meillo@93 1154 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93 1155 .Pn send .
meillo@97 1156 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@182 1157 At the time of writing, no more than 4 visible switches and 1 hidden switch
meillo@97 1158 have remained in mmh's
meillo@97 1159 .Pn send .
meillo@217 1160 These numbers include the two generic switches,
meillo@182 1161 .Sw -help
meillo@182 1162 and
meillo@183 1163 .Sw -Version .
meillo@217 1164 .P
meillo@183 1165 Hidden switches are ones not documented.
meillo@183 1166 In mmh, 12 tools have hidden switches.
meillo@183 1167 9 of them are
meillo@183 1168 .Sw -debug
meillo@183 1169 switches, the other 6 provide special interfaces for internal use.
meillo@93 1170 .P
meillo@217 1171 The following figure displays the number of switches for each of the tools
meillo@159 1172 that is available in both nmh and mmh.
meillo@100 1173 The tools are sorted by the number of switches they had in nmh.
meillo@217 1174 Both visible and hidden switches were counted,
meillo@97 1175 but not the generic help and version switches.
meillo@93 1176 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93 1177 now it has no more than 5 \(en only half as many.
meillo@93 1178 If the `no' switches and similar inverse variant are folded onto
meillo@100 1179 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100 1180 has 4 now.
meillo@93 1181 The total number of functional switches in mmh dropped from 465
meillo@182 1182 to 233.
meillo@58 1183
meillo@93 1184 .KS
meillo@93 1185 .in 1c
meillo@93 1186 .so input/switches.grap
meillo@93 1187 .KE
meillo@58 1188
meillo@93 1189 .P
meillo@93 1190 A part of the switches vanished after functions were removed.
meillo@93 1191 This was the case for network mail transfer, for instance.
meillo@97 1192 Sometimes, however, the work flow was the other way:
meillo@97 1193 I looked through the
meillo@97 1194 .Mp mh-chart (7)
meillo@97 1195 man page to identify the tools with apparently too many switches.
meillo@217 1196 Then I considered the benefit of each switch by examining
meillo@217 1197 the tool's man page and source code, aided by literature research
meillo@217 1198 and testing.
meillo@97 1199
meillo@58 1200
meillo@93 1201 .U3 "Draft Folder Facility
meillo@93 1202 .P
meillo@100 1203 A change early in the project was the complete transition from
meillo@217 1204 the single draft message to the draft folder facility
meillo@217 1205 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@164 1206 .\" XXX ref to section ...
meillo@109 1207 The draft folder facility was introduced in the mid-eighties, when
meillo@100 1208 Rose and Romine called it a ``relatively new feature''.
meillo@93 1209 .[
meillo@93 1210 rose romine real work
meillo@93 1211 .]
meillo@217 1212 Since then, the facility was included, inactive by default.
meillo@217 1213 By making it permanently active and by related rework of the tools, the
meillo@93 1214 .Sw -[no]draftfolder ,
meillo@93 1215 and
meillo@93 1216 .Sw -draftmessage
meillo@217 1217 switches could be removed from
meillo@93 1218 .Pn comp ,
meillo@93 1219 .Pn repl ,
meillo@93 1220 .Pn forw ,
meillo@93 1221 .Pn dist ,
meillo@93 1222 .Pn whatnow ,
meillo@93 1223 and
meillo@217 1224 .Pn send
meillo@217 1225 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@217 1226 The only flexibility lost with this change is having multiple
meillo@97 1227 draft folders within one profile.
meillo@97 1228 I consider this a theoretical problem only.
meillo@159 1229 At the same time, the
meillo@93 1230 .Sw -draft
meillo@93 1231 switch of
meillo@93 1232 .Pn anno ,
meillo@93 1233 .Pn refile ,
meillo@93 1234 and
meillo@93 1235 .Pn send
meillo@93 1236 was removed.
meillo@159 1237 The special treatment of \fIthe\fP draft message became irrelevant after
meillo@217 1238 the rework of the draft system
meillo@159 1239 (cf. Sec.
meillo@217 1240 .Cf draft-folder ).
meillo@164 1241 Furthermore,
meillo@95 1242 .Pn comp
meillo@164 1243 no longer needs a
meillo@95 1244 .Sw -file
meillo@164 1245 switch as the draft folder facility together with the
meillo@95 1246 .Sw -form
meillo@164 1247 switch are sufficient.
meillo@93 1248
meillo@95 1249
meillo@102 1250 .U3 "In Place Editing
meillo@93 1251 .P
meillo@93 1252 .Pn anno
meillo@93 1253 had the switches
meillo@93 1254 .Sw -[no]inplace
meillo@100 1255 to either annotate the message in place and thus preserve hard links,
meillo@217 1256 or annotate a copy to replace the original message.
meillo@217 1257 The latter approach broke hard links.
meillo@97 1258 Following the assumption that linked messages should truly be the
meillo@217 1259 same message and annotating it should not break the link, the
meillo@93 1260 .Sw -[no]inplace
meillo@93 1261 switches were removed and the previous default
meillo@93 1262 .Sw -inplace
meillo@217 1263 was made the definitive behavior
meillo@217 1264 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0 .
meillo@93 1265 The
meillo@93 1266 .Sw -[no]inplace
meillo@93 1267 switches of
meillo@93 1268 .Pn repl ,
meillo@93 1269 .Pn forw ,
meillo@93 1270 and
meillo@93 1271 .Pn dist
meillo@217 1272 could be removed, as well, as they were simply passed through to
meillo@93 1273 .Pn anno .
meillo@93 1274 .P
meillo@93 1275 .Pn burst
meillo@93 1276 also had
meillo@93 1277 .Sw -[no]inplace
meillo@217 1278 switches, but with a different meaning.
meillo@95 1279 With
meillo@95 1280 .Sw -inplace ,
meillo@95 1281 the digest had been replaced by the table of contents (i.e. the
meillo@110 1282 introduction text) and the burst messages were placed right
meillo@95 1283 after this message, renumbering all following messages.
meillo@95 1284 Also, any trailing text of the digest was lost, though,
meillo@95 1285 in practice, it usually consists of an end-of-digest marker only.
meillo@217 1286 Nonetheless, this behavior appeared less elegant than the
meillo@95 1287 .Sw -noinplace
meillo@95 1288 behavior, which already had been the default.
meillo@95 1289 Nmh's
meillo@95 1290 .Mp burst (1)
meillo@95 1291 man page reads:
meillo@98 1292 .QS
meillo@164 1293 If
meillo@164 1294 .Sw -noinplace
meillo@164 1295 is given, each digest is preserved, no table
meillo@93 1296 of contents is produced, and the messages contained within
meillo@93 1297 the digest are placed at the end of the folder. Other messages
meillo@93 1298 are not tampered with in any way.
meillo@98 1299 .QE
meillo@95 1300 .LP
meillo@93 1301 The decision to drop the
meillo@93 1302 .Sw -inplace
meillo@95 1303 behavior was supported by the code complexity and the possible data loss
meillo@95 1304 it caused.
meillo@93 1305 .Sw -noinplace
meillo@95 1306 was chosen to be the definitive behavior.
meillo@97 1307 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93 1308
meillo@95 1309
meillo@95 1310 .U3 "Forms and Format Strings
meillo@93 1311 .P
meillo@95 1312 Historically, the tools that had
meillo@95 1313 .Sw -form
meillo@95 1314 switches to supply a form file had
meillo@95 1315 .Sw -format
meillo@95 1316 switches as well to supply the contents of a form file as a string
meillo@95 1317 on the command line directly.
meillo@95 1318 In consequence, the following two lines equaled:
meillo@95 1319 .VS
meillo@95 1320 scan -form scan.mailx
meillo@217 1321 scan -format "`cat /path/to/scan.mailx`"
meillo@95 1322 VE
meillo@95 1323 The
meillo@95 1324 .Sw -format
meillo@95 1325 switches were dropped in favor for extending the
meillo@95 1326 .Sw -form
meillo@217 1327 switches
meillo@217 1328 .Ci f51956be123db66b00138f80464d06f030dbb88d .
meillo@217 1329 If their argument starts with an equal sign (`\fL=\fP'),
meillo@95 1330 then the rest of the argument is taken as a format string,
meillo@95 1331 otherwise the arguments is treated as the name of a format file.
meillo@95 1332 Thus, now the following two lines equal:
meillo@95 1333 .VS
meillo@95 1334 scan -form scan.mailx
meillo@217 1335 scan -form "=`cat /path/to/scan.mailx`"
meillo@95 1336 VE
meillo@95 1337 This rework removed the prefix collision between
meillo@95 1338 .Sw -form
meillo@95 1339 and
meillo@95 1340 .Sw -format .
meillo@217 1341 Typing `\fL-fo\fP' is sufficient to specify form file or format string.
meillo@95 1342 .P
meillo@95 1343 The different meaning of
meillo@95 1344 .Sw -format
meillo@95 1345 for
meillo@217 1346 .Pn forw
meillo@217 1347 and
meillo@95 1348 .Pn repl
meillo@95 1349 was removed in mmh.
meillo@95 1350 .Pn forw
meillo@95 1351 was completely switched to MIME-type forwarding, thus removing the
meillo@217 1352 .Sw -[no]format
meillo@217 1353 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1 .
meillo@95 1354 For
meillo@95 1355 .Pn repl ,
meillo@95 1356 the
meillo@95 1357 .Sw -[no]format
meillo@95 1358 switches were reworked to
meillo@95 1359 .Sw -[no]filter
meillo@217 1360 switches
meillo@217 1361 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6 .
meillo@95 1362 The
meillo@95 1363 .Sw -format
meillo@95 1364 switches of
meillo@95 1365 .Pn send
meillo@95 1366 and
meillo@95 1367 .Pn post ,
meillo@217 1368 which had a third meaning, were removed likewise
meillo@217 1369 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9 .
meillo@95 1370 Eventually, the ambiguity of the
meillo@95 1371 .Sw -format
meillo@217 1372 switches is resolved by not having such switches anymore in mmh.
meillo@95 1373
meillo@95 1374
meillo@95 1375 .U3 "MIME Tools
meillo@95 1376 .P
meillo@217 1377 The MIME tools, which once were part of
meillo@100 1378 .Pn mhn
meillo@164 1379 (whatever that stood for),
meillo@95 1380 had several switches that added little practical value to the programs.
meillo@95 1381 The
meillo@95 1382 .Sw -[no]realsize
meillo@95 1383 switches of
meillo@95 1384 .Pn mhbuild
meillo@95 1385 and
meillo@95 1386 .Pn mhlist
meillo@217 1387 were removed
meillo@217 1388 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c .
meillo@217 1389 Real size calculations are done always now because nmh's
meillo@159 1390 .Mp mhbuild (1)
meillo@217 1391 man page states that
meillo@217 1392 ``This provides an accurate count at the expense of a small delay''
meillo@217 1393 with the small delay not being noticable on modern systems.
meillo@95 1394 .P
meillo@95 1395 The
meillo@95 1396 .Sw -[no]check
meillo@95 1397 switches were removed together with the support for
meillo@95 1398 .Hd Content-MD5
meillo@217 1399 header fields [RFC\|1864]
meillo@154 1400 (cf. Sec.
meillo@154 1401 .Cf content-md5 )
meillo@217 1402 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda .
meillo@95 1403 .P
meillo@95 1404 The
meillo@95 1405 .Sw -[no]ebcdicsafe
meillo@95 1406 and
meillo@95 1407 .Sw -[no]rfc934mode
meillo@95 1408 switches of
meillo@95 1409 .Pn mhbuild
meillo@217 1410 were removed because they are considered obsolete
meillo@97 1411 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@217 1412 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88 .
meillo@95 1413 .P
meillo@95 1414 Content caching of external MIME parts, activated with the
meillo@95 1415 .Sw -rcache
meillo@95 1416 and
meillo@95 1417 .Sw -wcache
meillo@217 1418 switches was completely removed
meillo@217 1419 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269 .
meillo@97 1420 External MIME parts are rare today, having a caching facility
meillo@159 1421 for them appears to be unnecessary.
meillo@95 1422 .P
meillo@95 1423 In pre-MIME times,
meillo@95 1424 .Pn mhl
meillo@95 1425 had covered many tasks that are part of MIME handling today.
meillo@95 1426 Therefore,
meillo@95 1427 .Pn mhl
meillo@95 1428 could be simplified to a large extend, reducing the number of its
meillo@217 1429 switches from 21 to 6
meillo@97 1430 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@217 1431 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70 .
meillo@95 1432
meillo@95 1433
meillo@95 1434
meillo@95 1435
meillo@95 1436 .U3 "Header Printing
meillo@95 1437 .P
meillo@95 1438 .Pn folder 's
meillo@95 1439 data output is self-explaining enough that
meillo@159 1440 displaying the header line makes little sense.
meillo@95 1441 Hence, the
meillo@95 1442 .Sw -[no]header
meillo@217 1443 switch was removed and headers are never printed
meillo@217 1444 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7 .
meillo@95 1445 .P
meillo@95 1446 In
meillo@95 1447 .Pn mhlist ,
meillo@95 1448 the
meillo@95 1449 .Sw -[no]header
meillo@217 1450 switches were removed, as well
meillo@217 1451 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f .
meillo@217 1452 In this case, the headers are printed always because the output
meillo@217 1453 is not self-explaining.
meillo@95 1454 .P
meillo@95 1455 .Pn scan
meillo@95 1456 also had
meillo@95 1457 .Sw -[no]header
meillo@95 1458 switches.
meillo@217 1459 Printing this header had been sensible until the introduction of
meillo@217 1460 format strings made it impossible to display column headings.
meillo@95 1461 Only the folder name and the current date remained to be printed.
meillo@217 1462 As this information can be perfectly generated with
meillo@95 1463 .Pn folder
meillo@95 1464 and
meillo@95 1465 .Pn date ,
meillo@217 1466 the switches were removed
meillo@217 1467 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e .
meillo@95 1468 .P
meillo@95 1469 By removing all
meillo@95 1470 .Sw -header
meillo@95 1471 switches, the collision with
meillo@95 1472 .Sw -help
meillo@95 1473 on the first two letters was resolved.
meillo@95 1474 Currently,
meillo@95 1475 .Sw -h
meillo@95 1476 evaluates to
meillo@95 1477 .Sw -help
meillo@95 1478 for all tools of mmh.
meillo@95 1479
meillo@95 1480
meillo@139 1481 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95 1482 .P
meillo@95 1483 The
meillo@95 1484 .Sw -noedit
meillo@100 1485 switch of
meillo@95 1486 .Pn comp ,
meillo@95 1487 .Pn repl ,
meillo@95 1488 .Pn forw ,
meillo@95 1489 .Pn dist ,
meillo@95 1490 and
meillo@95 1491 .Pn whatnow
meillo@217 1492 was removed and replaced by specifying
meillo@95 1493 .Sw -editor
meillo@217 1494 with an empty argument
meillo@217 1495 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9 .
meillo@95 1496 (Specifying
meillo@159 1497 .Cl "-editor /bin/true
meillo@217 1498 is nearly the same. It differs only in setting the previous editor.)
meillo@95 1499 .P
meillo@95 1500 The more important change is the removal of the
meillo@95 1501 .Sw -nowhatnowproc
meillo@217 1502 switch
meillo@217 1503 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622 .
meillo@217 1504 This switch had once introduced an awkward behavior,
meillo@217 1505 as explained in nmh's man page for
meillo@95 1506 .Mp comp (1):
meillo@98 1507 .QS
meillo@164 1508 The
meillo@164 1509 .Sw -editor
meillo@164 1510 .Ar editor
meillo@164 1511 switch indicates the editor to use for
meillo@164 1512 the initial edit. Upon exiting from the editor,
meillo@164 1513 .Pn comp
meillo@164 1514 will invoke the
meillo@164 1515 .Pn whatnow
meillo@164 1516 program. See
meillo@164 1517 .Mp whatnow (1)
meillo@164 1518 for a discussion of available options.
meillo@164 1519 The invocation of this program can be
meillo@164 1520 inhibited by using the
meillo@164 1521 .Sw -nowhatnowproc
meillo@164 1522 switch. (In truth of fact, it is the
meillo@164 1523 .Pn whatnow
meillo@164 1524 program which starts the initial edit.
meillo@164 1525 Hence,
meillo@164 1526 .Sw -nowhatnowproc
meillo@164 1527 will prevent any edit from occurring.)
meillo@98 1528 .QE
meillo@95 1529 .P
meillo@95 1530 Effectively, the
meillo@95 1531 .Sw -nowhatnowproc
meillo@217 1532 switch caused only only a draft message to be created.
meillo@95 1533 As
meillo@159 1534 .Cl "-whatnowproc /bin/true
meillo@217 1535 does the same, the
meillo@95 1536 .Sw -nowhatnowproc
meillo@95 1537 switch was removed for being redundant.
meillo@95 1538
meillo@95 1539
meillo@95 1540
meillo@95 1541 .U3 "Various
meillo@95 1542 .BU
meillo@139 1543 With the removal of MMDF maildrop format support,
meillo@139 1544 .Pn packf
meillo@139 1545 and
meillo@139 1546 .Pn rcvpack
meillo@139 1547 no longer needed their
meillo@139 1548 .Sw -mbox
meillo@139 1549 and
meillo@139 1550 .Sw -mmdf
meillo@139 1551 switches.
meillo@217 1552 The behavior of
meillo@139 1553 .Sw -mbox
meillo@217 1554 is the sole behavior now
meillo@217 1555 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0 .
meillo@171 1556 Further rework in both tools made the
meillo@139 1557 .Sw -file
meillo@217 1558 switch unnecessary
meillo@217 1559 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e .
