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More cleanups.
author markus schnalke <meillo@marmaro.de>
date Mon, 16 Jul 2012 00:37:31 +0200
parents a1468cf505fd
children 77c87c38bff4
rev   line source
meillo@58 1 .H0 "Discussion
meillo@0 2 .P
meillo@169 3 This main chapter discusses the practical work accomplished in the
meillo@169 4 mmh project.
meillo@217 5 It is structured along the goals chosen for the project.
meillo@217 6 A selection of the work undertaken
meillo@217 7 is described.
meillo@217 8 .P
meillo@217 9 This discussion compares the present version of mmh with the state of
meillo@217 10 nmh at the time when the mmh project had started, i.e. fall 2011.
meillo@224 11 Recent changes in nmh are rarely part of the discussion.
meillo@187 12 .P
meillo@230 13 Whenever lines of code were counted, David A. Wheeler's \fIsloccount\fP
meillo@230 14 was used to measure the amount in a comparable way.
meillo@230 15 .P
meillo@187 16 For the reader's convenience, the structure of modern email systems
meillo@217 17 is depicted in the following figure.
meillo@187 18 It illustrates the path a message takes from sender to recipient.
meillo@217 19
meillo@217 20 .sp 1.5
meillo@187 21 .KS
meillo@187 22 .in 2c
meillo@187 23 .so input/mail-agents.pic
meillo@187 24 .KE
meillo@217 25 .sp 1.5
meillo@217 26
meillo@187 27 .LP
meillo@217 28 The ellipses denote mail agents, i.e. different jobs in email processing.
meillo@217 29 These are:
meillo@187 30 .IP "Mail User Agent (MUA)
meillo@217 31 The only program users directly interact with.
meillo@187 32 It includes functions to compose new mail, display received mail,
meillo@187 33 and to manage the mail storage.
meillo@217 34 It is called a \fImail client\fP as well.
meillo@187 35 .IP "Mail Submission Agent (MSA)
meillo@187 36 A special kind of Mail Transfer Agent, used to submit mail into the
meillo@187 37 mail transport system.
meillo@217 38 Often it is also called an MTA.
meillo@187 39 .IP "Mail Transfer Agent (MTA)
meillo@187 40 A node in the mail transport system.
meillo@217 41 It transfers incoming mail to a transport node nearer to the
meillo@217 42 final destination.
meillo@217 43 An MTA may be the final destination itself.
meillo@187 44 .IP "Mail Delivery Agent (MDA)
meillo@217 45 Delivers mail according to a set of rules.
meillo@217 46 Usually, the messages are stored to disk.
meillo@187 47 .IP "Mail Retrieval Agent (MRA)
meillo@217 48 Initiates the transfer of mail from a remote location to the local machine.
meillo@217 49 (The dashed arrow in the figure represents the pull request.)
meillo@217 50 .LP
meillo@217 51 The dashed boxes represent entities that usually reside on single machines.
meillo@217 52 The box on the lower left represents the sender's system.
meillo@187 53 The box on the upper left represents the first mail transfer node.
meillo@224 54 The box on the upper right represents the transfer node responsible
meillo@224 55 for the destination address.
meillo@217 56 The box on the lower right represents the recipient's system.
meillo@187 57 Often, the boxes above the dotted line are servers on the Internet.
meillo@217 58 Many mail clients, including nmh, include all of the components below
meillo@217 59 the dotted line.
meillo@217 60 This is not the case for mmh; it implements the MUA only.
meillo@187 61
meillo@187 62
meillo@187 63
meillo@58 64
meillo@58 65
meillo@58 66
meillo@133 67 .\" --------------------------------------------------------------
meillo@125 68 .H1 "Streamlining
meillo@58 69
meillo@0 70 .P
meillo@217 71 MH once provided a complete email system.
meillo@217 72 The community around nmh tries to keep nmh in similar shape.
meillo@178 73 In fundamental contrast, mmh shall be an MUA only.
meillo@87 74 I believe that the development of all-in-one mail systems is obsolete.
meillo@173 75 Today, email is too complex to be fully covered by a single project.
meillo@173 76 Such a project will not be able to excel in all aspects.
meillo@159 77 Instead, the aspects of email should be covered by multiple projects,
meillo@87 78 which then can be combined to form a complete system.
meillo@169 79 Excellent implementations for the various aspects of email already exist.
meillo@223 80 Just to name three examples: Postfix is a specialized MTA, Procmail
meillo@223 81 is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89 82 I believe that it is best to use such specialized tools instead of
meillo@217 83 providing the same function once more as a side component.
meillo@58 84 .P
meillo@169 85 Doing something well requires focusing on a small set of specific aspects.
meillo@217 86 Under the assumption that development which is focussed on a particular
meillo@217 87 area produces better results there, specialized projects will be superior
meillo@87 88 in their field of focus.
meillo@87 89 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87 90 or modular \(en will never be the best choice in any of the fields.
meillo@217 91 Even in providing the most consistent all-in-one system, they are likely
meillo@217 92 to be beaten by projects that focus exclusively on the creation
meillo@217 93 of a homogeneous system by integrating existing mail components.
meillo@87 94 .P
meillo@217 95 Usually, the limiting resource in the community development of
meillo@217 96 free software is man power.
meillo@217 97 If the development effort is spread over a large development area,
meillo@217 98 it becomes more difficult to compete with the specialists in the
meillo@87 99 various fields.
meillo@87 100 The concrete situation for MH-based mail systems is even tougher,
meillo@169 101 given their small and aged community, concerning both developers and users.
meillo@87 102 .P
meillo@87 103 In consequence, I believe that the available development resources
meillo@100 104 should focus on the point where MH is most unique.
meillo@87 105 This is clearly the user interface \(en the MUA.
meillo@125 106 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60 107
meillo@60 108
meillo@100 109 .H2 "Mail Transfer Facilities
meillo@154 110 .Id mail-transfer-facilities
meillo@60 111 .P
meillo@217 112 The removal of the mail transfer facilities, effectively dropping the
meillo@217 113 MSA and MRA, had been the first work task in the mmh project.
meillo@217 114 The desire for this change initiated the creation of the mmh project.
meillo@60 115 .P
meillo@169 116 Focusing on one mail agent role only, is motivated by Eric Allman's
meillo@105 117 experience with Sendmail.
meillo@217 118 He identified the limitation of Sendmail
meillo@217 119 to the MTA task as one reason for its success:
meillo@105 120 .[ [
meillo@105 121 costales sendmail
meillo@105 122 .], p. xviii]
meillo@105 123 .QS
meillo@105 124 Second, I limited myself to the routing function \(en
meillo@110 125 I wouldn't write user agents or delivery back-ends.
meillo@217 126 This was a departure of the dominant thought of the time,
meillo@105 127 in which routing logic, local delivery, and often the network code
meillo@105 128 were incorporated directly into the user agents.
meillo@105 129 .QE
meillo@105 130 .P
meillo@187 131 In nmh, the MSA is called \fIMessage Transfer Service\fP (MTS).
meillo@105 132 This facility, implemented by the
meillo@105 133 .Pn post
meillo@217 134 command, establishes network connections and spoke SMTP to submit
meillo@159 135 messages to be relayed to the outside world.
meillo@217 136 When email transfer changed, this part needed to be changed as well.
meillo@89 137 Encryption and authentication for network connections
meillo@87 138 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@217 139 This added complexity without improving the core functions.
meillo@217 140 Furthermore, keeping up with recent developments in the field of
meillo@87 141 mail transfer requires development power and specialists.
meillo@217 142 In mmh, this whole facility was simply cut off
meillo@76 143 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76 144 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@217 145 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b .
meillo@87 146 Instead, mmh depends on an external MSA.
meillo@217 147 All outgoing mail in mmh goes through the
meillo@60 148 .Pn sendmail
meillo@87 149 command, which almost any MSA provides.
meillo@87 150 If not, a wrapper program can be written.
meillo@87 151 It must read the message from the standard input, extract the
meillo@87 152 recipient addresses from the message header, and hand the message
meillo@87 153 over to the MSA.
meillo@223 154 For example, a wrapper script for qmail would be:
meillo@87 155 .VS
meillo@87 156 #!/bin/sh
meillo@138 157 exec qmail-inject # ignore command line arguments
meillo@87 158 VE
meillo@87 159 The requirement to parse the recipient addresses out of the message header
meillo@217 160 may be removed in the future.
meillo@217 161 Mmh could pass the recipient addresses as command line arguments.
meillo@100 162 This appears to be the better interface.
meillo@60 163 .P
meillo@60 164 To retrieve mail, the
meillo@60 165 .Pn inc
meillo@217 166 command in nmh acts as MRA.
meillo@217 167 It establishes network connections
meillo@217 168 and speaks POP3 to retrieve mail from remote servers.
meillo@76 169 As with mail submission, the network connections required encryption and
meillo@217 170 authentication, thus TLS and SASL were added to nmh.
meillo@169 171 Support for message retrieval through IMAP will soon become necessary
meillo@169 172 additions, too, and likewise for any other changes in mail transfer.
meillo@217 173 But not in mmh because it has dropped the support for retrieving mail
meillo@217 174 from remote locations
meillo@217 175 .Ci ab7b48411962d26439f92f35ed084d3d6275459c .
meillo@76 176 Instead, it depends on an external tool to cover this task.
meillo@169 177 Mmh has two paths for messages to enter mmh's mail storage:
meillo@100 178 (1) Mail can be incorporated with
meillo@60 179 .Pn inc
meillo@87 180 from the system maildrop, or (2) with
meillo@60 181 .Pn rcvstore
meillo@87 182 by reading them, one at a time, from the standard input.
meillo@60 183 .P
meillo@217 184 With the removal of the MSA and MRA, mmh converted from a complete
meillo@217 185 mail system to only an MUA.
meillo@60 186 Now, of course, mmh depends on third-party software.
meillo@87 187 An external MSA is required to transfer mail to the outside world;
meillo@60 188 an external MRA is required to retrieve mail from remote machines.
meillo@217 189 Excellent implementations of such software exist.
meillo@217 190 They likely are superior to the internal versions that were removed.
meillo@217 191 Additionally, the best suiting programs can be chosen freely.
meillo@60 192 .P
meillo@217 193 As it had already been possible to use an external MSA and MRA,
meillo@217 194 why should the internal version not be kept for convenience?
meillo@228 195 Transferred to a different area, the question,
meillo@224 196 whether there is sense in having a fall-back pager in all
meillo@224 197 the command line tools for the cases when
meillo@60 198 .Pn more
meillo@60 199 or
meillo@60 200 .Pn less
meillo@173 201 are not available, appears to be ridiculous.
meillo@100 202 Of course, MSAs and MRAs are more complex than text pagers
meillo@87 203 and not necessarily available but still the concept of orthogonal
meillo@217 204 design holds: ``Write programs that do one thing and do it well''.
meillo@87 205 .[
meillo@87 206 mcilroy unix phil
meillo@87 207 p. 53
meillo@87 208 .]
meillo@87 209 .[
meillo@87 210 mcilroy bstj foreword
meillo@87 211 .]
meillo@87 212 Here, this part of the Unix philosophy was applied not only
meillo@87 213 to the programs but to the project itself.
meillo@87 214 In other words:
meillo@164 215 Develop projects that focus on one thing and do it well.
meillo@169 216 Projects which have grown complex should be split, for the same
meillo@169 217 reasons that programs which have grown complex should be split.
meillo@100 218 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87 219 separate projects then they should be separated.
meillo@217 220 In my opinion, this is the case.
meillo@217 221 The RFCs suggest this separation by clearly distinguishing the
meillo@217 222 different mail handling tasks [RFC\|821].
meillo@217 223 The small interfaces between the mail agents support the
meillo@217 224 separation as well.
meillo@76 225 .P
meillo@217 226 Once, email had been small and simple.
meillo@100 227 At that time,
meillo@60 228 .Pn /bin/mail
meillo@169 229 had covered everything there was to email and still was small and simple.
meillo@100 230 Later, the essential complexity of email increased.
meillo@224 231 (Essential complexity is the complexity defined by the problem itself
meillo@217 232 .[ [
meillo@87 233 brooks no silver bullet
meillo@224 234 .]].)
meillo@217 235 Consequently, email systems grew.
meillo@100 236 RFCs started to introduce the concept of mail agents to separate the
meillo@217 237 various roles because they became more extensive and because
meillo@217 238 new roles appeared.
meillo@217 239 As mail system implementations grew, parts of them were split off.
meillo@169 240 For instance, a POP server was included in the original MH;
meillo@169 241 it was removed in nmh.
meillo@217 242 Now is the time to go one step further and split off the MSA and MRA,
meillo@217 243 as well.
meillo@87 244 Not only does this decrease the code size of the project,
meillo@169 245 more importantly, it unburdens mmh of the whole field of
meillo@217 246 message transfer, with all its implications for the project.
meillo@169 247 There is no more need for concern with changes in network transfer.
meillo@217 248 This independence is gained by depending on external components
meillo@217 249 that cover the field.
meillo@60 250 .P
meillo@217 251 In general, functionality can be added in three different ways:
meillo@171 252 .LI 1
meillo@217 253 By implementing the function in the project itself.
meillo@171 254 .LI 2
meillo@217 255 By depending on a library that provides the function.
meillo@171 256 .LI 3
meillo@217 257 By depending on a program that provides the function.
meillo@171 258 .LP
meillo@169 259 While implementing the function in the project itself leads to the
meillo@169 260 largest increase in code size and requires the most maintenance
meillo@169 261 and development work,
meillo@217 262 it keeps the project's dependence on other software lowest.
meillo@169 263 Using libraries or external programs requires less maintenance work
meillo@217 264 but introduces dependencies on external projects.
meillo@169 265 Programs have the smallest interfaces and provide the best separation,
meillo@87 266 but possibly limit the information exchange.
meillo@169 267 External libraries are more strongly connected than external programs,
meillo@169 268 thus information can be exchanged in a more flexible manner.
meillo@227 269 Obviously, adding code to a project increases the maintenance work.
meillo@217 270 As implementing complex functions in the project itself adds
meillo@217 271 a lot of code, this should be avoided if possible.
meillo@217 272 Thus, the dependencies only change in their character,
meillo@169 273 not in their existence.
meillo@66 274 In mmh, library dependencies on
meillo@66 275 .Pn libsasl2
meillo@66 276 and
meillo@66 277 .Pn libcrypto /\c
meillo@66 278 .Pn libssl
meillo@159 279 were traded against program dependencies on an MSA and an MRA.
meillo@159 280 This also meant trading build-time dependencies against run-time
meillo@87 281 dependencies.
meillo@169 282 Besides providing stronger separation and greater flexibility,
meillo@169 283 program dependencies also allowed
meillo@66 284 over 6\|000 lines of code to be removed from mmh.
meillo@66 285 This made mmh's code base about 12\|% smaller.
meillo@87 286 Reducing the project's code size by such an amount without actually
meillo@87 287 losing functionality is a convincing argument.
meillo@87 288 Actually, as external MSAs and MRAs are likely superior to the
meillo@87 289 project's internal versions, the common user even gains functionality.
meillo@66 290 .P
meillo@169 291 Users of MH should not have problems setting up an external MSA and MRA.
meillo@60 292 Also, the popular MSAs and MRAs have large communities and a lot
meillo@169 293 of available documentation.
meillo@217 294
meillo@223 295 Choices for MSAs range from small forwarders such as \fIssmtp\fP and
meillo@223 296 \fInullmailer\fP, over mid-size MTAs including \fImasqmail\fP and
meillo@223 297 \fIdma\fP, up to full-featured MTAs as for instance \fIPostfix\fP.
meillo@223 298 MRAs are provided for example by \fIfetchmail\fP, \fIgetmail\fP,
meillo@223 299 \fImpop\fP, and \fIfdm\fP.
meillo@60 300
meillo@60 301
meillo@100 302 .H2 "Non-MUA Tools
meillo@60 303 .P
meillo@217 304 One goal of mmh is to remove the tools that do not significantly
meillo@217 305 contribute to the MUA's job.
meillo@217 306 Loosely related and rarely used tools distract from a lean appearance,
meillo@217 307 and require maintenance work without adding much to the core task.
meillo@217 308 By removing these tools, mmh became more streamlined and focused.
meillo@62 309 .BU
meillo@58 310 .Pn conflict
meillo@87 311 was removed
meillo@76 312 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@217 313 because it is a mail system maintenance tool and not MUA-related.
meillo@87 314 It even checked
meillo@58 315 .Fn /etc/passwd
meillo@58 316 and
meillo@58 317 .Fn /etc/group
meillo@87 318 for consistency, which is completely unrelated to email.
meillo@87 319 A tool like
meillo@87 320 .Pn conflict
meillo@87 321 is surely useful, but it should not be shipped with mmh.
meillo@62 322 .BU
meillo@58 323 .Pn rcvtty
meillo@87 324 was removed
meillo@87 325 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89 326 because its use case of writing to the user's terminal
meillo@200 327 on reception of mail is obsolete.
meillo@87 328 If users like to be informed of new mail, the shell's
meillo@58 329 .Ev MAILPATH
meillo@87 330 variable or graphical notifications are technically more appealing.
meillo@217 331 Writing to terminals directly is hardly ever desired today.
meillo@169 332 If, though, one prefers this approach, the standard tool
meillo@58 333 .Pn write
meillo@58 334 can be used in a way similar to:
meillo@82 335 .VS
meillo@58 336 scan -file - | write `id -un`
meillo@82 337 VE
meillo@62 338 .BU
meillo@58 339 .Pn viamail
meillo@87 340 was removed
meillo@87 341 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87 342 when the new attachment system was activated, because
meillo@58 343 .Pn forw
meillo@76 344 could then cover the task itself.
meillo@62 345 The program
meillo@58 346 .Pn sendfiles
meillo@62 347 was rewritten as a shell script wrapper around
meillo@58 348 .Pn forw .
meillo@76 349 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62 350 .BU
meillo@58 351 .Pn msgchk
meillo@87 352 was removed
meillo@87 353 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87 354 because it lost its use case when POP support was removed.
meillo@76 355 A call to
meillo@58 356 .Pn msgchk
meillo@87 357 provided hardly more information than:
meillo@82 358 .VS
meillo@58 359 ls -l /var/mail/meillo
meillo@82 360 VE
meillo@217 361 Yet, it distinguished between old and new mail, but
meillo@169 362 these details can be retrieved with
meillo@76 363 .Pn stat (1),
meillo@62 364 too.
meillo@100 365 A small shell script could be written to print the information
meillo@76 366 in a similar way, if truly necessary.
meillo@76 367 As mmh's
meillo@76 368 .Pn inc
meillo@87 369 only incorporates mail from the user's local maildrop,
meillo@62 370 and thus no data transfers over slow networks are involved,
meillo@169 371 there is hardly any need to check for new mail before incorporating it.
meillo@62 372 .BU
meillo@58 373 .Pn msh
meillo@87 374 was removed
meillo@76 375 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87 376 because the tool was in conflict with the philosophy of MH.
meillo@217 377 It provided an interactive shell to access the features of MH.
meillo@217 378 However, it was not just a shell tailored to the needs of mail handling,
meillo@217 379 but one large program that had several MH tools built in.
meillo@217 380 This conflicted with the major feature of MH of being a tool chest.
meillo@76 381 .Pn msh 's
meillo@159 382 main use case had been accessing Bulletin Boards, which have ceased to
meillo@62 383 be popular.
meillo@62 384 .P
meillo@62 385 Removing
meillo@169 386 .Pn msh
meillo@212 387 together with the truly archaic code relics
meillo@58 388 .Pn vmh
meillo@58 389 and
meillo@169 390 .Pn wmh
meillo@62 391 saved more than 7\|000 lines of C code \(en
meillo@66 392 about 15\|% of the project's original source code amount.
meillo@100 393 Having less code \(en with equal readability, of course \(en
meillo@76 394 for the same functionality is an advantage.
meillo@63 395 Less code means less bugs and less maintenance work.
meillo@76 396 As
meillo@63 397 .Pn rcvtty
meillo@63 398 and
meillo@63 399 .Pn msgchk
meillo@87 400 are assumed to be rarely used and can be implemented in different ways,
meillo@87 401 why should one keep them?
meillo@217 402 Removing them streamlined mmh.
meillo@63 403 .Pn viamail 's
meillo@63 404 use case is now partly obsolete and partly covered by
meillo@63 405 .Pn forw ,
meillo@217 406 hence there is no reason to still maintain it.
meillo@63 407 .Pn conflict
meillo@76 408 is not related to the mail client, and
meillo@63 409 .Pn msh
meillo@63 410 conflicts with the basic concept of MH.
meillo@169 411 These two tools might still be useful, but they should not be part of mmh.
meillo@63 412 .P
meillo@220 413 .Id slocal
meillo@169 414 Finally, there is
meillo@217 415 .Pn slocal ,
meillo@217 416 which is an MDA and thus not directly MUA-related.
meillo@217 417 It should be removed from mmh because including it conflicts with
meillo@178 418 the idea that mmh is an MUA only.
meillo@87 419 However,
meillo@76 420 .Pn slocal
meillo@76 421 provides rule-based processing of messages, like filing them into
meillo@76 422 different folders, which is otherwise not available in mmh.
meillo@87 423 Although
meillo@76 424 .Pn slocal
meillo@169 425 neither pulls in dependencies, nor does it include a separate
meillo@154 426 technical area (cf. Sec.
meillo@154 427 .Cf mail-transfer-facilities ),
meillo@169 428 it still accounts for about 1\|000 lines of code that need to be maintained.
meillo@76 429 As
meillo@76 430 .Pn slocal
meillo@76 431 is almost self-standing, it should be split off into a separate project.
meillo@76 432 This would cut the strong connection between the MUA mmh and the MDA
meillo@76 433 .Pn slocal .
meillo@87 434 For anyone not using MH,
meillo@87 435 .Pn slocal
meillo@87 436 would become yet another independent MDA, like
meillo@87 437 .I procmail .
meillo@100 438 Then
meillo@87 439 .Pn slocal
meillo@217 440 could be installed without a complete MH system.
meillo@76 441 Likewise, mmh users could decide to use
meillo@76 442 .I procmail
meillo@217 443 without having a second, unused MDA, i.e.
meillo@87 444 .Pn slocal ,
meillo@76 445 installed.
meillo@100 446 That appears to be conceptionally the best solution.
meillo@76 447 Yet,
meillo@76 448 .Pn slocal
meillo@87 449 is not split off.
meillo@100 450 I defer the decision over
meillo@78 451 .Pn slocal
meillo@169 452 out of a need for deeper investigation.
meillo@217 453 In the meanwhile, it remains part of mmh
meillo@217 454 as its continued existence is not significant;
meillo@100 455 .Pn slocal
meillo@100 456 is unrelated to the rest of the project.
meillo@0 457
meillo@58 458
meillo@133 459
meillo@134 460 .H2 "Displaying Messages
meillo@155 461 .Id mhshow
meillo@131 462 .P
meillo@133 463 Since the very beginning, already in the first concept paper,
meillo@227 464 .[
meillo@227 465 original memo rand mh shapiro gaines
meillo@227 466 .]
meillo@58 467 .Pn show
meillo@62 468 had been MH's message display program.
meillo@58 469 .Pn show
meillo@76 470 mapped message numbers and sequences to files and invoked
meillo@58 471 .Pn mhl
meillo@89 472 to have the files formatted.
meillo@173 473 With MIME, this approach was not sufficient anymore.
meillo@217 474 MIME messages can consist of multiple parts.
meillo@217 475 Some parts, like binary attachments or text content in foreign charsets,
meillo@217 476 are not directly displayable.
meillo@58 477 .Pn show 's
meillo@76 478 understanding of messages and
meillo@58 479 .Pn mhl 's
meillo@173 480 display capabilities could not cope with the task any longer.
meillo@62 481 .P
meillo@88 482 Instead of extending these tools, additional tools were written from
meillo@217 483 scratch and were added to the MH tool chest.
meillo@88 484 Doing so is encouraged by the tool chest approach.
meillo@88 485 Modular design is a great advantage for extending a system,
meillo@88 486 as new tools can be added without interfering with existing ones.
meillo@62 487 First, the new MIME features were added in form of the single program
meillo@58 488 .Pn mhn .
meillo@58 489 The command
meillo@82 490 .Cl "mhn -show 42
meillo@217 491 had then shown the message number
meillo@217 492 .Fn 42 ,
meillo@217 493 interpreting MIME.
meillo@58 494 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58 495 the split of
meillo@58 496 .Pn mhn
meillo@88 497 into a set of specialized tools, which together covered the
meillo@88 498 multiple aspects of MIME.
meillo@88 499 One of them was
meillo@69 500 .Pn mhshow ,
meillo@88 501 which replaced
meillo@88 502 .Cl "mhn -show" .
meillo@88 503 It was capable of displaying MIME messages appropriately.
meillo@62 504 .P
meillo@88 505 From then on, two message display tools were part of nmh,
meillo@76 506 .Pn show
meillo@76 507 and
meillo@76 508 .Pn mhshow .
meillo@88 509 To ease the life of users,
meillo@69 510 .Pn show
meillo@69 511 was extended to automatically hand the job over to
meillo@69 512 .Pn mhshow
meillo@69 513 if displaying the message would be beyond
meillo@69 514 .Pn show 's
meillo@69 515 abilities.
meillo@88 516 In consequence, the user would simply invoke
meillo@69 517 .Pn show
meillo@69 518 (possibly through
meillo@69 519 .Pn next
meillo@69 520 or
meillo@69 521 .Pn prev )
meillo@69 522 and get the message printed with either
meillo@69 523 .Pn show
meillo@69 524 or
meillo@69 525 .Pn mhshow ,
meillo@69 526 whatever was more appropriate.
meillo@69 527 .P
meillo@217 528 Having two similar tools for basically the same task is redundancy.
meillo@217 529 Usually, users do not distinguish between
meillo@88 530 .Pn show
meillo@88 531 and
meillo@88 532 .Pn mhshow
meillo@88 533 in their daily mail reading.
meillo@217 534 Having two separate display programs was therefore unnecessary
meillo@88 535 from a user's point of view.
meillo@88 536 Besides, the development of both programs needed to be in sync,
meillo@76 537 to ensure that the programs behaved in a similar way,
meillo@76 538 because they were used like a single tool.
meillo@76 539 Different behavior would have surprised the user.
meillo@69 540 .P
meillo@69 541 Today, non-MIME messages are rather seen to be a special case of
meillo@100 542 MIME messages, although it is the other way round.
meillo@69 543 As
meillo@69 544 .Pn mhshow
meillo@217 545 already had been able to display non-MIME messages, it appeared natural
meillo@69 546 to drop
meillo@69 547 .Pn show
meillo@69 548 in favor of using
meillo@69 549 .Pn mhshow
meillo@217 550 exclusively
meillo@217 551 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853 .
meillo@88 552 Removing
meillo@88 553 .Pn show
meillo@217 554 is no loss in function, because
meillo@88 555 .Pn mhshow
meillo@88 556 covers it completely.
meillo@217 557 Yet, the old behavior of
meillo@88 558 .Pn show
meillo@88 559 can still be emulated with the simple command line:
meillo@88 560 .VS
meillo@88 561 mhl `mhpath c`
meillo@88 562 VE
meillo@88 563 .P
meillo@76 564 For convenience,
meillo@76 565 .Pn mhshow
meillo@88 566 was renamed to
meillo@88 567 .Pn show
meillo@88 568 after
meillo@88 569 .Pn show
meillo@88 570 was gone.
meillo@88 571 It is clear that such a rename may confuse future developers when
meillo@88 572 trying to understand the history.
meillo@88 573 Nevertheless, I consider the convenience on the user's side,
meillo@217 574 to outweigh the inconvenience for understanding the evolution
meillo@217 575 of the tools.
meillo@69 576 .P
meillo@88 577 To prepare for the transition,
meillo@69 578 .Pn mhshow
meillo@69 579 was reworked to behave more like
meillo@69 580 .Pn show
meillo@217 581 first (cf. Sec.
meillo@217 582 .Cf mhshow ).
meillo@88 583 Once the tools behaved more alike, the replacing appeared to be
meillo@88 584 even more natural.
meillo@88 585 Today, mmh's new
meillo@69 586 .Pn show
meillo@217 587 has become the one single message display program once again,
meillo@159 588 with the difference
meillo@88 589 that today it handles MIME messages as well as non-MIME messages.
meillo@217 590 The outcomes of the transition are one program less to maintain,
meillo@88 591 no second display program for users to deal with,
meillo@88 592 and less system complexity.
meillo@69 593 .P
meillo@88 594 Still, removing the old
meillo@69 595 .Pn show
meillo@88 596 hurts in one regard: It had been such a simple program.
meillo@159 597 Its lean elegance is missing from the new
meillo@159 598 .Pn show ,
meillo@225 599 but there is no alternative;
meillo@159 600 supporting MIME demands higher essential complexity.
meillo@58 601
meillo@131 602
meillo@133 603
meillo@100 604 .H2 "Configure Options
meillo@58 605 .P
meillo@76 606 Customization is a double-edged sword.
meillo@76 607 It allows better suiting setups, but not for free.
meillo@76 608 There is the cost of code complexity to be able to customize.
meillo@76 609 There is the cost of less tested setups, because there are
meillo@171 610 more possible setups and especially corner cases.
meillo@226 611 Steve Johnson confirms:
meillo@226 612 .[ [
meillo@226 613 eric raymond the art of unix programming
meillo@226 614 .], p. 233]
meillo@226 615 .QS
meillo@226 616 Unless it is done very carefully, the addition of an on/off
meillo@226 617 configuration option can lead to a need to double the amount of
meillo@226 618 testing. Since in practice one never does double the amount of testing,
meillo@226 619 the practical effect is to reduce the amount of testing that any
meillo@226 620 given configuration receives. Ten options leads to 1024 times as much
meillo@226 621 testing, and pretty soon you are talking real reliability problems.
meillo@226 622 .QE
meillo@226 623 .LP
meillo@159 624 Additionally, there is the cost of choice itself.
meillo@76 625 The code complexity directly affects the developers.
meillo@173 626 Less tested code affects both users and developers.
meillo@217 627 The problem of choice affects the users, for once by having to choose
meillo@159 628 but also by more complex interfaces that require more documentation.
meillo@159 629 Whenever options add few advantages but increase the complexity of the
meillo@159 630 system, they should be considered for removal.
meillo@72 631 I have reduced the number of project-specific configure options from
meillo@217 632 15 to 3.
meillo@74 633
meillo@76 634 .U3 "Mail Transfer Facilities
meillo@74 635 .P
meillo@227 636 With the removal of the mail transfer facilities (cf. Sec.
meillo@227 637 .Cf mail-transfer-facilities )
meillo@227 638 five configure options vanished:
meillo@85 639 .P
meillo@85 640 The switches
meillo@85 641 .Sw --with-tls
meillo@85 642 and
meillo@85 643 .Sw --with-cyrus-sasl
meillo@89 644 had activated the support for transfer encryption and authentication.
meillo@217 645 They are not needed anymore.
meillo@85 646 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85 647 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85 648 .P
meillo@85 649 The configure switch
meillo@85 650 .Sw --enable-pop
meillo@227 651 had activated the message retrieval facility.
meillo@217 652 Whereas the code area that had been conditionally compiled in
meillo@217 653 for TLS and SASL support was small,
meillo@217 654 the conditionally compiled code area for POP support was much larger.
meillo@217 655 The code base had only changed slightly on toggling TLS or SASL
meillo@217 656 support but it had changed much on toggling POP support.
meillo@85 657 The changes in the code base could hardly be overviewed.
meillo@159 658 By having POP support togglable, a second code base had been created,
meillo@85 659 one that needed to be tested.
meillo@85 660 This situation is basically similar for the conditional TLS and SASL
meillo@85 661 code, but there the changes are minor and can yet be overviewed.
meillo@85 662 Still, conditional compilation of a code base creates variations
meillo@85 663 of the original program.
meillo@85 664 More variations require more testing and maintenance work.
meillo@85 665 .P
meillo@227 666 Two other options had only specified default configuration values:
meillo@100 667 .Sw --with-mts
meillo@217 668 defined the default transport service
meillo@217 669 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226 .
meillo@85 670 With
meillo@100 671 .Sw --with-smtpservers
meillo@227 672 default SMTP servers could be set
meillo@217 673 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9 .
meillo@164 674 Both of them became irrelevant when the SMTP transport service was removed.
meillo@164 675 In mmh, all messages are handed over to
meillo@164 676 .Pn sendmail
meillo@164 677 for transportation.
meillo@164 678
meillo@72 679
meillo@74 680 .U3 "Backup Prefix
meillo@74 681 .P
meillo@76 682 The backup prefix is the string that was prepended to message
meillo@76 683 filenames to tag them as deleted.
meillo@173 684 By default it had been the comma character (`\fL,\fP').
meillo@78 685 In July 2000, Kimmo Suominen introduced
meillo@78 686 the configure option
meillo@78 687 .Sw --with-hash-backup
meillo@173 688 to change the default to the hash character `\f(CW#\fP'.
meillo@217 689 This choice was probably personal preference, but,
meillo@217 690 being related or not, words that start with the hash character
meillo@78 691 introduce a comment in the Unix shell.
meillo@72 692 Thus, the command line
meillo@72 693 .Cl "rm #13 #15
meillo@72 694 calls
meillo@72 695 .Pn rm
meillo@217 696 without arguments because the first hash character starts a comment
meillo@72 697 that reaches until the end of the line.
meillo@72 698 To delete the backup files,
meillo@72 699 .Cl "rm ./#13 ./#15"
meillo@72 700 needs to be used.
meillo@217 701 Thus, using the hash as backup prefix may be seen as a precaution
meillo@217 702 against backup loss.
meillo@78 703 .P
meillo@159 704 First, I removed the configure option but added the profile entry
meillo@217 705 .Pe Backup-Prefix ,
meillo@217 706 which allowed to specify an arbitrary string as backup prefix
meillo@217 707 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086 .
meillo@76 708 This change did not remove the choice but moved it to a location where
meillo@217 709 it suited better, in my eyes.
meillo@76 710 .P
meillo@217 711 Eventually however, the new trash folder concept
meillo@154 712 (cf. Sec.
meillo@154 713 .Cf trash-folder )
meillo@164 714 removed the need for the backup prefix completely.
meillo@78 715 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133 716 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133 717
meillo@76 718
meillo@76 719 .U3 "Editor and Pager
meillo@227 720 .Id editor-pager
meillo@74 721 .P
meillo@74 722 The two configure options
meillo@74 723 .CW --with-editor=EDITOR
meillo@74 724 .CW --with-pager=PAGER
meillo@74 725 were used to specify the default editor and pager at configure time.
meillo@109 726 Doing so at configure time made sense in the eighties,
meillo@76 727 when the set of available editors and pagers varied much across
meillo@76 728 different systems.
meillo@89 729 Today, the situation is more homogeneous.
meillo@74 730 The programs
meillo@74 731 .Pn vi
meillo@74 732 and
meillo@74 733 .Pn more
meillo@76 734 can be expected to be available on every Unix system,
meillo@74 735 as they are specified by POSIX since two decades.
meillo@74 736 (The specifications for
meillo@74 737 .Pn vi
meillo@74 738 and
meillo@74 739 .Pn more
meillo@74 740 appeared in
meillo@74 741 .[
meillo@74 742 posix 1987
meillo@74 743 .]
meillo@74 744 and,
meillo@74 745 .[
meillo@74 746 posix 1992
meillo@74 747 .]
meillo@74 748 respectively.)
meillo@217 749 As a first step, these two tools were hard-coded as defaults
meillo@217 750 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f .
meillo@74 751 Not changed were the
meillo@74 752 .Pe editor
meillo@74 753 and
meillo@74 754 .Pe moreproc
meillo@76 755 profile entries, which allowed the user to override the system defaults.
meillo@217 756 Later, the concept was reworked again to respect the standard
meillo@217 757 environment variables
meillo@74 758 .Ev VISUAL
meillo@74 759 and
meillo@74 760 .Ev PAGER
meillo@76 761 if they are set.
meillo@74 762 Today, mmh determines the editor to use in the following order,
meillo@217 763 taking the first available and non-empty item
meillo@217 764 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b :
meillo@171 765 .LI 1
meillo@74 766 Environment variable
meillo@74 767 .Ev MMHEDITOR
meillo@171 768 .LI 2
meillo@74 769 Profile entry
meillo@74 770 .Pe Editor
meillo@171 771 .LI 3
meillo@74 772 Environment variable
meillo@74 773 .Ev VISUAL
meillo@171 774 .LI 4
meillo@74 775 Environment variable
meillo@74 776 .Ev EDITOR
meillo@171 777 .LI 5
meillo@74 778 Command
meillo@74 779 .Pn vi .
meillo@171 780 .LP
meillo@217 781 The pager to use is determined in a similar order
meillo@217 782 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e :
meillo@171 783 .LI 1
meillo@74 784 Environment variable
meillo@74 785 .Ev MMHPAGER
meillo@171 786 .LI 2
meillo@74 787 Profile entry
meillo@74 788 .Pe Pager
meillo@74 789 (replaces
meillo@74 790 .Pe moreproc )
meillo@171 791 .LI 3
meillo@74 792 Environment variable
meillo@74 793 .Ev PAGER
meillo@171 794 .LI 4
meillo@74 795 Command
meillo@74 796 .Pn more .
meillo@171 797 .LP
meillo@76 798 By respecting the
meillo@74 799 .Ev VISUAL /\c
meillo@74 800 .Ev EDITOR
meillo@74 801 and
meillo@74 802 .Ev PAGER
meillo@76 803 environment variables,
meillo@217 804 the new behavior complies with the common style on Unix systems.
meillo@217 805 It is more uniform and clearer for users.
meillo@72 806
meillo@72 807
meillo@76 808 .U3 "ndbm
meillo@72 809 .P
meillo@74 810 .Pn slocal
meillo@217 811 used to depend on the database library
meillo@217 812 .I ndbm .
meillo@217 813 The database is used to store the
meillo@217 814 .Hd Message-ID
meillo@217 815 header field values of all messages delivered.
meillo@217 816 This enabled
meillo@74 817 .Pn slocal
meillo@74 818 to suppress delivering the same message to the same user twice.
meillo@217 819 This features was enabled by the
meillo@74 820 .Sw -suppressdup
meillo@217 821 switch.
meillo@74 822 .P
meillo@217 823 As a variety of versions of the database library exist,
meillo@78 824 .[
meillo@78 825 wolter unix incompat notes dbm
meillo@78 826 .]
meillo@217 827 complicated autoconf code was needed to detect them correctly.
meillo@181 828 Furthermore, the configure switches
meillo@74 829 .Sw --with-ndbm=ARG
meillo@74 830 and
meillo@74 831 .Sw --with-ndbmheader=ARG
meillo@74 832 were added to help with difficult setups that would
meillo@217 833 not be detected automatically or not correctly.
meillo@74 834 .P
meillo@74 835 By removing the suppress duplicates feature of
meillo@74 836 .Pn slocal ,
meillo@74 837 the dependency on
meillo@74 838 .I ndbm
meillo@217 839 vanished and 120 lines of complex autoconf code could be saved
meillo@217 840 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf .
meillo@217 841 The change removed functionality but that is considered minor to the
meillo@217 842 improvement of dropping the dependency and the complex autoconf code.
meillo@225 843
meillo@72 844
meillo@217 845 .U3 "MH-E Support
meillo@72 846 .P
meillo@74 847 The configure option
meillo@74 848 .Sw --disable-mhe
meillo@217 849 was removed when the MH-E support was reworked.
meillo@217 850 MH-E is the Emacs front-end to MH.
meillo@76 851 It requires MH to provide minor additional functions.
meillo@76 852 The
meillo@76 853 .Sw --disable-mhe
meillo@217 854 configure option had switched off these extensions.
meillo@217 855 After removing the support for old versions of MH-E,
meillo@74 856 only the
meillo@74 857 .Sw -build
meillo@76 858 switches of
meillo@74 859 .Pn forw
meillo@74 860 and
meillo@74 861 .Pn repl
meillo@217 862 are left to be MH-E extensions.
meillo@76 863 They are now always built in because they add little code and complexity.
meillo@76 864 In consequence, the
meillo@74 865 .Sw --disable-mhe
meillo@76 866 configure option was removed
meillo@217 867 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643 .
meillo@217 868 Dropping the option also removed a variant of the code base
meillo@217 869 that would have needed to be tested.
meillo@217 870 This change was undertaken in January 2012 in nmh and
meillo@217 871 thereafter merged into mmh.
meillo@217 872
meillo@72 873
meillo@74 874 .U3 "Masquerading
meillo@72 875 .P
meillo@74 876 The configure option
meillo@74 877 .Sw --enable-masquerade
meillo@76 878 could take up to three arguments:
meillo@217 879 .Ar draft_from ,
meillo@217 880 .Ar mmailid ,
meillo@217 881 and
meillo@217 882 .Ar username_extension .
meillo@74 883 They activated different types of address masquerading.
meillo@74 884 All of them were implemented in the SMTP-speaking
meillo@74 885 .Pn post
meillo@217 886 command.
meillo@76 887 Address masquerading is an MTA's task and mmh does not cover
meillo@76 888 this field anymore.
meillo@76 889 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74 890 .P
meillo@74 891 The
meillo@74 892 .I mmailid
meillo@74 893 masquerading type is the oldest one of the three and the only one
meillo@74 894 available in the original MH.
meillo@74 895 It provided a
meillo@74 896 .I username
meillo@74 897 to
meillo@74 898 .I fakeusername
meillo@217 899 mapping, based on the
meillo@217 900 .Fn passwd 's
meillo@217 901 GECOS field.
meillo@217 902 Nmh's man page
meillo@181 903 .Mp mh-tailor (5)
meillo@74 904 described the use case as being the following:
meillo@98 905 .QS
meillo@74 906 This is useful if you want the messages you send to always
meillo@74 907 appear to come from the name of an MTA alias rather than your
meillo@74 908 actual account name. For instance, many organizations set up
meillo@74 909 `First.Last' sendmail aliases for all users. If this is
meillo@74 910 the case, the GECOS field for each user should look like:
meillo@74 911 ``First [Middle] Last <First.Last>''
meillo@98 912 .QE
meillo@74 913 .P
meillo@74 914 As mmh sends outgoing mail via the local MTA only,
meillo@76 915 the best location to do such global rewrites is there.
meillo@74 916 Besides, the MTA is conceptionally the right location because it
meillo@74 917 does the reverse mapping for incoming mail (aliasing), too.
meillo@181 918 Furthermore, masquerading set up there is readily available for all
meillo@74 919 mail software on the system.
meillo@76 920 Hence, mmailid masquerading was removed.
meillo@74 921 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74 922 .P
meillo@74 923 The
meillo@74 924 .I username_extension
meillo@76 925 masquerading type did not replace the username but would append a suffix,
meillo@76 926 specified by the
meillo@74 927 .Ev USERNAME_EXTENSION
meillo@76 928 environment variable, to it.
meillo@76 929 This provided support for the
meillo@74 930 .I user-extension
meillo@217 931 feature of qmail
meillo@217 932 .[ [
meillo@217 933 sill qmail handbook
meillo@217 934 .], p. 141]
meillo@217 935 and the similar
meillo@74 936 .I "plussed user
meillo@217 937 processing of Sendmail.
meillo@217 938 .[ [
meillo@217 939 sendmail costales
meillo@217 940 .], p. 476]
meillo@217 941 The decision to remove this username_extension masquerading
meillo@217 942 was motivated by the fact that
meillo@74 943 .Pn spost
meillo@217 944 had not supported it yet.
meillo@217 945 Username extensions can be used in mmh, but less convenient.
meillo@225 946 .\" XXX In the format file: %(getenv USERNAME_EXTENSION)
meillo@217 947 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@74 948 .P
meillo@74 949 The
meillo@74 950 .I draft_from
meillo@74 951 masquerading type instructed
meillo@74 952 .Pn post
meillo@84 953 to use the value of the
meillo@84 954 .Hd From
meillo@84 955 header field as SMTP envelope sender.
meillo@76 956 Sender addresses could be replaced completely.
meillo@76 957 Mmh offers a kind of masquerading similar in effect, but
meillo@74 958 with technical differences.
meillo@76 959 As mmh does not transfer messages itself, the local MTA has final control
meillo@217 960 over the sender's address.
meillo@217 961 Any masquerading mmh introduces may be reverted by the MTA.
meillo@76 962 In times of pedantic spam checking, an MTA will take care to use
meillo@76 963 sensible envelope sender addresses to keep its own reputation up.
meillo@84 964 Nonetheless, the MUA can set the
meillo@84 965 .Hd From
meillo@217 966 header field and thereby propose a sender address to the MTA.
meillo@74 967 The MTA may then decide to take that one or generate the canonical sender
meillo@74 968 address for use as envelope sender address.
meillo@217 969 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@74 970 .P
meillo@74 971 In mmh, the MTA will always extract the recipient and sender from the
meillo@84 972 message header (\c
meillo@74 973 .Pn sendmail 's
meillo@74 974 .Sw -t
meillo@74 975 switch).
meillo@84 976 The
meillo@84 977 .Hd From
meillo@84 978 header field of the draft may be set arbitrary by the user.
meillo@74 979 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74 980
meillo@74 981 .U3 "Remaining Options
meillo@74 982 .P
meillo@74 983 Two configure options remain in mmh.
meillo@74 984 One is the locking method to use:
meillo@74 985 .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@217 986 The idea of removing all methods except the portable
meillo@217 987 .I "dot locking
meillo@76 988 and having that one as the default is appealing, but this change
meillo@76 989 requires deeper technical investigation into the topic.
meillo@76 990 The other option,
meillo@74 991 .Sw --enable-debug ,
meillo@217 992 compiles the programs with debugging symbols.
meillo@74 993 This option is likely to stay.
meillo@72 994
meillo@72 995
meillo@58 996
meillo@63 997
meillo@100 998 .H2 "Command Line Switches
meillo@58 999 .P
meillo@227 1000 The command line switches of MH tools are similar in style to the
meillo@227 1001 switches in the X Window System.
meillo@227 1002 They consist of a single dash (`\fL-\fP') followed by a word.
meillo@217 1003 For example
meillo@217 1004 .Cl -truncate .
meillo@212 1005 To ease typing, the word can be abbreviated, given the remaining
meillo@217 1006 prefix is unambiguous.
meillo@212 1007 If no other switch starts with the letter `t', then any of
meillo@212 1008 .Cl "-truncate" ,
meillo@212 1009 .Cl "-trunc" ,
meillo@212 1010 .Cl "-tr" ,
meillo@212 1011 and
meillo@212 1012 .Cl "-t
meillo@212 1013 is equal.
meillo@212 1014 As a result, switches can neither be grouped (as in
meillo@212 1015 .Cl "ls -ltr" )
meillo@212 1016 nor can switch arguments be appended directly to the switch (as in
meillo@212 1017 .Cl "sendmail -q30m" ).
meillo@212 1018 Many switches have negating counter-parts, which start with `no'.
meillo@212 1019 For example
meillo@212 1020 .Cl "-notruncate
meillo@212 1021 inverts the
meillo@212 1022 .Cl "-truncate
meillo@212 1023 switch.
meillo@212 1024 They exist to override the effect of default switches in the profile.
meillo@93 1025 Every program in mmh has two generic switches:
meillo@93 1026 .Sw -help ,
meillo@93 1027 to print a short message on how to use the program, and
meillo@159 1028 .Sw -Version
meillo@164 1029 (with capital `V'), to tell what version of mmh the program belongs to.
meillo@93 1030 .P
meillo@93 1031 Switches change the behavior of programs.
meillo@93 1032 Programs that do one thing in one way require no switches.
meillo@93 1033 In most cases, doing something in exactly one way is too limiting.
meillo@217 1034 If one task should be accomplished in various ways,
meillo@217 1035 switches are a good approach to alter the behavior of a program.
meillo@93 1036 Changing the behavior of programs provides flexibility and customization
meillo@217 1037 to users, but at the same time it complicates the code,
meillo@217 1038 the documentation, and the usage of the program.