meillo@139 1560
meillo@139 1561 .BU
meillo@217 1562 Mmh's tools do no longer clear the screen (\c
meillo@139 1563 .Pn scan 's
meillo@139 1564 and
meillo@139 1565 .Pn mhl 's
meillo@139 1566 .Sw -[no]clear
meillo@139 1567 switches
meillo@139 1568 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139 1569 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@217 1570 Neither does
meillo@139 1571 .Pn mhl
meillo@139 1572 ring the bell (\c
meillo@139 1573 .Sw -[no]bell
meillo@139 1574 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@217 1575 nor does it page the output itself (\c
meillo@139 1576 .Sw -length
meillo@139 1577 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@159 1578 .\" XXX Ref
meillo@139 1579 Generally, the pager to use is no longer specified with the
meillo@139 1580 .Sw -[no]moreproc
meillo@139 1581 command line switches for
meillo@139 1582 .Pn mhl
meillo@139 1583 and
meillo@139 1584 .Pn show /\c
meillo@217 1585 .Pn mhshow
meillo@217 1586 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a .
meillo@139 1587
meillo@139 1588 .BU
meillo@96 1589 In order to avoid prefix collisions among switch names, the
meillo@95 1590 .Sw -version
meillo@95 1591 switch was renamed to
meillo@95 1592 .Sw -Version
meillo@217 1593 (with capital `V')
meillo@217 1594 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a .
meillo@95 1595 Every program has the
meillo@95 1596 .Sw -version
meillo@95 1597 switch but its first three letters collided with the
meillo@95 1598 .Sw -verbose
meillo@95 1599 switch, present in many programs.
meillo@95 1600 The rename solved this problem once for all.
meillo@95 1601 Although this rename breaks a basic interface, having the
meillo@95 1602 .Sw -V
meillo@95 1603 abbreviation to display the version information, isn't all too bad.
meillo@139 1604
meillo@95 1605 .BU
meillo@95 1606 .Sw -[no]preserve
meillo@95 1607 of
meillo@95 1608 .Pn refile
meillo@168 1609 was removed
meillo@168 1610 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 1611 because what use was it anyway?
meillo@168 1612 Quoting nmh's man page
meillo@165 1613 .Mp refile (1):
meillo@98 1614 .QS
meillo@95 1615 Normally when a message is refiled, for each destination
meillo@95 1616 folder it is assigned the number which is one above the current
meillo@95 1617 highest message number in that folder. Use of the
meillo@164 1618 .Sw -preserv
meillo@164 1619 [sic!] switch will override this message renaming, and try
meillo@95 1620 to preserve the number of the message. If a conflict for a
meillo@164 1621 particular folder occurs when using the
meillo@164 1622 .Sw -preserve
meillo@164 1623 switch, then
meillo@164 1624 .Pn refile
meillo@164 1625 will use the next available message number which
meillo@95 1626 is above the message number you wish to preserve.
meillo@98 1627 .QE
meillo@139 1628
meillo@95 1629 .BU
meillo@95 1630 The removal of the
meillo@95 1631 .Sw -[no]reverse
meillo@95 1632 switches of
meillo@95 1633 .Pn scan
meillo@97 1634 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@217 1635 is a bug fix.
meillo@217 1636 This is supported by the comments
meillo@95 1637 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95 1638 by Rose and
meillo@95 1639 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@217 1640 This should be considered a bug'' by Romine in the changelogs.
meillo@217 1641 The question remains why neither Rose nor Romine have fixed this
meillo@217 1642 bug in the eighties when they wrote these comments.
meillo@93 1643
meillo@93 1644
meillo@93 1645
meillo@102 1646
meillo@102 1647
meillo@95 1648
meillo@95 1649
meillo@133 1650 .\" --------------------------------------------------------------
meillo@74 1651 .H1 "Modernizing
meillo@102 1652 .P
meillo@164 1653 In the more than thirty years of MH's existence, its code base was
meillo@159 1654 increasingly extended.
meillo@118 1655 New features entered the project and became alternatives to the
meillo@118 1656 existing behavior.
meillo@217 1657 Relics from several decades have gathered in the code base
meillo@118 1658 but seldom obsolete features were dropped.
meillo@118 1659 This section describes the removing of old code
meillo@118 1660 and the modernizing of the default setup.
meillo@118 1661 It focuses on the functional aspect only;
meillo@154 1662 the non-functional aspects of code style are discussed in Sec.
meillo@154 1663 .Cf code-style .
meillo@58 1664
meillo@58 1665
meillo@212 1666 .H2 "Code Relics
meillo@0 1667 .P
meillo@217 1668 My position regarding the removal of obsolete code
meillo@159 1669 is much more revolutional than the nmh community appreciates.
meillo@217 1670 Working on an experimental version, I was able to quickly drop
meillo@217 1671 functionality that I considered ancient.
meillo@104 1672 The need for consensus with peers would have slowed this process down.
meillo@104 1673 Without the need to justify my decisions, I was able to rush forward.
meillo@217 1674 .P
meillo@110 1675 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104 1676 do the work:
meillo@104 1677 .[
meillo@104 1678 paul vixie edginess nmh-workers
meillo@104 1679 .]
meillo@104 1680 .QS
meillo@104 1681 let's stop walking on egg shells with this code base. there's no need to
meillo@104 1682 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104 1683 we don't need a separate branch for removing vmh
meillo@104 1684 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@164 1685 or depending on pure ansi/posix ``libc''.
meillo@104 1686 .QP
meillo@164 1687 these things should each be a day or two of work and the ``main branch''
meillo@104 1688 should just be modern. [...]
meillo@104 1689 let's push forward, aggressively.
meillo@104 1690 .QE
meillo@104 1691 .LP
meillo@104 1692 I did so already in the months before.
meillo@104 1693 I pushed forward.
meillo@159 1694 .\" XXX semicolon ?
meillo@104 1695 I simply dropped the cruft.
meillo@104 1696 .P
meillo@104 1697 The decision to drop a feature was based on literature research and
meillo@159 1698 careful thinking, but whether having had contact with this particular
meillo@104 1699 feature within my own computer life served as a rule of thumb.
meillo@159 1700 I explained my reasons in the commit messages
meillo@109 1701 in the version control system.
meillo@104 1702 Hence, others can comprehend my view and argue for undoing the change
meillo@104 1703 if I have missed an important aspect.
meillo@109 1704 I was quick in dropping parts.
meillo@179 1705 I rather include falsely dropped parts again, than going at a slower pace.
meillo@179 1706 Mmh is experimental work; it requires tough decisions.
meillo@159 1707 .\" XXX ``exp. work'' schon oft gesagt
meillo@12 1708
meillo@102 1709
meillo@217 1710 .U3 "Process Forking
meillo@12 1711 .P
meillo@109 1712 Being a tool chest, MH creates many processes.
meillo@104 1713 In earlier times
meillo@104 1714 .Fu fork()
meillo@104 1715 had been an expensive system call, because the process's image needed
meillo@159 1716 to be completely duplicated at once.
meillo@200 1717 This expensive work was especially unnecessary in the commonly occurring
meillo@159 1718 case wherein the image is replaced by a call to
meillo@104 1719 .Fu exec()
meillo@104 1720 right after having forked the child process.
meillo@104 1721 The
meillo@104 1722 .Fu vfork()
meillo@104 1723 system call was invented to speed up this particular case.
meillo@104 1724 It completely omits the duplication of the image.
meillo@104 1725 On old systems this resulted in significant speed ups.
meillo@104 1726 Therefore MH used
meillo@104 1727 .Fu vfork()
meillo@104 1728 whenever possible.
meillo@12 1729 .P
meillo@104 1730 Modern memory management units support copy-on-write semantics, which make
meillo@104 1731 .Fu fork()
meillo@104 1732 almost as fast as
meillo@104 1733 .Fu vfork() .
meillo@104 1734 The man page of
meillo@104 1735 .Mp vfork (2)
meillo@104 1736 in FreeBSD 8.0 states:
meillo@104 1737 .QS
meillo@104 1738 This system call will be eliminated when proper system sharing mechanisms
meillo@104 1739 are implemented. Users should not depend on the memory sharing semantics
meillo@104 1740 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104 1741 .QE
meillo@104 1742 .LP
meillo@104 1743 Vixie supports the removal with the note that ``the last
meillo@104 1744 system on which fork was so slow that an mh user would notice it, was
meillo@104 1745 Eunice. that was 1987''.
meillo@104 1746 .[
meillo@104 1747 nmh-workers vixie edginess
meillo@104 1748 .]
meillo@104 1749 I replaced all calls to
meillo@104 1750 .Fu vfork()
meillo@104 1751 with calls to
meillo@217 1752 .Fu fork()
meillo@217 1753 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d .
meillo@104 1754 .P
meillo@104 1755 Related to the costs of
meillo@104 1756 .Fu fork()
meillo@104 1757 is the probability of its success.
meillo@109 1758 In the eighties, on heavy loaded systems, calls to
meillo@104 1759 .Fu fork()
meillo@104 1760 were prone to failure.
meillo@104 1761 Hence, many of the
meillo@104 1762 .Fu fork()
meillo@104 1763 calls in the code were wrapped into loops to retry the
meillo@104 1764 .Fu fork()
meillo@217 1765 several times, to increase the chances to succeed eventually.
meillo@109 1766 On modern systems, a failing
meillo@104 1767 .Fu fork()
meillo@109 1768 call is unusual.
meillo@104 1769 Hence, in the rare case when
meillo@104 1770 .Fu fork()
meillo@217 1771 fails, mmh programs simply abort
meillo@217 1772 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6 .
meillo@12 1773
meillo@12 1774
meillo@109 1775 .U3 "Header Fields
meillo@104 1776 .BU
meillo@84 1777 The
meillo@84 1778 .Hd Encrypted
meillo@104 1779 header field was introduced by RFC\|822,
meillo@109 1780 but already marked as legacy in RFC\|2822.
meillo@109 1781 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104 1782 messages [RFC\|4880, RFC\|3156].
meillo@109 1783 Hence, the support for
meillo@104 1784 .Hd Encrypted
meillo@217 1785 header fields is removed in mmh
meillo@217 1786 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857 .
meillo@104 1787 .BU
meillo@159 1788 The native support for
meillo@84 1789 .Hd Face
meillo@217 1790 header fields has been removed, as well
meillo@217 1791 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23 .
meillo@104 1792 This feature is similar to the
meillo@84 1793 .Hd X-Face
meillo@84 1794 header field in its intent,
meillo@21 1795 but takes a different approach to store the image.
meillo@84 1796 Instead of encoding the image data directly into the header field,
meillo@109 1797 it contains the hostname and UDP port where the image
meillo@109 1798 date can be retrieved.
meillo@159 1799 There is even a third Face system,
meillo@109 1800 which is the successor of
meillo@109 1801 .Hd X-Face ,
meillo@109 1802 although it re-uses the
meillo@104 1803 .Hd Face
meillo@217 1804 header field name.
meillo@109 1805 It was invented in 2005 and supports colored PNG images.
meillo@104 1806 None of the Face systems described here is popular today.
meillo@104 1807 Hence, mmh has no direct support for them.
meillo@104 1808 .BU
meillo@154 1809 .Id content-md5
meillo@104 1810 The
meillo@104 1811 .Hd Content-MD5
meillo@104 1812 header field was introduced by RFC\|1864.
meillo@104 1813 It provides detection of data corruption during the transfer.
meillo@104 1814 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104 1815 [RFC\|1864].
meillo@104 1816 The proper approach to verify content integrity in an
meillo@166 1817 end-to-end relationship is the use of digital signatures.
meillo@104 1818 .\" XXX (RFCs FIXME).
meillo@104 1819 On the other hand, transfer protocols should detect corruption during
meillo@109 1820 the transmission.
meillo@109 1821 The TCP includes a checksum field therefore.
meillo@104 1822 These two approaches in combinations render the
meillo@104 1823 .Hd Content-MD5
meillo@104 1824 header field superfluous.
meillo@109 1825 Not a single one out of 4\|200 messages from two decades
meillo@217 1826 in the nmh-workers mailing list archive
meillo@217 1827 .[
meillo@217 1828 nmh-workers mailing list archive website
meillo@217 1829 .]
meillo@217 1830 contains a
meillo@104 1831 .Hd Content-MD5
meillo@104 1832 header field.
meillo@104 1833 Neither did any of the 60\|000 messages in my personal mail storage.
meillo@217 1834 Removing the support for this header field
meillo@217 1835 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda ,
meillo@104 1836 removed the last place where MD5 computation was needed.
meillo@104 1837 Hence, the MD5 code could be removed as well.
meillo@104 1838 Over 500 lines of code vanished by this one change.
meillo@104 1839
meillo@104 1840
meillo@104 1841 .U3 "MMDF maildrop support
meillo@21 1842 .P
meillo@217 1843 This type of maildrop format is conceptionally similar to the mbox format,
meillo@139 1844 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139 1845 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104 1846 Mbox is the de-facto standard maildrop format on Unix,
meillo@159 1847 whereas the MMDF maildrop format is now forgotten.
meillo@217 1848 Mbox remains as the only packed mailbox format, supported in mmh.
meillo@104 1849 .P
meillo@109 1850 The simplifications within the code were moderate.
meillo@109 1851 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109 1852 But also, switches of
meillo@109 1853 .Pn packf
meillo@104 1854 and
meillo@109 1855 .Pn rcvpack
meillo@217 1856 could be removed
meillo@217 1857 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0 .
meillo@109 1858 In the message parsing function
meillo@109 1859 .Fn sbr/m_getfld.c ,
meillo@217 1860 knowledge of MMDF packed mail boxes was removed
meillo@217 1861 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754 .
meillo@109 1862 Further code structure simplifications may be possible there,
meillo@109 1863 because only one single packed mailbox format is left to be supported.
meillo@104 1864 I have not worked on them yet because
meillo@104 1865 .Fu m_getfld()
meillo@104 1866 is heavily optimized and thus dangerous to touch.
meillo@104 1867 The risk of damaging the intricate workings of the optimized code is
meillo@104 1868 too high.
meillo@104 1869
meillo@12 1870
meillo@101 1871 .U3 "Prompter's Control Keys
meillo@20 1872 .P
meillo@20 1873 The program
meillo@20 1874 .Pn prompter
meillo@104 1875 queries the user to fill in a message form.
meillo@217 1876 When used as
meillo@104 1877 .Cl "comp -editor prompter" ,
meillo@20 1878 the resulting behavior is similar to
meillo@20 1879 .Pn mailx .
meillo@51 1880 Apparently,
meillo@20 1881 .Pn prompter
meillo@173 1882 had not been touched lately.
meillo@104 1883 Otherwise it's hardly explainable why it
meillo@20 1884 still offered the switches
meillo@84 1885 .Sw -erase
meillo@84 1886 .Ar chr
meillo@20 1887 and
meillo@84 1888 .Sw -kill
meillo@84 1889 .Ar chr
meillo@20 1890 to name the characters for command line editing.
meillo@21 1891 The times when this had been necessary are long time gone.
meillo@20 1892 Today these things work out-of-the-box, and if not, are configured
meillo@20 1893 with the standard tool
meillo@20 1894 .Pn stty .
meillo@104 1895 The switches are removed now
meillo@104 1896 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20 1897
meillo@104 1898
meillo@109 1899 .U3 "Hardcopy Terminal Support
meillo@21 1900 .P
meillo@109 1901 More of a funny anecdote is a check for being connected to a
meillo@109 1902 hardcopy terminal.
meillo@159 1903 It remained in the code until spring 2012, when I finally removed it
meillo@104 1904 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@21 1905 .P
meillo@109 1906 The check only prevented a pager to be placed between the printing
meillo@104 1907 program (\c
meillo@104 1908 .Pn mhl )
meillo@104 1909 and the terminal.
meillo@109 1910 In nmh, this could have been ensured statically with the
meillo@104 1911 .Sw -nomoreproc
meillo@109 1912 at the command line, too.
meillo@121 1913 In mmh, setting the profile entry
meillo@104 1914 .Pe Pager
meillo@104 1915 or the environment variable
meillo@104 1916 .Ev PAGER
meillo@104 1917 to
meillo@109 1918 .Pn cat
meillo@159 1919 is sufficient.
meillo@104 1920
meillo@104 1921
meillo@21 1922
meillo@12 1923
meillo@58 1924 .H2 "Attachments
meillo@22 1925 .P
meillo@101 1926 The mind model of email attachments is unrelated to MIME.
meillo@217 1927 Although the MIME RFCs [RFC\|2045\(en2049] define the technical
meillo@217 1928 requirements for having attachments, they do not mention the term.
meillo@101 1929 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101 1930 [RFC\|2045], a more general concept.
meillo@101 1931 Multi-part messages are messages
meillo@101 1932 ``in which one or more different
meillo@101 1933 sets of data are combined in a single body''
meillo@101 1934 [RFC\|2046].
meillo@101 1935 MIME keeps its descriptions generic;
meillo@101 1936 it does not imply specific usage models.
meillo@217 1937 Today, one usage model is prevalent: attachments.
meillo@101 1938 The idea is having a main text document with files of arbitrary kind
meillo@101 1939 attached to it.
meillo@101 1940 In MIME terms, this is a multi-part message having a text part first
meillo@110 1941 and parts of arbitrary type following.
meillo@101 1942 .P
meillo@101 1943 MH's MIME support is a direct implementation of the RFCs.
meillo@101 1944 The perception of the topic described in the RFCs is clearly visible
meillo@101 1945 in MH's implementation.
meillo@159 1946 .\" XXX rewrite ``no idea''.
meillo@159 1947 As a result,
meillo@159 1948 MH had all the MIME features but no idea of attachments.
meillo@173 1949 But users do not need all the MIME features,
meillo@109 1950 they want convenient attachment handling.
meillo@109 1951
meillo@102 1952
meillo@102 1953 .U3 "Composing MIME Messages
meillo@102 1954 .P
meillo@102 1955 In order to improve the situation on the message composing side,
meillo@217 1956 Jon Steinhart had added an attachment system to nmh in 2002
meillo@217 1957 .Ci 7480dbc14bc90f2d872d434205c0784704213252 .
meillo@102 1958 In the file
meillo@102 1959 .Fn docs/README-ATTACHMENTS ,
meillo@217 1960 he described his motivation to do so:
meillo@101 1961 .QS
meillo@159 1962 Although nmh contains the necessary functionality for MIME message
meillo@159 1963 handing [sic!], the interface to this functionality is pretty obtuse.
meillo@101 1964 There's no way that I'm ever going to convince my partner to write
meillo@101 1965 .Pn mhbuild
meillo@101 1966 composition files!
meillo@101 1967 .QE
meillo@102 1968 .LP
meillo@102 1969 With this change, the mind model of attachments entered nmh.
meillo@102 1970 In the same document:
meillo@101 1971 .QS
meillo@101 1972 These changes simplify the task of managing attachments on draft files.
meillo@101 1973 They allow attachments to be added, listed, and deleted.
meillo@101 1974 MIME messages are automatically created when drafts with attachments
meillo@101 1975 are sent.
meillo@101 1976 .QE
meillo@102 1977 .LP
meillo@217 1978 Unfortunately, the attachment system, like every new facilities in nmh,
meillo@110 1979 was inactive by default.
meillo@101 1980 .P
meillo@217 1981 During my time in Argentina, I tried to improve the attachment system.
meillo@217 1982 But, after long discussions my patch died as a proposal on the
meillo@217 1983 mailing list because of great opposition in the nmh community.
meillo@101 1984 .[
meillo@101 1985 nmh-workers attachment proposal
meillo@101 1986 .]
meillo@217 1987 In January 2012, I extended the patch and applied it to mmh
meillo@217 1988 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1 .
meillo@102 1989 In mmh, the attachment system is active by default.
meillo@102 1990 Instead of command line switches, the
meillo@102 1991 .Pe Attachment-Header
meillo@102 1992 profile entry is used to specify
meillo@102 1993 the name of the attachment header field.
meillo@102 1994 It is pre-defined to
meillo@102 1995 .Hd Attach .
meillo@101 1996 .P
meillo@159 1997 To add an attachment to a draft, a header line needs to be added:
meillo@101 1998 .VS
meillo@101 1999 To: bob
meillo@101 2000 Subject: The file you wanted
meillo@101 2001 Attach: /path/to/the/file-bob-wanted
meillo@101 2002 --------
meillo@101 2003 Here it is.
meillo@101 2004 VE
meillo@101 2005 The header field can be added to the draft manually in the editor,
meillo@102 2006 or by using the `attach' command at the WhatNow prompt, or
meillo@102 2007 non-interactively with
meillo@101 2008 .Pn anno :
meillo@101 2009 .VS
meillo@102 2010 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101 2011 VE
meillo@102 2012 Drafts with attachment headers are converted to MIME automatically by
meillo@102 2013 .Pn send .
meillo@102 2014 The conversion to MIME is invisible to the user.
meillo@159 2015 The draft stored in the draft folder is always in source form with
meillo@101 2016 attachment headers.
meillo@179 2017 If the MIMEification fails (e.g. because the file to attach
meillo@179 2018 is not accessible) the original draft is not changed.
meillo@101 2019 .P
meillo@102 2020 The attachment system handles the forwarding of messages, too.
meillo@173 2021 If the attachment header value starts with a plus character (`\fL+\fP'),
meillo@101 2022 like in
meillo@101 2023 .Cl "Attach: +bob 30 42" ,
meillo@159 2024 the given messages in the specified folder will be attached.
meillo@101 2025 This allowed to simplify
meillo@217 2026 .Pn forw
meillo@217 2027 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550 .
meillo@101 2028 .P
meillo@101 2029 Closely related to attachments is non-ASCII text content,
meillo@217 2030 because it requires MIME as well.
meillo@102 2031 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101 2032 to have the draft converted to MIME.
meillo@102 2033 This was necessary whenever the draft contained non-ASCII characters.
meillo@101 2034 If the user did not call `mime', a broken message would be sent.
meillo@101 2035 Therefore, the
meillo@101 2036 .Pe automimeproc
meillo@101 2037 profile entry could be specified to have the `mime' command invoked
meillo@102 2038 automatically each time.
meillo@179 2039 Unfortunately, this approach conflicted with the attachment system
meillo@101 2040 because the draft would already be in MIME format at the time
meillo@101 2041 when the attachment system wanted to MIMEify it.
meillo@102 2042 To use nmh's attachment system, `mime' must not be called at the
meillo@102 2043 WhatNow prompt and
meillo@101 2044 .Pe automimeproc
meillo@102 2045 must not be set in the profile.
meillo@101 2046 But then the case of non-ASCII text without attachment headers was
meillo@101 2047 not caught.
meillo@102 2048 All in all, the solution was complex and irritating.
meillo@168 2049 My patch from December 2010
meillo@168 2050 .[
meillo@168 2051 nmh-workers attachment proposal
meillo@168 2052 .]
meillo@168 2053 would have simplified the situation.
meillo@102 2054 .P
meillo@101 2055 Mmh's current solution is even more elaborate.
meillo@101 2056 Any necessary MIMEification is done automatically.
meillo@101 2057 There is no `mime' command at the WhatNow prompt anymore.
meillo@102 2058 The draft will be converted automatically to MIME when either an
meillo@102 2059 attachment header or non-ASCII text is present.
meillo@173 2060 Furthermore, the hash character (`\fL#\fP') is not special any more
meillo@159 2061 at line beginnings in the draft message.
meillo@159 2062 .\" XXX REF ?
meillo@159 2063 Users need not concern themselves with the whole topic at all.
meillo@101 2064 .P
meillo@102 2065 Although the new approach does not anymore support arbitrary MIME
meillo@102 2066 compositions directly, the full power of
meillo@101 2067 .Pn mhbuild
meillo@101 2068 can still be accessed.
meillo@217 2069 Given no attachment headers are included, users can create
meillo@101 2070 .Pn mhbuild
meillo@102 2071 composition drafts like in nmh.
meillo@217 2072 Then, at the WhatNow prompt, they can invoke
meillo@101 2073 .Cl "edit mhbuild
meillo@217 2074 to convert the draft to MIME.
meillo@217 2075 Because the resulting draft neither contains non-ASCII characters
meillo@102 2076 nor has it attachment headers, the attachment system will not touch it.
meillo@101 2077 .P
meillo@159 2078 The approach taken in mmh is tailored towards today's most common case:
meillo@159 2079 a text part, possibly with attachments.
meillo@159 2080 This case was simplified.
meillo@102 2081
meillo@112 2082
meillo@102 2083 .U3 "MIME Type Guessing
meillo@102 2084 .P
meillo@159 2085 From the programmer's point of view, the use of
meillo@101 2086 .Pn mhbuild
meillo@159 2087 composition drafts had one notable advantage over attachment headers:
meillo@159 2088 The user provides the appropriate MIME types for files to include.
meillo@217 2089 The new attachment system needs to find out the correct MIME type itself.
meillo@217 2090 This is a difficult task.
meillo@102 2091 Determining the correct MIME type of content is partly mechanical,
meillo@102 2092 partly intelligent work.
meillo@102 2093 Forcing the user to find out the correct MIME type,
meillo@102 2094 forces him to do partly mechanical work.
meillo@179 2095 Letting the computer do the work can lead to bad choices for difficult
meillo@102 2096 content.
meillo@217 2097 For mmh, the latter option was chosen to spare the user the work
meillo@217 2098 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6 .
meillo@102 2099 .P
meillo@102 2100 Determining the MIME type by the suffix of the file name is a dumb
meillo@102 2101 approach, yet it is simple to implement and provides good results
meillo@102 2102 for the common cases.
meillo@217 2103 If no MIME type can be determined, text content is sent as `text/plain',
meillo@217 2104 anything else under the generic fall-back type `application/octet-stream'.
meillo@102 2105 Mmh implements this approach in the
meillo@102 2106 .Pn print-mimetype
meillo@217 2107 script
meillo@217 2108 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44 .
meillo@102 2109 .P
meillo@112 2110 A far better, though less portable, approach is the use of
meillo@102 2111 .Pn file .
meillo@102 2112 This standard tool tries to determine the type of files.
meillo@102 2113 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102 2114 Additionally, its output was only intended for human beings,
meillo@102 2115 but not to be used by programs.
meillo@102 2116 Nevertheless, modern versions of GNU
meillo@102 2117 .Pn file ,
meillo@217 2118 which are prevalent on the popular GNU/Linux systems,
meillo@159 2119 provide MIME type output in machine-readable form.
meillo@217 2120 Although this solution is system-dependent,
meillo@102 2121 it solves the difficult problem well.
meillo@102 2122 On systems where GNU
meillo@102 2123 .Pn file ,
meillo@102 2124 version 5.04 or higher, is available it should be used.
meillo@102 2125 One needs to specify the following profile entry to do so:
meillo@102 2126 .VS
meillo@102 2127 Mime-Type-Query: file -b --mime
meillo@102 2128 VE
meillo@102 2129 .LP
meillo@102 2130 Other versions of
meillo@102 2131 .Pn file
meillo@217 2132 might possibly be usable with wrapper scripts that reformat the output.
meillo@102 2133 The diversity among
meillo@102 2134 .Pn file
meillo@102 2135 implementations is great; one needs to check the local variant.
meillo@102 2136 .P
meillo@102 2137 It is not possible in mmh to override the automatic MIME type guessing
meillo@102 2138 for a specific file.
meillo@159 2139 To do so, either the user would need to know in advance for which file
meillo@217 2140 the automatic guessing fails or the system would require interaction.
meillo@102 2141 I consider both cases impractical.
meillo@102 2142 The existing solution should be sufficient.
meillo@102 2143 If not, the user may always fall back to
meillo@102 2144 .Pn mhbuild
meillo@217 2145 composition drafts and bypass the attachment system.
meillo@101 2146
meillo@102 2147
meillo@102 2148 .U3 "Storing Attachments
meillo@102 2149 .P
meillo@169 2150 Extracting MIME parts of a message and storing them to disk is performed by
meillo@108 2151 .Pn mhstore .
meillo@108 2152 The program has two operation modes,
meillo@108 2153 .Sw -auto
meillo@108 2154 and
meillo@108 2155 .Sw -noauto .
meillo@108 2156 With the former one, each part is stored under the filename given in the
meillo@108 2157 MIME part's meta information, if available.
meillo@108 2158 This naming information is usually available for modern attachments.
meillo@108 2159 If no filename is available, this MIME part is stored as if
meillo@108 2160 .Sw -noauto
meillo@108 2161 would have been specified.
meillo@108 2162 In the
meillo@108 2163 .Sw -noauto
meillo@108 2164 mode, the parts are processed according to rules, defined by
meillo@108 2165 .Pe mhstore-store-*
meillo@108 2166 profile entries.
meillo@108 2167 These rules define generic filename templates for storing
meillo@108 2168 or commands to post-process the contents in arbitrary ways.
meillo@108 2169 If no matching rule is available the part is stored under a generic
meillo@108 2170 filename, built from message number, MIME part number, and MIME type.
meillo@108 2171 .P
meillo@108 2172 The
meillo@108 2173 .Sw -noauto
meillo@108 2174 mode had been the default in nmh because it was considered safe,
meillo@108 2175 in contrast to the
meillo@108 2176 .Sw -auto
meillo@108 2177 mode.
meillo@108 2178 In mmh,
meillo@108 2179 .Sw -auto
meillo@108 2180 is not dangerous anymore.
meillo@108 2181 Two changes were necessary:
meillo@171 2182 .LI 1
meillo@108 2183 Any directory path is removed from the proposed filename.
meillo@108 2184 Thus, the files are always stored in the expected directory.
meillo@108 2185 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@171 2186 .LI 2
meillo@108 2187 Tar files are not extracted automatically any more.
meillo@108 2188 Thus, the rest of the file system will not be touched.
meillo@108 2189 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@217 2190 .P
meillo@217 2191 In mmh, the result of
meillo@108 2192 .Cl "mhstore -auto
meillo@110 2193 can be foreseen from the output of
meillo@108 2194 .Cl "mhlist -verbose" .
meillo@217 2195 Although the
meillo@108 2196 .Sw -noauto
meillo@217 2197 mode is considered to be more powerful, it is less convenient and
meillo@108 2198 .Sw -auto
meillo@217 2199 is safe now.
meillo@217 2200 Additionally, storing attachments under their original name
meillo@217 2201 is intuitive.
meillo@108 2202 Hence,
meillo@108 2203 .Sw -auto
meillo@217 2204 serves better as the default option
meillo@217 2205 .Ci 3410b680416c49a7617491af38bc1929855a331d .
meillo@108 2206 .P
meillo@108 2207 Files are stored into the directory given by the
meillo@108 2208 .Pe Nmh-Storage
meillo@108 2209 profile entry, if set, or
meillo@108 2210 into the current working directory, otherwise.
meillo@108 2211 Storing to different directories is only possible with
meillo@108 2212 .Pe mhstore-store-*
meillo@108 2213 profile entries.
meillo@108 2214 .P
meillo@217 2215 Still existing files get overwritten silently in both modes.
meillo@108 2216 This can be considered a bug.
meillo@108 2217 Yet, each other behavior has its draw-backs, too.
meillo@108 2218 Refusing to replace files requires adding a
meillo@108 2219 .Sw -force
meillo@217 2220 switch.
meillo@108 2221 Users will likely need to invoke
meillo@108 2222 .Pn mhstore
meillo@108 2223 a second time with
meillo@159 2224 .Sw -force .
meillo@159 2225 Eventually, only the user can decide in the specific case.
meillo@108 2226 This requires interaction, which I like to avoid if possible.
meillo@108 2227 Appending a unique suffix to the filename is another bad option.
meillo@108 2228 For now, the behavior remains as it is.
meillo@108 2229 .P
meillo@108 2230 In mmh, only MIME parts of type message are special in
meillo@108 2231 .Pn mhstore 's
meillo@108 2232 .Sw -auto
meillo@108 2233 mode.
meillo@108 2234 Instead of storing message/rfc822 parts as files to disk,
meillo@108 2235 they are stored as messages into the current mail folder.
meillo@159 2236 The same applies to message/partial, although the parts are
meillo@159 2237 automatically reassembled beforehand.
meillo@159 2238 MIME parts of type message/external-body are not automatically retrieved
meillo@159 2239 anymore.
meillo@159 2240 Instead, information on how to retrieve them is output.
meillo@217 2241 Not supporting this rare case saved nearly one thousand lines of code
meillo@217 2242 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32 .
meillo@108 2243 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108 2244 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@217 2245 The MIME type `application/octet-stream; type=tar' is not special anymore.
meillo@217 2246 The automatically extracting of such MIME parts had been the
meillo@217 2247 dangerous part of the
meillo@108 2248 .Sw -auto
meillo@217 2249 mode
meillo@217 2250 .Ci 94c80042eae3383c812d9552089953f9846b1bb6 .
meillo@108 2251
meillo@102 2252
meillo@102 2253
meillo@102 2254 .U3 "Showing MIME Messages
meillo@102 2255 .P
meillo@114 2256 The program
meillo@114 2257 .Pn mhshow
meillo@217 2258 was written to display MIME messages.
meillo@114 2259 It implemented the conceptional view of the MIME RFCs.
meillo@114 2260 Nmh's
meillo@114 2261 .Pn mhshow
meillo@217 2262 handles each MIME part independently, presenting them separately
meillo@114 2263 to the user.
meillo@114 2264 This does not match today's understanding of email attachments,
meillo@114 2265 where displaying a message is seen to be a single, integrated operation.
meillo@114 2266 Today, email messages are expected to consist of a main text part
meillo@114 2267 plus possibly attachments.
meillo@217 2268 They are no more seen to be arbitrary MIME hierarchies with
meillo@114 2269 information on how to display the individual parts.
meillo@114 2270 I adjusted
meillo@114 2271 .Pn mhshow 's
meillo@114 2272 behavior to the modern view on the topic.
meillo@114 2273 .P
meillo@217 2274 (One should note that this section completely ignores the original
meillo@114 2275 .Pn show
meillo@114 2276 program, because it was not capable to display MIME messages
meillo@114 2277 and is no longer part of mmh.
meillo@179 2278 .\" XXX ref to other section
meillo@114 2279 Although
meillo@114 2280 .Pn mhshow
meillo@114 2281 was renamed to
meillo@114 2282 .Pn show
meillo@114 2283 in mmh, this section uses the name
meillo@114 2284 .Pn mhshow ,
meillo@217 2285 in order to avoid confusion.)
meillo@114 2286 .P
meillo@114 2287 In mmh, the basic idea is that
meillo@114 2288 .Pn mhshow
meillo@114 2289 should display a message in one single pager session.
meillo@114 2290 Therefore,
meillo@114 2291 .Pn mhshow
meillo@114 2292 invokes a pager session for all its output,
meillo@217 2293 whenever it prints to a terminal
meillo@217 2294 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e .
meillo@114 2295 In consequence,
meillo@114 2296 .Pn mhl
meillo@217 2297 does no more invoke a pager
meillo@217 2298 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70 .
meillo@114 2299 With
meillo@114 2300 .Pn mhshow
meillo@114 2301 replacing the original
meillo@114 2302 .Pn show ,
meillo@217 2303 the output of
meillo@114 2304 .Pn mhl
meillo@217 2305 no longer goes to the terminal directly, but through
meillo@114 2306 .Pn mhshow .
meillo@114 2307 Hence,
meillo@114 2308 .Pn mhl
meillo@114 2309 does not need to invoke a pager.
meillo@114 2310 The one and only job of
meillo@114 2311 .Pn mhl
meillo@114 2312 is to format messages or parts of them.
meillo@114 2313 The only place in mmh, where a pager is invoked is
meillo@114 2314 .Pn mhshow .
meillo@114 2315 .P
meillo@217 2316 In the intended setup, only text content is be displayed,
meillo@217 2317 in a single pager session.
meillo@217 2318 Non-text content needs to be converted to text by appropriate
meillo@217 2319 .Pe mhshow-show-*
meillo@217 2320 profile entries before, if this is possible and wanted.
meillo@217 2321 A common example for this are PDF files.
meillo@217 2322 .ig \"XXX
meillo@114 2323 .Pe mhshow-show-*
meillo@114 2324 profile entries can be used to display MIME parts in a specific way.