meillo@93 1039 Therefore, the number of switches should be kept small.
meillo@217 1040 A small set of well-chosen switches is best.
meillo@217 1041 Usually, the number of switches increases over time.
meillo@93 1042 Already in 1985, Rose and Romine have identified this as a major
meillo@93 1043 problem of MH:
meillo@93 1044 .[ [
meillo@93 1045 rose romine real work
meillo@93 1046 .], p. 12]
meillo@98 1047 .QS
meillo@93 1048 A complaint often heard about systems which undergo substantial development
meillo@93 1049 by many people over a number of years, is that more and more options are
meillo@93 1050 introduced which add little to the functionality but greatly increase the
meillo@93 1051 amount of information a user needs to know in order to get useful work done.
meillo@93 1052 This is usually referred to as creeping featurism.
meillo@93 1053 .QP
meillo@93 1054 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93 1055 ten or so well-meaning programmers (the present authors included),
meillo@93 1056 suffers mightily from this.
meillo@98 1057 .QE
meillo@93 1058 .P
meillo@217 1059 Being reluctant to adding new switches (or \fIoptions\fP,
meillo@217 1060 as Rose and Romine call them) is one part of a counter-action,
meillo@97 1061 the other part is removing hardly used switches.
meillo@217 1062 Nmh's tools have lots of switches already implemented.
meillo@217 1063 Hence, cleaning up by removing some of them was the more important part
meillo@97 1064 of the counter-action.
meillo@93 1065 Removing existing functionality is always difficult because it
meillo@93 1066 breaks programs that use these functions.
meillo@93 1067 Also, for every obsolete feature, there'll always be someone who still
meillo@93 1068 uses it and thus opposes its removal.
meillo@93 1069 This puts the developer into the position,
meillo@93 1070 where sensible improvements to style are regarded as destructive acts.
meillo@97 1071 Yet, living with the featurism is far worse, in my eyes, because
meillo@97 1072 future needs will demand adding further features,
meillo@93 1073 worsening the situation more and more.
meillo@93 1074 Rose and Romine added in a footnote,
meillo@93 1075 ``[...]
meillo@93 1076 .Pn send
meillo@217 1077 will no doubt acquire an endless number of switches in the years to come''
meillo@217 1078 .[ [
meillo@217 1079 rose romine real work
meillo@217 1080 .], p. 12].
meillo@97 1081 Although clearly humorous, the comment points to the nature of the problem.
meillo@97 1082 Refusing to add any new switches would encounter the problem at its root,
meillo@97 1083 but this is not practical.
meillo@97 1084 New needs will require new switches and it would be unwise to block
meillo@97 1085 them strictly.
meillo@97 1086 Nevertheless, removing obsolete switches still is an effective approach
meillo@97 1087 to deal with the problem.
meillo@97 1088 Working on an experimental branch without an established user base,
meillo@97 1089 eased my work because I did not offend users when I removed existing
meillo@110 1090 functions.
meillo@93 1091 .P
meillo@93 1092 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93 1093 .Pn send .
meillo@97 1094 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@182 1095 At the time of writing, no more than 4 visible switches and 1 hidden switch
meillo@97 1096 have remained in mmh's
meillo@97 1097 .Pn send .
meillo@217 1098 These numbers include the two generic switches,
meillo@182 1099 .Sw -help
meillo@182 1100 and
meillo@183 1101 .Sw -Version .
meillo@217 1102 .P
meillo@183 1103 Hidden switches are ones not documented.
meillo@183 1104 In mmh, 12 tools have hidden switches.
meillo@183 1105 9 of them are
meillo@183 1106 .Sw -debug
meillo@183 1107 switches, the other 6 provide special interfaces for internal use.
meillo@93 1108 .P
meillo@217 1109 The following figure displays the number of switches for each of the tools
meillo@159 1110 that is available in both nmh and mmh.
meillo@100 1111 The tools are sorted by the number of switches they had in nmh.
meillo@217 1112 Both visible and hidden switches were counted,
meillo@97 1113 but not the generic help and version switches.
meillo@93 1114 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93 1115 now it has no more than 5 \(en only half as many.
meillo@93 1116 If the `no' switches and similar inverse variant are folded onto
meillo@100 1117 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100 1118 has 4 now.
meillo@93 1119 The total number of functional switches in mmh dropped from 465
meillo@182 1120 to 233.
meillo@58 1121
meillo@93 1122 .KS
meillo@93 1123 .in 1c
meillo@93 1124 .so input/switches.grap
meillo@93 1125 .KE
meillo@58 1126
meillo@93 1127 .P
meillo@93 1128 A part of the switches vanished after functions were removed.
meillo@93 1129 This was the case for network mail transfer, for instance.
meillo@97 1130 Sometimes, however, the work flow was the other way:
meillo@97 1131 I looked through the
meillo@97 1132 .Mp mh-chart (7)
meillo@97 1133 man page to identify the tools with apparently too many switches.
meillo@217 1134 Then I considered the benefit of each switch by examining
meillo@217 1135 the tool's man page and source code, aided by literature research
meillo@217 1136 and testing.
meillo@97 1137
meillo@58 1138
meillo@93 1139 .U3 "Draft Folder Facility
meillo@93 1140 .P
meillo@100 1141 A change early in the project was the complete transition from
meillo@217 1142 the single draft message to the draft folder facility
meillo@227 1143 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@227 1144 (cf. Sec.
meillo@227 1145 .Cf draft-folder ).
meillo@109 1146 The draft folder facility was introduced in the mid-eighties, when
meillo@100 1147 Rose and Romine called it a ``relatively new feature''.
meillo@93 1148 .[
meillo@93 1149 rose romine real work
meillo@93 1150 .]
meillo@217 1151 Since then, the facility was included, inactive by default.
meillo@217 1152 By making it permanently active and by related rework of the tools, the
meillo@93 1153 .Sw -[no]draftfolder ,
meillo@93 1154 and
meillo@93 1155 .Sw -draftmessage
meillo@217 1156 switches could be removed from
meillo@93 1157 .Pn comp ,
meillo@93 1158 .Pn repl ,
meillo@93 1159 .Pn forw ,
meillo@93 1160 .Pn dist ,
meillo@93 1161 .Pn whatnow ,
meillo@93 1162 and
meillo@217 1163 .Pn send
meillo@217 1164 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@217 1165 The only flexibility lost with this change is having multiple
meillo@97 1166 draft folders within one profile.
meillo@97 1167 I consider this a theoretical problem only.
meillo@159 1168 At the same time, the
meillo@93 1169 .Sw -draft
meillo@93 1170 switch of
meillo@93 1171 .Pn anno ,
meillo@93 1172 .Pn refile ,
meillo@93 1173 and
meillo@93 1174 .Pn send
meillo@93 1175 was removed.
meillo@159 1176 The special treatment of \fIthe\fP draft message became irrelevant after
meillo@217 1177 the rework of the draft system
meillo@159 1178 (cf. Sec.
meillo@217 1179 .Cf draft-folder ).
meillo@93 1180
meillo@95 1181
meillo@102 1182 .U3 "In Place Editing
meillo@93 1183 .P
meillo@93 1184 .Pn anno
meillo@93 1185 had the switches
meillo@93 1186 .Sw -[no]inplace
meillo@100 1187 to either annotate the message in place and thus preserve hard links,
meillo@217 1188 or annotate a copy to replace the original message.
meillo@217 1189 The latter approach broke hard links.
meillo@97 1190 Following the assumption that linked messages should truly be the
meillo@217 1191 same message and annotating it should not break the link, the
meillo@93 1192 .Sw -[no]inplace
meillo@93 1193 switches were removed and the previous default
meillo@93 1194 .Sw -inplace
meillo@217 1195 was made the definitive behavior
meillo@217 1196 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0 .
meillo@93 1197 The
meillo@93 1198 .Sw -[no]inplace
meillo@93 1199 switches of
meillo@93 1200 .Pn repl ,
meillo@93 1201 .Pn forw ,
meillo@93 1202 and
meillo@93 1203 .Pn dist
meillo@217 1204 could be removed, as well, as they were simply passed through to
meillo@93 1205 .Pn anno .
meillo@93 1206 .P
meillo@93 1207 .Pn burst
meillo@93 1208 also had
meillo@93 1209 .Sw -[no]inplace
meillo@217 1210 switches, but with a different meaning.
meillo@95 1211 With
meillo@95 1212 .Sw -inplace ,
meillo@95 1213 the digest had been replaced by the table of contents (i.e. the
meillo@110 1214 introduction text) and the burst messages were placed right
meillo@95 1215 after this message, renumbering all following messages.
meillo@95 1216 Also, any trailing text of the digest was lost, though,
meillo@95 1217 in practice, it usually consists of an end-of-digest marker only.
meillo@217 1218 Nonetheless, this behavior appeared less elegant than the
meillo@95 1219 .Sw -noinplace
meillo@95 1220 behavior, which already had been the default.
meillo@95 1221 Nmh's
meillo@95 1222 .Mp burst (1)
meillo@95 1223 man page reads:
meillo@98 1224 .QS
meillo@164 1225 If
meillo@164 1226 .Sw -noinplace
meillo@164 1227 is given, each digest is preserved, no table
meillo@93 1228 of contents is produced, and the messages contained within
meillo@93 1229 the digest are placed at the end of the folder. Other messages
meillo@93 1230 are not tampered with in any way.
meillo@98 1231 .QE
meillo@95 1232 .LP
meillo@93 1233 The decision to drop the
meillo@93 1234 .Sw -inplace
meillo@95 1235 behavior was supported by the code complexity and the possible data loss
meillo@95 1236 it caused.
meillo@93 1237 .Sw -noinplace
meillo@95 1238 was chosen to be the definitive behavior.
meillo@97 1239 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93 1240
meillo@95 1241
meillo@95 1242 .U3 "Forms and Format Strings
meillo@93 1243 .P
meillo@95 1244 Historically, the tools that had
meillo@95 1245 .Sw -form
meillo@95 1246 switches to supply a form file had
meillo@95 1247 .Sw -format
meillo@95 1248 switches as well to supply the contents of a form file as a string
meillo@95 1249 on the command line directly.
meillo@95 1250 In consequence, the following two lines equaled:
meillo@95 1251 .VS
meillo@95 1252 scan -form scan.mailx
meillo@217 1253 scan -format "`cat /path/to/scan.mailx`"
meillo@95 1254 VE
meillo@95 1255 The
meillo@95 1256 .Sw -format
meillo@95 1257 switches were dropped in favor for extending the
meillo@95 1258 .Sw -form
meillo@217 1259 switches
meillo@217 1260 .Ci f51956be123db66b00138f80464d06f030dbb88d .
meillo@217 1261 If their argument starts with an equal sign (`\fL=\fP'),
meillo@95 1262 then the rest of the argument is taken as a format string,
meillo@95 1263 otherwise the arguments is treated as the name of a format file.
meillo@95 1264 Thus, now the following two lines equal:
meillo@95 1265 .VS
meillo@95 1266 scan -form scan.mailx
meillo@217 1267 scan -form "=`cat /path/to/scan.mailx`"
meillo@95 1268 VE
meillo@95 1269 This rework removed the prefix collision between
meillo@95 1270 .Sw -form
meillo@95 1271 and
meillo@95 1272 .Sw -format .
meillo@217 1273 Typing `\fL-fo\fP' is sufficient to specify form file or format string.
meillo@95 1274 .P
meillo@95 1275 The different meaning of
meillo@95 1276 .Sw -format
meillo@95 1277 for
meillo@217 1278 .Pn forw
meillo@217 1279 and
meillo@95 1280 .Pn repl
meillo@95 1281 was removed in mmh.
meillo@95 1282 .Pn forw
meillo@95 1283 was completely switched to MIME-type forwarding, thus removing the
meillo@217 1284 .Sw -[no]format
meillo@217 1285 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1 .
meillo@95 1286 For
meillo@95 1287 .Pn repl ,
meillo@95 1288 the
meillo@95 1289 .Sw -[no]format
meillo@95 1290 switches were reworked to
meillo@95 1291 .Sw -[no]filter
meillo@217 1292 switches
meillo@217 1293 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6 .
meillo@95 1294 The
meillo@95 1295 .Sw -format
meillo@95 1296 switches of
meillo@95 1297 .Pn send
meillo@95 1298 and
meillo@95 1299 .Pn post ,
meillo@217 1300 which had a third meaning, were removed likewise
meillo@217 1301 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9 .
meillo@95 1302 Eventually, the ambiguity of the
meillo@95 1303 .Sw -format
meillo@217 1304 switches is resolved by not having such switches anymore in mmh.
meillo@95 1305
meillo@95 1306
meillo@95 1307 .U3 "MIME Tools
meillo@95 1308 .P
meillo@217 1309 The MIME tools, which once were part of
meillo@100 1310 .Pn mhn
meillo@164 1311 (whatever that stood for),
meillo@95 1312 had several switches that added little practical value to the programs.
meillo@95 1313 The
meillo@95 1314 .Sw -[no]realsize
meillo@95 1315 switches of
meillo@95 1316 .Pn mhbuild
meillo@95 1317 and
meillo@95 1318 .Pn mhlist
meillo@217 1319 were removed
meillo@217 1320 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c .
meillo@217 1321 Real size calculations are done always now because nmh's
meillo@159 1322 .Mp mhbuild (1)
meillo@217 1323 man page states that
meillo@217 1324 ``This provides an accurate count at the expense of a small delay''
meillo@228 1325 with the small delay not being noticeable on modern systems.
meillo@95 1326 .P
meillo@95 1327 The
meillo@95 1328 .Sw -[no]check
meillo@95 1329 switches were removed together with the support for
meillo@95 1330 .Hd Content-MD5
meillo@217 1331 header fields [RFC\|1864]
meillo@154 1332 (cf. Sec.
meillo@154 1333 .Cf content-md5 )
meillo@217 1334 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda .
meillo@95 1335 .P
meillo@95 1336 The
meillo@95 1337 .Sw -[no]ebcdicsafe
meillo@95 1338 and
meillo@95 1339 .Sw -[no]rfc934mode
meillo@95 1340 switches of
meillo@95 1341 .Pn mhbuild
meillo@217 1342 were removed because they are considered obsolete
meillo@97 1343 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@217 1344 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88 .
meillo@95 1345 .P
meillo@95 1346 Content caching of external MIME parts, activated with the
meillo@95 1347 .Sw -rcache
meillo@95 1348 and
meillo@95 1349 .Sw -wcache
meillo@217 1350 switches was completely removed
meillo@217 1351 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269 .
meillo@97 1352 External MIME parts are rare today, having a caching facility
meillo@159 1353 for them appears to be unnecessary.
meillo@95 1354 .P
meillo@95 1355 In pre-MIME times,
meillo@95 1356 .Pn mhl
meillo@95 1357 had covered many tasks that are part of MIME handling today.
meillo@95 1358 Therefore,
meillo@95 1359 .Pn mhl
meillo@95 1360 could be simplified to a large extend, reducing the number of its
meillo@217 1361 switches from 21 to 6
meillo@97 1362 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@217 1363 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70 .
meillo@95 1364
meillo@95 1365
meillo@95 1366
meillo@95 1367
meillo@95 1368 .U3 "Header Printing
meillo@95 1369 .P
meillo@95 1370 .Pn folder 's
meillo@95 1371 data output is self-explaining enough that
meillo@159 1372 displaying the header line makes little sense.
meillo@95 1373 Hence, the
meillo@95 1374 .Sw -[no]header
meillo@217 1375 switch was removed and headers are never printed
meillo@217 1376 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7 .
meillo@95 1377 .P
meillo@95 1378 In
meillo@95 1379 .Pn mhlist ,
meillo@95 1380 the
meillo@95 1381 .Sw -[no]header
meillo@217 1382 switches were removed, as well
meillo@217 1383 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f .
meillo@217 1384 In this case, the headers are printed always because the output
meillo@217 1385 is not self-explaining.
meillo@95 1386 .P
meillo@95 1387 .Pn scan
meillo@95 1388 also had
meillo@95 1389 .Sw -[no]header
meillo@95 1390 switches.
meillo@217 1391 Printing this header had been sensible until the introduction of
meillo@217 1392 format strings made it impossible to display column headings.
meillo@95 1393 Only the folder name and the current date remained to be printed.
meillo@217 1394 As this information can be perfectly generated with
meillo@95 1395 .Pn folder
meillo@95 1396 and
meillo@95 1397 .Pn date ,
meillo@217 1398 the switches were removed
meillo@217 1399 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e .
meillo@95 1400 .P
meillo@95 1401 By removing all
meillo@95 1402 .Sw -header
meillo@95 1403 switches, the collision with
meillo@95 1404 .Sw -help
meillo@95 1405 on the first two letters was resolved.
meillo@95 1406 Currently,
meillo@95 1407 .Sw -h
meillo@95 1408 evaluates to
meillo@95 1409 .Sw -help
meillo@95 1410 for all tools of mmh.
meillo@95 1411
meillo@95 1412
meillo@139 1413 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95 1414 .P
meillo@95 1415 The
meillo@95 1416 .Sw -noedit
meillo@100 1417 switch of
meillo@95 1418 .Pn comp ,
meillo@95 1419 .Pn repl ,
meillo@95 1420 .Pn forw ,
meillo@95 1421 .Pn dist ,
meillo@95 1422 and
meillo@95 1423 .Pn whatnow
meillo@217 1424 was removed and replaced by specifying
meillo@95 1425 .Sw -editor
meillo@217 1426 with an empty argument
meillo@217 1427 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9 .
meillo@95 1428 (Specifying
meillo@159 1429 .Cl "-editor /bin/true
meillo@217 1430 is nearly the same. It differs only in setting the previous editor.)
meillo@95 1431 .P
meillo@95 1432 The more important change is the removal of the
meillo@95 1433 .Sw -nowhatnowproc
meillo@217 1434 switch
meillo@217 1435 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622 .
meillo@217 1436 This switch had once introduced an awkward behavior,
meillo@217 1437 as explained in nmh's man page for
meillo@95 1438 .Mp comp (1):
meillo@98 1439 .QS
meillo@164 1440 The
meillo@164 1441 .Sw -editor
meillo@164 1442 .Ar editor
meillo@164 1443 switch indicates the editor to use for
meillo@164 1444 the initial edit. Upon exiting from the editor,
meillo@164 1445 .Pn comp
meillo@164 1446 will invoke the
meillo@164 1447 .Pn whatnow
meillo@164 1448 program. See
meillo@164 1449 .Mp whatnow (1)
meillo@164 1450 for a discussion of available options.
meillo@164 1451 The invocation of this program can be
meillo@164 1452 inhibited by using the
meillo@164 1453 .Sw -nowhatnowproc
meillo@164 1454 switch. (In truth of fact, it is the
meillo@164 1455 .Pn whatnow
meillo@164 1456 program which starts the initial edit.
meillo@164 1457 Hence,
meillo@164 1458 .Sw -nowhatnowproc
meillo@164 1459 will prevent any edit from occurring.)
meillo@98 1460 .QE
meillo@95 1461 .P
meillo@95 1462 Effectively, the
meillo@95 1463 .Sw -nowhatnowproc
meillo@217 1464 switch caused only only a draft message to be created.
meillo@95 1465 As
meillo@159 1466 .Cl "-whatnowproc /bin/true
meillo@217 1467 does the same, the
meillo@95 1468 .Sw -nowhatnowproc
meillo@95 1469 switch was removed for being redundant.
meillo@95 1470
meillo@95 1471
meillo@95 1472
meillo@95 1473 .U3 "Various
meillo@95 1474 .BU
meillo@139 1475 With the removal of MMDF maildrop format support,
meillo@139 1476 .Pn packf
meillo@139 1477 and
meillo@139 1478 .Pn rcvpack
meillo@139 1479 no longer needed their
meillo@139 1480 .Sw -mbox
meillo@139 1481 and
meillo@139 1482 .Sw -mmdf
meillo@139 1483 switches.
meillo@217 1484 The behavior of
meillo@139 1485 .Sw -mbox
meillo@217 1486 is the sole behavior now
meillo@217 1487 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0 .
meillo@171 1488 Further rework in both tools made the
meillo@139 1489 .Sw -file
meillo@217 1490 switch unnecessary
meillo@217 1491 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e .
meillo@139 1492
meillo@139 1493 .BU
meillo@217 1494 Mmh's tools do no longer clear the screen (\c
meillo@139 1495 .Pn scan 's
meillo@139 1496 and
meillo@139 1497 .Pn mhl 's
meillo@139 1498 .Sw -[no]clear
meillo@139 1499 switches
meillo@139 1500 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139 1501 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@217 1502 Neither does
meillo@139 1503 .Pn mhl
meillo@139 1504 ring the bell (\c
meillo@139 1505 .Sw -[no]bell
meillo@139 1506 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@217 1507 nor does it page the output itself (\c
meillo@139 1508 .Sw -length
meillo@139 1509 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@139 1510 Generally, the pager to use is no longer specified with the
meillo@139 1511 .Sw -[no]moreproc
meillo@139 1512 command line switches for
meillo@139 1513 .Pn mhl
meillo@139 1514 and
meillo@139 1515 .Pn show /\c
meillo@217 1516 .Pn mhshow
meillo@217 1517 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a .
meillo@139 1518
meillo@139 1519 .BU
meillo@96 1520 In order to avoid prefix collisions among switch names, the
meillo@95 1521 .Sw -version
meillo@95 1522 switch was renamed to
meillo@95 1523 .Sw -Version
meillo@217 1524 (with capital `V')
meillo@217 1525 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a .
meillo@95 1526 Every program has the
meillo@95 1527 .Sw -version
meillo@95 1528 switch but its first three letters collided with the
meillo@95 1529 .Sw -verbose
meillo@95 1530 switch, present in many programs.
meillo@95 1531 The rename solved this problem once for all.
meillo@95 1532 Although this rename breaks a basic interface, having the
meillo@95 1533 .Sw -V
meillo@95 1534 abbreviation to display the version information, isn't all too bad.
meillo@139 1535
meillo@95 1536 .BU
meillo@95 1537 .Sw -[no]preserve
meillo@95 1538 of
meillo@95 1539 .Pn refile
meillo@168 1540 was removed
meillo@168 1541 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 1542 because what use was it anyway?
meillo@168 1543 Quoting nmh's man page
meillo@165 1544 .Mp refile (1):
meillo@98 1545 .QS
meillo@95 1546 Normally when a message is refiled, for each destination
meillo@95 1547 folder it is assigned the number which is one above the current
meillo@95 1548 highest message number in that folder. Use of the
meillo@164 1549 .Sw -preserv
meillo@164 1550 [sic!] switch will override this message renaming, and try
meillo@95 1551 to preserve the number of the message. If a conflict for a
meillo@164 1552 particular folder occurs when using the
meillo@164 1553 .Sw -preserve
meillo@164 1554 switch, then
meillo@164 1555 .Pn refile
meillo@164 1556 will use the next available message number which
meillo@95 1557 is above the message number you wish to preserve.
meillo@98 1558 .QE
meillo@139 1559
meillo@95 1560 .BU
meillo@95 1561 The removal of the
meillo@95 1562 .Sw -[no]reverse
meillo@95 1563 switches of
meillo@95 1564 .Pn scan
meillo@97 1565 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@217 1566 is a bug fix.
meillo@217 1567 This is supported by the comments
meillo@95 1568 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95 1569 by Rose and
meillo@95 1570 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@217 1571 This should be considered a bug'' by Romine in the changelogs.
meillo@217 1572 The question remains why neither Rose nor Romine have fixed this
meillo@217 1573 bug in the eighties when they wrote these comments.
meillo@93 1574
meillo@93 1575
meillo@93 1576
meillo@102 1577
meillo@102 1578
meillo@95 1579
meillo@95 1580
meillo@133 1581 .\" --------------------------------------------------------------
meillo@74 1582 .H1 "Modernizing
meillo@102 1583 .P
meillo@164 1584 In the more than thirty years of MH's existence, its code base was
meillo@159 1585 increasingly extended.
meillo@118 1586 New features entered the project and became alternatives to the
meillo@118 1587 existing behavior.