meillo@114 2325 to display them in the terminal.
meillo@217 2326 ..
meillo@217 2327 In mmh, MIME parts are always displayed serially.
meillo@114 2328 The request to display the MIME type `multipart/parallel' in parallel
meillo@114 2329 is ignored.
meillo@217 2330 It is simply treated as `multipart/mixed'
meillo@217 2331 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6 .
meillo@217 2332 This was already possible to requested with the, now removed,
meillo@114 2333 .Sw -serialonly
meillo@114 2334 switch of
meillo@114 2335 .Pn mhshow .
meillo@179 2336 As MIME parts are always processed exclusively, i.e. serially,
meillo@217 2337 the `\fL%e\fP' escape in
meillo@114 2338 .Pe mhshow-show-*
meillo@217 2339 profile entries became useless and was thus removed
meillo@217 2340 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae .
meillo@114 2341 .P
meillo@114 2342 Other kinds of attachments are ignored.
meillo@114 2343 With
meillo@114 2344 .Pe mhshow-show-*
meillo@114 2345 profile entries for them, they can be displayed serially along
meillo@114 2346 the message.
meillo@114 2347 For parallel display, the attachments need to be stored to disk first.
meillo@114 2348 .P
meillo@114 2349 To display text content in foreign charsets, they need to be converted
meillo@114 2350 to the native charset.
meillo@114 2351 Therefore,
meillo@114 2352 .Pe mhshow-charset-*
meillo@217 2353 profile entries were needed.
meillo@169 2354 In mmh, the conversion is performed automatically by piping the
meillo@169 2355 text through the
meillo@114 2356 .Pn iconv
meillo@217 2357 command, if necessary
meillo@217 2358 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60 .
meillo@114 2359 Custom
meillo@114 2360 .Pe mhshow-show-*
meillo@114 2361 rules for textual content might need a
meillo@114 2362 .Cl "iconv -f %c %f |
meillo@114 2363 prefix to have the text converted to the native charset.
meillo@114 2364 .P
meillo@121 2365 Although the conversion of foreign charsets to the native one
meillo@114 2366 has improved, it is not consistent enough.
meillo@114 2367 Further work needs to be done and
meillo@114 2368 the basic concepts in this field need to be re-thought.
meillo@114 2369 Though, the default setup of mmh displays message in foreign charsets
meillo@114 2370 correctly without the need to configure anything.
meillo@114 2371
meillo@114 2372
meillo@114 2373 .ig
meillo@114 2374
meillo@114 2375 .P
meillo@114 2376 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@173 2377 These tools will not download the contents automatically anymore. Instead,
meillo@114 2378 they print the information needed to get the contents. If someone should
meillo@114 2379 really receive one of those rare message/external-body messages, he can
meillo@114 2380 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114 2381 it!
meillo@114 2382 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114 2383 ~/.netrc are gone now.)
meillo@114 2384 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114 2385
meillo@114 2386 ..
meillo@102 2387
meillo@58 2388
meillo@58 2389
meillo@166 2390 .H2 "Signing and Encrypting
meillo@22 2391 .P
meillo@166 2392 Nmh offers no direct support for digital signatures and message encryption.
meillo@157 2393 This functionality needed to be added through third-party software.
meillo@217 2394 In mmh, the functionality is included because it
meillo@217 2395 is a part of modern email and is likely wanted by users of mmh.
meillo@217 2396 A fresh mmh installation supports signing and encrypting
meillo@157 2397 out-of-the-box.
meillo@157 2398 Therefore, Neil Rickert's
meillo@157 2399 .Pn mhsign
meillo@157 2400 and
meillo@157 2401 .Pn mhpgp
meillo@157 2402 scripts
meillo@157 2403 .[
meillo@157 2404 neil rickert mhsign mhpgp
meillo@157 2405 .]
meillo@217 2406 were included
meillo@177 2407 .Ci f45cdc98117a84f071759462c7ae212f4bc5ab2e
meillo@177 2408 .Ci 58cf09aa36e9f7f352a127158bbf1c5678bc6ed8 .
meillo@177 2409 The scripts fit well because they are lightweight and
meillo@177 2410 similar of style to the existing tools.
meillo@217 2411 Additionally, no licensing difficulties appeared
meillo@157 2412 as they are part of the public domain.
meillo@112 2413 .P
meillo@157 2414 .Pn mhsign
meillo@157 2415 handles the signing and encrypting part.
meillo@157 2416 It comprises about 250 lines of shell code and interfaces between
meillo@217 2417 .Pn gnupg "
meillo@217 2418 .[
meillo@217 2419 gnupg website
meillo@217 2420 .]
meillo@217 2421 and the MH system.
meillo@177 2422 It was meant to be invoked manually at the WhatNow prompt, but in mmh,
meillo@157 2423 .Pn send
meillo@177 2424 invokes
meillo@217 2425 .Pn mhsign
meillo@177 2426 automatically
meillo@177 2427 .Ci c7b5e1df086bcc37ff40163ee67571f076cf6683 .
meillo@177 2428 Special header fields were introduced to request this action.
meillo@157 2429 If a draft contains the
meillo@157 2430 .Hd Sign
meillo@157 2431 header field,
meillo@157 2432 .Pn send
meillo@177 2433 will initiate the signing.
meillo@217 2434 The signing key is either chosen automatically or it is specified by the
meillo@157 2435 .Pe Pgpkey
meillo@157 2436 profile entry.
meillo@157 2437 .Pn send
meillo@217 2438 always create signatures using the PGP/MIME standard [RFC\|4880],
meillo@217 2439 but by invoking
meillo@217 2440 .Pn mhsign
meillo@217 2441 manually, old-style non-MIME signatures can be created as well.
meillo@177 2442 To encrypt an outgoing message, the draft needs to contain an
meillo@157 2443 .Hd Enc
meillo@157 2444 header field.
meillo@177 2445 Public keys of all recipients are searched for in the gnupg keyring and
meillo@177 2446 in a file called
meillo@177 2447 .Fn pgpkeys ,
meillo@177 2448 which contains exceptions and overrides.
meillo@157 2449 Unless public keys are found for all recipients,
meillo@177 2450 .Pn mhsign
meillo@177 2451 will refuse to encrypt it.
meillo@157 2452 Currently, messages with hidden (BCC) recipients can not be encrypted.
meillo@171 2453 This work is pending because it requires a structurally more complex
meillo@171 2454 approach.
meillo@157 2455 .P
meillo@177 2456 .Pn mhpgp
meillo@177 2457 is the companion to
meillo@177 2458 .Pn mhsign .
meillo@177 2459 It verifies signatures and decrypts messages.
meillo@217 2460 Encrypted messages can be either temporarily decrypted and displayed
meillo@177 2461 or permanently decrypted and stored into the current folder.
meillo@177 2462 Currently,
meillo@177 2463 .Pn mhpgp
meillo@177 2464 needs to be invoked manually.
meillo@177 2465 The integration into
meillo@177 2466 .Pn show
meillo@177 2467 and
meillo@177 2468 .Pn mhstore
meillo@217 2469 to verify signatures and decrypt messages as needed
meillo@217 2470 is planned but not yet realized.
meillo@177 2471 .P
meillo@217 2472 Both scripts were written for nmh.
meillo@217 2473 Hence they needed to be adjust
meillo@177 2474 according to the differences between nmh and mmh.
meillo@177 2475 For instance, they use the backup prefix no longer.
meillo@181 2476 Furthermore, compatibility support for old PGP features was dropped.
meillo@177 2477 .P
meillo@157 2478 The integrated message signing and encrypting support is one of the
meillo@157 2479 most recent features in mmh.
meillo@217 2480 It has not had the time to mature.
meillo@177 2481 User feedback and personal experience need to be accumulated to
meillo@177 2482 direct the further development of the facility.
meillo@217 2483 Already it seems to be worthwhile to consider adding
meillo@157 2484 .Sw -[no]sign
meillo@157 2485 and
meillo@157 2486 .Sw -[no]enc
meillo@157 2487 switches to
meillo@157 2488 .Pn send ,
meillo@177 2489 to be able to override the corresponding header fields.
meillo@177 2490 A profile entry:
meillo@157 2491 .VS
meillo@157 2492 send: -sign
meillo@157 2493 VE
meillo@177 2494 would then activate signing for all outgoing messages.
meillo@177 2495 With the present approach, a
meillo@177 2496 .Hd Send
meillo@177 2497 header component needs to be added to each draft template
meillo@177 2498 to achieve the same result.
meillo@177 2499 Adding the switches would ease the work greatly and keep the
meillo@177 2500 template files clean.
meillo@157 2501
meillo@58 2502
meillo@58 2503
meillo@102 2504
meillo@133 2505 .H2 "Draft and Trash Folder
meillo@131 2506 .P
meillo@58 2507
meillo@131 2508 .U3 "Draft Folder
meillo@154 2509 .Id draft-folder
meillo@131 2510 .P
meillo@131 2511 In the beginning, MH had the concept of a draft message.
meillo@217 2512 This was a file named
meillo@131 2513 .Fn draft
meillo@217 2514 in the MH directory, which was treated special.
meillo@131 2515 On composing a message, this draft file was used.
meillo@131 2516 When starting to compose another message before the former one was sent,
meillo@131 2517 the user had to decide among:
meillo@171 2518 .LI 1
meillo@168 2519 Using the old draft to finish and send it before starting with a new one.
meillo@171 2520 .LI 2
meillo@168 2521 Discarding the old draft and replacing it with a new one.
meillo@171 2522 .LI 3
meillo@168 2523 Preserving the old draft by refiling it to a folder.
meillo@171 2524 .LP
meillo@217 2525 Working on multiple drafts was only possible in alternation.
meillo@217 2526 For that, the current draft needed to be refiled to a folder and
meillo@168 2527 another one re-used for editing.
meillo@131 2528 Working on multiple drafts at the same time was impossible.
meillo@131 2529 The usual approach of switching to a different MH context did not
meillo@168 2530 help anything.
meillo@131 2531 .P
meillo@131 2532 The draft folder facility exists to
meillo@131 2533 allow true parallel editing of drafts, in a straight forward way.
meillo@131 2534 It was introduced by Marshall T. Rose, already in 1984.
meillo@131 2535 Similar to other new features, the draft folder was inactive by default.
meillo@131 2536 Even in nmh, the highly useful draft folder was not available
meillo@131 2537 out-of-the-box.
meillo@131 2538 At least, Richard Coleman added the man page
meillo@131 2539 .Mp mh-draft (5)
meillo@131 2540 to better document the feature.
meillo@131 2541 .P
meillo@131 2542 Not using the draft folder facility has the single advantage of having
meillo@131 2543 the draft file at a static location.
meillo@131 2544 This is simple in simple cases but the concept does not scale for more
meillo@131 2545 complex cases.
meillo@217 2546 The concept of the draft message is too limited for the problem
meillo@217 2547 it tries to solve.
meillo@131 2548 Therefore the draft folder was introduced.
meillo@131 2549 It is the more powerful and more natural concept.
meillo@131 2550 The draft folder is a folder like any other folder in MH.
meillo@131 2551 Its messages can be listed like any other messages.
meillo@131 2552 A draft message is no longer a special case.
meillo@131 2553 Tools do not need special switches to work on the draft message.
meillo@171 2554 Hence corner cases were removed.
meillo@131 2555 .P
meillo@131 2556 The trivial part of the work was activating the draft folder with a
meillo@131 2557 default name.
meillo@131 2558 I chose the name
meillo@217 2559 .Fn +drafts ,
meillo@131 2560 for obvious reasons.
meillo@131 2561 In consequence, the command line switches
meillo@131 2562 .Sw -draftfolder
meillo@131 2563 and
meillo@131 2564 .Sw -draftmessage
meillo@131 2565 could be removed.
meillo@131 2566 More difficult but also more improving was updating the tools to the
meillo@131 2567 new concept.
meillo@131 2568 For nearly three decades, the tools needed to support two draft handling
meillo@131 2569 approaches.
meillo@217 2570 By fully switching to the draft folder, the tools could be
meillo@217 2571 simplified by dropping the awkward draft message handling code.
meillo@131 2572 .Sw -draft
meillo@131 2573 switches were removed because operating on a draft message is no longer
meillo@131 2574 special.
meillo@131 2575 It became indistinguishable to operating on any other message.
meillo@168 2576 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@168 2577 .P
meillo@168 2578 There is no more need to query the user for draft handling
meillo@168 2579 .Ci 2d48b455c303a807041c35e4248955f8bec59eeb .
meillo@131 2580 It is always possible to add another new draft.
meillo@131 2581 Refiling drafts is without difference to refiling other messages.
meillo@168 2582 All of these special cases are gone.
meillo@131 2583 Yet, one draft-related switch remained.
meillo@131 2584 .Pn comp
meillo@131 2585 still has
meillo@131 2586 .Sw -[no]use
meillo@131 2587 for switching between two modes:
meillo@171 2588 .LI 1
meillo@217 2589 Modifying an existing draft, with
meillo@217 2590 .Sw -use .
meillo@171 2591 .LI 2
meillo@217 2592 Composing a new draft, possibly taking some existing message as template,
meillo@217 2593 with
meillo@217 2594 .Sw -nouse ,
meillo@217 2595 the default.
meillo@171 2596 .LP
meillo@131 2597 In either case, the behavior of
meillo@131 2598 .Pn comp
meillo@131 2599 is deterministic.
meillo@131 2600 .P
meillo@131 2601 .Pn send
meillo@131 2602 now operates on the current message in the draft folder by default.
meillo@131 2603 As message and folder can both be overridden by specifying them on
meillo@131 2604 the command line, it is possible to send any message in the mail storage
meillo@131 2605 by simply specifying its number and folder.
meillo@131 2606 In contrast to the other tools,
meillo@131 2607 .Pn send
meillo@131 2608 takes the draft folder as its default folder.
meillo@131 2609 .P
meillo@131 2610 Dropping the draft message concept in favor for the draft folder concept,
meillo@217 2611 replaced special cases with regular cases.
meillo@131 2612 This simplified the source code of the tools, as well as the concepts.
meillo@131 2613 In mmh, draft management does not break with the MH concepts
meillo@131 2614 but applies them.
meillo@133 2615 .Cl "scan +drafts" ,
meillo@133 2616 for instance, is a truly natural request.
meillo@217 2617 .P
meillo@169 2618 Most of the work was already performed by Rose in the eighties.
meillo@133 2619 The original improvement of mmh is dropping the old draft message approach
meillo@217 2620 and thus simplifying the tools, the documentation,
meillo@217 2621 and the system as a whole.
meillo@131 2622 Although my part in the draft handling improvement was small,
meillo@217 2623 it was important.
meillo@131 2624
meillo@131 2625
meillo@131 2626 .U3 "Trash Folder
meillo@154 2627 .Id trash-folder
meillo@131 2628 .P
meillo@131 2629 Similar to the situation for drafts is the situation for removed messages.
meillo@131 2630 Historically, a message was ``deleted'' by prepending a specific
meillo@173 2631 \fIbackup prefix\fP, usually the comma character,
meillo@173 2632 to the file name.
meillo@164 2633 The specific file would then be ignored by MH because only files with
meillo@164 2634 names consisting of digits only are treated as messages.
meillo@131 2635 Although files remained in the file system,
meillo@168 2636 the messages were no longer visible in MH.
meillo@168 2637 To truly delete them, a maintenance job was needed.
meillo@168 2638 Usually a cron job was installed to delete them after a grace time.
meillo@131 2639 For instance:
meillo@131 2640 .VS
meillo@131 2641 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131 2642 VE
meillo@168 2643 In such a setup, the original message could be restored
meillo@131 2644 within the grace time interval by stripping the
meillo@217 2645 backup prefix from the file name \(en usually but not always.
meillo@168 2646 If the last message of a folder with six messages (\fL1-6\fP) was removed,
meillo@131 2647 message
meillo@131 2648 .Fn 6 ,
meillo@168 2649 became file
meillo@131 2650 .Fn ,6 .
meillo@168 2651 If then a new message entered the same folder, it would be named with
meillo@168 2652 the number one above the highest existing message number.
meillo@168 2653 In this case the message would be named
meillo@217 2654 .Fn 6 ,
meillo@217 2655 reusing the number.
meillo@168 2656 If this new message would be removed as well,
meillo@217 2657 then the backup of the former message becomes overwritten.
meillo@168 2658 Hence, the ability to restore removed messages did not only depend on
meillo@181 2659 the sweeping cron job but also on the removing of further messages.
meillo@131 2660 It is undesirable to have such obscure and complex mechanisms.
meillo@168 2661 The user should be given a small set of clear assertions, such as
meillo@131 2662 ``Removed files are restorable within a seven-day grace time.''
meillo@131 2663 With the addition ``... unless a message with the same name in the
meillo@131 2664 same folder is removed before.'' the statement becomes complex.
meillo@217 2665 A user will hardly be able to keep track of all removals to know
meillo@131 2666 if the assertion still holds true for a specific file.
meillo@164 2667 In practice, the real mechanism is unclear to the user.
meillo@131 2668 .P
meillo@217 2669 Furthermore, the backup files were scattered within the whole mail storage.
meillo@217 2670 This complicated managing them.
meillo@217 2671 It was possible with the help of
meillo@131 2672 .Pn find ,
meillo@217 2673 but everything is more convenient
meillo@217 2674 if the deleted messages are collected in one place.
meillo@131 2675 .P
meillo@131 2676 The profile entry
meillo@131 2677 .Pe rmmproc
meillo@131 2678 (previously named
meillo@131 2679 .Pe Delete-Prog )
meillo@131 2680 was introduced very early to improve the situation.
meillo@164 2681 It could be set to any command, which would be executed to remove
meillo@131 2682 the specified messages.
meillo@217 2683 This had overridden the default action, described above.
meillo@217 2684 Refiling the to-be-removed files to a trash folder was the usual example.
meillo@131 2685 Nmh's man page
meillo@131 2686 .Mp rmm (1)
meillo@131 2687 proposes to set the
meillo@131 2688 .Pe rmmproc
meillo@131 2689 to
meillo@131 2690 .Cl "refile +d
meillo@217 2691 to move messages to the trash folder
meillo@217 2692 .Fn +d
meillo@131 2693 instead of renaming them with the backup prefix.
meillo@217 2694 The man page additionally proposes the expunge command
meillo@131 2695 .Cl "rm `mhpath +d all`
meillo@168 2696 to empty the trash folder.
meillo@131 2697 .P
meillo@217 2698 Removing messages in such a way has advantages:
meillo@217 2699 .LI 1
meillo@131 2700 The mail storage is prevented from being cluttered with removed messages
meillo@131 2701 because they are all collected in one place.
meillo@131 2702 Existing and removed messages are thus separated more strictly.
meillo@217 2703 .LI 2
meillo@131 2704 No backup files are silently overwritten.
meillo@217 2705 .LI 3
meillo@217 2706 Most important, however, removed messages are kept in the MH domain.
meillo@131 2707 Messages in the trash folder can be listed like those in any other folder.
meillo@131 2708 Deleted messages can be displayed like any other messages.
meillo@169 2709 .Pn refile
meillo@169 2710 can restore deleted messages.
meillo@131 2711 All operations on deleted files are still covered by the MH tools.
meillo@131 2712 The trash folder is just like any other folder in the mail storage.
meillo@131 2713 .P
meillo@131 2714 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131 2715 in favor for replacing it by the better suiting trash folder system.
meillo@131 2716 Hence,
meillo@131 2717 .Pn rmm
meillo@131 2718 calls
meillo@131 2719 .Pn refile
meillo@131 2720 to move the to-be-removed message to the trash folder,
meillo@131 2721 .Fn +trash
meillo@131 2722 by default.
meillo@164 2723 To sweep it clean, the user can use
meillo@131 2724 .Cl "rmm -unlink +trash a" ,
meillo@131 2725 where the
meillo@131 2726 .Sw -unlink
meillo@131 2727 switch causes the files to be unlinked.
meillo@168 2728 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 2729 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@131 2730 .P
meillo@217 2731 Dropping the legacy approach and converting to the new approach
meillo@217 2732 completely, simplified the code base.
meillo@131 2733 The relationship between
meillo@131 2734 .Pn rmm
meillo@131 2735 and
meillo@131 2736 .Pn refile
meillo@131 2737 was inverted.
meillo@131 2738 In mmh,
meillo@131 2739 .Pn rmm
meillo@131 2740 invokes
meillo@217 2741 .Pn refile .
meillo@217 2742 That used to be the other way round.
meillo@131 2743 Yet, the relationship is simpler now.
meillo@164 2744 Loops, like described in nmh's man page for
meillo@131 2745 .Mp refile (1),
meillo@164 2746 can no longer occur:
meillo@131 2747 .QS
meillo@131 2748 Since
meillo@131 2749 .Pn refile
meillo@131 2750 uses your
meillo@131 2751 .Pe rmmproc
meillo@131 2752 to delete the message, the
meillo@131 2753 .Pe rmmproc
meillo@131 2754 must NOT call
meillo@131 2755 .Pn refile
meillo@131 2756 without specifying
meillo@131 2757 .Sw -normmproc
meillo@131 2758 or you will create an infinite loop.
meillo@131 2759 .QE
meillo@131 2760 .LP
meillo@131 2761 .Pn rmm
meillo@131 2762 either unlinks a message with
meillo@131 2763 .Fu unlink()
meillo@131 2764 or invokes
meillo@131 2765 .Pn refile
meillo@131 2766 to move it to the trash folder.
meillo@131 2767 .Pn refile
meillo@131 2768 does not invoke any tools.
meillo@131 2769 .P
meillo@136 2770 By generalizing the message removal in the way that it became covered
meillo@136 2771 by the MH concepts made the whole system more powerful.
meillo@131 2772
meillo@131 2773
meillo@131 2774
meillo@131 2775
meillo@131 2776
meillo@133 2777 .H2 "Modern Defaults
meillo@133 2778 .P
meillo@133 2779 Nmh has a bunch of convenience-improving features inactive by default,
meillo@217 2780 although one can expect every new user to want them active.
meillo@133 2781 The reason they are inactive by default is the wish to stay compatible
meillo@133 2782 with old versions.
meillo@217 2783 But what are old versions?
meillo@136 2784 Still, the highly useful draft folder facility has not been activated
meillo@136 2785 by default although it was introduced over twenty-five years ago.
meillo@133 2786 .[
meillo@133 2787 rose romine real work
meillo@133 2788 .]
meillo@136 2789 The community seems not to care.
meillo@217 2790 .P
meillo@217 2791 In nmh, new users are required to first build up
meillo@217 2792 a profile before they can access the modern features.
meillo@136 2793 Without an extensive profile, the setup is hardly usable
meillo@133 2794 for modern emailing.
meillo@133 2795 The point is not the customization of the setup,
meillo@136 2796 but the need to activate generally useful facilities.
meillo@217 2797 Yet, the real problem lies less in enabling the features,
meillo@217 2798 as this is straight forward as soon as one knows what he wants.
meillo@168 2799 The real problem is that new users need deep insight into the project
meillo@217 2800 to discover the available but inactive features.
meillo@133 2801 To give an example, I needed one year of using nmh
meillo@133 2802 before I became aware of the existence of the attachment system.
meillo@133 2803 One could argue that this fact disqualifies my reading of the
meillo@133 2804 documentation.
meillo@133 2805 If I would have installed nmh from source back then, I could agree.
meillo@217 2806 Yet, I had used a pre-packaged version and had expected that it would
meillo@133 2807 just work.
meillo@133 2808 Nevertheless, I had been convinced by the concepts of MH already
meillo@133 2809 and I am a software developer,
meillo@133 2810 still I required a lot of time to discover the cool features.
meillo@133 2811 How can we expect users to be even more advanced than me,
meillo@217 2812 just to enable them to use MH in a convenient and modern way?
meillo@133 2813 Unless they are strongly convinced of the concepts, they will fail.
meillo@133 2814 I have seen friends of me giving up disappointed
meillo@133 2815 before they truly used the system,
meillo@133 2816 although they had been motivated in the beginning.
meillo@217 2817 New users suffer hard enough to get used to the tool chest approach,
meillo@179 2818 we developers should spare them further inconveniences.
meillo@133 2819 .P
meillo@136 2820 Maintaining compatibility for its own sake is bad,
meillo@217 2821 because the code base will collect more and more compatibility code.
meillo@200 2822 Sticking to the compatibility code means remaining limited;
meillo@168 2823 whereas adjusting to the changes renders the compatibility unnecessary.
meillo@217 2824 Keeping unused alternatives in the code for longer than a short
meillo@217 2825 grace time is a bad choice as they likely
meillo@217 2826 gather bugs by not being constantly tested.
meillo@136 2827 Also, the increased code size and the greater number of conditions
meillo@136 2828 increase the maintenance costs.
meillo@133 2829 If any MH implementation would be the back-end of widespread
meillo@133 2830 email clients with large user bases, compatibility would be more
meillo@133 2831 important.
meillo@133 2832 Yet, it appears as if this is not the case.
meillo@133 2833 Hence, compatibility is hardly important for technical reasons.
meillo@217 2834 Its importance originates from personal reasons rather.
meillo@133 2835 Nmh's user base is small and old.
meillo@217 2836 Changing the interfaces causes inconvenience to long-term users of MH.
meillo@217 2837 It forces them to change their many years old MH configurations.
meillo@168 2838 I do understand this aspect, but by sticking to the old users,
meillo@217 2839 new users are kept from entering the world of MH.
meillo@217 2840 But the future lies in new users.
meillo@168 2841 In consequence, mmh invites new users by providing a convenient
meillo@168 2842 and modern setup, readily usable out-of-the-box.
meillo@133 2843 .P
meillo@136 2844 In mmh, all modern features are active by default and many previous
meillo@217 2845 approaches are removed or only accessible in a manual way.
meillo@136 2846 New default features include:
meillo@133 2847 .BU
meillo@133 2848 The attachment system (\c
meillo@217 2849 .Hd Attach )
meillo@217 2850 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1 .
meillo@133 2851 .BU
meillo@133 2852 The draft folder facility (\c
meillo@217 2853 .Fn +drafts )
meillo@217 2854 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@133 2855 .BU
meillo@133 2856 The unseen sequence (`u')
meillo@133 2857 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@217 2858 and the sequence negation prefix (`!')
meillo@217 2859 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc .
meillo@133 2860 .BU
meillo@217 2861 Quoting the original message in the reply
meillo@217 2862 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6 .
meillo@133 2863 .BU
meillo@217 2864 Forwarding messages using MIME
meillo@217 2865 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1 .
meillo@171 2866 .LP
meillo@217 2867 An mmh setup with a profile that defines only the path to the
meillo@136 2868 mail storage, is already convenient to use.
meillo@217 2869 Again, Paul Vixie's supports the direction I took:
meillo@136 2870 ``the `main branch' should just be modern''.
meillo@136 2871 .[
meillo@136 2872 paul vixie edginess nmh-workers
meillo@136 2873 .]
meillo@131 2874
meillo@133 2875
meillo@133 2876
meillo@133 2877
meillo@133 2878
meillo@133 2879 .\" --------------------------------------------------------------
meillo@131 2880 .H1 "Styling
meillo@22 2881 .P
meillo@118 2882 Kernighan and Pike have emphasized the importance of style in the
meillo@219 2883 preface of \fPThe Practice of Programming\fP:
meillo@118 2884 .[ [
meillo@118 2885 kernighan pike practice of programming
meillo@118 2886 .], p. x]
meillo@118 2887 .QS
meillo@118 2888 Chapter 1 discusses programming style.
meillo@219 2889 Good style is so important to good programming that we have chosen
meillo@118 2890 to cover it first.
meillo@118 2891 .QE
meillo@168 2892 This section covers changes in mmh that were guided by the desire
meillo@118 2893 to improve on style.
meillo@219 2894 Many of them follow the advice given in the quoted book.
meillo@118 2895
meillo@118 2896
meillo@127 2897
meillo@127 2898
meillo@127 2899 .H2 "Code Style
meillo@154 2900 .Id code-style
meillo@118 2901 .P
meillo@118 2902 .U3 "Indentation Style
meillo@118 2903 .P
meillo@219 2904 Indentation styles are the holy cow of programming.
meillo@219 2905 Kernighan and Pike write:
meillo@118 2906 .[ [
meillo@118 2907 kernighan pike practice of programming
meillo@118 2908 .], p. 10]
meillo@118 2909 .QS
meillo@118 2910 Programmers have always argued about the layout of programs,
meillo@118 2911 but the specific style is much less important than its consistent
meillo@118 2912 application.
meillo@121 2913 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118 2914 time arguing.
meillo@118 2915 .QE
meillo@118 2916 .P
meillo@118 2917 I agree that the constant application is most important,
meillo@118 2918 but I believe that some styles have advantages over others.
meillo@118 2919 For instance the indentation with tab characters only.
meillo@219 2920 The number of tabs corresponds to the nesting level \(en
meillo@118 2921 one tab, one level.
meillo@219 2922 Tab characters provide flexible visual appearance because developers
meillo@219 2923 can adjust their width as prefered.
meillo@219 2924 There is no more need to check for the correct mixture of
meillo@219 2925 tabs and spaces.
meillo@219 2926 Two simple rules ensure the integrity and flexibility of the visual
meillo@219 2927 appearance:
meillo@219 2928 .LI 1
meillo@219 2929 Leading whitespace must consist of tabs only.
meillo@219 2930 .LI 2
meillo@219 2931 All other whitespace should be spaces.
meillo@219 2932 .LP
meillo@121 2933 Although reformatting existing code should be avoided, I did it.
meillo@200 2934 I did not waste time arguing; I just reformatted the code.
meillo@118 2935 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118 2936
meillo@118 2937 .U3 "Comments
meillo@118 2938 .P
meillo@219 2939 Kernighan and Pike demand: ``Don't belabor the obvious''.
meillo@118 2940 .[ [
meillo@118 2941 kernighan pike practice of programming
meillo@118 2942 .], p. 23]
meillo@219 2943 Following the advice, I removed unnecessary comments.
meillo@219 2944 For instance, I removed all comments in the following code excerpt
meillo@219 2945 .Ci 426543622b377fc5d091455cba685e114b6df674 :
meillo@118 2946 .VS
meillo@120 2947 context_replace(curfolder, folder); /* update current folder */
meillo@120 2948 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120 2949 seq_save(mp); /* synchronize message sequences */
meillo@120 2950 folder_free(mp); /* free folder/message structure */
meillo@120 2951 context_save(); /* save the context file */
meillo@120 2952
meillo@120 2953 [...]
meillo@120 2954
meillo@120 2955 int c; /* current character */
meillo@120 2956 char *cp; /* miscellaneous character pointer */
meillo@120 2957
meillo@120 2958 [...]
meillo@120 2959
meillo@120 2960 /* NUL-terminate the field */
meillo@120 2961 *cp = '\0';
meillo@118 2962 VE
meillo@118 2963 .P
meillo@219 2964 The information in each of the comments was present in the code
meillo@219 2965 statements already, except for the NUL-termination, which became
meillo@219 2966 obvious from the context.
meillo@136 2967
meillo@118 2968
meillo@118 2969 .U3 "Names
meillo@118 2970 .P
meillo@219 2971 Regarding this topic, Kernighan and Pike suggest:
meillo@118 2972 ``Use active names for functions''.
meillo@118 2973 .[ [
meillo@118 2974 kernighan pike practice of programming
meillo@118 2975 .], p. 4]
meillo@118 2976 One application of this rule was the rename of
meillo@118 2977 .Fu check_charset()
meillo@118 2978 to
meillo@219 2979 .Fu is_native_charset()
meillo@219 2980 .Ci 8d77b48284c58c135a6b2787e721597346ab056d .
meillo@219 2981 The same change additionally fixed a violation of ``Be accurate'',
meillo@181 2982 .[ [
meillo@181 2983 kernighan pike practice of programming
meillo@181 2984 .], p. 4]
meillo@219 2985 as the code did not match the expectation the function suggested.
meillo@219 2986 It did not compare charset names but prefixes of them only.
meillo@219 2987 In case the native charset was `ISO-8859-1', then
meillo@219 2988 .VS
meillo@219 2989 check_charset("ISO-8859-11", strlen("ISO-8859-11"))
meillo@219 2990 VE
meillo@219 2991 had returned true although the upper halves of the code pages
meillo@219 2992 are different.
meillo@118 2993 .P
meillo@118 2994 More important than using active names is using descriptive names.
meillo@145 2995 .VS
meillo@145 2996 m_unknown(in); /* the MAGIC invocation... */
meillo@145 2997 VE
meillo@145 2998 Renaming the obscure
meillo@118 2999 .Fu m_unknown()
meillo@219 3000 function was a delightful event, although it made the code less funny
meillo@219 3001 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846 .
meillo@118 3002 .P
meillo@118 3003 Magic numbers are generally considered bad style.
meillo@118 3004 Obviously, Kernighan and Pike agree:
meillo@118 3005 ``Give names to magic numbers''.
meillo@118 3006 .[ [
meillo@118 3007 kernighan pike practice of programming
meillo@118 3008 .], p. 19]
meillo@219 3009 .P
meillo@219 3010 The argument
meillo@219 3011 .CW outnum
meillo@219 3012 of the function
meillo@219 3013 .Fu scan()
meillo@219 3014 in
meillo@219 3015 .Fn uip/scansbr.c
meillo@219 3016 holds the number of the message to be created.
meillo@219 3017 As well it encodes program logic with negative numbers and zero.
meillo@219 3018 This led to obscure code.
meillo@219 3019 I clarified the code by introducing two variables that extracted
meillo@219 3020 the hidden information:
meillo@219 3021 .VS
meillo@219 3022 int incing = (outnum > 0);
meillo@219 3023 int ismbox = (outnum != 0);
meillo@219 3024 VE
meillo@219 3025 The readable names are thus used in conditions;
meillo@219 3026 the variable
meillo@219 3027 .CW outnum
meillo@219 3028 is used only to extract ordinary message numbers
meillo@219 3029 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f .
meillo@219 3030 .P
meillo@219 3031 Through the clarity improvement of the change detours in the program
meillo@219 3032 logic of related code parts became apparent.
meillo@219 3033 The implementation was simplified.
meillo@219 3034 This possibility to improve had been invisible before
meillo@219 3035 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723 .
meillo@219 3036 .P
meillo@219 3037 The names just described were a first step, yet the situation
meillo@219 3038 was further improved by giving names to the magic values of
meillo@219 3039 .CW outnum :
meillo@118 3040 .VS
meillo@118 3041 #define SCN_MBOX (-1)
meillo@118 3042 #define SCN_FOLD 0
meillo@118 3043 VE
meillo@219 3044 The two variables were updated thereafter as well:
meillo@219 3045 .VS
meillo@219 3046 int incing = (outnum != SCN_MBOX && outnum != SCN_FOLD);
meillo@219 3047 int scanfolder = (outnum == SCN_FOLD);
meillo@219 3048 VE
meillo@219 3049 Furthermore,
meillo@219 3050 .CW ismbox
meillo@219 3051 was replaced by
meillo@219 3052 .CW scanfolder
meillo@219 3053 because that matched better to the program logic.
meillo@118 3054 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@219 3055
meillo@118 3056
meillo@133 3057
meillo@133 3058
meillo@133 3059 .H2 "Structural Rework
meillo@133 3060 .P
meillo@219 3061 Although the stylistic changes described already improve the
meillo@219 3062 readability of the source code, all of them were changes ``in the small''.
meillo@219 3063 Structural changes, in contrast, affect much larger code areas.
meillo@219 3064 They are more difficult to accomplish but lead to larger improvements,
meillo@219 3065 especially as they often influence the outer shape of the tools as well.