meillo@217 1588 Relics from several decades have gathered in the code base
meillo@118 1589 but seldom obsolete features were dropped.
meillo@118 1590 This section describes the removing of old code
meillo@118 1591 and the modernizing of the default setup.
meillo@118 1592 It focuses on the functional aspect only;
meillo@154 1593 the non-functional aspects of code style are discussed in Sec.
meillo@154 1594 .Cf code-style .
meillo@58 1595
meillo@58 1596
meillo@212 1597 .H2 "Code Relics
meillo@0 1598 .P
meillo@217 1599 My position regarding the removal of obsolete code
meillo@159 1600 is much more revolutional than the nmh community appreciates.
meillo@217 1601 Working on an experimental version, I was able to quickly drop
meillo@217 1602 functionality that I considered ancient.
meillo@104 1603 The need for consensus with peers would have slowed this process down.
meillo@104 1604 Without the need to justify my decisions, I was able to rush forward.
meillo@217 1605 .P
meillo@110 1606 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104 1607 do the work:
meillo@104 1608 .[
meillo@104 1609 paul vixie edginess nmh-workers
meillo@104 1610 .]
meillo@104 1611 .QS
meillo@104 1612 let's stop walking on egg shells with this code base. there's no need to
meillo@104 1613 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104 1614 we don't need a separate branch for removing vmh
meillo@104 1615 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@164 1616 or depending on pure ansi/posix ``libc''.
meillo@104 1617 .QP
meillo@164 1618 these things should each be a day or two of work and the ``main branch''
meillo@104 1619 should just be modern. [...]
meillo@104 1620 let's push forward, aggressively.
meillo@104 1621 .QE
meillo@104 1622 .LP
meillo@104 1623 I did so already in the months before.
meillo@104 1624 I pushed forward.
meillo@104 1625 I simply dropped the cruft.
meillo@104 1626 .P
meillo@104 1627 The decision to drop a feature was based on literature research and
meillo@159 1628 careful thinking, but whether having had contact with this particular
meillo@104 1629 feature within my own computer life served as a rule of thumb.
meillo@159 1630 I explained my reasons in the commit messages
meillo@109 1631 in the version control system.
meillo@104 1632 Hence, others can comprehend my view and argue for undoing the change
meillo@104 1633 if I have missed an important aspect.
meillo@109 1634 I was quick in dropping parts.
meillo@179 1635 I rather include falsely dropped parts again, than going at a slower pace.
meillo@179 1636 Mmh is experimental work; it requires tough decisions.
meillo@12 1637
meillo@102 1638
meillo@217 1639 .U3 "Process Forking
meillo@12 1640 .P
meillo@109 1641 Being a tool chest, MH creates many processes.
meillo@104 1642 In earlier times
meillo@104 1643 .Fu fork()
meillo@104 1644 had been an expensive system call, because the process's image needed
meillo@159 1645 to be completely duplicated at once.
meillo@200 1646 This expensive work was especially unnecessary in the commonly occurring
meillo@159 1647 case wherein the image is replaced by a call to
meillo@104 1648 .Fu exec()
meillo@104 1649 right after having forked the child process.
meillo@104 1650 The
meillo@104 1651 .Fu vfork()
meillo@104 1652 system call was invented to speed up this particular case.
meillo@104 1653 It completely omits the duplication of the image.
meillo@104 1654 On old systems this resulted in significant speed ups.
meillo@104 1655 Therefore MH used
meillo@104 1656 .Fu vfork()
meillo@104 1657 whenever possible.
meillo@12 1658 .P
meillo@104 1659 Modern memory management units support copy-on-write semantics, which make
meillo@104 1660 .Fu fork()
meillo@104 1661 almost as fast as
meillo@104 1662 .Fu vfork() .
meillo@104 1663 The man page of
meillo@104 1664 .Mp vfork (2)
meillo@104 1665 in FreeBSD 8.0 states:
meillo@104 1666 .QS
meillo@104 1667 This system call will be eliminated when proper system sharing mechanisms
meillo@104 1668 are implemented. Users should not depend on the memory sharing semantics
meillo@104 1669 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104 1670 .QE
meillo@104 1671 .LP
meillo@104 1672 Vixie supports the removal with the note that ``the last
meillo@104 1673 system on which fork was so slow that an mh user would notice it, was
meillo@104 1674 Eunice. that was 1987''.
meillo@104 1675 .[
meillo@104 1676 nmh-workers vixie edginess
meillo@104 1677 .]
meillo@104 1678 I replaced all calls to
meillo@104 1679 .Fu vfork()
meillo@104 1680 with calls to
meillo@217 1681 .Fu fork()
meillo@217 1682 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d .
meillo@104 1683 .P
meillo@104 1684 Related to the costs of
meillo@104 1685 .Fu fork()
meillo@104 1686 is the probability of its success.
meillo@109 1687 In the eighties, on heavy loaded systems, calls to
meillo@104 1688 .Fu fork()
meillo@104 1689 were prone to failure.
meillo@104 1690 Hence, many of the
meillo@104 1691 .Fu fork()
meillo@104 1692 calls in the code were wrapped into loops to retry the
meillo@104 1693 .Fu fork()
meillo@217 1694 several times, to increase the chances to succeed eventually.
meillo@109 1695 On modern systems, a failing
meillo@104 1696 .Fu fork()
meillo@109 1697 call is unusual.
meillo@104 1698 Hence, in the rare case when
meillo@104 1699 .Fu fork()
meillo@217 1700 fails, mmh programs simply abort
meillo@217 1701 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6 .
meillo@12 1702
meillo@12 1703
meillo@109 1704 .U3 "Header Fields
meillo@104 1705 .BU
meillo@84 1706 The
meillo@84 1707 .Hd Encrypted
meillo@104 1708 header field was introduced by RFC\|822,
meillo@109 1709 but already marked as legacy in RFC\|2822.
meillo@109 1710 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104 1711 messages [RFC\|4880, RFC\|3156].
meillo@109 1712 Hence, the support for
meillo@104 1713 .Hd Encrypted
meillo@217 1714 header fields is removed in mmh
meillo@217 1715 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857 .
meillo@104 1716 .BU
meillo@159 1717 The native support for
meillo@84 1718 .Hd Face
meillo@217 1719 header fields has been removed, as well
meillo@217 1720 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23 .
meillo@104 1721 This feature is similar to the
meillo@84 1722 .Hd X-Face
meillo@84 1723 header field in its intent,
meillo@21 1724 but takes a different approach to store the image.
meillo@84 1725 Instead of encoding the image data directly into the header field,
meillo@109 1726 it contains the hostname and UDP port where the image
meillo@109 1727 date can be retrieved.
meillo@159 1728 There is even a third Face system,
meillo@109 1729 which is the successor of
meillo@109 1730 .Hd X-Face ,
meillo@109 1731 although it re-uses the
meillo@104 1732 .Hd Face
meillo@217 1733 header field name.
meillo@109 1734 It was invented in 2005 and supports colored PNG images.
meillo@104 1735 None of the Face systems described here is popular today.
meillo@104 1736 Hence, mmh has no direct support for them.
meillo@104 1737 .BU
meillo@154 1738 .Id content-md5
meillo@104 1739 The
meillo@104 1740 .Hd Content-MD5
meillo@104 1741 header field was introduced by RFC\|1864.
meillo@104 1742 It provides detection of data corruption during the transfer.
meillo@104 1743 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104 1744 [RFC\|1864].
meillo@104 1745 The proper approach to verify content integrity in an
meillo@227 1746 end-to-end relationship is the use of digital signatures [RFC\|4880].
meillo@104 1747 On the other hand, transfer protocols should detect corruption during
meillo@109 1748 the transmission.
meillo@109 1749 The TCP includes a checksum field therefore.
meillo@104 1750 These two approaches in combinations render the
meillo@104 1751 .Hd Content-MD5
meillo@104 1752 header field superfluous.
meillo@109 1753 Not a single one out of 4\|200 messages from two decades
meillo@217 1754 in the nmh-workers mailing list archive
meillo@217 1755 .[
meillo@217 1756 nmh-workers mailing list archive website
meillo@217 1757 .]
meillo@217 1758 contains a
meillo@104 1759 .Hd Content-MD5
meillo@104 1760 header field.
meillo@104 1761 Neither did any of the 60\|000 messages in my personal mail storage.
meillo@217 1762 Removing the support for this header field
meillo@217 1763 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda ,
meillo@104 1764 removed the last place where MD5 computation was needed.
meillo@104 1765 Hence, the MD5 code could be removed as well.
meillo@104 1766 Over 500 lines of code vanished by this one change.
meillo@104 1767
meillo@104 1768
meillo@104 1769 .U3 "MMDF maildrop support
meillo@21 1770 .P
meillo@217 1771 This type of maildrop format is conceptionally similar to the mbox format,
meillo@139 1772 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139 1773 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104 1774 Mbox is the de-facto standard maildrop format on Unix,
meillo@159 1775 whereas the MMDF maildrop format is now forgotten.
meillo@217 1776 Mbox remains as the only packed mailbox format, supported in mmh.
meillo@104 1777 .P
meillo@109 1778 The simplifications within the code were moderate.
meillo@109 1779 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109 1780 But also, switches of
meillo@109 1781 .Pn packf
meillo@104 1782 and
meillo@109 1783 .Pn rcvpack
meillo@217 1784 could be removed
meillo@217 1785 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0 .
meillo@109 1786 In the message parsing function
meillo@109 1787 .Fn sbr/m_getfld.c ,
meillo@217 1788 knowledge of MMDF packed mail boxes was removed
meillo@217 1789 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754 .
meillo@109 1790 Further code structure simplifications may be possible there,
meillo@109 1791 because only one single packed mailbox format is left to be supported.
meillo@104 1792 I have not worked on them yet because
meillo@104 1793 .Fu m_getfld()
meillo@104 1794 is heavily optimized and thus dangerous to touch.
meillo@104 1795 The risk of damaging the intricate workings of the optimized code is
meillo@104 1796 too high.
meillo@104 1797
meillo@12 1798
meillo@101 1799 .U3 "Prompter's Control Keys
meillo@20 1800 .P
meillo@20 1801 The program
meillo@20 1802 .Pn prompter
meillo@104 1803 queries the user to fill in a message form.
meillo@217 1804 When used as
meillo@104 1805 .Cl "comp -editor prompter" ,
meillo@20 1806 the resulting behavior is similar to
meillo@20 1807 .Pn mailx .
meillo@51 1808 Apparently,
meillo@20 1809 .Pn prompter
meillo@173 1810 had not been touched lately.
meillo@104 1811 Otherwise it's hardly explainable why it
meillo@20 1812 still offered the switches
meillo@84 1813 .Sw -erase
meillo@84 1814 .Ar chr
meillo@20 1815 and
meillo@84 1816 .Sw -kill
meillo@84 1817 .Ar chr
meillo@20 1818 to name the characters for command line editing.
meillo@21 1819 The times when this had been necessary are long time gone.
meillo@20 1820 Today these things work out-of-the-box, and if not, are configured
meillo@20 1821 with the standard tool
meillo@20 1822 .Pn stty .
meillo@104 1823 The switches are removed now
meillo@104 1824 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20 1825
meillo@104 1826
meillo@109 1827 .U3 "Hardcopy Terminal Support
meillo@21 1828 .P
meillo@109 1829 More of a funny anecdote is a check for being connected to a
meillo@109 1830 hardcopy terminal.
meillo@159 1831 It remained in the code until spring 2012, when I finally removed it
meillo@104 1832 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@21 1833 .P
meillo@109 1834 The check only prevented a pager to be placed between the printing
meillo@104 1835 program (\c
meillo@104 1836 .Pn mhl )
meillo@104 1837 and the terminal.
meillo@109 1838 In nmh, this could have been ensured statically with the
meillo@104 1839 .Sw -nomoreproc
meillo@109 1840 at the command line, too.
meillo@121 1841 In mmh, setting the profile entry
meillo@104 1842 .Pe Pager
meillo@104 1843 or the environment variable
meillo@104 1844 .Ev PAGER
meillo@104 1845 to
meillo@109 1846 .Pn cat
meillo@159 1847 is sufficient.
meillo@104 1848
meillo@104 1849
meillo@21 1850
meillo@12 1851
meillo@58 1852 .H2 "Attachments
meillo@22 1853 .P
meillo@101 1854 The mind model of email attachments is unrelated to MIME.
meillo@217 1855 Although the MIME RFCs [RFC\|2045\(en2049] define the technical
meillo@217 1856 requirements for having attachments, they do not mention the term.
meillo@101 1857 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101 1858 [RFC\|2045], a more general concept.
meillo@101 1859 Multi-part messages are messages
meillo@101 1860 ``in which one or more different
meillo@101 1861 sets of data are combined in a single body''
meillo@101 1862 [RFC\|2046].
meillo@101 1863 MIME keeps its descriptions generic;
meillo@101 1864 it does not imply specific usage models.
meillo@217 1865 Today, one usage model is prevalent: attachments.
meillo@101 1866 The idea is having a main text document with files of arbitrary kind
meillo@101 1867 attached to it.
meillo@101 1868 In MIME terms, this is a multi-part message having a text part first
meillo@110 1869 and parts of arbitrary type following.
meillo@101 1870 .P
meillo@101 1871 MH's MIME support is a direct implementation of the RFCs.
meillo@101 1872 The perception of the topic described in the RFCs is clearly visible
meillo@101 1873 in MH's implementation.
meillo@159 1874 As a result,
meillo@159 1875 MH had all the MIME features but no idea of attachments.
meillo@173 1876 But users do not need all the MIME features,
meillo@109 1877 they want convenient attachment handling.
meillo@109 1878
meillo@102 1879
meillo@102 1880 .U3 "Composing MIME Messages
meillo@102 1881 .P
meillo@102 1882 In order to improve the situation on the message composing side,
meillo@217 1883 Jon Steinhart had added an attachment system to nmh in 2002
meillo@217 1884 .Ci 7480dbc14bc90f2d872d434205c0784704213252 .
meillo@102 1885 In the file
meillo@102 1886 .Fn docs/README-ATTACHMENTS ,
meillo@217 1887 he described his motivation to do so:
meillo@101 1888 .QS
meillo@159 1889 Although nmh contains the necessary functionality for MIME message
meillo@159 1890 handing [sic!], the interface to this functionality is pretty obtuse.
meillo@101 1891 There's no way that I'm ever going to convince my partner to write
meillo@101 1892 .Pn mhbuild
meillo@101 1893 composition files!
meillo@101 1894 .QE
meillo@102 1895 .LP
meillo@102 1896 With this change, the mind model of attachments entered nmh.
meillo@102 1897 In the same document:
meillo@101 1898 .QS
meillo@101 1899 These changes simplify the task of managing attachments on draft files.
meillo@101 1900 They allow attachments to be added, listed, and deleted.
meillo@101 1901 MIME messages are automatically created when drafts with attachments
meillo@101 1902 are sent.
meillo@101 1903 .QE
meillo@102 1904 .LP
meillo@217 1905 Unfortunately, the attachment system, like every new facilities in nmh,
meillo@110 1906 was inactive by default.
meillo@101 1907 .P
meillo@217 1908 During my time in Argentina, I tried to improve the attachment system.
meillo@217 1909 But, after long discussions my patch died as a proposal on the
meillo@217 1910 mailing list because of great opposition in the nmh community.
meillo@101 1911 .[
meillo@101 1912 nmh-workers attachment proposal
meillo@101 1913 .]
meillo@217 1914 In January 2012, I extended the patch and applied it to mmh
meillo@217 1915 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1 .
meillo@102 1916 In mmh, the attachment system is active by default.
meillo@102 1917 Instead of command line switches, the
meillo@102 1918 .Pe Attachment-Header
meillo@102 1919 profile entry is used to specify
meillo@102 1920 the name of the attachment header field.
meillo@102 1921 It is pre-defined to
meillo@102 1922 .Hd Attach .
meillo@101 1923 .P
meillo@159 1924 To add an attachment to a draft, a header line needs to be added:
meillo@101 1925 .VS
meillo@101 1926 To: bob
meillo@101 1927 Subject: The file you wanted
meillo@101 1928 Attach: /path/to/the/file-bob-wanted
meillo@101 1929 --------
meillo@101 1930 Here it is.
meillo@101 1931 VE
meillo@101 1932 The header field can be added to the draft manually in the editor,
meillo@102 1933 or by using the `attach' command at the WhatNow prompt, or
meillo@102 1934 non-interactively with
meillo@101 1935 .Pn anno :
meillo@101 1936 .VS
meillo@102 1937 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101 1938 VE
meillo@102 1939 Drafts with attachment headers are converted to MIME automatically by
meillo@102 1940 .Pn send .
meillo@102 1941 The conversion to MIME is invisible to the user.
meillo@159 1942 The draft stored in the draft folder is always in source form with
meillo@101 1943 attachment headers.
meillo@179 1944 If the MIMEification fails (e.g. because the file to attach
meillo@179 1945 is not accessible) the original draft is not changed.
meillo@101 1946 .P
meillo@102 1947 The attachment system handles the forwarding of messages, too.
meillo@173 1948 If the attachment header value starts with a plus character (`\fL+\fP'),
meillo@101 1949 like in
meillo@101 1950 .Cl "Attach: +bob 30 42" ,
meillo@159 1951 the given messages in the specified folder will be attached.
meillo@101 1952 This allowed to simplify
meillo@217 1953 .Pn forw
meillo@217 1954 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550 .
meillo@101 1955 .P
meillo@101 1956 Closely related to attachments is non-ASCII text content,
meillo@217 1957 because it requires MIME as well.
meillo@102 1958 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101 1959 to have the draft converted to MIME.
meillo@102 1960 This was necessary whenever the draft contained non-ASCII characters.
meillo@101 1961 If the user did not call `mime', a broken message would be sent.
meillo@101 1962 Therefore, the
meillo@101 1963 .Pe automimeproc
meillo@101 1964 profile entry could be specified to have the `mime' command invoked
meillo@102 1965 automatically each time.
meillo@179 1966 Unfortunately, this approach conflicted with the attachment system
meillo@101 1967 because the draft would already be in MIME format at the time
meillo@101 1968 when the attachment system wanted to MIMEify it.
meillo@102 1969 To use nmh's attachment system, `mime' must not be called at the
meillo@102 1970 WhatNow prompt and
meillo@101 1971 .Pe automimeproc
meillo@102 1972 must not be set in the profile.
meillo@101 1973 But then the case of non-ASCII text without attachment headers was
meillo@101 1974 not caught.
meillo@102 1975 All in all, the solution was complex and irritating.
meillo@168 1976 My patch from December 2010
meillo@168 1977 .[
meillo@168 1978 nmh-workers attachment proposal
meillo@168 1979 .]
meillo@168 1980 would have simplified the situation.
meillo@102 1981 .P
meillo@101 1982 Mmh's current solution is even more elaborate.
meillo@101 1983 Any necessary MIMEification is done automatically.
meillo@101 1984 There is no `mime' command at the WhatNow prompt anymore.
meillo@102 1985 The draft will be converted automatically to MIME when either an
meillo@102 1986 attachment header or non-ASCII text is present.
meillo@173 1987 Furthermore, the hash character (`\fL#\fP') is not special any more
meillo@159 1988 at line beginnings in the draft message.
meillo@159 1989 Users need not concern themselves with the whole topic at all.
meillo@101 1990 .P
meillo@102 1991 Although the new approach does not anymore support arbitrary MIME
meillo@102 1992 compositions directly, the full power of
meillo@101 1993 .Pn mhbuild
meillo@101 1994 can still be accessed.
meillo@217 1995 Given no attachment headers are included, users can create
meillo@101 1996 .Pn mhbuild
meillo@102 1997 composition drafts like in nmh.
meillo@217 1998 Then, at the WhatNow prompt, they can invoke
meillo@101 1999 .Cl "edit mhbuild
meillo@217 2000 to convert the draft to MIME.
meillo@217 2001 Because the resulting draft neither contains non-ASCII characters
meillo@102 2002 nor has it attachment headers, the attachment system will not touch it.
meillo@101 2003 .P
meillo@159 2004 The approach taken in mmh is tailored towards today's most common case:
meillo@159 2005 a text part, possibly with attachments.
meillo@159 2006 This case was simplified.
meillo@102 2007
meillo@112 2008
meillo@102 2009 .U3 "MIME Type Guessing
meillo@102 2010 .P
meillo@159 2011 From the programmer's point of view, the use of
meillo@101 2012 .Pn mhbuild
meillo@159 2013 composition drafts had one notable advantage over attachment headers:
meillo@159 2014 The user provides the appropriate MIME types for files to include.
meillo@217 2015 The new attachment system needs to find out the correct MIME type itself.
meillo@217 2016 This is a difficult task.
meillo@102 2017 Determining the correct MIME type of content is partly mechanical,
meillo@102 2018 partly intelligent work.
meillo@102 2019 Forcing the user to find out the correct MIME type,
meillo@102 2020 forces him to do partly mechanical work.
meillo@179 2021 Letting the computer do the work can lead to bad choices for difficult
meillo@102 2022 content.
meillo@217 2023 For mmh, the latter option was chosen to spare the user the work
meillo@217 2024 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6 .
meillo@102 2025 .P
meillo@102 2026 Determining the MIME type by the suffix of the file name is a dumb
meillo@102 2027 approach, yet it is simple to implement and provides good results
meillo@102 2028 for the common cases.
meillo@217 2029 If no MIME type can be determined, text content is sent as `text/plain',
meillo@217 2030 anything else under the generic fall-back type `application/octet-stream'.
meillo@102 2031 Mmh implements this approach in the
meillo@102 2032 .Pn print-mimetype
meillo@217 2033 script
meillo@217 2034 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44 .
meillo@102 2035 .P
meillo@112 2036 A far better, though less portable, approach is the use of
meillo@102 2037 .Pn file .
meillo@102 2038 This standard tool tries to determine the type of files.
meillo@102 2039 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102 2040 Additionally, its output was only intended for human beings,
meillo@102 2041 but not to be used by programs.
meillo@102 2042 Nevertheless, modern versions of GNU
meillo@102 2043 .Pn file ,
meillo@217 2044 which are prevalent on the popular GNU/Linux systems,
meillo@159 2045 provide MIME type output in machine-readable form.
meillo@217 2046 Although this solution is system-dependent,
meillo@102 2047 it solves the difficult problem well.
meillo@102 2048 On systems where GNU
meillo@102 2049 .Pn file ,
meillo@102 2050 version 5.04 or higher, is available it should be used.
meillo@102 2051 One needs to specify the following profile entry to do so:
meillo@102 2052 .VS
meillo@102 2053 Mime-Type-Query: file -b --mime
meillo@102 2054 VE
meillo@102 2055 .LP
meillo@102 2056 Other versions of
meillo@102 2057 .Pn file
meillo@217 2058 might possibly be usable with wrapper scripts that reformat the output.
meillo@102 2059 The diversity among
meillo@102 2060 .Pn file
meillo@102 2061 implementations is great; one needs to check the local variant.
meillo@102 2062 .P
meillo@102 2063 It is not possible in mmh to override the automatic MIME type guessing
meillo@102 2064 for a specific file.
meillo@159 2065 To do so, either the user would need to know in advance for which file
meillo@217 2066 the automatic guessing fails or the system would require interaction.
meillo@102 2067 I consider both cases impractical.
meillo@102 2068 The existing solution should be sufficient.
meillo@102 2069 If not, the user may always fall back to
meillo@102 2070 .Pn mhbuild
meillo@217 2071 composition drafts and bypass the attachment system.
meillo@101 2072
meillo@102 2073
meillo@102 2074 .U3 "Storing Attachments
meillo@102 2075 .P
meillo@169 2076 Extracting MIME parts of a message and storing them to disk is performed by
meillo@108 2077 .Pn mhstore .
meillo@108 2078 The program has two operation modes,
meillo@108 2079 .Sw -auto
meillo@108 2080 and
meillo@108 2081 .Sw -noauto .
meillo@108 2082 With the former one, each part is stored under the filename given in the
meillo@108 2083 MIME part's meta information, if available.
meillo@108 2084 This naming information is usually available for modern attachments.
meillo@108 2085 If no filename is available, this MIME part is stored as if
meillo@108 2086 .Sw -noauto
meillo@108 2087 would have been specified.
meillo@108 2088 In the
meillo@108 2089 .Sw -noauto
meillo@108 2090 mode, the parts are processed according to rules, defined by
meillo@108 2091 .Pe mhstore-store-*
meillo@108 2092 profile entries.
meillo@108 2093 These rules define generic filename templates for storing
meillo@108 2094 or commands to post-process the contents in arbitrary ways.
meillo@108 2095 If no matching rule is available the part is stored under a generic
meillo@108 2096 filename, built from message number, MIME part number, and MIME type.
meillo@108 2097 .P
meillo@108 2098 The
meillo@108 2099 .Sw -noauto
meillo@108 2100 mode had been the default in nmh because it was considered safe,
meillo@108 2101 in contrast to the
meillo@108 2102 .Sw -auto
meillo@108 2103 mode.
meillo@108 2104 In mmh,
meillo@108 2105 .Sw -auto
meillo@108 2106 is not dangerous anymore.
meillo@108 2107 Two changes were necessary:
meillo@171 2108 .LI 1
meillo@108 2109 Any directory path is removed from the proposed filename.
meillo@108 2110 Thus, the files are always stored in the expected directory.
meillo@108 2111 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@171 2112 .LI 2
meillo@108 2113 Tar files are not extracted automatically any more.
meillo@108 2114 Thus, the rest of the file system will not be touched.
meillo@108 2115 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@217 2116 .P
meillo@217 2117 In mmh, the result of
meillo@108 2118 .Cl "mhstore -auto
meillo@110 2119 can be foreseen from the output of
meillo@108 2120 .Cl "mhlist -verbose" .
meillo@217 2121 Although the
meillo@108 2122 .Sw -noauto
meillo@217 2123 mode is considered to be more powerful, it is less convenient and
meillo@108 2124 .Sw -auto
meillo@217 2125 is safe now.
meillo@217 2126 Additionally, storing attachments under their original name
meillo@217 2127 is intuitive.
meillo@108 2128 Hence,
meillo@108 2129 .Sw -auto
meillo@217 2130 serves better as the default option
meillo@217 2131 .Ci 3410b680416c49a7617491af38bc1929855a331d .
meillo@108 2132 .P
meillo@108 2133 Files are stored into the directory given by the
meillo@108 2134 .Pe Nmh-Storage
meillo@108 2135 profile entry, if set, or
meillo@108 2136 into the current working directory, otherwise.
meillo@108 2137 Storing to different directories is only possible with
meillo@108 2138 .Pe mhstore-store-*
meillo@108 2139 profile entries.
meillo@108 2140 .P
meillo@217 2141 Still existing files get overwritten silently in both modes.
meillo@108 2142 This can be considered a bug.
meillo@108 2143 Yet, each other behavior has its draw-backs, too.
meillo@108 2144 Refusing to replace files requires adding a
meillo@108 2145 .Sw -force
meillo@217 2146 switch.
meillo@108 2147 Users will likely need to invoke
meillo@108 2148 .Pn mhstore
meillo@108 2149 a second time with
meillo@159 2150 .Sw -force .
meillo@159 2151 Eventually, only the user can decide in the specific case.
meillo@108 2152 This requires interaction, which I like to avoid if possible.
meillo@108 2153 Appending a unique suffix to the filename is another bad option.
meillo@108 2154 For now, the behavior remains as it is.
meillo@108 2155 .P
meillo@108 2156 In mmh, only MIME parts of type message are special in
meillo@108 2157 .Pn mhstore 's
meillo@108 2158 .Sw -auto
meillo@108 2159 mode.
meillo@108 2160 Instead of storing message/rfc822 parts as files to disk,
meillo@108 2161 they are stored as messages into the current mail folder.
meillo@159 2162 The same applies to message/partial, although the parts are
meillo@159 2163 automatically reassembled beforehand.
meillo@159 2164 MIME parts of type message/external-body are not automatically retrieved
meillo@159 2165 anymore.
meillo@159 2166 Instead, information on how to retrieve them is output.
meillo@217 2167 Not supporting this rare case saved nearly one thousand lines of code
meillo@217 2168 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32 .
meillo@217 2169 The MIME type `application/octet-stream; type=tar' is not special anymore.
meillo@217 2170 The automatically extracting of such MIME parts had been the
meillo@217 2171 dangerous part of the
meillo@108 2172 .Sw -auto
meillo@217 2173 mode
meillo@217 2174 .Ci 94c80042eae3383c812d9552089953f9846b1bb6 .
meillo@108 2175
meillo@102 2176
meillo@102 2177
meillo@102 2178 .U3 "Showing MIME Messages
meillo@227 2179 .Id showing-mime-msgs
meillo@102 2180 .P
meillo@114 2181 The program
meillo@114 2182 .Pn mhshow
meillo@217 2183 was written to display MIME messages.
meillo@114 2184 It implemented the conceptional view of the MIME RFCs.
meillo@114 2185 Nmh's
meillo@114 2186 .Pn mhshow
meillo@217 2187 handles each MIME part independently, presenting them separately
meillo@114 2188 to the user.
meillo@114 2189 This does not match today's understanding of email attachments,
meillo@114 2190 where displaying a message is seen to be a single, integrated operation.
meillo@114 2191 Today, email messages are expected to consist of a main text part
meillo@114 2192 plus possibly attachments.
meillo@217 2193 They are no more seen to be arbitrary MIME hierarchies with
meillo@114 2194 information on how to display the individual parts.
meillo@114 2195 I adjusted
meillo@114 2196 .Pn mhshow 's
meillo@114 2197 behavior to the modern view on the topic.
meillo@114 2198 .P
meillo@224 2199 One should note that this section completely ignores the original
meillo@114 2200 .Pn show
meillo@114 2201 program, because it was not capable to display MIME messages
meillo@227 2202 and is no longer part of mmh
meillo@227 2203 (cf. Sec.
meillo@227 2204 .Cf mhshow ).
meillo@114 2205 Although
meillo@114 2206 .Pn mhshow
meillo@114 2207 was renamed to
meillo@114 2208 .Pn show
meillo@114 2209 in mmh, this section uses the name
meillo@114 2210 .Pn mhshow ,
meillo@224 2211 in order to avoid confusion.
meillo@114 2212 .P
meillo@114 2213 In mmh, the basic idea is that
meillo@114 2214 .Pn mhshow
meillo@114 2215 should display a message in one single pager session.
meillo@114 2216 Therefore,
meillo@114 2217 .Pn mhshow
meillo@114 2218 invokes a pager session for all its output,
meillo@217 2219 whenever it prints to a terminal
meillo@217 2220 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e .
meillo@114 2221 In consequence,
meillo@114 2222 .Pn mhl
meillo@217 2223 does no more invoke a pager
meillo@217 2224 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70 .
meillo@114 2225 With
meillo@114 2226 .Pn mhshow
meillo@114 2227 replacing the original
meillo@114 2228 .Pn show ,
meillo@217 2229 the output of
meillo@114 2230 .Pn mhl
meillo@217 2231 no longer goes to the terminal directly, but through
meillo@114 2232 .Pn mhshow .
meillo@114 2233 Hence,
meillo@114 2234 .Pn mhl
meillo@114 2235 does not need to invoke a pager.
meillo@114 2236 The one and only job of
meillo@114 2237 .Pn mhl
meillo@114 2238 is to format messages or parts of them.
meillo@114 2239 The only place in mmh, where a pager is invoked is
meillo@114 2240 .Pn mhshow .
meillo@114 2241 .P
meillo@227 2242 Only text content is displayed.
meillo@227 2243 Other kinds of attachments are ignored.
meillo@217 2244 Non-text content needs to be converted to text by appropriate
meillo@217 2245 .Pe mhshow-show-*
meillo@217 2246 profile entries before, if this is possible and wanted.
meillo@217 2247 A common example for this are PDF files.
meillo@227 2248 .P
meillo@227 2249 MIME parts are always displayed serially.
meillo@114 2250 The request to display the MIME type `multipart/parallel' in parallel
meillo@114 2251 is ignored.
meillo@217 2252 It is simply treated as `multipart/mixed'
meillo@217 2253 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6 .
meillo@217 2254 This was already possible to requested with the, now removed,
meillo@114 2255 .Sw -serialonly
meillo@114 2256 switch of
meillo@114 2257 .Pn mhshow .
meillo@179 2258 As MIME parts are always processed exclusively, i.e. serially,
meillo@217 2259 the `\fL%e\fP' escape in
meillo@114 2260 .Pe mhshow-show-*
meillo@217 2261 profile entries became useless and was thus removed
meillo@217 2262 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae .
meillo@114 2263 For parallel display, the attachments need to be stored to disk first.
meillo@114 2264 .P
meillo@114 2265 To display text content in foreign charsets, they need to be converted
meillo@114 2266 to the native charset.
meillo@114 2267 Therefore,
meillo@114 2268 .Pe mhshow-charset-*
meillo@217 2269 profile entries were needed.
meillo@169 2270 In mmh, the conversion is performed automatically by piping the
meillo@169 2271 text through the
meillo@114 2272 .Pn iconv
meillo@217 2273 command, if necessary
meillo@217 2274 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60 .
meillo@114 2275 Custom
meillo@114 2276 .Pe mhshow-show-*
meillo@114 2277 rules for textual content might need a
meillo@114 2278 .Cl "iconv -f %c %f |
meillo@114 2279 prefix to have the text converted to the native charset.
meillo@114 2280 .P
meillo@121 2281 Although the conversion of foreign charsets to the native one
meillo@114 2282 has improved, it is not consistent enough.
meillo@114 2283 Further work needs to be done and
meillo@114 2284 the basic concepts in this field need to be re-thought.
meillo@114 2285 Though, the default setup of mmh displays message in foreign charsets
meillo@114 2286 correctly without the need to configure anything.
meillo@114 2287
meillo@114 2288
meillo@114 2289 .ig
meillo@114 2290
meillo@114 2291 .P
meillo@114 2292 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@173 2293 These tools will not download the contents automatically anymore. Instead,
meillo@114 2294 they print the information needed to get the contents. If someone should
meillo@114 2295 really receive one of those rare message/external-body messages, he can
meillo@114 2296 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114 2297 it!
meillo@114 2298 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114 2299 ~/.netrc are gone now.)
meillo@114 2300 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114 2301
meillo@114 2302 ..
meillo@102 2303
meillo@58 2304
meillo@58 2305
meillo@166 2306 .H2 "Signing and Encrypting
meillo@22 2307 .P
meillo@166 2308 Nmh offers no direct support for digital signatures and message encryption.
meillo@157 2309 This functionality needed to be added through third-party software.
meillo@217 2310 In mmh, the functionality is included because it
meillo@217 2311 is a part of modern email and is likely wanted by users of mmh.
meillo@217 2312 A fresh mmh installation supports signing and encrypting
meillo@157 2313 out-of-the-box.
meillo@157 2314 Therefore, Neil Rickert's
meillo@157 2315 .Pn mhsign
meillo@157 2316 and
meillo@157 2317 .Pn mhpgp
meillo@157 2318 scripts
meillo@157 2319 .[
meillo@157 2320 neil rickert mhsign mhpgp
meillo@157 2321 .]
meillo@217 2322 were included
meillo@177 2323 .Ci f45cdc98117a84f071759462c7ae212f4bc5ab2e
meillo@177 2324 .Ci 58cf09aa36e9f7f352a127158bbf1c5678bc6ed8 .
meillo@177 2325 The scripts fit well because they are lightweight and
meillo@177 2326 similar of style to the existing tools.
meillo@217 2327 Additionally, no licensing difficulties appeared
meillo@157 2328 as they are part of the public domain.
meillo@112 2329 .P
meillo@157 2330 .Pn mhsign
meillo@157 2331 handles the signing and encrypting part.
meillo@157 2332 It comprises about 250 lines of shell code and interfaces between
meillo@223 2333 .Pn gnupg
meillo@217 2334 and the MH system.
meillo@177 2335 It was meant to be invoked manually at the WhatNow prompt, but in mmh,
meillo@157 2336 .Pn send
meillo@177 2337 invokes
meillo@217 2338 .Pn mhsign
meillo@177 2339 automatically
meillo@177 2340 .Ci c7b5e1df086bcc37ff40163ee67571f076cf6683 .
meillo@177 2341 Special header fields were introduced to request this action.
meillo@157 2342 If a draft contains the
meillo@157 2343 .Hd Sign
meillo@157 2344 header field,
meillo@157 2345 .Pn send
meillo@177 2346 will initiate the signing.
meillo@217 2347 The signing key is either chosen automatically or it is specified by the
meillo@157 2348 .Pe Pgpkey
meillo@157 2349 profile entry.
meillo@157 2350 .Pn send
meillo@217 2351 always create signatures using the PGP/MIME standard [RFC\|4880],
meillo@217 2352 but by invoking
meillo@217 2353 .Pn mhsign
meillo@217 2354 manually, old-style non-MIME signatures can be created as well.
meillo@177 2355 To encrypt an outgoing message, the draft needs to contain an
meillo@157 2356 .Hd Enc
meillo@157 2357 header field.
meillo@177 2358 Public keys of all recipients are searched for in the gnupg keyring and
meillo@177 2359 in a file called
meillo@177 2360 .Fn pgpkeys ,
meillo@177 2361 which contains exceptions and overrides.
meillo@157 2362 Unless public keys are found for all recipients,
meillo@177 2363 .Pn mhsign
meillo@177 2364 will refuse to encrypt it.
meillo@157 2365 Currently, messages with hidden (BCC) recipients can not be encrypted.
meillo@171 2366 This work is pending because it requires a structurally more complex
meillo@171 2367 approach.
meillo@157 2368 .P
meillo@177 2369 .Pn mhpgp
meillo@177 2370 is the companion to
meillo@177 2371 .Pn mhsign .
meillo@177 2372 It verifies signatures and decrypts messages.
meillo@217 2373 Encrypted messages can be either temporarily decrypted and displayed
meillo@177 2374 or permanently decrypted and stored into the current folder.
meillo@177 2375 Currently,
meillo@177 2376 .Pn mhpgp
meillo@177 2377 needs to be invoked manually.
meillo@177 2378 The integration into
meillo@177 2379 .Pn show
meillo@177 2380 and
meillo@177 2381 .Pn mhstore
meillo@217 2382 to verify signatures and decrypt messages as needed
meillo@217 2383 is planned but not yet realized.
meillo@177 2384 .P
meillo@217 2385 Both scripts were written for nmh.
meillo@217 2386 Hence they needed to be adjust
meillo@177 2387 according to the differences between nmh and mmh.
meillo@177 2388 For instance, they use the backup prefix no longer.
meillo@181 2389 Furthermore, compatibility support for old PGP features was dropped.
meillo@177 2390 .P
meillo@157 2391 The integrated message signing and encrypting support is one of the
meillo@157 2392 most recent features in mmh.
meillo@217 2393 It has not had the time to mature.
meillo@177 2394 User feedback and personal experience need to be accumulated to
meillo@177 2395 direct the further development of the facility.
meillo@217 2396 Already it seems to be worthwhile to consider adding
meillo@157 2397 .Sw -[no]sign
meillo@157 2398 and
meillo@157 2399 .Sw -[no]enc
meillo@157 2400 switches to
meillo@157 2401 .Pn send ,
meillo@177 2402 to be able to override the corresponding header fields.
meillo@177 2403 A profile entry:
meillo@157 2404 .VS
meillo@157 2405 send: -sign
meillo@157 2406 VE
meillo@177 2407 would then activate signing for all outgoing messages.
meillo@177 2408 With the present approach, a
meillo@177 2409 .Hd Send
meillo@177 2410 header component needs to be added to each draft template
meillo@177 2411 to achieve the same result.
meillo@177 2412 Adding the switches would ease the work greatly and keep the
meillo@177 2413 template files clean.
meillo@157 2414
meillo@58 2415
meillo@58 2416
meillo@102 2417
meillo@133 2418 .H2 "Draft and Trash Folder
meillo@131 2419 .P
meillo@58 2420
meillo@131 2421 .U3 "Draft Folder
meillo@154 2422 .Id draft-folder
meillo@131 2423 .P
meillo@131 2424 In the beginning, MH had the concept of a draft message.
meillo@217 2425 This was a file named
meillo@131 2426 .Fn draft
meillo@217 2427 in the MH directory, which was treated special.
meillo@131 2428 On composing a message, this draft file was used.
meillo@131 2429 When starting to compose another message before the former one was sent,
meillo@131 2430 the user had to decide among:
meillo@171 2431 .LI 1
meillo@168 2432 Using the old draft to finish and send it before starting with a new one.
meillo@171 2433 .LI 2
meillo@168 2434 Discarding the old draft and replacing it with a new one.
meillo@171 2435 .LI 3
meillo@168 2436 Preserving the old draft by refiling it to a folder.
meillo@171 2437 .LP
meillo@217 2438 Working on multiple drafts was only possible in alternation.
meillo@217 2439 For that, the current draft needed to be refiled to a folder and
meillo@168 2440 another one re-used for editing.
meillo@131 2441 Working on multiple drafts at the same time was impossible.
meillo@131 2442 The usual approach of switching to a different MH context did not
meillo@168 2443 help anything.
meillo@131 2444 .P
meillo@131 2445 The draft folder facility exists to
meillo@131 2446 allow true parallel editing of drafts, in a straight forward way.
meillo@131 2447 It was introduced by Marshall T. Rose, already in 1984.
meillo@131 2448 Similar to other new features, the draft folder was inactive by default.
meillo@131 2449 Even in nmh, the highly useful draft folder was not available
meillo@131 2450 out-of-the-box.
meillo@131 2451 At least, Richard Coleman added the man page
meillo@131 2452 .Mp mh-draft (5)
meillo@131 2453 to better document the feature.
meillo@131 2454 .P
meillo@131 2455 Not using the draft folder facility has the single advantage of having
meillo@131 2456 the draft file at a static location.
meillo@131 2457 This is simple in simple cases but the concept does not scale for more
meillo@131 2458 complex cases.
meillo@217 2459 The concept of the draft message is too limited for the problem
meillo@217 2460 it tries to solve.
meillo@131 2461 Therefore the draft folder was introduced.
meillo@131 2462 It is the more powerful and more natural concept.
meillo@131 2463 The draft folder is a folder like any other folder in MH.
meillo@131 2464 Its messages can be listed like any other messages.
meillo@131 2465 A draft message is no longer a special case.
meillo@131 2466 Tools do not need special switches to work on the draft message.
meillo@171 2467 Hence corner cases were removed.
meillo@131 2468 .P
meillo@131 2469 The trivial part of the work was activating the draft folder with a
meillo@131 2470 default name.
meillo@131 2471 I chose the name
meillo@217 2472 .Fn +drafts ,
meillo@131 2473 for obvious reasons.
meillo@131 2474 In consequence, the command line switches
meillo@131 2475 .Sw -draftfolder
meillo@131 2476 and
meillo@131 2477 .Sw -draftmessage
meillo@131 2478 could be removed.
meillo@131 2479 More difficult but also more improving was updating the tools to the
meillo@131 2480 new concept.
meillo@131 2481 For nearly three decades, the tools needed to support two draft handling
meillo@131 2482 approaches.
meillo@217 2483 By fully switching to the draft folder, the tools could be
meillo@217 2484 simplified by dropping the awkward draft message handling code.
meillo@131 2485 .Sw -draft
meillo@131 2486 switches were removed because operating on a draft message is no longer
meillo@131 2487 special.
meillo@131 2488 It became indistinguishable to operating on any other message.
meillo@168 2489 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@168 2490 .P
meillo@168 2491 There is no more need to query the user for draft handling
meillo@168 2492 .Ci 2d48b455c303a807041c35e4248955f8bec59eeb .
meillo@131 2493 It is always possible to add another new draft.
meillo@131 2494 Refiling drafts is without difference to refiling other messages.
meillo@168 2495 All of these special cases are gone.
meillo@131 2496 Yet, one draft-related switch remained.
meillo@131 2497 .Pn comp
meillo@131 2498 still has
meillo@131 2499 .Sw -[no]use
meillo@131 2500 for switching between two modes:
meillo@171 2501 .LI 1
meillo@217 2502 Modifying an existing draft, with
meillo@217 2503 .Sw -use .
meillo@171 2504 .LI 2
meillo@217 2505 Composing a new draft, possibly taking some existing message as template,
meillo@217 2506 with
meillo@217 2507 .Sw -nouse ,
meillo@217 2508 the default.
meillo@171 2509 .LP
meillo@131 2510 In either case, the behavior of
meillo@131 2511 .Pn comp
meillo@131 2512 is deterministic.
meillo@131 2513 .P
meillo@131 2514 .Pn send
meillo@131 2515 now operates on the current message in the draft folder by default.
meillo@131 2516 As message and folder can both be overridden by specifying them on
meillo@131 2517 the command line, it is possible to send any message in the mail storage
meillo@131 2518 by simply specifying its number and folder.
meillo@131 2519 In contrast to the other tools,
meillo@131 2520 .Pn send
meillo@131 2521 takes the draft folder as its default folder.
meillo@131 2522 .P
meillo@131 2523 Dropping the draft message concept in favor for the draft folder concept,
meillo@217 2524 replaced special cases with regular cases.
meillo@131 2525 This simplified the source code of the tools, as well as the concepts.
meillo@131 2526 In mmh, draft management does not break with the MH concepts
meillo@131 2527 but applies them.
meillo@133 2528 .Cl "scan +drafts" ,
meillo@133 2529 for instance, is a truly natural request.
meillo@217 2530 .P
meillo@169 2531 Most of the work was already performed by Rose in the eighties.
meillo@133 2532 The original improvement of mmh is dropping the old draft message approach
meillo@217 2533 and thus simplifying the tools, the documentation,
meillo@217 2534 and the system as a whole.
meillo@131 2535 Although my part in the draft handling improvement was small,
meillo@217 2536 it was important.
meillo@131 2537
meillo@131 2538
meillo@131 2539 .U3 "Trash Folder
meillo@154 2540 .Id trash-folder
meillo@131 2541 .P
meillo@131 2542 Similar to the situation for drafts is the situation for removed messages.
meillo@131 2543 Historically, a message was ``deleted'' by prepending a specific
meillo@173 2544 \fIbackup prefix\fP, usually the comma character,
meillo@173 2545 to the file name.
meillo@164 2546 The specific file would then be ignored by MH because only files with
meillo@164 2547 names consisting of digits only are treated as messages.
meillo@131 2548 Although files remained in the file system,
meillo@168 2549 the messages were no longer visible in MH.
meillo@168 2550 To truly delete them, a maintenance job was needed.
meillo@168 2551 Usually a cron job was installed to delete them after a grace time.
meillo@131 2552 For instance:
meillo@131 2553 .VS
meillo@131 2554 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131 2555 VE
meillo@168 2556 In such a setup, the original message could be restored
meillo@131 2557 within the grace time interval by stripping the
meillo@217 2558 backup prefix from the file name \(en usually but not always.
meillo@168 2559 If the last message of a folder with six messages (\fL1-6\fP) was removed,
meillo@131 2560 message
meillo@131 2561 .Fn 6 ,
meillo@168 2562 became file
meillo@131 2563 .Fn ,6 .
meillo@168 2564 If then a new message entered the same folder, it would be named with
meillo@168 2565 the number one above the highest existing message number.
meillo@168 2566 In this case the message would be named
meillo@217 2567 .Fn 6 ,
meillo@217 2568 reusing the number.
meillo@168 2569 If this new message would be removed as well,
meillo@217 2570 then the backup of the former message becomes overwritten.
meillo@168 2571 Hence, the ability to restore removed messages did not only depend on
meillo@181 2572 the sweeping cron job but also on the removing of further messages.
meillo@131 2573 It is undesirable to have such obscure and complex mechanisms.
meillo@168 2574 The user should be given a small set of clear assertions, such as
meillo@131 2575 ``Removed files are restorable within a seven-day grace time.''
meillo@131 2576 With the addition ``... unless a message with the same name in the
meillo@131 2577 same folder is removed before.'' the statement becomes complex.