meillo@118 3066 .P
meillo@118 3067 At the end of their chapter on style,
meillo@118 3068 Kernighan and Pike ask: ``But why worry about style?''
meillo@181 3069 .[ [
meillo@181 3070 kernighan pike practice of programming
meillo@219 3071 .], p. 28].
meillo@219 3072 Following are two examples of structural rework that demonstrate
meillo@136 3073 why style is important in the first place.
meillo@136 3074
meillo@136 3075
meillo@136 3076 .U3 "Rework of \f(CWanno\fP
meillo@118 3077 .P
meillo@120 3078 Until 2002,
meillo@120 3079 .Pn anno
meillo@219 3080 had six functional command line switches:
meillo@120 3081 .Sw -component
meillo@120 3082 and
meillo@120 3083 .Sw -text ,
meillo@219 3084 each with an argument,
meillo@120 3085 and the two pairs of flags,
meillo@120 3086 .Sw -[no]date
meillo@120 3087 and
meillo@120 3088 .Sw -[no]inplace .
meillo@120 3089 Then Jon Steinhart introduced his attachment system.
meillo@120 3090 In need for more advanced annotation handling, he extended
meillo@120 3091 .Pn anno .
meillo@120 3092 He added five more switches:
meillo@120 3093 .Sw -draft ,
meillo@120 3094 .Sw -list ,
meillo@120 3095 .Sw -delete ,
meillo@120 3096 .Sw -append ,
meillo@120 3097 and
meillo@120 3098 .Sw -number ,
meillo@219 3099 the last one taking an argument
meillo@219 3100 .Ci 7480dbc14bc90f2d872d434205c0784704213252 .
meillo@120 3101 Later,
meillo@120 3102 .Sw -[no]preserve
meillo@219 3103 was added as well
meillo@219 3104 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f .
meillo@120 3105 Then, the Synopsis section of the man page
meillo@120 3106 .Mp anno (1)
meillo@120 3107 read:
meillo@120 3108 .VS
meillo@219 3109 anno [+folder] [msgs] [-component f(CIfieldfP] [-inplace | -noinplace]
meillo@120 3110 [-date | -nodate] [-draft] [-append] [-list] [-delete]
meillo@219 3111 [-number [f(CInumfP|fPallfP]] [-preserve | -nopreserve] [-version]
meillo@219 3112 [-help] [-text f(CIbodyfP]
meillo@120 3113 VE
meillo@120 3114 .LP
meillo@120 3115 The implementation followed the same structure.
meillo@120 3116 Problems became visible when
meillo@120 3117 .Cl "anno -list -number 42
meillo@219 3118 worked on the current message instead of on message number 42,
meillo@120 3119 and
meillo@120 3120 .Cl "anno -list -number l:5
meillo@124 3121 did not work on the last five messages but failed with the mysterious
meillo@120 3122 error message: ``anno: missing argument to -list''.
meillo@121 3123 Yet, the invocation matched the specification in the man page.
meillo@120 3124 There, the correct use of
meillo@120 3125 .Sw -number
meillo@120 3126 was defined as being
meillo@120 3127 .Cl "[-number [num|all]]
meillo@120 3128 and the textual description for the combination with
meillo@120 3129 .Sw -list
meillo@120 3130 read:
meillo@120 3131 .QS
meillo@164 3132 The
meillo@164 3133 .Sw -list
meillo@164 3134 option produces a listing of the field bodies for
meillo@120 3135 header fields with names matching the specified component,
meillo@164 3136 one per line. The listing is numbered, starting at 1, if the
meillo@164 3137 .Sw -number
meillo@164 3138 option is also used.
meillo@120 3139 .QE
meillo@120 3140 .LP
meillo@120 3141 The problem was manifold.
meillo@120 3142 Semantically, the argument to the
meillo@120 3143 .Sw -number
meillo@120 3144 switch is only necessary in combination with
meillo@120 3145 .Sw -delete ,
meillo@120 3146 but not with
meillo@120 3147 .Sw -list .
meillo@219 3148 The code, however, required a numeric argument in any case.
meillo@219 3149 If the argument was missing or non-numeric,
meillo@219 3150 .Pn anno
meillo@219 3151 aborted with an error message that additionally had an off-by-one error.
meillo@219 3152 It printed the name of the switch one before the concerned one.
meillo@120 3153 .P
meillo@219 3154 Trying to fix these problems on the surface would not have solved them.
meillo@219 3155 They originate from a discrepance between the
meillo@120 3156 structure of the problem and the structure implemented in the program.
meillo@219 3157 Such structural differences can only be solved by adjusting the
meillo@219 3158 structure of the implementation to the structure of the problem.
meillo@120 3159 .P
meillo@219 3160 Steinhart had added the new
meillo@120 3161 .Sw -list
meillo@120 3162 and
meillo@120 3163 .Sw -delete
meillo@219 3164 switches in a style similar to the other switches though
meillo@219 3165 they are of structural different type.
meillo@120 3166 Semantically,
meillo@120 3167 .Sw -list
meillo@120 3168 and
meillo@120 3169 .Sw -delete
meillo@219 3170 introduce operation modes.
meillo@120 3171 Historically,
meillo@120 3172 .Pn anno
meillo@120 3173 had only one operation mode: adding header fields.
meillo@219 3174 With the extension, two more modes were added:
meillo@120 3175 listing and deleting header fields.
meillo@120 3176 The structure of the code changes did not pay respect to this
meillo@219 3177 fundamental change.
meillo@120 3178 Neither the implementation nor the documentation did clearly
meillo@219 3179 declare the exclusive operation modes as such.
meillo@120 3180 Having identified the problem, I solved it by putting structure into
meillo@120 3181 .Pn anno
meillo@219 3182 and its documentation
meillo@219 3183 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11 .
meillo@120 3184 .P
meillo@173 3185 The difference is visible in both the code and the documentation.
meillo@219 3186 For instance in the following code excerpt:
meillo@120 3187 .VS
meillo@120 3188 int delete = -2; /* delete header element if set */
meillo@120 3189 int list = 0; /* list header elements if set */
meillo@120 3190 [...]
meillo@121 3191 case DELETESW: /* delete annotations */
meillo@121 3192 delete = 0;
meillo@121 3193 continue;
meillo@121 3194 case LISTSW: /* produce a listing */
meillo@121 3195 list = 1;
meillo@121 3196 continue;
meillo@120 3197 VE
meillo@121 3198 .LP
meillo@219 3199 which was replaced by:
meillo@120 3200 .VS
meillo@120 3201 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120 3202 [...]
meillo@121 3203 case DELETESW: /* delete annotations */
meillo@121 3204 mode = MODE_DEL;
meillo@121 3205 continue;
meillo@121 3206 case LISTSW: /* produce a listing */
meillo@121 3207 mode = MODE_LIST;
meillo@121 3208 continue;
meillo@120 3209 VE
meillo@120 3210 .LP
meillo@121 3211 The replacement code does not only reflect the problem's structure better,
meillo@121 3212 it is easier to understand as well.
meillo@121 3213 The same applies to the documentation.
meillo@120 3214 The man page was completely reorganized to propagate the same structure.
meillo@219 3215 This is already visible in the Synopsis section:
meillo@120 3216 .VS
meillo@219 3217 anno [+folder] [msgs] [-component f(CIfieldfP] [-text fPbodyfP]
meillo@120 3218 [-append] [-date | -nodate] [-preserve | -nopreserve]
meillo@120 3219 [-Version] [-help]
meillo@120 3220
meillo@219 3221 anno -delete [+folder] [msgs] [-component fPfieldfP] [-text
meillo@219 3222 fPbodyfP] [-number fPnum fP| fPall fP] [-preserve | -nopreserve]
meillo@120 3223 [-Version] [-help]
meillo@120 3224
meillo@219 3225 anno -list [+folder] [msgs] [-component fPfieldfP] [-number]
meillo@120 3226 [-Version] [-help]
meillo@120 3227 VE
meillo@118 3228
meillo@58 3229
meillo@58 3230
meillo@133 3231 .U3 "Path Conversion
meillo@133 3232 .P
meillo@134 3233 Four kinds of path names can appear in MH:
meillo@171 3234 .LI 1
meillo@134 3235 Absolute Unix directory paths, like
meillo@134 3236 .Fn /etc/passwd .
meillo@171 3237 .LI 2
meillo@134 3238 Relative Unix directory paths, like
meillo@134 3239 .Fn ./foo/bar .
meillo@171 3240 .LI 3
meillo@134 3241 Absolute MH folder paths, like
meillo@219 3242 .Fn +projects/mmh .
meillo@171 3243 .LI 4
meillo@134 3244 Relative MH folder paths, like
meillo@134 3245 .Fn @subfolder .
meillo@171 3246 .LP
meillo@219 3247 Relative MH folder paths, are hardly documented
meillo@219 3248 although they are useful for large mail storages.
meillo@134 3249 The current mail folder is specified as `\c
meillo@134 3250 .Fn @ ',
meillo@134 3251 just like the current directory is specified as `\c
meillo@134 3252 .Fn . '.
meillo@134 3253 .P
meillo@134 3254 To allow MH tools to understand all four notations,
meillo@219 3255 they need to be able to convert between them.
meillo@134 3256 In nmh, these path name conversion functions were located in the files
meillo@134 3257 .Fn sbr/path.c
meillo@134 3258 (``return a pathname'') and
meillo@134 3259 .Fn sbr/m_maildir.c
meillo@134 3260 (``get the path for the mail directory'').
meillo@134 3261 The seven functions in the two files were documented with no more
meillo@134 3262 than two comments, which described obvious information.
meillo@219 3263 The signatures of the four exported functions did not explain their
meillo@219 3264 semantics:
meillo@219 3265 .LI 1
meillo@219 3266 .CW "char *path(char *, int);
meillo@219 3267 .LI 2
meillo@219 3268 .CW "char *pluspath(char *);
meillo@219 3269 .LI 3
meillo@219 3270 .CW "char *m_mailpath(char *);
meillo@219 3271 .LI 4
meillo@219 3272 .CW "char *m_maildir(char *);
meillo@134 3273 .P
meillo@219 3274 My investigations provided the following descriptions:
meillo@171 3275 .LI 1
meillo@134 3276 The second parameter of
meillo@134 3277 .Fu path()
meillo@219 3278 defines the type as which the path given in the first parameter should
meillo@219 3279 be treated.
meillo@134 3280 Directory paths are converted to absolute directory paths.
meillo@134 3281 Folder paths are converted to absolute folder paths.
meillo@173 3282 Folder paths must not include a leading `\fL@\fP' character.
meillo@134 3283 Leading plus characters are preserved.
meillo@134 3284 The result is a pointer to newly allocated memory.
meillo@171 3285 .LI 2
meillo@134 3286 .Fu pluspath()
meillo@134 3287 is a convenience-wrapper to
meillo@134 3288 .Fu path() ,
meillo@134 3289 to convert folder paths only.
meillo@134 3290 This function can not be used for directory paths.
meillo@134 3291 An empty string parameter causes a buffer overflow.
meillo@171 3292 .LI 3
meillo@134 3293 .Fu m_mailpath()
meillo@134 3294 converts directory paths to absolute directory paths.
meillo@173 3295 The characters `\fL+\fP' or `\fL@\fP' at the beginning of the path name are
meillo@134 3296 treated literal, i.e. as the first character of a relative directory path.
meillo@134 3297 Hence, this function can not be used for folder paths.
meillo@219 3298 In any case, the result is an absolute directory path,
meillo@219 3299 returned as a pointer to newly allocated memory.
meillo@171 3300 .LI 4
meillo@134 3301 .Fu m_maildir()
meillo@134 3302 returns the parameter unchanged if it is an absolute directory path
meillo@173 3303 or begins with the entry `\fL.\fP' or `\fL..\fP'.
meillo@134 3304 All other strings are prepended with the current working directory.
meillo@219 3305 Hence, this function can not be used for folder paths.
meillo@134 3306 The result is either an absolute directory path or a relative
meillo@219 3307 directory path, starting with dot or dot-dot.
meillo@134 3308 In contrast to the other functions, the result is a pointer to
meillo@134 3309 static memory.
meillo@134 3310 .P
meillo@134 3311 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@219 3312 Additionally, no clear terminology was used to name the different
meillo@219 3313 kinds of path names.
meillo@219 3314 Sometimes, the names were even misleading, much as the first argument of
meillo@134 3315 .Fu m_mailpath() ,
meillo@219 3316 which was named
meillo@219 3317 .CW folder ,
meillo@219 3318 although
meillo@134 3319 .Fu m_mailpath()
meillo@219 3320 could not be used with MH folder arguments.
meillo@134 3321 .P
meillo@219 3322 I clarified the path name conversion by complete rework.
meillo@134 3323 First of all, the terminology needed to be defined.
meillo@134 3324 A path name is either in the Unix domain, then it is called
meillo@219 3325 \fIdirectory path\fP (\fIdirpath\fP for short) or it is in the MH domain,
meillo@219 3326 then it is called \fIfolder path\fP (\fIfolpath\fP for short).
meillo@134 3327 The two terms need to be used with strict distinction.
meillo@219 3328 Often a clear terminology indicates that the problem is understood.
meillo@134 3329 Second, I exploited the concept of path type indicators.
meillo@219 3330 By requiring every path name to start with a distinct type identifier,
meillo@219 3331 the conversion between the types could be fully automated.
meillo@219 3332 This allows the tools to accept paths of any type from the user.
meillo@134 3333 Therefore, it was necessary to require relative directory paths to be
meillo@134 3334 prefixed with a dot character.
meillo@134 3335 In consequence, the dot character could no longer be an alias for the
meillo@134 3336 current message.
meillo@134 3337 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134 3338 Third, I created three new functions to replace the previous mess:
meillo@171 3339 .LI 1
meillo@134 3340 .Fu expandfol()
meillo@219 3341 converts folder paths to absolute folder paths.
meillo@134 3342 Directory paths are simply passed through.
meillo@134 3343 This function is to be used for folder paths only, thus the name.
meillo@134 3344 The result is a pointer to static memory.
meillo@171 3345 .LI 2
meillo@134 3346 .Fu expanddir()
meillo@134 3347 converts directory paths to absolute directory paths.
meillo@134 3348 Folder paths are treated as relative directory paths.
meillo@134 3349 This function is to be used for directory paths only, thus the name.
meillo@134 3350 The result is a pointer to static memory.
meillo@171 3351 .LI 3
meillo@134 3352 .Fu toabsdir()
meillo@134 3353 converts any type of path to an absolute directory path.
meillo@134 3354 This is the function of choice for path conversion.
meillo@134 3355 Absolute directory paths are the most general representation of a
meillo@134 3356 path name.
meillo@134 3357 The result is a pointer to static memory.
meillo@134 3358 .P
meillo@180 3359 .\" XXX ueberfluessig?
meillo@134 3360 The new functions have names that indicate their use.
meillo@134 3361 Two of the functions convert relative to absolute path names of the
meillo@134 3362 same type.
meillo@134 3363 The third function converts any path name type to the most general one,
meillo@134 3364 the absolute directory path.
meillo@134 3365 All of the functions return pointers to static memory.
meillo@219 3366 The file
meillo@219 3367 .Fn sbr/path.c
meillo@219 3368 contains the implementation of the functions;
meillo@134 3369 .Fn sbr/m_maildir.c
meillo@219 3370 was removed.
meillo@168 3371 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3372 .P
meillo@134 3373 Along with the path conversion rework, I also replaced
meillo@134 3374 .Fu getfolder(FDEF)
meillo@134 3375 with
meillo@134 3376 .Fu getdeffol()
meillo@134 3377 and
meillo@134 3378 .Fu getfolder(FCUR)
meillo@134 3379 with
meillo@134 3380 .Fu getcurfol() ,
meillo@219 3381 which only wraps
meillo@219 3382 .Fu expandfol(""@"")
meillo@219 3383 for convenience.
meillo@134 3384 This code was moved from
meillo@134 3385 .Fn sbr/getfolder.c
meillo@219 3386 into
meillo@219 3387 .Fn sbr/path.c
meillo@219 3388 as well.
meillo@168 3389 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3390 .P
meillo@134 3391 The related function
meillo@134 3392 .Fu etcpath()
meillo@219 3393 is now included in
meillo@134 3394 .Fn sbr/path.c ,
meillo@168 3395 too
meillo@168 3396 .Ci b4c29794c12099556151d93a860ee51badae2e35 .
meillo@134 3397 Previously, it had been located in
meillo@219 3398 .Fn config/config.c .
meillo@134 3399 .P
meillo@219 3400 Now,
meillo@134 3401 .Fn sbr/path.c
meillo@219 3402 contains all path handling code.
meillo@219 3403 Besides being less code, its readability is highly improved.
meillo@219 3404 The functions follow a common style and are well documented.
meillo@133 3405
meillo@133 3406
meillo@133 3407
meillo@133 3408
meillo@133 3409 .H2 "Profile Reading
meillo@133 3410 .P
meillo@220 3411 The MH profile contains the configuration of a user-specific MH setup.
meillo@220 3412 MH tools read the profile right after starting up
meillo@220 3413 because it contains the location of the user's mail storage
meillo@138 3414 and similar settings that influence the whole setup.
meillo@220 3415 Furthermore, the profile contains the default switches for the tools
meillo@220 3416 as well.
meillo@220 3417 The context file is read along with the profile.
meillo@138 3418 .P
meillo@138 3419 For historic reasons, some MH tools did not read the profile and context.
meillo@138 3420 Among them were
meillo@138 3421 .Pn post /\c
meillo@138 3422 .Pn spost ,
meillo@138 3423 .Pn mhmail ,
meillo@138 3424 and
meillo@138 3425 .Pn slocal .
meillo@138 3426 The reason why these tools ignored the profile were not clearly stated.
meillo@220 3427 During a discussion on the nmh-workers mailing list,
meillo@181 3428 David Levine posted an explanation, quoting John Romine:
meillo@138 3429 .[
meillo@138 3430 nmh-workers levine post profile
meillo@138 3431 .]