meillo@217 2578 A user will hardly be able to keep track of all removals to know
meillo@131 2579 if the assertion still holds true for a specific file.
meillo@164 2580 In practice, the real mechanism is unclear to the user.
meillo@131 2581 .P
meillo@217 2582 Furthermore, the backup files were scattered within the whole mail storage.
meillo@217 2583 This complicated managing them.
meillo@217 2584 It was possible with the help of
meillo@131 2585 .Pn find ,
meillo@217 2586 but everything is more convenient
meillo@217 2587 if the deleted messages are collected in one place.
meillo@131 2588 .P
meillo@131 2589 The profile entry
meillo@131 2590 .Pe rmmproc
meillo@131 2591 (previously named
meillo@131 2592 .Pe Delete-Prog )
meillo@131 2593 was introduced very early to improve the situation.
meillo@164 2594 It could be set to any command, which would be executed to remove
meillo@131 2595 the specified messages.
meillo@217 2596 This had overridden the default action, described above.
meillo@217 2597 Refiling the to-be-removed files to a trash folder was the usual example.
meillo@131 2598 Nmh's man page
meillo@131 2599 .Mp rmm (1)
meillo@131 2600 proposes to set the
meillo@131 2601 .Pe rmmproc
meillo@131 2602 to
meillo@131 2603 .Cl "refile +d
meillo@217 2604 to move messages to the trash folder
meillo@217 2605 .Fn +d
meillo@131 2606 instead of renaming them with the backup prefix.
meillo@217 2607 The man page additionally proposes the expunge command
meillo@131 2608 .Cl "rm `mhpath +d all`
meillo@168 2609 to empty the trash folder.
meillo@131 2610 .P
meillo@217 2611 Removing messages in such a way has advantages:
meillo@217 2612 .LI 1
meillo@131 2613 The mail storage is prevented from being cluttered with removed messages
meillo@131 2614 because they are all collected in one place.
meillo@131 2615 Existing and removed messages are thus separated more strictly.
meillo@217 2616 .LI 2
meillo@131 2617 No backup files are silently overwritten.
meillo@217 2618 .LI 3
meillo@217 2619 Most important, however, removed messages are kept in the MH domain.
meillo@131 2620 Messages in the trash folder can be listed like those in any other folder.
meillo@131 2621 Deleted messages can be displayed like any other messages.
meillo@169 2622 .Pn refile
meillo@169 2623 can restore deleted messages.
meillo@131 2624 All operations on deleted files are still covered by the MH tools.
meillo@131 2625 The trash folder is just like any other folder in the mail storage.
meillo@131 2626 .P
meillo@131 2627 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131 2628 in favor for replacing it by the better suiting trash folder system.
meillo@131 2629 Hence,
meillo@131 2630 .Pn rmm
meillo@131 2631 calls
meillo@131 2632 .Pn refile
meillo@131 2633 to move the to-be-removed message to the trash folder,
meillo@131 2634 .Fn +trash
meillo@131 2635 by default.
meillo@164 2636 To sweep it clean, the user can use
meillo@131 2637 .Cl "rmm -unlink +trash a" ,
meillo@131 2638 where the
meillo@131 2639 .Sw -unlink
meillo@131 2640 switch causes the files to be unlinked.
meillo@168 2641 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168 2642 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@131 2643 .P
meillo@217 2644 Dropping the legacy approach and converting to the new approach
meillo@217 2645 completely, simplified the code base.
meillo@131 2646 The relationship between
meillo@131 2647 .Pn rmm
meillo@131 2648 and
meillo@131 2649 .Pn refile
meillo@131 2650 was inverted.
meillo@131 2651 In mmh,
meillo@131 2652 .Pn rmm
meillo@131 2653 invokes
meillo@217 2654 .Pn refile .
meillo@217 2655 That used to be the other way round.
meillo@131 2656 Yet, the relationship is simpler now.
meillo@164 2657 Loops, like described in nmh's man page for
meillo@131 2658 .Mp refile (1),
meillo@164 2659 can no longer occur:
meillo@131 2660 .QS
meillo@131 2661 Since
meillo@131 2662 .Pn refile
meillo@131 2663 uses your
meillo@131 2664 .Pe rmmproc
meillo@131 2665 to delete the message, the
meillo@131 2666 .Pe rmmproc
meillo@131 2667 must NOT call
meillo@131 2668 .Pn refile
meillo@131 2669 without specifying
meillo@131 2670 .Sw -normmproc
meillo@131 2671 or you will create an infinite loop.
meillo@131 2672 .QE
meillo@131 2673 .LP
meillo@131 2674 .Pn rmm
meillo@131 2675 either unlinks a message with
meillo@131 2676 .Fu unlink()
meillo@131 2677 or invokes
meillo@131 2678 .Pn refile
meillo@131 2679 to move it to the trash folder.
meillo@131 2680 .Pn refile
meillo@131 2681 does not invoke any tools.
meillo@131 2682 .P
meillo@136 2683 By generalizing the message removal in the way that it became covered
meillo@136 2684 by the MH concepts made the whole system more powerful.
meillo@131 2685
meillo@131 2686
meillo@131 2687
meillo@131 2688
meillo@131 2689
meillo@133 2690 .H2 "Modern Defaults
meillo@133 2691 .P
meillo@133 2692 Nmh has a bunch of convenience-improving features inactive by default,
meillo@217 2693 although one can expect every new user to want them active.
meillo@133 2694 The reason they are inactive by default is the wish to stay compatible
meillo@133 2695 with old versions.
meillo@217 2696 But what are old versions?
meillo@136 2697 Still, the highly useful draft folder facility has not been activated
meillo@136 2698 by default although it was introduced over twenty-five years ago.
meillo@133 2699 .[
meillo@133 2700 rose romine real work
meillo@133 2701 .]
meillo@136 2702 The community seems not to care.
meillo@217 2703 .P
meillo@217 2704 In nmh, new users are required to first build up
meillo@217 2705 a profile before they can access the modern features.
meillo@136 2706 Without an extensive profile, the setup is hardly usable
meillo@133 2707 for modern emailing.
meillo@133 2708 The point is not the customization of the setup,
meillo@136 2709 but the need to activate generally useful facilities.
meillo@217 2710 Yet, the real problem lies less in enabling the features,
meillo@217 2711 as this is straight forward as soon as one knows what he wants.
meillo@168 2712 The real problem is that new users need deep insight into the project
meillo@217 2713 to discover the available but inactive features.
meillo@133 2714 To give an example, I needed one year of using nmh
meillo@133 2715 before I became aware of the existence of the attachment system.
meillo@133 2716 One could argue that this fact disqualifies my reading of the
meillo@133 2717 documentation.
meillo@133 2718 If I would have installed nmh from source back then, I could agree.
meillo@217 2719 Yet, I had used a pre-packaged version and had expected that it would
meillo@133 2720 just work.
meillo@133 2721 Nevertheless, I had been convinced by the concepts of MH already
meillo@133 2722 and I am a software developer,
meillo@133 2723 still I required a lot of time to discover the cool features.
meillo@133 2724 How can we expect users to be even more advanced than me,
meillo@217 2725 just to enable them to use MH in a convenient and modern way?
meillo@133 2726 Unless they are strongly convinced of the concepts, they will fail.
meillo@133 2727 I have seen friends of me giving up disappointed
meillo@133 2728 before they truly used the system,
meillo@133 2729 although they had been motivated in the beginning.
meillo@217 2730 New users suffer hard enough to get used to the tool chest approach,
meillo@179 2731 we developers should spare them further inconveniences.
meillo@133 2732 .P
meillo@136 2733 Maintaining compatibility for its own sake is bad,
meillo@217 2734 because the code base will collect more and more compatibility code.
meillo@200 2735 Sticking to the compatibility code means remaining limited;
meillo@168 2736 whereas adjusting to the changes renders the compatibility unnecessary.
meillo@217 2737 Keeping unused alternatives in the code for longer than a short
meillo@217 2738 grace time is a bad choice as they likely
meillo@217 2739 gather bugs by not being constantly tested.
meillo@136 2740 Also, the increased code size and the greater number of conditions
meillo@136 2741 increase the maintenance costs.
meillo@133 2742 If any MH implementation would be the back-end of widespread
meillo@133 2743 email clients with large user bases, compatibility would be more
meillo@133 2744 important.
meillo@133 2745 Yet, it appears as if this is not the case.
meillo@133 2746 Hence, compatibility is hardly important for technical reasons.
meillo@217 2747 Its importance originates from personal reasons rather.
meillo@133 2748 Nmh's user base is small and old.
meillo@217 2749 Changing the interfaces causes inconvenience to long-term users of MH.
meillo@217 2750 It forces them to change their many years old MH configurations.
meillo@168 2751 I do understand this aspect, but by sticking to the old users,
meillo@217 2752 new users are kept from entering the world of MH.
meillo@217 2753 But the future lies in new users.
meillo@168 2754 In consequence, mmh invites new users by providing a convenient
meillo@168 2755 and modern setup, readily usable out-of-the-box.
meillo@133 2756 .P
meillo@136 2757 In mmh, all modern features are active by default and many previous
meillo@217 2758 approaches are removed or only accessible in a manual way.
meillo@136 2759 New default features include:
meillo@133 2760 .BU
meillo@133 2761 The attachment system (\c
meillo@217 2762 .Hd Attach )
meillo@217 2763 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1 .
meillo@133 2764 .BU
meillo@133 2765 The draft folder facility (\c
meillo@217 2766 .Fn +drafts )
meillo@217 2767 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860 .
meillo@133 2768 .BU
meillo@133 2769 The unseen sequence (`u')
meillo@133 2770 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@217 2771 and the sequence negation prefix (`!')
meillo@217 2772 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc .
meillo@133 2773 .BU
meillo@217 2774 Quoting the original message in the reply
meillo@217 2775 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6 .
meillo@133 2776 .BU
meillo@217 2777 Forwarding messages using MIME
meillo@217 2778 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1 .
meillo@171 2779 .LP
meillo@217 2780 An mmh setup with a profile that defines only the path to the
meillo@136 2781 mail storage, is already convenient to use.
meillo@217 2782 Again, Paul Vixie's supports the direction I took:
meillo@136 2783 ``the `main branch' should just be modern''.
meillo@136 2784 .[
meillo@136 2785 paul vixie edginess nmh-workers
meillo@136 2786 .]
meillo@131 2787
meillo@133 2788
meillo@133 2789
meillo@133 2790
meillo@133 2791
meillo@133 2792 .\" --------------------------------------------------------------
meillo@131 2793 .H1 "Styling
meillo@22 2794 .P
meillo@118 2795 Kernighan and Pike have emphasized the importance of style in the
meillo@219 2796 preface of \fPThe Practice of Programming\fP:
meillo@118 2797 .[ [
meillo@118 2798 kernighan pike practice of programming
meillo@118 2799 .], p. x]
meillo@118 2800 .QS
meillo@118 2801 Chapter 1 discusses programming style.
meillo@219 2802 Good style is so important to good programming that we have chosen
meillo@118 2803 to cover it first.
meillo@118 2804 .QE
meillo@168 2805 This section covers changes in mmh that were guided by the desire
meillo@118 2806 to improve on style.
meillo@219 2807 Many of them follow the advice given in the quoted book.
meillo@118 2808
meillo@118 2809
meillo@127 2810
meillo@127 2811
meillo@127 2812 .H2 "Code Style
meillo@154 2813 .Id code-style
meillo@118 2814 .P
meillo@118 2815 .U3 "Indentation Style
meillo@118 2816 .P
meillo@219 2817 Indentation styles are the holy cow of programming.
meillo@219 2818 Kernighan and Pike write:
meillo@118 2819 .[ [
meillo@118 2820 kernighan pike practice of programming
meillo@118 2821 .], p. 10]
meillo@118 2822 .QS
meillo@118 2823 Programmers have always argued about the layout of programs,
meillo@118 2824 but the specific style is much less important than its consistent
meillo@118 2825 application.
meillo@121 2826 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118 2827 time arguing.
meillo@118 2828 .QE
meillo@118 2829 .P
meillo@118 2830 I agree that the constant application is most important,
meillo@118 2831 but I believe that some styles have advantages over others.
meillo@118 2832 For instance the indentation with tab characters only.
meillo@219 2833 The number of tabs corresponds to the nesting level \(en
meillo@118 2834 one tab, one level.
meillo@219 2835 Tab characters provide flexible visual appearance because developers
meillo@228 2836 can adjust their width as preferred.
meillo@219 2837 There is no more need to check for the correct mixture of
meillo@219 2838 tabs and spaces.
meillo@219 2839 Two simple rules ensure the integrity and flexibility of the visual
meillo@219 2840 appearance:
meillo@219 2841 .LI 1
meillo@219 2842 Leading whitespace must consist of tabs only.
meillo@219 2843 .LI 2
meillo@219 2844 All other whitespace should be spaces.
meillo@219 2845 .LP
meillo@121 2846 Although reformatting existing code should be avoided, I did it.
meillo@200 2847 I did not waste time arguing; I just reformatted the code.
meillo@118 2848 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118 2849
meillo@118 2850 .U3 "Comments
meillo@118 2851 .P
meillo@219 2852 Kernighan and Pike demand: ``Don't belabor the obvious''.
meillo@118 2853 .[ [
meillo@118 2854 kernighan pike practice of programming
meillo@118 2855 .], p. 23]
meillo@219 2856 Following the advice, I removed unnecessary comments.
meillo@219 2857 For instance, I removed all comments in the following code excerpt
meillo@219 2858 .Ci 426543622b377fc5d091455cba685e114b6df674 :
meillo@118 2859 .VS
meillo@120 2860 context_replace(curfolder, folder); /* update current folder */
meillo@120 2861 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120 2862 seq_save(mp); /* synchronize message sequences */
meillo@120 2863 folder_free(mp); /* free folder/message structure */
meillo@120 2864 context_save(); /* save the context file */
meillo@120 2865
meillo@120 2866 [...]
meillo@120 2867
meillo@120 2868 int c; /* current character */
meillo@120 2869 char *cp; /* miscellaneous character pointer */
meillo@120 2870
meillo@120 2871 [...]
meillo@120 2872
meillo@120 2873 /* NUL-terminate the field */
meillo@120 2874 *cp = '\0';
meillo@118 2875 VE
meillo@118 2876 .P
meillo@219 2877 The information in each of the comments was present in the code
meillo@219 2878 statements already, except for the NUL-termination, which became
meillo@219 2879 obvious from the context.
meillo@136 2880
meillo@118 2881
meillo@118 2882 .U3 "Names
meillo@118 2883 .P
meillo@219 2884 Regarding this topic, Kernighan and Pike suggest:
meillo@118 2885 ``Use active names for functions''.
meillo@118 2886 .[ [
meillo@118 2887 kernighan pike practice of programming
meillo@118 2888 .], p. 4]
meillo@118 2889 One application of this rule was the rename of
meillo@118 2890 .Fu check_charset()
meillo@118 2891 to
meillo@219 2892 .Fu is_native_charset()
meillo@219 2893 .Ci 8d77b48284c58c135a6b2787e721597346ab056d .
meillo@219 2894 The same change additionally fixed a violation of ``Be accurate'',
meillo@181 2895 .[ [
meillo@181 2896 kernighan pike practice of programming
meillo@181 2897 .], p. 4]
meillo@219 2898 as the code did not match the expectation the function suggested.
meillo@219 2899 It did not compare charset names but prefixes of them only.
meillo@219 2900 In case the native charset was `ISO-8859-1', then
meillo@219 2901 .VS
meillo@219 2902 check_charset("ISO-8859-11", strlen("ISO-8859-11"))
meillo@219 2903 VE
meillo@219 2904 had returned true although the upper halves of the code pages
meillo@219 2905 are different.
meillo@118 2906 .P
meillo@118 2907 More important than using active names is using descriptive names.
meillo@145 2908 .VS
meillo@145 2909 m_unknown(in); /* the MAGIC invocation... */
meillo@145 2910 VE
meillo@145 2911 Renaming the obscure
meillo@118 2912 .Fu m_unknown()
meillo@219 2913 function was a delightful event, although it made the code less funny
meillo@219 2914 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846 .
meillo@118 2915 .P
meillo@118 2916 Magic numbers are generally considered bad style.
meillo@118 2917 Obviously, Kernighan and Pike agree:
meillo@118 2918 ``Give names to magic numbers''.
meillo@118 2919 .[ [
meillo@118 2920 kernighan pike practice of programming
meillo@118 2921 .], p. 19]
meillo@219 2922 .P
meillo@219 2923 The argument
meillo@219 2924 .CW outnum
meillo@219 2925 of the function
meillo@219 2926 .Fu scan()
meillo@219 2927 in
meillo@219 2928 .Fn uip/scansbr.c
meillo@219 2929 holds the number of the message to be created.
meillo@219 2930 As well it encodes program logic with negative numbers and zero.
meillo@219 2931 This led to obscure code.
meillo@219 2932 I clarified the code by introducing two variables that extracted
meillo@219 2933 the hidden information:
meillo@219 2934 .VS
meillo@219 2935 int incing = (outnum > 0);
meillo@219 2936 int ismbox = (outnum != 0);
meillo@219 2937 VE
meillo@219 2938 The readable names are thus used in conditions;
meillo@219 2939 the variable
meillo@219 2940 .CW outnum
meillo@219 2941 is used only to extract ordinary message numbers
meillo@219 2942 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f .
meillo@219 2943 .P
meillo@219 2944 Through the clarity improvement of the change detours in the program
meillo@219 2945 logic of related code parts became apparent.
meillo@219 2946 The implementation was simplified.
meillo@219 2947 This possibility to improve had been invisible before
meillo@219 2948 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723 .
meillo@219 2949 .P
meillo@219 2950 The names just described were a first step, yet the situation
meillo@219 2951 was further improved by giving names to the magic values of
meillo@219 2952 .CW outnum :
meillo@118 2953 .VS
meillo@118 2954 #define SCN_MBOX (-1)
meillo@118 2955 #define SCN_FOLD 0
meillo@118 2956 VE
meillo@219 2957 The two variables were updated thereafter as well:
meillo@219 2958 .VS
meillo@219 2959 int incing = (outnum != SCN_MBOX && outnum != SCN_FOLD);
meillo@219 2960 int scanfolder = (outnum == SCN_FOLD);
meillo@219 2961 VE
meillo@219 2962 Furthermore,
meillo@219 2963 .CW ismbox
meillo@219 2964 was replaced by
meillo@219 2965 .CW scanfolder
meillo@219 2966 because that matched better to the program logic.
meillo@118 2967 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@219 2968
meillo@118 2969
meillo@133 2970
meillo@133 2971
meillo@133 2972 .H2 "Structural Rework
meillo@133 2973 .P
meillo@219 2974 Although the stylistic changes described already improve the
meillo@219 2975 readability of the source code, all of them were changes ``in the small''.
meillo@219 2976 Structural changes, in contrast, affect much larger code areas.
meillo@219 2977 They are more difficult to accomplish but lead to larger improvements,
meillo@219 2978 especially as they often influence the outer shape of the tools as well.
meillo@118 2979 .P
meillo@118 2980 At the end of their chapter on style,
meillo@118 2981 Kernighan and Pike ask: ``But why worry about style?''
meillo@181 2982 .[ [
meillo@181 2983 kernighan pike practice of programming
meillo@219 2984 .], p. 28].
meillo@219 2985 Following are two examples of structural rework that demonstrate
meillo@136 2986 why style is important in the first place.
meillo@136 2987
meillo@136 2988
meillo@136 2989 .U3 "Rework of \f(CWanno\fP
meillo@118 2990 .P
meillo@120 2991 Until 2002,
meillo@120 2992 .Pn anno
meillo@219 2993 had six functional command line switches:
meillo@120 2994 .Sw -component
meillo@120 2995 and
meillo@120 2996 .Sw -text ,
meillo@219 2997 each with an argument,
meillo@120 2998 and the two pairs of flags,
meillo@120 2999 .Sw -[no]date
meillo@120 3000 and
meillo@120 3001 .Sw -[no]inplace .
meillo@120 3002 Then Jon Steinhart introduced his attachment system.
meillo@120 3003 In need for more advanced annotation handling, he extended
meillo@120 3004 .Pn anno .
meillo@120 3005 He added five more switches:
meillo@120 3006 .Sw -draft ,
meillo@120 3007 .Sw -list ,
meillo@120 3008 .Sw -delete ,
meillo@120 3009 .Sw -append ,
meillo@120 3010 and
meillo@120 3011 .Sw -number ,
meillo@219 3012 the last one taking an argument
meillo@219 3013 .Ci 7480dbc14bc90f2d872d434205c0784704213252 .
meillo@120 3014 Later,
meillo@120 3015 .Sw -[no]preserve
meillo@219 3016 was added as well
meillo@219 3017 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f .
meillo@120 3018 Then, the Synopsis section of the man page
meillo@120 3019 .Mp anno (1)
meillo@120 3020 read:
meillo@120 3021 .VS
meillo@219 3022 anno [+folder] [msgs] [-component f(CIfieldfP] [-inplace | -noinplace]
meillo@120 3023 [-date | -nodate] [-draft] [-append] [-list] [-delete]
meillo@219 3024 [-number [f(CInumfP|fPallfP]] [-preserve | -nopreserve] [-version]
meillo@219 3025 [-help] [-text f(CIbodyfP]
meillo@120 3026 VE
meillo@120 3027 .LP
meillo@120 3028 The implementation followed the same structure.
meillo@120 3029 Problems became visible when
meillo@120 3030 .Cl "anno -list -number 42
meillo@219 3031 worked on the current message instead of on message number 42,
meillo@120 3032 and
meillo@120 3033 .Cl "anno -list -number l:5
meillo@124 3034 did not work on the last five messages but failed with the mysterious
meillo@120 3035 error message: ``anno: missing argument to -list''.
meillo@121 3036 Yet, the invocation matched the specification in the man page.
meillo@120 3037 There, the correct use of
meillo@120 3038 .Sw -number
meillo@120 3039 was defined as being
meillo@120 3040 .Cl "[-number [num|all]]
meillo@120 3041 and the textual description for the combination with
meillo@120 3042 .Sw -list
meillo@120 3043 read:
meillo@120 3044 .QS
meillo@164 3045 The
meillo@164 3046 .Sw -list
meillo@164 3047 option produces a listing of the field bodies for
meillo@120 3048 header fields with names matching the specified component,
meillo@164 3049 one per line. The listing is numbered, starting at 1, if the
meillo@164 3050 .Sw -number
meillo@164 3051 option is also used.
meillo@120 3052 .QE
meillo@120 3053 .LP
meillo@120 3054 The problem was manifold.
meillo@120 3055 Semantically, the argument to the
meillo@120 3056 .Sw -number
meillo@120 3057 switch is only necessary in combination with
meillo@120 3058 .Sw -delete ,
meillo@120 3059 but not with
meillo@120 3060 .Sw -list .
meillo@219 3061 The code, however, required a numeric argument in any case.
meillo@219 3062 If the argument was missing or non-numeric,
meillo@219 3063 .Pn anno
meillo@219 3064 aborted with an error message that additionally had an off-by-one error.
meillo@219 3065 It printed the name of the switch one before the concerned one.
meillo@120 3066 .P
meillo@219 3067 Trying to fix these problems on the surface would not have solved them.
meillo@219 3068 They originate from a discrepance between the
meillo@120 3069 structure of the problem and the structure implemented in the program.
meillo@219 3070 Such structural differences can only be solved by adjusting the
meillo@219 3071 structure of the implementation to the structure of the problem.
meillo@120 3072 .P
meillo@219 3073 Steinhart had added the new
meillo@120 3074 .Sw -list
meillo@120 3075 and
meillo@120 3076 .Sw -delete
meillo@219 3077 switches in a style similar to the other switches though
meillo@219 3078 they are of structural different type.
meillo@120 3079 Semantically,
meillo@120 3080 .Sw -list
meillo@120 3081 and
meillo@120 3082 .Sw -delete
meillo@219 3083 introduce operation modes.
meillo@120 3084 Historically,
meillo@120 3085 .Pn anno
meillo@120 3086 had only one operation mode: adding header fields.
meillo@219 3087 With the extension, two more modes were added:
meillo@120 3088 listing and deleting header fields.