meillo@220 3432
meillo@138 3433 .QS
meillo@138 3434 I asked John Romine and here's what he had to say, which
meillo@138 3435 agrees and provides an example that convinces me:
meillo@138 3436 .QS
meillo@164 3437 My take on this is that
meillo@164 3438 .Pn post
meillo@164 3439 should not be called by users directly, and it doesn't read the
meillo@164 3440 .Fn .mh_profile
meillo@138 3441 (only front-end UI programs read the profile).
meillo@138 3442 .QP
meillo@164 3443 For example, there can be contexts where
meillo@164 3444 .Pn post
meillo@164 3445 is called by a helper program (like `\c
meillo@164 3446 .Pn mhmail ')
meillo@164 3447 which may be run by a non-MH user.
meillo@164 3448 We don't want this to prompt the user to create an MH profile, etc.
meillo@138 3449 .QP
meillo@164 3450 My suggestion would be to have
meillo@164 3451 .Pn send
meillo@164 3452 pass a (hidden) `\c
meillo@164 3453 .Sw -fileproc
meillo@164 3454 .Ar proc '
meillo@164 3455 option to
meillo@164 3456 .Pn post
meillo@164 3457 if needed.
meillo@164 3458 You could also
meillo@164 3459 use an environment variable (I think
meillo@164 3460 .Pn send /\c
meillo@164 3461 .Pn whatnow
meillo@164 3462 do this).
meillo@138 3463 .QE
meillo@220 3464 .sp \n(PDu
meillo@164 3465 I think that's the way to go.
meillo@164 3466 My personal preference is to use a command line option,
meillo@164 3467 not an environment variable.
meillo@138 3468 .QE
meillo@220 3469
meillo@138 3470 .P
meillo@220 3471 To solve the problem that
meillo@138 3472 .Pn post
meillo@220 3473 does not honor the
meillo@138 3474 .Pe fileproc
meillo@138 3475 profile entry,
meillo@138 3476 the community roughly agreed that a switch
meillo@138 3477 .Sw -fileproc
meillo@138 3478 should be added to
meillo@138 3479 .Pn post
meillo@138 3480 to be able to pass a different fileproc.
meillo@138 3481 I strongly disagree with this approach because it does not solve
meillo@138 3482 the problem; it only removes a single symptom.
meillo@220 3483 The actual problem is that
meillo@138 3484 .Pn post
meillo@220 3485 does not behave as expected,
meillo@220 3486 though all programs should behave as expected.
meillo@220 3487 Clear and general concepts are a precondition for this.
meillo@220 3488 Thus, there should be no separation into ``front-end UI programs''
meillo@220 3489 and ones that ``should not be called by users directly''.
meillo@220 3490 The real solution is having all MH tools read the profile.
meillo@138 3491 .P
meillo@220 3492 But the problem has a further aspect,
meillo@220 3493 which originates from
meillo@220 3494 .Pn mhmail
meillo@220 3495 mainly.
meillo@138 3496 .Pn mhmail
meillo@138 3497 was intended to be a replacement for
meillo@138 3498 .Pn mailx
meillo@138 3499 on systems with MH installations.
meillo@220 3500 In difference to
meillo@220 3501 .Pn mailx ,
meillo@138 3502 .Pn mhmail
meillo@220 3503 used MH's
meillo@138 3504 .Pn post
meillo@220 3505 to send the message.
meillo@220 3506 The idea was that using
meillo@138 3507 .Pn mhmail
meillo@220 3508 should not be influenced whether the user had
meillo@138 3509 MH set up for himself or not.
meillo@220 3510 Therefore
meillo@138 3511 .Pn mhmail
meillo@220 3512 had not read the profile.
meillo@138 3513 As
meillo@138 3514 .Pn mhmail
meillo@138 3515 used
meillo@138 3516 .Pn post ,
meillo@138 3517 .Pn post
meillo@220 3518 was not allowed to read the profile neither.
meillo@138 3519 This is the reason for the actual problem.
meillo@220 3520 Yet, this was not considered much of a problem because
meillo@138 3521 .Pn post
meillo@138 3522 was not intended to be used by users directly.
meillo@220 3523 To invoke
meillo@220 3524 .Pn post ,
meillo@138 3525 .Pn send
meillo@220 3526 was used an a front-end.
meillo@138 3527 .Pn send
meillo@138 3528 read the profile and passed all relevant values on the command line to
meillo@138 3529 .Pn post
meillo@138 3530 \(en an awkward solution.
meillo@138 3531 .P
meillo@138 3532 The important insight is that
meillo@138 3533 .Pn mhmail
meillo@220 3534 is a wolf in sheep's clothing.
meillo@220 3535 This alien tool broke the concepts because it was treated like
meillo@220 3536 a normal MH tool.
meillo@138 3537 Instead it should have been treated accordingly to its foreign style.
meillo@220 3538 .P
meillo@220 3539 The solution is not to prevent the tools from reading the profile but
meillo@220 3540 to instruct them to read a different profile.
meillo@138 3541 .Pn mhmail
meillo@220 3542 could have set up a well-defined profile and caused the following
meillo@138 3543 .Pn post
meillo@220 3544 to use this profile by exporting an environment variable.
meillo@220 3545 With this approach, no special cases would have been introduced
meillo@220 3546 and no surprises would have been caused.
meillo@220 3547 By writing a wrapper program to provide a clean temporary profile,
meillo@220 3548 the concept could have been generalized orthogonally to the whole
meillo@220 3549 MH tool chest.
meillo@220 3550 .P
meillo@220 3551 In mmh, the wish to have
meillo@220 3552 .Pn mhmail
meillo@220 3553 as a replacement for
meillo@220 3554 .Pn mailx
meillo@220 3555 is considered obsolete.
meillo@220 3556 Mmh's
meillo@220 3557 .Pn mhmail
meillo@220 3558 does no longer cover this use-case
meillo@220 3559 .Ci d36e56e695fe1c482c7920644bfbb6386ac9edb0 .
meillo@220 3560 Currently,
meillo@220 3561 .Pn mhmail
meillo@220 3562 is in a transition state
meillo@220 3563 .Ci 32d4f9daaa70519be3072479232ff7be0500d009 .
meillo@220 3564 It may become a front-end to
meillo@220 3565 .Pn comp ,
meillo@220 3566 which provides an alternative interface which can be more convenient
meillo@220 3567 in some cases.
meillo@220 3568 This would convert
meillo@220 3569 .Pn mhmail
meillo@220 3570 into an ordinary MH tool.
meillo@220 3571 If, however, this idea does not convince, then
meillo@220 3572 .Pn mhmail
meillo@220 3573 will be removed.
meillo@220 3574 .P
meillo@220 3575 In the mmh tool chest, every program reads the profile.
meillo@220 3576 (\c
meillo@220 3577 .Pn slocal
meillo@220 3578 is not considered part of the mmh tool chest (cf. Sec.
meillo@220 3579 .Cf slocal ).)
meillo@220 3580 Mmh has no
meillo@220 3581 .Pn post
meillo@220 3582 program, but it has
meillo@220 3583 .Pn spost ,
meillo@220 3584 which now does read the profile
meillo@220 3585 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8 .
meillo@220 3586 Following this change,
meillo@220 3587 .Pn send
meillo@220 3588 and
meillo@220 3589 .Pn spost
meillo@220 3590 can be considered for merging.
meillo@220 3591 Besides
meillo@220 3592 .Pn send ,
meillo@220 3593 .Pn spost
meillo@220 3594 is only invoked directly by the to-be-changed
meillo@220 3595 .Pn mhmail
meillo@220 3596 implementation and by
meillo@220 3597 .Pn rcvdist ,
meillo@220 3598 which requires rework anyway.
meillo@220 3599
meillo@220 3600 .P
meillo@220 3601 Jeffrey Honig quoted Marshall T. Rose explaining the decision that
meillo@220 3602 .Pn post
meillo@220 3603 ignores the profile:
meillo@138 3604 .[
meillo@197 3605 nmh-workers honig post profile
meillo@138 3606 .]
meillo@138 3607 .QS
meillo@138 3608 when you run mh commands in a script, you want all the defaults to be
meillo@138 3609 what the man page says.
meillo@138 3610 when you run a command by hand, then you want your own defaults...
meillo@138 3611 .QE
meillo@138 3612 .LP
meillo@220 3613 The explanation neither matches the problem concered exactly
meillo@220 3614 nor is the interpretation clear.
meillo@220 3615 If the described desire addresses the technical level,
meillo@220 3616 then it conflicts fundametally with the Unix philosophy,
meillo@220 3617 precisely because the indistinquishability of human and script
meillo@220 3618 input is the main reason for the huge software leverage in Unix.
meillo@220 3619 If, however, the described desire addresses the user's view,
meillo@220 3620 then different technical solutions are more appropriate.
meillo@220 3621 The two cases can be regarded simply as two different MH setups.
meillo@220 3622 Hence, mapping the problem of different behavior between interactive and
meillo@220 3623 automated use on the concept of switching between different profiles,
meillo@220 3624 marks it already solved.
meillo@133 3625
meillo@133 3626
meillo@127 3627
meillo@121 3628 .H2 "Standard Libraries
meillo@22 3629 .P
meillo@121 3630 MH is one decade older than the POSIX and ANSI C standards.
meillo@121 3631 Hence, MH included own implementations of functions
meillo@220 3632 that were neither standardized nor widely available, back then.
meillo@220 3633 Today, twenty years after POSIX and ANSI C were published,
meillo@220 3634 developers can expect that systems comply with these standards.
meillo@121 3635 In consequence, MH-specific replacements for standard functions
meillo@121 3636 can and should be dropped.
meillo@220 3637 Kernighan and Pike advise: ``Use standard libraries''.
meillo@121 3638 .[ [
meillo@121 3639 kernighan pike practice of programming
meillo@121 3640 .], p. 196]
meillo@121 3641 Actually, MH had followed this advice in history,
meillo@220 3642 but it had not adjusted to more recent changes in this field.
meillo@121 3643 The
meillo@121 3644 .Fu snprintf()
meillo@121 3645 function, for instance, was standardized with C99 and is available
meillo@121 3646 almost everywhere because of its high usefulness.
meillo@220 3647 Thus, the project's own implementation of
meillo@121 3648 .Fu snprintf()
meillo@123 3649 was dropped in March 2012 in favor for using the one of the
meillo@220 3650 standard library
meillo@220 3651 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@123 3652 Such decisions limit the portability of mmh
meillo@173 3653 if systems do not support these standardized and widespread functions.
meillo@123 3654 This compromise is made because mmh focuses on the future.
meillo@121 3655 .P
meillo@180 3656 .\" XXX kuerzen und mit dem naechsten Absatz vereinen
meillo@220 3657 As I am still in my twenties, have no programming experience from
meillo@220 3658 past decades.
meillo@220 3659 I have not followed the evolution of C through time.
meillo@220 3660 I have not suffered from the the Unix wars.
meillo@121 3661 I have not longed for standardization.
meillo@121 3662 All my programming experience is from a time when ANSI C and POSIX
meillo@121 3663 were well established already.
meillo@220 3664 Thus, I needed to learn about the history in retrospective.
meillo@121 3665 I have only read a lot of books about the (good) old times.
meillo@220 3666 This put me in a difficult position when working with old code.
meillo@123 3667 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123 3668 programming styles, whereas older programmers know these things by
meillo@123 3669 heart from their own experience.
meillo@123 3670 Being aware of the situation, I rather let people with more historic
meillo@220 3671 experience do the transition from ancient code constructs to
meillo@220 3672 standardized ones.
meillo@121 3673 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121 3674 He converted project-specific functions to POSIX replacements,
meillo@121 3675 also removing the conditionals compilation of now standardized features.
meillo@220 3676 Ken Hornstein and David Levine had their part in this work, as well.
meillo@220 3677 Often, I only pulled the changes over from nmh into mmh.
meillo@220 3678 These changes include many commits, among them:
meillo@121 3679 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121 3680 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102 3681 .P
meillo@220 3682 Nevertheless, I worked on the task as well, tidying up the
meillo@220 3683 \fIMH standard library\fP,
meillo@220 3684 .Fn libmh.a .
meillo@220 3685 It is located in the
meillo@123 3686 .Fn sbr
meillo@220 3687 (``subroutines'') directory in the source tree and
meillo@220 3688 includes functions that mmh tools usually need.
meillo@123 3689 Among them are MH-specific functions for profile, context, sequence,
meillo@123 3690 and folder handling, but as well
meillo@123 3691 MH-independent functions, such as auxiliary string functions,
meillo@123 3692 portability interfaces and error-checking wrappers for critical
meillo@123 3693 functions of the standard library.
meillo@220 3694 .BU
meillo@123 3695 I have replaced the
meillo@121 3696 .Fu atooi()
meillo@121 3697 function with calls to
meillo@220 3698 .Fu strtoul() ,
meillo@220 3699 setting the third parameter, the base, to eight.
meillo@123 3700 .Fu strtoul()
meillo@220 3701 is part of C89 and thus considered safe to use
meillo@220 3702 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74 .
meillo@220 3703 .BU
meillo@121 3704 I did remove project-included fallback implementations of
meillo@121 3705 .Fu memmove()
meillo@121 3706 and
meillo@220 3707 .Fu strerror()
meillo@220 3708 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215 ,
meillo@121 3709 although Peter Maydell had re-included them into nmh in 2008
meillo@121 3710 to support SunOS 4.
meillo@121 3711 Nevertheless, these functions are part of ANSI C.
meillo@121 3712 Systems that do not even provide full ANSI C support should not
meillo@121 3713 put a load on mmh.
meillo@220 3714 .BU
meillo@121 3715 The
meillo@121 3716 .Fu copy()
meillo@180 3717 function copies the string in parameter one to the location in
meillo@180 3718 parameter two.
meillo@121 3719 In contrast to
meillo@121 3720 .Fu strcpy() ,
meillo@121 3721 it returns a pointer to the terminating null-byte in the destination area.
meillo@123 3722 The code was adjusted to replace
meillo@121 3723 .Fu copy()
meillo@123 3724 with
meillo@121 3725 .Fu strcpy() ,
meillo@121 3726 except within
meillo@121 3727 .Fu concat() ,
meillo@121 3728 where
meillo@121 3729 .Fu copy()
meillo@123 3730 was more convenient.
meillo@123 3731 Therefore, the definition of
meillo@121 3732 .Fu copy()
meillo@123 3733 was moved into the source file of
meillo@121 3734 .Fu concat()
meillo@220 3735 and its visibility it limited to that
meillo@220 3736 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb .
meillo@220 3737 .BU
meillo@121 3738 The function
meillo@121 3739 .Fu r1bindex()
meillo@121 3740 had been a generalized version of
meillo@121 3741 .Fu basename()
meillo@121 3742 with minor differences.
meillo@121 3743 As all calls to
meillo@121 3744 .Fu r1bindex()
meillo@220 3745 had the slash (`\fL/\fP') as delimiter anyway,
meillo@121 3746 replacing
meillo@121 3747 .Fu r1bindex()
meillo@121 3748 with the more specific and better-named function
meillo@121 3749 .Fu basename()
meillo@121 3750 became desirable.
meillo@121 3751 Unfortunately, many of the 54 calls to
meillo@121 3752 .Fu r1bindex()
meillo@123 3753 depended on a special behavior,
meillo@121 3754 which differed from the POSIX specification for
meillo@121 3755 .Fu basename() .
meillo@121 3756 Hence,
meillo@121 3757 .Fu r1bindex()
meillo@121 3758 was kept but renamed to
meillo@123 3759 .Fu mhbasename() ,
meillo@220 3760 setting the delimiter to the slash
meillo@220 3761 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60 .
meillo@121 3762 For possible uses of
meillo@121 3763 .Fu r1bindex()
meillo@121 3764 with a different delimiter,
meillo@121 3765 the ANSI C function
meillo@121 3766 .Fu strrchr()
meillo@121 3767 provides the core functionality.
meillo@220 3768 .BU
meillo@121 3769 The
meillo@121 3770 .Fu ssequal()
meillo@121 3771 function \(en apparently for ``substring equal'' \(en
meillo@121 3772 was renamed to
meillo@121 3773 .Fu isprefix() ,
meillo@220 3774 because this is what it actually checked
meillo@220 3775 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711.
meillo@220 3776 Its source file had included both of the following comments, no joke.
meillo@220 3777 .in -\n(PIu
meillo@121 3778 .VS
meillo@121 3779 /*
meillo@121 3780 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121 3781 * It is actually checking if s1 is a PREFIX of s2.
meillo@121 3782 * All calls to this function need to be checked to see
meillo@121 3783 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121 3784 * should be kept if it's sufficient.
meillo@121 3785 */
meillo@121 3786
meillo@121 3787 /*
meillo@121 3788 * Check if s1 is a substring of s2.
meillo@121 3789 * If yes, then return 1, else return 0.
meillo@121 3790 */
meillo@121 3791 VE
meillo@220 3792 .in +\n(PIu
meillo@220 3793 Eventually, the function was completely replaced with calls to
meillo@220 3794 .Fu strncmp()
meillo@220 3795 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb .
meillo@121 3796
meillo@102 3797
meillo@102 3798
meillo@102 3799
meillo@133 3800
meillo@133 3801 .H2 "User Data Locations
meillo@133 3802 .P
meillo@133 3803 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133 3804 The profile is a file named
meillo@133 3805 .Fn \&.mh_profile
meillo@133 3806 in the user's home directory.
meillo@133 3807 It contains the static configuration.
meillo@133 3808 It also contains the location of the MH directory in the profile entry
meillo@133 3809 .Pe Path .
meillo@133 3810 The MH directory contains the mail storage and is the first
meillo@220 3811 place to search for form files, scan formats, and similar
meillo@133 3812 configuration files.
meillo@133 3813 The location of the MH directory can be chosen freely by the user.
meillo@220 3814 The usual name is a directory named
meillo@133 3815 .Fn Mail
meillo@220 3816 in the user's home directory.
meillo@133 3817 .P
meillo@200 3818 The way MH data is split between profile and MH directory is a legacy.