meillo@120 3089 The structure of the code changes did not pay respect to this
meillo@219 3090 fundamental change.
meillo@120 3091 Neither the implementation nor the documentation did clearly
meillo@219 3092 declare the exclusive operation modes as such.
meillo@120 3093 Having identified the problem, I solved it by putting structure into
meillo@120 3094 .Pn anno
meillo@219 3095 and its documentation
meillo@219 3096 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11 .
meillo@120 3097 .P
meillo@173 3098 The difference is visible in both the code and the documentation.
meillo@219 3099 For instance in the following code excerpt:
meillo@120 3100 .VS
meillo@120 3101 int delete = -2; /* delete header element if set */
meillo@120 3102 int list = 0; /* list header elements if set */
meillo@120 3103 [...]
meillo@121 3104 case DELETESW: /* delete annotations */
meillo@121 3105 delete = 0;
meillo@121 3106 continue;
meillo@121 3107 case LISTSW: /* produce a listing */
meillo@121 3108 list = 1;
meillo@121 3109 continue;
meillo@120 3110 VE
meillo@121 3111 .LP
meillo@219 3112 which was replaced by:
meillo@120 3113 .VS
meillo@120 3114 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120 3115 [...]
meillo@121 3116 case DELETESW: /* delete annotations */
meillo@121 3117 mode = MODE_DEL;
meillo@121 3118 continue;
meillo@121 3119 case LISTSW: /* produce a listing */
meillo@121 3120 mode = MODE_LIST;
meillo@121 3121 continue;
meillo@120 3122 VE
meillo@120 3123 .LP
meillo@121 3124 The replacement code does not only reflect the problem's structure better,
meillo@121 3125 it is easier to understand as well.
meillo@121 3126 The same applies to the documentation.
meillo@120 3127 The man page was completely reorganized to propagate the same structure.
meillo@219 3128 This is already visible in the Synopsis section:
meillo@120 3129 .VS
meillo@219 3130 anno [+folder] [msgs] [-component f(CIfieldfP] [-text fPbodyfP]
meillo@120 3131 [-append] [-date | -nodate] [-preserve | -nopreserve]
meillo@120 3132 [-Version] [-help]
meillo@120 3133
meillo@219 3134 anno -delete [+folder] [msgs] [-component fPfieldfP] [-text
meillo@219 3135 fPbodyfP] [-number fPnum fP| fPall fP] [-preserve | -nopreserve]
meillo@120 3136 [-Version] [-help]
meillo@120 3137
meillo@219 3138 anno -list [+folder] [msgs] [-component fPfieldfP] [-number]
meillo@120 3139 [-Version] [-help]
meillo@120 3140 VE
meillo@118 3141
meillo@58 3142
meillo@58 3143
meillo@133 3144 .U3 "Path Conversion
meillo@133 3145 .P
meillo@134 3146 Four kinds of path names can appear in MH:
meillo@171 3147 .LI 1
meillo@134 3148 Absolute Unix directory paths, like
meillo@134 3149 .Fn /etc/passwd .
meillo@171 3150 .LI 2
meillo@134 3151 Relative Unix directory paths, like
meillo@134 3152 .Fn ./foo/bar .
meillo@171 3153 .LI 3
meillo@134 3154 Absolute MH folder paths, like
meillo@219 3155 .Fn +projects/mmh .
meillo@171 3156 .LI 4
meillo@134 3157 Relative MH folder paths, like
meillo@134 3158 .Fn @subfolder .
meillo@171 3159 .LP
meillo@219 3160 Relative MH folder paths, are hardly documented
meillo@219 3161 although they are useful for large mail storages.
meillo@134 3162 The current mail folder is specified as `\c
meillo@134 3163 .Fn @ ',
meillo@134 3164 just like the current directory is specified as `\c
meillo@134 3165 .Fn . '.
meillo@134 3166 .P
meillo@134 3167 To allow MH tools to understand all four notations,
meillo@219 3168 they need to be able to convert between them.
meillo@134 3169 In nmh, these path name conversion functions were located in the files
meillo@134 3170 .Fn sbr/path.c
meillo@134 3171 (``return a pathname'') and
meillo@134 3172 .Fn sbr/m_maildir.c
meillo@134 3173 (``get the path for the mail directory'').
meillo@134 3174 The seven functions in the two files were documented with no more
meillo@134 3175 than two comments, which described obvious information.
meillo@219 3176 The signatures of the four exported functions did not explain their
meillo@219 3177 semantics:
meillo@219 3178 .LI 1
meillo@219 3179 .CW "char *path(char *, int);
meillo@219 3180 .LI 2
meillo@219 3181 .CW "char *pluspath(char *);
meillo@219 3182 .LI 3
meillo@219 3183 .CW "char *m_mailpath(char *);
meillo@219 3184 .LI 4
meillo@219 3185 .CW "char *m_maildir(char *);
meillo@134 3186 .P
meillo@219 3187 My investigations provided the following descriptions:
meillo@171 3188 .LI 1
meillo@134 3189 The second parameter of
meillo@134 3190 .Fu path()
meillo@219 3191 defines the type as which the path given in the first parameter should
meillo@219 3192 be treated.
meillo@134 3193 Directory paths are converted to absolute directory paths.
meillo@134 3194 Folder paths are converted to absolute folder paths.
meillo@173 3195 Folder paths must not include a leading `\fL@\fP' character.
meillo@134 3196 Leading plus characters are preserved.
meillo@134 3197 The result is a pointer to newly allocated memory.
meillo@171 3198 .LI 2
meillo@134 3199 .Fu pluspath()
meillo@134 3200 is a convenience-wrapper to
meillo@134 3201 .Fu path() ,
meillo@134 3202 to convert folder paths only.
meillo@134 3203 This function can not be used for directory paths.
meillo@134 3204 An empty string parameter causes a buffer overflow.
meillo@171 3205 .LI 3
meillo@134 3206 .Fu m_mailpath()
meillo@134 3207 converts directory paths to absolute directory paths.
meillo@173 3208 The characters `\fL+\fP' or `\fL@\fP' at the beginning of the path name are
meillo@134 3209 treated literal, i.e. as the first character of a relative directory path.
meillo@134 3210 Hence, this function can not be used for folder paths.
meillo@219 3211 In any case, the result is an absolute directory path,
meillo@219 3212 returned as a pointer to newly allocated memory.
meillo@171 3213 .LI 4
meillo@134 3214 .Fu m_maildir()
meillo@134 3215 returns the parameter unchanged if it is an absolute directory path
meillo@173 3216 or begins with the entry `\fL.\fP' or `\fL..\fP'.
meillo@134 3217 All other strings are prepended with the current working directory.
meillo@219 3218 Hence, this function can not be used for folder paths.
meillo@134 3219 The result is either an absolute directory path or a relative
meillo@219 3220 directory path, starting with dot or dot-dot.
meillo@134 3221 In contrast to the other functions, the result is a pointer to
meillo@134 3222 static memory.
meillo@134 3223 .P
meillo@134 3224 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@219 3225 Additionally, no clear terminology was used to name the different
meillo@219 3226 kinds of path names.
meillo@219 3227 Sometimes, the names were even misleading, much as the first argument of
meillo@134 3228 .Fu m_mailpath() ,
meillo@219 3229 which was named
meillo@219 3230 .CW folder ,
meillo@219 3231 although
meillo@134 3232 .Fu m_mailpath()
meillo@219 3233 could not be used with MH folder arguments.
meillo@134 3234 .P
meillo@219 3235 I clarified the path name conversion by complete rework.
meillo@134 3236 First of all, the terminology needed to be defined.
meillo@134 3237 A path name is either in the Unix domain, then it is called
meillo@227 3238 \fIdirectory path\fP or it is in the MH domain,
meillo@227 3239 then it is called \fIfolder path\fP.
meillo@134 3240 The two terms need to be used with strict distinction.
meillo@134 3241 Second, I exploited the concept of path type indicators.
meillo@219 3242 By requiring every path name to start with a distinct type identifier,
meillo@219 3243 the conversion between the types could be fully automated.
meillo@227 3244 This allows the tools to accept path names of any type from the user.
meillo@134 3245 Therefore, it was necessary to require relative directory paths to be
meillo@134 3246 prefixed with a dot character.
meillo@134 3247 In consequence, the dot character could no longer be an alias for the
meillo@227 3248 current message
meillo@227 3249 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01 .
meillo@134 3250 Third, I created three new functions to replace the previous mess:
meillo@171 3251 .LI 1
meillo@134 3252 .Fu expandfol()
meillo@219 3253 converts folder paths to absolute folder paths.
meillo@134 3254 Directory paths are simply passed through.
meillo@134 3255 This function is to be used for folder paths only, thus the name.
meillo@134 3256 The result is a pointer to static memory.
meillo@171 3257 .LI 2
meillo@134 3258 .Fu expanddir()
meillo@134 3259 converts directory paths to absolute directory paths.
meillo@134 3260 Folder paths are treated as relative directory paths.
meillo@134 3261 This function is to be used for directory paths only, thus the name.
meillo@134 3262 The result is a pointer to static memory.
meillo@171 3263 .LI 3
meillo@134 3264 .Fu toabsdir()
meillo@134 3265 converts any type of path to an absolute directory path.
meillo@134 3266 This is the function of choice for path conversion.
meillo@134 3267 Absolute directory paths are the most general representation of a
meillo@134 3268 path name.
meillo@134 3269 The result is a pointer to static memory.
meillo@134 3270 .P
meillo@134 3271 The new functions have names that indicate their use.
meillo@134 3272 Two of the functions convert relative to absolute path names of the
meillo@134 3273 same type.
meillo@134 3274 The third function converts any path name type to the most general one,
meillo@134 3275 the absolute directory path.
meillo@134 3276 All of the functions return pointers to static memory.
meillo@219 3277 The file
meillo@219 3278 .Fn sbr/path.c
meillo@219 3279 contains the implementation of the functions;
meillo@134 3280 .Fn sbr/m_maildir.c
meillo@219 3281 was removed.
meillo@168 3282 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3283 .P
meillo@134 3284 Along with the path conversion rework, I also replaced
meillo@134 3285 .Fu getfolder(FDEF)
meillo@134 3286 with
meillo@134 3287 .Fu getdeffol()
meillo@134 3288 and
meillo@134 3289 .Fu getfolder(FCUR)
meillo@134 3290 with
meillo@134 3291 .Fu getcurfol() ,
meillo@219 3292 which only wraps
meillo@219 3293 .Fu expandfol(""@"")
meillo@219 3294 for convenience.
meillo@134 3295 This code was moved from
meillo@134 3296 .Fn sbr/getfolder.c
meillo@219 3297 into
meillo@219 3298 .Fn sbr/path.c
meillo@219 3299 as well.
meillo@168 3300 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134 3301 .P
meillo@134 3302 The related function
meillo@134 3303 .Fu etcpath()
meillo@219 3304 is now included in
meillo@134 3305 .Fn sbr/path.c ,
meillo@168 3306 too
meillo@168 3307 .Ci b4c29794c12099556151d93a860ee51badae2e35 .
meillo@134 3308 Previously, it had been located in
meillo@219 3309 .Fn config/config.c .
meillo@134 3310 .P
meillo@219 3311 Now,
meillo@134 3312 .Fn sbr/path.c
meillo@219 3313 contains all path handling code.
meillo@219 3314 Besides being less code, its readability is highly improved.
meillo@219 3315 The functions follow a common style and are well documented.
meillo@133 3316
meillo@133 3317
meillo@133 3318
meillo@133 3319
meillo@133 3320 .H2 "Profile Reading
meillo@133 3321 .P
meillo@220 3322 The MH profile contains the configuration of a user-specific MH setup.
meillo@220 3323 MH tools read the profile right after starting up
meillo@220 3324 because it contains the location of the user's mail storage
meillo@138 3325 and similar settings that influence the whole setup.
meillo@220 3326 Furthermore, the profile contains the default switches for the tools
meillo@220 3327 as well.
meillo@220 3328 The context file is read along with the profile.
meillo@138 3329 .P
meillo@138 3330 For historic reasons, some MH tools did not read the profile and context.
meillo@138 3331 Among them were
meillo@138 3332 .Pn post /\c
meillo@138 3333 .Pn spost ,
meillo@138 3334 .Pn mhmail ,
meillo@138 3335 and
meillo@138 3336 .Pn slocal .
meillo@138 3337 The reason why these tools ignored the profile were not clearly stated.
meillo@220 3338 During a discussion on the nmh-workers mailing list,
meillo@181 3339 David Levine posted an explanation, quoting John Romine:
meillo@138 3340 .[
meillo@138 3341 nmh-workers levine post profile
meillo@138 3342 .]
meillo@220 3343
meillo@138 3344 .QS
meillo@138 3345 I asked John Romine and here's what he had to say, which
meillo@138 3346 agrees and provides an example that convinces me:
meillo@138 3347 .QS
meillo@164 3348 My take on this is that
meillo@164 3349 .Pn post
meillo@164 3350 should not be called by users directly, and it doesn't read the
meillo@164 3351 .Fn .mh_profile
meillo@138 3352 (only front-end UI programs read the profile).
meillo@138 3353 .QP
meillo@164 3354 For example, there can be contexts where
meillo@164 3355 .Pn post
meillo@164 3356 is called by a helper program (like `\c
meillo@164 3357 .Pn mhmail ')
meillo@164 3358 which may be run by a non-MH user.
meillo@164 3359 We don't want this to prompt the user to create an MH profile, etc.
meillo@138 3360 .QP
meillo@164 3361 My suggestion would be to have
meillo@164 3362 .Pn send
meillo@164 3363 pass a (hidden) `\c
meillo@164 3364 .Sw -fileproc
meillo@164 3365 .Ar proc '
meillo@164 3366 option to
meillo@164 3367 .Pn post
meillo@164 3368 if needed.
meillo@164 3369 You could also
meillo@164 3370 use an environment variable (I think
meillo@164 3371 .Pn send /\c
meillo@164 3372 .Pn whatnow
meillo@164 3373 do this).
meillo@138 3374 .QE
meillo@220 3375 .sp \n(PDu
meillo@164 3376 I think that's the way to go.
meillo@164 3377 My personal preference is to use a command line option,
meillo@164 3378 not an environment variable.
meillo@138 3379 .QE
meillo@220 3380
meillo@138 3381 .P
meillo@220 3382 To solve the problem that
meillo@138 3383 .Pn post
meillo@220 3384 does not honor the
meillo@138 3385 .Pe fileproc
meillo@138 3386 profile entry,
meillo@138 3387 the community roughly agreed that a switch
meillo@138 3388 .Sw -fileproc
meillo@138 3389 should be added to
meillo@138 3390 .Pn post
meillo@138 3391 to be able to pass a different fileproc.
meillo@138 3392 I strongly disagree with this approach because it does not solve
meillo@138 3393 the problem; it only removes a single symptom.
meillo@220 3394 The actual problem is that
meillo@138 3395 .Pn post
meillo@220 3396 does not behave as expected,
meillo@220 3397 though all programs should behave as expected.
meillo@220 3398 Clear and general concepts are a precondition for this.
meillo@220 3399 Thus, there should be no separation into ``front-end UI programs''
meillo@220 3400 and ones that ``should not be called by users directly''.
meillo@220 3401 The real solution is having all MH tools read the profile.
meillo@138 3402 .P
meillo@220 3403 But the problem has a further aspect,
meillo@220 3404 which originates from
meillo@220 3405 .Pn mhmail
meillo@220 3406 mainly.
meillo@138 3407 .Pn mhmail
meillo@138 3408 was intended to be a replacement for
meillo@138 3409 .Pn mailx
meillo@138 3410 on systems with MH installations.
meillo@220 3411 In difference to
meillo@220 3412 .Pn mailx ,
meillo@138 3413 .Pn mhmail
meillo@220 3414 used MH's
meillo@138 3415 .Pn post
meillo@220 3416 to send the message.
meillo@220 3417 The idea was that using
meillo@138 3418 .Pn mhmail
meillo@220 3419 should not be influenced whether the user had
meillo@138 3420 MH set up for himself or not.
meillo@220 3421 Therefore
meillo@138 3422 .Pn mhmail
meillo@220 3423 had not read the profile.
meillo@138 3424 As
meillo@138 3425 .Pn mhmail
meillo@138 3426 used
meillo@138 3427 .Pn post ,
meillo@138 3428 .Pn post
meillo@220 3429 was not allowed to read the profile neither.
meillo@138 3430 This is the reason for the actual problem.
meillo@220 3431 Yet, this was not considered much of a problem because
meillo@138 3432 .Pn post
meillo@138 3433 was not intended to be used by users directly.
meillo@220 3434 To invoke
meillo@220 3435 .Pn post ,
meillo@138 3436 .Pn send
meillo@220 3437 was used an a front-end.
meillo@138 3438 .Pn send
meillo@138 3439 read the profile and passed all relevant values on the command line to
meillo@138 3440 .Pn post
meillo@138 3441 \(en an awkward solution.
meillo@138 3442 .P
meillo@138 3443 The important insight is that
meillo@138 3444 .Pn mhmail
meillo@220 3445 is a wolf in sheep's clothing.
meillo@220 3446 This alien tool broke the concepts because it was treated like
meillo@220 3447 a normal MH tool.
meillo@138 3448 Instead it should have been treated accordingly to its foreign style.
meillo@220 3449 .P
meillo@220 3450 The solution is not to prevent the tools from reading the profile but
meillo@220 3451 to instruct them to read a different profile.
meillo@138 3452 .Pn mhmail
meillo@220 3453 could have set up a well-defined profile and caused the following
meillo@138 3454 .Pn post
meillo@220 3455 to use this profile by exporting an environment variable.
meillo@220 3456 With this approach, no special cases would have been introduced
meillo@220 3457 and no surprises would have been caused.
meillo@220 3458 By writing a wrapper program to provide a clean temporary profile,
meillo@220 3459 the concept could have been generalized orthogonally to the whole
meillo@220 3460 MH tool chest.
meillo@220 3461 .P
meillo@220 3462 In mmh, the wish to have
meillo@220 3463 .Pn mhmail
meillo@220 3464 as a replacement for
meillo@220 3465 .Pn mailx
meillo@220 3466 is considered obsolete.
meillo@220 3467 Mmh's
meillo@220 3468 .Pn mhmail
meillo@220 3469 does no longer cover this use-case
meillo@220 3470 .Ci d36e56e695fe1c482c7920644bfbb6386ac9edb0 .
meillo@220 3471 Currently,
meillo@220 3472 .Pn mhmail
meillo@220 3473 is in a transition state
meillo@220 3474 .Ci 32d4f9daaa70519be3072479232ff7be0500d009 .
meillo@220 3475 It may become a front-end to
meillo@220 3476 .Pn comp ,
meillo@220 3477 which provides an alternative interface which can be more convenient
meillo@220 3478 in some cases.
meillo@220 3479 This would convert
meillo@220 3480 .Pn mhmail
meillo@220 3481 into an ordinary MH tool.
meillo@220 3482 If, however, this idea does not convince, then
meillo@220 3483 .Pn mhmail
meillo@220 3484 will be removed.
meillo@220 3485 .P
meillo@220 3486 In the mmh tool chest, every program reads the profile.
meillo@220 3487 (\c
meillo@220 3488 .Pn slocal
meillo@220 3489 is not considered part of the mmh tool chest (cf. Sec.
meillo@220 3490 .Cf slocal ).)
meillo@220 3491 Mmh has no
meillo@220 3492 .Pn post
meillo@220 3493 program, but it has
meillo@220 3494 .Pn spost ,
meillo@220 3495 which now does read the profile
meillo@220 3496 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8 .
meillo@220 3497 Following this change,
meillo@220 3498 .Pn send
meillo@220 3499 and
meillo@220 3500 .Pn spost
meillo@220 3501 can be considered for merging.
meillo@220 3502 Besides
meillo@220 3503 .Pn send ,
meillo@220 3504 .Pn spost
meillo@220 3505 is only invoked directly by the to-be-changed
meillo@220 3506 .Pn mhmail
meillo@220 3507 implementation and by
meillo@220 3508 .Pn rcvdist ,
meillo@220 3509 which requires rework anyway.
meillo@220 3510
meillo@220 3511 .P
meillo@220 3512 Jeffrey Honig quoted Marshall T. Rose explaining the decision that
meillo@220 3513 .Pn post
meillo@220 3514 ignores the profile:
meillo@138 3515 .[
meillo@197 3516 nmh-workers honig post profile
meillo@138 3517 .]
meillo@138 3518 .QS
meillo@138 3519 when you run mh commands in a script, you want all the defaults to be
meillo@138 3520 what the man page says.
meillo@138 3521 when you run a command by hand, then you want your own defaults...
meillo@138 3522 .QE
meillo@138 3523 .LP
meillo@228 3524 The explanation neither matches the problem concerned exactly
meillo@220 3525 nor is the interpretation clear.
meillo@220 3526 If the described desire addresses the technical level,
meillo@228 3527 then it conflicts fundamentally with the Unix philosophy,
meillo@220 3528 precisely because the indistinquishability of human and script
meillo@220 3529 input is the main reason for the huge software leverage in Unix.
meillo@220 3530 If, however, the described desire addresses the user's view,
meillo@220 3531 then different technical solutions are more appropriate.
meillo@220 3532 The two cases can be regarded simply as two different MH setups.
meillo@220 3533 Hence, mapping the problem of different behavior between interactive and
meillo@220 3534 automated use on the concept of switching between different profiles,
meillo@220 3535 marks it already solved.
meillo@133 3536
meillo@133 3537
meillo@127 3538
meillo@121 3539 .H2 "Standard Libraries
meillo@22 3540 .P
meillo@121 3541 MH is one decade older than the POSIX and ANSI C standards.
meillo@121 3542 Hence, MH included own implementations of functions
meillo@220 3543 that were neither standardized nor widely available, back then.
meillo@220 3544 Today, twenty years after POSIX and ANSI C were published,
meillo@220 3545 developers can expect that systems comply with these standards.
meillo@121 3546 In consequence, MH-specific replacements for standard functions
meillo@121 3547 can and should be dropped.
meillo@220 3548 Kernighan and Pike advise: ``Use standard libraries''.
meillo@121 3549 .[ [
meillo@121 3550 kernighan pike practice of programming
meillo@121 3551 .], p. 196]
meillo@121 3552 Actually, MH had followed this advice in history,
meillo@220 3553 but it had not adjusted to more recent changes in this field.
meillo@121 3554 The
meillo@121 3555 .Fu snprintf()
meillo@121 3556 function, for instance, was standardized with C99 and is available
meillo@121 3557 almost everywhere because of its high usefulness.
meillo@220 3558 Thus, the project's own implementation of
meillo@121 3559 .Fu snprintf()
meillo@123 3560 was dropped in March 2012 in favor for using the one of the
meillo@220 3561 standard library
meillo@220 3562 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@123 3563 Such decisions limit the portability of mmh
meillo@173 3564 if systems do not support these standardized and widespread functions.
meillo@123 3565 This compromise is made because mmh focuses on the future.
meillo@121 3566 .P
meillo@220 3567 As I am still in my twenties, have no programming experience from
meillo@220 3568 past decades.
meillo@220 3569 I have not followed the evolution of C through time.
meillo@220 3570 I have not suffered from the the Unix wars.
meillo@121 3571 I have not longed for standardization.
meillo@121 3572 All my programming experience is from a time when ANSI C and POSIX
meillo@121 3573 were well established already.
meillo@220 3574 Thus, I needed to learn about the history in retrospective.
meillo@121 3575 I have only read a lot of books about the (good) old times.
meillo@220 3576 This put me in a difficult position when working with old code.
meillo@123 3577 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123 3578 programming styles, whereas older programmers know these things by
meillo@123 3579 heart from their own experience.
meillo@123 3580 Being aware of the situation, I rather let people with more historic
meillo@220 3581 experience do the transition from ancient code constructs to
meillo@220 3582 standardized ones.
meillo@121 3583 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121 3584 He converted project-specific functions to POSIX replacements,
meillo@121 3585 also removing the conditionals compilation of now standardized features.
meillo@220 3586 Ken Hornstein and David Levine had their part in this work, as well.
meillo@220 3587 Often, I only pulled the changes over from nmh into mmh.
meillo@220 3588 These changes include many commits, among them:
meillo@121 3589 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121 3590 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102 3591 .P
meillo@220 3592 Nevertheless, I worked on the task as well, tidying up the
meillo@220 3593 \fIMH standard library\fP,
meillo@220 3594 .Fn libmh.a .
meillo@220 3595 It is located in the
meillo@123 3596 .Fn sbr
meillo@220 3597 (``subroutines'') directory in the source tree and
meillo@220 3598 includes functions that mmh tools usually need.
meillo@123 3599 Among them are MH-specific functions for profile, context, sequence,
meillo@123 3600 and folder handling, but as well
meillo@123 3601 MH-independent functions, such as auxiliary string functions,
meillo@123 3602 portability interfaces and error-checking wrappers for critical
meillo@123 3603 functions of the standard library.
meillo@220 3604 .BU
meillo@123 3605 I have replaced the
meillo@121 3606 .Fu atooi()
meillo@121 3607 function with calls to
meillo@220 3608 .Fu strtoul() ,
meillo@220 3609 setting the third parameter, the base, to eight.
meillo@123 3610 .Fu strtoul()
meillo@220 3611 is part of C89 and thus considered safe to use
meillo@220 3612 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74 .
meillo@220 3613 .BU
meillo@121 3614 I did remove project-included fallback implementations of
meillo@121 3615 .Fu memmove()
meillo@121 3616 and
meillo@220 3617 .Fu strerror()
meillo@220 3618 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215 ,
meillo@121 3619 although Peter Maydell had re-included them into nmh in 2008
meillo@121 3620 to support SunOS 4.
meillo@121 3621 Nevertheless, these functions are part of ANSI C.
meillo@121 3622 Systems that do not even provide full ANSI C support should not
meillo@121 3623 put a load on mmh.
meillo@220 3624 .BU
meillo@121 3625 The
meillo@121 3626 .Fu copy()
meillo@180 3627 function copies the string in parameter one to the location in
meillo@180 3628 parameter two.
meillo@121 3629 In contrast to
meillo@121 3630 .Fu strcpy() ,
meillo@121 3631 it returns a pointer to the terminating null-byte in the destination area.
meillo@123 3632 The code was adjusted to replace
meillo@121 3633 .Fu copy()
meillo@123 3634 with
meillo@121 3635 .Fu strcpy() ,
meillo@121 3636 except within
meillo@121 3637 .Fu concat() ,
meillo@121 3638 where
meillo@121 3639 .Fu copy()
meillo@123 3640 was more convenient.
meillo@123 3641 Therefore, the definition of
meillo@121 3642 .Fu copy()
meillo@123 3643 was moved into the source file of
meillo@121 3644 .Fu concat()
meillo@220 3645 and its visibility it limited to that
meillo@220 3646 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb .
meillo@220 3647 .BU
meillo@121 3648 The function
meillo@121 3649 .Fu r1bindex()
meillo@121 3650 had been a generalized version of
meillo@121 3651 .Fu basename()
meillo@121 3652 with minor differences.
meillo@121 3653 As all calls to
meillo@121 3654 .Fu r1bindex()
meillo@220 3655 had the slash (`\fL/\fP') as delimiter anyway,
meillo@121 3656 replacing
meillo@121 3657 .Fu r1bindex()
meillo@121 3658 with the more specific and better-named function
meillo@121 3659 .Fu basename()
meillo@121 3660 became desirable.
meillo@121 3661 Unfortunately, many of the 54 calls to
meillo@121 3662 .Fu r1bindex()
meillo@123 3663 depended on a special behavior,
meillo@121 3664 which differed from the POSIX specification for
meillo@121 3665 .Fu basename() .
meillo@121 3666 Hence,
meillo@121 3667 .Fu r1bindex()
meillo@121 3668 was kept but renamed to
meillo@123 3669 .Fu mhbasename() ,
meillo@220 3670 setting the delimiter to the slash
meillo@220 3671 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60 .
meillo@121 3672 For possible uses of
meillo@121 3673 .Fu r1bindex()
meillo@121 3674 with a different delimiter,
meillo@121 3675 the ANSI C function
meillo@121 3676 .Fu strrchr()
meillo@121 3677 provides the core functionality.
meillo@220 3678 .BU
meillo@121 3679 The
meillo@121 3680 .Fu ssequal()
meillo@121 3681 function \(en apparently for ``substring equal'' \(en
meillo@121 3682 was renamed to
meillo@121 3683 .Fu isprefix() ,
meillo@220 3684 because this is what it actually checked
meillo@220 3685 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711.
meillo@220 3686 Its source file had included both of the following comments, no joke.
meillo@220 3687 .in -\n(PIu
meillo@121 3688 .VS
meillo@121 3689 /*
meillo@121 3690 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121 3691 * It is actually checking if s1 is a PREFIX of s2.
meillo@121 3692 * All calls to this function need to be checked to see
meillo@121 3693 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121 3694 * should be kept if it's sufficient.
meillo@121 3695 */
meillo@121 3696
meillo@121 3697 /*
meillo@121 3698 * Check if s1 is a substring of s2.
meillo@121 3699 * If yes, then return 1, else return 0.
meillo@121 3700 */
meillo@121 3701 VE
meillo@220 3702 .in +\n(PIu
meillo@220 3703 Eventually, the function was completely replaced with calls to
meillo@220 3704 .Fu strncmp()
meillo@220 3705 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb .
meillo@121 3706
meillo@102 3707
meillo@102 3708
meillo@102 3709
meillo@133 3710
meillo@133 3711 .H2 "User Data Locations
meillo@133 3712 .P
meillo@133 3713 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133 3714 The profile is a file named
meillo@133 3715 .Fn \&.mh_profile
meillo@133 3716 in the user's home directory.
meillo@133 3717 It contains the static configuration.
meillo@133 3718 It also contains the location of the MH directory in the profile entry
meillo@133 3719 .Pe Path .
meillo@133 3720 The MH directory contains the mail storage and is the first
meillo@220 3721 place to search for form files, scan formats, and similar
meillo@133 3722 configuration files.
meillo@133 3723 The location of the MH directory can be chosen freely by the user.
meillo@220 3724 The usual name is a directory named
meillo@133 3725 .Fn Mail
meillo@220 3726 in the user's home directory.
meillo@133 3727 .P
meillo@200 3728 The way MH data is split between profile and MH directory is a legacy.
meillo@133 3729 It is only sensible in a situation where the profile is the only
meillo@133 3730 configuration file.
meillo@133 3731 Why else should the mail storage and the configuration files be intermixed?
meillo@220 3732 They are of different kind:
meillo@220 3733 One kind is the data to be operated on and the other kind is
meillo@220 3734 the configuration to change how tools operate.
meillo@133 3735 Splitting the configuration between the profile and the MH directory
meillo@220 3736 is inappropriate, as well.
meillo@220 3737 I improved the situation by breaking compatibility.
meillo@133 3738 .P
meillo@220 3739 In mmh, personal data is grouped by type.
meillo@220 3740 This results in two distinct parts:
meillo@171 3741 the mail storage and the configuration.
meillo@220 3742 The mail storage directory still contains all the messages,
meillo@133 3743 but, in exception of public sequences files, nothing else.
meillo@133 3744 In difference to nmh, the auxiliary configuration files are no longer
meillo@133 3745 located there.
meillo@133 3746 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@220 3747 but the user's \fImail storage\fP.
meillo@133 3748 Its location is still user-chosen, with the default name
meillo@220 3749 .Fn Mail
meillo@133 3750 in the user's home directory.
meillo@220 3751 The configuration is grouped together in the hidden directory
meillo@133 3752 .Fn \&.mmh
meillo@133 3753 in the user's home directory.
meillo@133 3754 This \fImmh directory\fP contains the context file, personal forms,
meillo@133 3755 scan formats, and the like, but also the user's profile, now named
meillo@133 3756 .Fn profile .
meillo@220 3757 The path to the profile is no longer
meillo@133 3758 .Fn $HOME/.mh_profile
meillo@220 3759 but
meillo@133 3760 .Fn $HOME/.mmh/profile .
meillo@220 3761 (The alternative of having file
meillo@133 3762 .Fn $HOME/.mh_profile
meillo@220 3763 and a configuration directory
meillo@133 3764 .Fn $HOME/.mmh
meillo@220 3765 appeared to be inconsistent.)
meillo@220 3766 .P
meillo@133 3767 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133 3768 Unix users.
meillo@220 3769 The main achievement of the change is the clear and sensible separation
meillo@220 3770 of the mail storage and the configuration.
meillo@168 3771 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3772 .P
meillo@220 3773 As MH allows users to have multiple MH setups,
meillo@220 3774 it is necessary to switch the profile.
meillo@133 3775 The profile is the single entry point to access the rest of a
meillo@133 3776 personal MH setup.
meillo@133 3777 In nmh, the environment variable
meillo@133 3778 .Ev MH
meillo@220 3779 is used to specify a different profile.
meillo@220 3780 To operate in the same MH setup with a separate context, the
meillo@133 3781 .Ev MHCONTEXT
meillo@220 3782 environment variable is used.
meillo@220 3783 This allows having a separate current folder in each terminal at
meillo@220 3784 the same time, for instance.
meillo@220 3785 In mmh, three environment variables replace the two of nmh.
meillo@133 3786 .Ev MMH
meillo@133 3787 overrides the default location of the mmh directory (\c
meillo@133 3788 .Fn .mmh ).
meillo@133 3789 .Ev MMHP
meillo@133 3790 and
meillo@133 3791 .Ev MMHC
meillo@220 3792 override the paths to the profile and context file, respectively.
meillo@133 3793 This approach allows the set of personal configuration files to be chosen
meillo@220 3794 independently of the profile, context, and mail storage.
meillo@133 3795 The new approach has no functional disadvantages,
meillo@133 3796 as every setup I can imagine can be implemented with both approaches,
meillo@220 3797 possibly even easier with the new one.
meillo@220 3798 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133 3799
meillo@133 3800
meillo@133 3801
meillo@133 3802
meillo@133 3803
meillo@118 3804 .H2 "Modularization
meillo@220 3805 .Id modularization
meillo@118 3806 .P
meillo@123 3807 The source code of the mmh tools is located in the
meillo@122 3808 .Fn uip
meillo@123 3809 (``user interface programs'') directory.
meillo@180 3810 Each tool has a source file with the name of the command.
meillo@122 3811 For example,
meillo@122 3812 .Pn rmm
meillo@122 3813 is built from
meillo@122 3814 .Fn uip/rmm.c .
meillo@123 3815 Some source files are used for multiple programs.
meillo@122 3816 For example
meillo@122 3817 .Fn uip/scansbr.c
meillo@173 3818 is used for both
meillo@122 3819 .Pn scan
meillo@122 3820 and
meillo@122 3821 .Pn inc .
meillo@122 3822 In nmh, 49 tools were built from 76 source files.
meillo@123 3823 This is a ratio of 1.6 source files per program.
meillo@123 3824 32 programs depended on multiple source files;
meillo@123 3825 17 programs depended on one source file only.
meillo@122 3826 In mmh, 39 tools are built from 51 source files.
meillo@123 3827 This is a ratio of 1.3 source files per program.
meillo@123 3828 18 programs depend on multiple source files;
meillo@123 3829 21 programs depend on one source file only.
meillo@123 3830 (These numbers and the ones in the following text ignore the MH library
meillo@123 3831 as well as shell scripts and multiple names for the same program.)
meillo@122 3832 .P
meillo@123 3833 Splitting the source code of a large program into multiple files can
meillo@220 3834 increase the readability of its source code,
meillo@220 3835 but most of the mmh tools are small and straight-forward programs.
meillo@220 3836 In exception of the MIME handling tools (i.e.
meillo@122 3837 .Pn mhbuild ,
meillo@122 3838 .Pn mhstore ,
meillo@122 3839 .Pn show ,
meillo@220 3840 etc.),
meillo@220 3841 .Pn pick
meillo@220 3842 is the only tool with more than one thousand lines of source code.
meillo@220 3843 Splitting programs with less than one thousand lines of code into
meillo@220 3844 multiple source files leads seldom to better readability.
meillo@220 3845 For such tools, splitting still makes sense
meillo@220 3846 when parts of the code are reused in other programs
meillo@179 3847 and the reused code fragment is (1) not general enough
meillo@179 3848 for including it in the MH library
meillo@179 3849 or (2) has dependencies on a library that only few programs need.
meillo@122 3850 .Fn uip/packsbr.c ,
meillo@122 3851 for instance, provides the core program logic for the
meillo@122 3852 .Pn packf
meillo@122 3853 and
meillo@122 3854 .Pn rcvpack
meillo@122 3855 programs.
meillo@122 3856 .Fn uip/packf.c
meillo@122 3857 and
meillo@122 3858 .Fn uip/rcvpack.c
meillo@122 3859 mainly wrap the core function appropriately.
meillo@122 3860 No other tools use the folder packing functions.
meillo@123 3861 As another example,
meillo@123 3862 .Fn uip/termsbr.c
meillo@220 3863 accesses terminal properties, which requires linking with the
meillo@220 3864 \fItermcap\fP or a \fIcurses\fP library.
meillo@220 3865 If
meillo@123 3866 .Fn uip/termsbr.c
meillo@220 3867 is included in the MH library, then every program needs to be linked
meillo@220 3868 with termcap or curses, although only few of the programs use
meillo@220 3869 the library.
meillo@122 3870 .P
meillo@122 3871 The task of MIME handling is complex enough that splitting its code
meillo@122 3872 into multiple source files improves the readability.
meillo@122 3873 The program
meillo@122 3874 .Pn mhstore ,
meillo@122 3875 for instance, is compiled out of seven source files with 2\|500
meillo@122 3876 lines of code in summary.
meillo@122 3877 The main code file
meillo@122 3878 .Fn uip/mhstore.c
meillo@220 3879 consists of 800 lines; the other 1\|700 lines are code reused in
meillo@123 3880 other MIME handling tools.
meillo@123 3881 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123 3882 a MH-MIME library, as a companion to the MH standard library.
meillo@220 3883 This is left to be done.
meillo@122 3884 .P
meillo@169 3885 The work already accomplished focussed on the non-MIME tools.
meillo@122 3886 The amount of code compiled into each program was reduced.
meillo@123 3887 This eases the understanding of the code base.
meillo@122 3888 In nmh,
meillo@122 3889 .Pn comp
meillo@122 3890 was built from six source files:
meillo@122 3891 .Fn comp.c ,
meillo@122 3892 .Fn whatnowproc.c ,
meillo@122 3893 .Fn whatnowsbr.c ,
meillo@122 3894 .Fn sendsbr.c ,
meillo@122 3895 .Fn annosbr.c ,
meillo@122 3896 and
meillo@122 3897 .Fn distsbr.c .
meillo@122 3898 In mmh, it builds from only two:
meillo@122 3899 .Fn comp.c
meillo@122 3900 and
meillo@122 3901 .Fn whatnowproc.c .
meillo@123 3902 In nmh's
meillo@123 3903 .Pn comp ,
meillo@123 3904 the core function of
meillo@122 3905 .Pn whatnow ,
meillo@122 3906 .Pn send ,
meillo@122 3907 and
meillo@122 3908 .Pn anno
meillo@220 3909 were all compiled into
meillo@122 3910 .Pn comp .
meillo@123 3911 This saved the need to execute these programs with
meillo@220 3912 the expensive system calls
meillo@122 3913 .Fu fork()
meillo@122 3914 and
meillo@220 3915 .Fu exec() .
meillo@171 3916 Whereas this approach improved the time performance,
meillo@171 3917 it interwove the source code.
meillo@122 3918 Core functionalities were not encapsulated into programs but into
meillo@122 3919 function, which were then wrapped by programs.
meillo@122 3920 For example,
meillo@122 3921 .Fn uip/annosbr.c
meillo@122 3922 included the function
meillo@122 3923 .Fu annotate() .
meillo@122 3924 Each program that wanted to annotate messages, included the source file
meillo@123 3925 .Fn uip/annosbr.c
meillo@123 3926 and called
meillo@123 3927 .Fu annotate() .
meillo@123 3928 Because the function
meillo@123 3929 .Fu annotate()
meillo@123 3930 was used like the tool
meillo@123 3931 .Pn anno ,
meillo@123 3932 it had seven parameters, reflecting the command line switches of the tool.
meillo@122 3933 When another pair of command line switches was added to
meillo@122 3934 .Pn anno ,
meillo@122 3935 a rather ugly hack was implemented to avoid adding another parameter
meillo@220 3936 to the function
meillo@220 3937 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f .
meillo@122 3938 .P
meillo@122 3939 In mmh, the relevant code of
meillo@122 3940 .Pn comp
meillo@122 3941 comprises the two files
meillo@122 3942 .Fn uip/comp.c
meillo@122 3943 and
meillo@122 3944 .Fn uip/whatnowproc.c ,
meillo@220 3945 together 210 lines of code,
meillo@220 3946 whereas in nmh,
meillo@122 3947 .Pn comp
meillo@122 3948 comprises six files with 2\|450 lines.
meillo@220 3949 Not all of the code in these six files is actually used by
meillo@122 3950 .Pn comp ,
meillo@220 3951 but the reader needed to read it all to know which parts are relevant.
meillo@220 3952 Understanding nmh's
meillo@122 3953 .Pn comp ,
meillo@123 3954 required understanding the inner workings of
meillo@122 3955 .Fn uip/annosbr.c
meillo@122 3956 first.
meillo@123 3957 To be sure to fully understand a program, its whole source code needs
meillo@122 3958 to be examined.
meillo@123 3959 Not doing so is a leap of faith, assuming that the developers
meillo@122 3960 have avoided obscure programming techniques.
meillo@220 3961 Here, it should be recalled that information passed in obscure ways
meillo@220 3962 through the program's source base, due to the aforementioned hack
meillo@220 3963 to save an additional parameter in nmh's
meillo@220 3964 .Pn anno .
meillo@220 3965 .P
meillo@220 3966 In mmh, understanding
meillo@220 3967 .Pn comp
meillo@220 3968 requires to read only 210 lines of code to read, whereas the amount
meillo@220 3969 is ten times more for nmh's
meillo@220 3970 .Pn comp .
meillo@220 3971 .P
meillo@220 3972 By separating the tools on the program-level,
meillo@220 3973 the boundaries are clearly visible, as the interfaces are calls to
meillo@122 3974 .Fu exec()
meillo@122 3975 rather than arbitrary function calls.
meillo@220 3976 Additionally, this kind of separation is more strict because
meillo@220 3977 it is technically enforced by the operating system;
meillo@220 3978 it can not be simply bypassed with global variables.
meillo@220 3979 Good separation simplifies the understanding of program code
meillo@220 3980 because the area influenced by any particular statement is small.
meillo@220 3981 As I have read a lot in nmh's code base during the last two years,
meillo@220 3982 I have learned about the easy and the difficult parts.
meillo@220 3983 In my observation, the understanding of code is enormously eased
meillo@220 3984 if the influenced area is small and clearly bounded.
meillo@123 3985 .P
meillo@220 3986 Yet, the real problem is another:
meillo@123 3987 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123 3988 Understanding
meillo@122 3989 .Pn comp
meillo@123 3990 requires understanding
meillo@123 3991 .Fn uip/annosbr.c
meillo@123 3992 and
meillo@123 3993 .Fn uip/sendsbr.c
meillo@123 3994 because
meillo@123 3995 .Pn comp
meillo@220 3996 annotates and sends messages.
meillo@220 3997 In nmh, there surely exist the tools
meillo@220 3998 .Pn anno
meillo@220 3999 and
meillo@122 4000 .Pn send ,
meillo@220 4001 which cover these jobs,
meillo@220 4002 but
meillo@122 4003 .Pn comp
meillo@123 4004 and
meillo@122 4005 .Pn repl
meillo@122 4006 and
meillo@122 4007 .Pn forw
meillo@122 4008 and
meillo@122 4009 .Pn dist
meillo@122 4010 and
meillo@122 4011 .Pn whatnow
meillo@122 4012 and
meillo@220 4013 .Pn viamail
meillo@220 4014 \(en they all (!) \(en
meillo@220 4015 have the same annotating and sending functions included, once more.
meillo@220 4016 As a result,
meillo@123 4017 .Pn comp
meillo@123 4018 sends messages without using
meillo@123 4019 .Pn send .
meillo@123 4020 The situation is the same as if
meillo@123 4021 .Pn grep
meillo@220 4022 would page its output without using
meillo@123 4023 .Pn more
meillo@123 4024 just because both programs are part of the same code base.
meillo@123 4025 .P
meillo@220 4026 The clear separation on the surface of nmh
meillo@220 4027 \(en the tool chest approach \(en
meillo@123 4028 is violated on the level below.
meillo@122 4029 This violation is for the sake of time performance.
meillo@220 4030 Decades ago, sacrificing readability and conceptional beauty
meillo@220 4031 for speed might have been necessary to prevent MH from being
meillo@220 4032 unusably slow, but today this is not the case anymore.
meillo@220 4033 No longer should speed improvements that became unnecessary be kept.
meillo@220 4034 No longer should readability or conceptional beauty be sacrificed.
meillo@220 4035 No longer should the Unix philosophy's ``one tool, one job''
meillo@220 4036 guideline be violated.
meillo@123 4037 Therefore, mmh's
meillo@123 4038 .Pn comp
meillo@220 4039 no longer sends messages.
meillo@220 4040 .P
meillo@123 4041 In mmh, different jobs are divided among separate programs that
meillo@122 4042 invoke each other as needed.
meillo@123 4043 In consequence,
meillo@123 4044 .Pn comp
meillo@123 4045 invokes
meillo@123 4046 .Pn whatnow
meillo@123 4047 which thereafter invokes
meillo@220 4048 .Pn send
meillo@168 4049 .Ci 3df5ab3c116e6d4a2fb4bb5cc9dfc5f781825815
meillo@220 4050 .Ci c73c00bfccd22ec77e9593f47462aeca4a8cd9c0 .
meillo@123 4051 The clear separation on the surface is maintained on the level below.
meillo@220 4052 Human users and other tools use the same interface \(en
meillo@123 4053 annotations, for example, are made by invoking
meillo@123 4054 .Pn anno ,
meillo@220 4055 no matter if requested by programs or by human beings
meillo@168 4056 .Ci 469a4163c2a1a43731d412eaa5d9cae7d670c48b
meillo@168 4057 .Ci aed384169af5204b8002d06e7a22f89197963d2d
meillo@220 4058 .Ci 3caf9e298a8861729ca8b8a84f57022b6f3ea742 .
meillo@123 4059 The decrease of tools built from multiple source files and thus
meillo@123 4060 the decrease of
meillo@123 4061 .Fn uip/*sbr.c
meillo@220 4062 files confirm the improvement
meillo@168 4063 .Ci 9e6d91313f01c96b4058d6bf419a8ca9a207bc33
meillo@168 4064 .ci 81744a46ac9f845d6c2b9908074d269275178d2e
meillo@168 4065 .Ci f0f858069d21111f0dbea510044593f89c9b0829
meillo@168 4066 .Ci 0503a6e9be34f24858b55b555a5c948182b9f24b
meillo@168 4067 .Ci 27826f9353e0f0b04590b7d0f8f83e60462b90f0
meillo@168 4068 .Ci d1da1f94ce62160aebb30df4063ccbc53768656b
meillo@220 4069 .Ci c42222869e318fff5dec395eca3e776db3075455 .
meillo@220 4070 This is also visible in the complexity of the build dependency graphs:
meillo@145 4071
meillo@220 4072 .sp
meillo@220 4073 Nmh:
meillo@220 4074 .BP input/deps-nmh.eps .5i
meillo@220 4075 .EP
meillo@220 4076 .sp
meillo@220 4077 Mmh:
meillo@220 4078 .BP input/deps-mmh.eps .8i
meillo@220 4079 .EP
meillo@145 4080
meillo@226 4081 The figures display all program to source file relationships where
meillo@226 4082 programs (ellipses) are built from multiple source files (rectangles).
meillo@220 4083 The primary source file of each program is omited from the graph.