meillo@133 3819 It is only sensible in a situation where the profile is the only
meillo@133 3820 configuration file.
meillo@133 3821 Why else should the mail storage and the configuration files be intermixed?
meillo@220 3822 They are of different kind:
meillo@220 3823 One kind is the data to be operated on and the other kind is
meillo@220 3824 the configuration to change how tools operate.
meillo@133 3825 Splitting the configuration between the profile and the MH directory
meillo@220 3826 is inappropriate, as well.
meillo@220 3827 I improved the situation by breaking compatibility.
meillo@133 3828 .P
meillo@220 3829 In mmh, personal data is grouped by type.
meillo@220 3830 This results in two distinct parts:
meillo@171 3831 the mail storage and the configuration.
meillo@220 3832 The mail storage directory still contains all the messages,
meillo@133 3833 but, in exception of public sequences files, nothing else.
meillo@133 3834 In difference to nmh, the auxiliary configuration files are no longer
meillo@133 3835 located there.
meillo@133 3836 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@220 3837 but the user's \fImail storage\fP.
meillo@133 3838 Its location is still user-chosen, with the default name
meillo@220 3839 .Fn Mail
meillo@133 3840 in the user's home directory.
meillo@220 3841 The configuration is grouped together in the hidden directory
meillo@133 3842 .Fn \&.mmh
meillo@133 3843 in the user's home directory.
meillo@133 3844 This \fImmh directory\fP contains the context file, personal forms,
meillo@133 3845 scan formats, and the like, but also the user's profile, now named
meillo@133 3846 .Fn profile .
meillo@220 3847 The path to the profile is no longer
meillo@133 3848 .Fn $HOME/.mh_profile
meillo@220 3849 but
meillo@133 3850 .Fn $HOME/.mmh/profile .
meillo@220 3851 (The alternative of having file
meillo@133 3852 .Fn $HOME/.mh_profile
meillo@220 3853 and a configuration directory
meillo@133 3854 .Fn $HOME/.mmh
meillo@220 3855 appeared to be inconsistent.)
meillo@220 3856 .P
meillo@133 3857 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133 3858 Unix users.
meillo@220 3859 The main achievement of the change is the clear and sensible separation
meillo@220 3860 of the mail storage and the configuration.
meillo@168 3861 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3862 .P
meillo@220 3863 As MH allows users to have multiple MH setups,
meillo@220 3864 it is necessary to switch the profile.
meillo@133 3865 The profile is the single entry point to access the rest of a
meillo@133 3866 personal MH setup.
meillo@133 3867 In nmh, the environment variable
meillo@133 3868 .Ev MH
meillo@220 3869 is used to specify a different profile.
meillo@220 3870 To operate in the same MH setup with a separate context, the
meillo@133 3871 .Ev MHCONTEXT
meillo@220 3872 environment variable is used.
meillo@220 3873 This allows having a separate current folder in each terminal at
meillo@220 3874 the same time, for instance.
meillo@220 3875 In mmh, three environment variables replace the two of nmh.
meillo@133 3876 .Ev MMH
meillo@133 3877 overrides the default location of the mmh directory (\c
meillo@133 3878 .Fn .mmh ).
meillo@133 3879 .Ev MMHP
meillo@133 3880 and
meillo@133 3881 .Ev MMHC
meillo@220 3882 override the paths to the profile and context file, respectively.
meillo@133 3883 This approach allows the set of personal configuration files to be chosen
meillo@220 3884 independently of the profile, context, and mail storage.
meillo@133 3885 The new approach has no functional disadvantages,
meillo@133 3886 as every setup I can imagine can be implemented with both approaches,
meillo@220 3887 possibly even easier with the new one.
meillo@220 3888 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3889
meillo@133 3890
meillo@133 3891
meillo@133 3892
meillo@133 3893
meillo@118 3894 .H2 "Modularization
meillo@220 3895 .Id modularization
meillo@118 3896 .P
meillo@123 3897 The source code of the mmh tools is located in the
meillo@122 3898 .Fn uip
meillo@123 3899 (``user interface programs'') directory.
meillo@180 3900 Each tool has a source file with the name of the command.
meillo@122 3901 For example,
meillo@122 3902 .Pn rmm
meillo@122 3903 is built from
meillo@122 3904 .Fn uip/rmm.c .
meillo@123 3905 Some source files are used for multiple programs.
meillo@122 3906 For example
meillo@122 3907 .Fn uip/scansbr.c
meillo@173 3908 is used for both
meillo@122 3909 .Pn scan
meillo@122 3910 and
meillo@122 3911 .Pn inc .
meillo@122 3912 In nmh, 49 tools were built from 76 source files.
meillo@123 3913 This is a ratio of 1.6 source files per program.
meillo@123 3914 32 programs depended on multiple source files;
meillo@123 3915 17 programs depended on one source file only.
meillo@122 3916 In mmh, 39 tools are built from 51 source files.
meillo@123 3917 This is a ratio of 1.3 source files per program.
meillo@123 3918 18 programs depend on multiple source files;
meillo@123 3919 21 programs depend on one source file only.
meillo@123 3920 (These numbers and the ones in the following text ignore the MH library
meillo@123 3921 as well as shell scripts and multiple names for the same program.)
meillo@180 3922 .\" XXX graph
meillo@122 3923 .P
meillo@123 3924 Splitting the source code of a large program into multiple files can
meillo@220 3925 increase the readability of its source code,
meillo@220 3926 but most of the mmh tools are small and straight-forward programs.
meillo@220 3927 In exception of the MIME handling tools (i.e.
meillo@122 3928 .Pn mhbuild ,
meillo@122 3929 .Pn mhstore ,
meillo@122 3930 .Pn show ,
meillo@220 3931 etc.),
meillo@220 3932 .Pn pick
meillo@220 3933 is the only tool with more than one thousand lines of source code.
meillo@220 3934 Splitting programs with less than one thousand lines of code into
meillo@220 3935 multiple source files leads seldom to better readability.
meillo@220 3936 For such tools, splitting still makes sense
meillo@220 3937 when parts of the code are reused in other programs
meillo@179 3938 and the reused code fragment is (1) not general enough
meillo@179 3939 for including it in the MH library
meillo@179 3940 or (2) has dependencies on a library that only few programs need.
meillo@122 3941 .Fn uip/packsbr.c ,
meillo@122 3942 for instance, provides the core program logic for the
meillo@122 3943 .Pn packf
meillo@122 3944 and
meillo@122 3945 .Pn rcvpack
meillo@122 3946 programs.
meillo@122 3947 .Fn uip/packf.c
meillo@122 3948 and
meillo@122 3949 .Fn uip/rcvpack.c
meillo@122 3950 mainly wrap the core function appropriately.
meillo@122 3951 No other tools use the folder packing functions.
meillo@123 3952 As another example,
meillo@123 3953 .Fn uip/termsbr.c
meillo@220 3954 accesses terminal properties, which requires linking with the
meillo@220 3955 \fItermcap\fP or a \fIcurses\fP library.
meillo@220 3956 If
meillo@123 3957 .Fn uip/termsbr.c
meillo@220 3958 is included in the MH library, then every program needs to be linked
meillo@220 3959 with termcap or curses, although only few of the programs use
meillo@220 3960 the library.
meillo@122 3961 .P
meillo@122 3962 The task of MIME handling is complex enough that splitting its code
meillo@122 3963 into multiple source files improves the readability.
meillo@122 3964 The program
meillo@122 3965 .Pn mhstore ,
meillo@122 3966 for instance, is compiled out of seven source files with 2\|500
meillo@122 3967 lines of code in summary.
meillo@122 3968 The main code file
meillo@122 3969 .Fn uip/mhstore.c
meillo@220 3970 consists of 800 lines; the other 1\|700 lines are code reused in
meillo@123 3971 other MIME handling tools.
meillo@123 3972 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123 3973 a MH-MIME library, as a companion to the MH standard library.
meillo@220 3974 This is left to be done.
meillo@122 3975 .P
meillo@169 3976 The work already accomplished focussed on the non-MIME tools.
meillo@122 3977 The amount of code compiled into each program was reduced.
meillo@123 3978 This eases the understanding of the code base.
meillo@122 3979 In nmh,
meillo@122 3980 .Pn comp
meillo@122 3981 was built from six source files:
meillo@122 3982 .Fn comp.c ,
meillo@122 3983 .Fn whatnowproc.c ,
meillo@122 3984 .Fn whatnowsbr.c ,
meillo@122 3985 .Fn sendsbr.c ,
meillo@122 3986 .Fn annosbr.c ,
meillo@122 3987 and
meillo@122 3988 .Fn distsbr.c .
meillo@122 3989 In mmh, it builds from only two:
meillo@122 3990 .Fn comp.c
meillo@122 3991 and
meillo@122 3992 .Fn whatnowproc.c .
meillo@123 3993 In nmh's
meillo@123 3994 .Pn comp ,
meillo@123 3995 the core function of
meillo@122 3996 .Pn whatnow ,
meillo@122 3997 .Pn send ,
meillo@122 3998 and
meillo@122 3999 .Pn anno
meillo@220 4000 were all compiled into
meillo@122 4001 .Pn comp .
meillo@123 4002 This saved the need to execute these programs with
meillo@220 4003 the expensive system calls
meillo@122 4004 .Fu fork()
meillo@122 4005 and
meillo@220 4006 .Fu exec() .
meillo@171 4007 Whereas this approach improved the time performance,
meillo@171 4008 it interwove the source code.
meillo@122 4009 Core functionalities were not encapsulated into programs but into
meillo@122 4010 function, which were then wrapped by programs.
meillo@122 4011 For example,
meillo@122 4012 .Fn uip/annosbr.c
meillo@122 4013 included the function
meillo@122 4014 .Fu annotate() .
meillo@122 4015 Each program that wanted to annotate messages, included the source file
meillo@123 4016 .Fn uip/annosbr.c
meillo@123 4017 and called
meillo@123 4018 .Fu annotate() .
meillo@123 4019 Because the function
meillo@123 4020 .Fu annotate()
meillo@123 4021 was used like the tool
meillo@123 4022 .Pn anno ,
meillo@123 4023 it had seven parameters, reflecting the command line switches of the tool.
meillo@122 4024 When another pair of command line switches was added to
meillo@122 4025 .Pn anno ,
meillo@122 4026 a rather ugly hack was implemented to avoid adding another parameter
meillo@220 4027 to the function
meillo@220 4028 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f .
meillo@122 4029 .P
meillo@122 4030 In mmh, the relevant code of
meillo@122 4031 .Pn comp
meillo@122 4032 comprises the two files
meillo@122 4033 .Fn uip/comp.c
meillo@122 4034 and
meillo@122 4035 .Fn uip/whatnowproc.c ,
meillo@220 4036 together 210 lines of code,
meillo@220 4037 whereas in nmh,
meillo@122 4038 .Pn comp
meillo@122 4039 comprises six files with 2\|450 lines.
meillo@220 4040 Not all of the code in these six files is actually used by
meillo@122 4041 .Pn comp ,
meillo@220 4042 but the reader needed to read it all to know which parts are relevant.
meillo@220 4043 Understanding nmh's
meillo@122 4044 .Pn comp ,
meillo@123 4045 required understanding the inner workings of
meillo@122 4046 .Fn uip/annosbr.c
meillo@122 4047 first.
meillo@123 4048 To be sure to fully understand a program, its whole source code needs
meillo@122 4049 to be examined.
meillo@123 4050 Not doing so is a leap of faith, assuming that the developers
meillo@122 4051 have avoided obscure programming techniques.
meillo@220 4052 Here, it should be recalled that information passed in obscure ways
meillo@220 4053 through the program's source base, due to the aforementioned hack
meillo@220 4054 to save an additional parameter in nmh's
meillo@220 4055 .Pn anno .
meillo@220 4056 .P
meillo@220 4057 In mmh, understanding
meillo@220 4058 .Pn comp
meillo@220 4059 requires to read only 210 lines of code to read, whereas the amount
meillo@220 4060 is ten times more for nmh's
meillo@220 4061 .Pn comp .
meillo@220 4062 .P
meillo@220 4063 By separating the tools on the program-level,
meillo@220 4064 the boundaries are clearly visible, as the interfaces are calls to
meillo@122 4065 .Fu exec()
meillo@122 4066 rather than arbitrary function calls.
meillo@220 4067 Additionally, this kind of separation is more strict because
meillo@220 4068 it is technically enforced by the operating system;
meillo@220 4069 it can not be simply bypassed with global variables.
meillo@220 4070 Good separation simplifies the understanding of program code
meillo@220 4071 because the area influenced by any particular statement is small.
meillo@220 4072 As I have read a lot in nmh's code base during the last two years,
meillo@220 4073 I have learned about the easy and the difficult parts.
meillo@220 4074 In my observation, the understanding of code is enormously eased
meillo@220 4075 if the influenced area is small and clearly bounded.
meillo@123 4076 .P
meillo@220 4077 Yet, the real problem is another:
meillo@123 4078 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123 4079 Understanding
meillo@122 4080 .Pn comp
meillo@123 4081 requires understanding
meillo@123 4082 .Fn uip/annosbr.c
meillo@123 4083 and
meillo@123 4084 .Fn uip/sendsbr.c
meillo@123 4085 because
meillo@123 4086 .Pn comp
meillo@220 4087 annotates and sends messages.
meillo@220 4088 In nmh, there surely exist the tools
meillo@220 4089 .Pn anno
meillo@220 4090 and
meillo@122 4091 .Pn send ,
meillo@220 4092 which cover these jobs,
meillo@220 4093 but
meillo@122 4094 .Pn comp
meillo@123 4095 and
meillo@122 4096 .Pn repl
meillo@122 4097 and
meillo@122 4098 .Pn forw
meillo@122 4099 and
meillo@122 4100 .Pn dist
meillo@122 4101 and
meillo@122 4102 .Pn whatnow
meillo@122 4103 and
meillo@220 4104 .Pn viamail
meillo@220 4105 \(en they all (!) \(en
meillo@220 4106 have the same annotating and sending functions included, once more.
meillo@220 4107 As a result,
meillo@123 4108 .Pn comp
meillo@123 4109 sends messages without using
meillo@123 4110 .Pn send .
meillo@123 4111 The situation is the same as if
meillo@123 4112 .Pn grep
meillo@220 4113 would page its output without using
meillo@123 4114 .Pn more
meillo@123 4115 just because both programs are part of the same code base.
meillo@123 4116 .P
meillo@220 4117 The clear separation on the surface of nmh
meillo@220 4118 \(en the tool chest approach \(en
meillo@123 4119 is violated on the level below.
meillo@122 4120 This violation is for the sake of time performance.
meillo@220 4121 Decades ago, sacrificing readability and conceptional beauty
meillo@220 4122 for speed might have been necessary to prevent MH from being
meillo@220 4123 unusably slow, but today this is not the case anymore.
meillo@220 4124 No longer should speed improvements that became unnecessary be kept.
meillo@220 4125 No longer should readability or conceptional beauty be sacrificed.
meillo@220 4126 No longer should the Unix philosophy's ``one tool, one job''
meillo@220 4127 guideline be violated.
meillo@123 4128 Therefore, mmh's
meillo@123 4129 .Pn comp
meillo@220 4130 no longer sends messages.
meillo@220 4131 .P
meillo@123 4132 In mmh, different jobs are divided among separate programs that
meillo@122 4133 invoke each other as needed.
meillo@123 4134 In consequence,
meillo@123 4135 .Pn comp
meillo@123 4136 invokes
meillo@123 4137 .Pn whatnow
meillo@123 4138 which thereafter invokes
meillo@220 4139 .Pn send
meillo@168 4140 .Ci 3df5ab3c116e6d4a2fb4bb5cc9dfc5f781825815
meillo@220 4141 .Ci c73c00bfccd22ec77e9593f47462aeca4a8cd9c0 .
meillo@123 4142 The clear separation on the surface is maintained on the level below.
meillo@220 4143 Human users and other tools use the same interface \(en
meillo@123 4144 annotations, for example, are made by invoking
meillo@123 4145 .Pn anno ,
meillo@220 4146 no matter if requested by programs or by human beings
meillo@168 4147 .Ci 469a4163c2a1a43731d412eaa5d9cae7d670c48b
meillo@168 4148 .Ci aed384169af5204b8002d06e7a22f89197963d2d
meillo@220 4149 .Ci 3caf9e298a8861729ca8b8a84f57022b6f3ea742 .
meillo@123 4150 The decrease of tools built from multiple source files and thus
meillo@123 4151 the decrease of
meillo@123 4152 .Fn uip/*sbr.c
meillo@220 4153 files confirm the improvement
meillo@168 4154 .Ci 9e6d91313f01c96b4058d6bf419a8ca9a207bc33
meillo@168 4155 .ci 81744a46ac9f845d6c2b9908074d269275178d2e
meillo@168 4156 .Ci f0f858069d21111f0dbea510044593f89c9b0829
meillo@168 4157 .Ci 0503a6e9be34f24858b55b555a5c948182b9f24b
meillo@168 4158 .Ci 27826f9353e0f0b04590b7d0f8f83e60462b90f0
meillo@168 4159 .Ci d1da1f94ce62160aebb30df4063ccbc53768656b
meillo@220 4160 .Ci c42222869e318fff5dec395eca3e776db3075455 .
meillo@220 4161 This is also visible in the complexity of the build dependency graphs:
meillo@145 4162
meillo@220 4163 .sp
meillo@220 4164 Nmh:
meillo@220 4165 .BP input/deps-nmh.eps .5i
meillo@220 4166 .EP
meillo@220 4167 .sp
meillo@220 4168 Mmh:
meillo@220 4169 .BP input/deps-mmh.eps .8i
meillo@220 4170 .EP
meillo@145 4171
meillo@220 4172 The figures display all program to source file relationships
meillo@220 4173 that are not one-to-one,
meillo@220 4174 i.e. all programs that are built from multiple source files.
meillo@220 4175 The primary source file of each program is omited from the graph.