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annotate ch03.roff @ 20:7a100c80fa91

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Some new text (show/mhshow; prompter).
author markus schnalke <meillo@marmaro.de>
date Sun, 06 May 2012 17:33:45 +0200
parents ab5253e48c74
children bb8a8be49024
rev   line source
meillo@0 1 .H0 "Work Report
meillo@0 2 .P
meillo@0 3 foo
meillo@0 4 .P
meillo@0 5 bar
meillo@0 6
meillo@12 7 .H1 "Removal of Code Relicts
meillo@0 8 .P
meillo@20 9 The code base of mmh originates from the late 70s, had been extensively
meillo@12 10 worked on in the mid 80s, and had been partly reorganized and extended
meillo@12 11 in the 90s. Relicts of all those times had gathered in the code base.
meillo@12 12 My goal was to remove any ancient code parts. One part of the task was
meillo@12 13 converting obsolete code constructs to standard constructs, the other part
meillo@12 14 was dropping obsolete functions.
meillo@12 15 .P
meillo@12 16 As I'm not even thirty years old and have no more than seven years of
meillo@12 17 Unix experience, I needed to learn about the history in retroperspective.
meillo@12 18 Older people likely have used those ancient constructs themself
meillo@12 19 and have suffered from their incompatiblities and have longed for
meillo@12 20 standardization. Unfortunately, I have only read that others had done so.
meillo@12 21 This put me in a much more difficult positions when working on the old
meillo@12 22 code. I needed to recherche what other would have known by heart from
meillo@12 23 experience. All my programming experience comes from a time past ANSI C
meillo@12 24 and past POSIX. Although I knew about the times before, I took the
meillo@12 25 current state implicitely for granted most of the time.
meillo@12 26 .P
meillo@12 27 Being aware of
meillo@12 28 these facts, I rather let people with more historic experience solve the
meillo@12 29 task of converting the ancient code constructs to standardized ones.
meillo@12 30 Luckily, Lyndon Nerenberg focused on this task at the nmh project.
meillo@12 31 He converted large parts of the code to POSIX constructs, removing
meillo@12 32 the conditionals compilation for now standardized features.
meillo@12 33 I'm thankful for this task being solved. I only pulled the changes into
meillo@12 34 mmh.
meillo@12 35 .P
meillo@20 36 The other task \(en dropping ancient functionality to remove old code \(en
meillo@12 37 I did myself, though. My position to strip mmh to the bare minimum of
meillo@12 38 frequently used features is much more revolutional than the nmh community
meillo@20 39 likes it. Without the need to justify my decisions, I was able to quickly
meillo@20 40 remove functionality I considered ancient.
meillo@20 41 The need to discuss my decisions with
meillo@20 42 peers likely would have slowed this process down. Of course, I researched
meillo@12 43 if a particular feature really should be dropped. Having not had any
meillo@12 44 contact to this feature within my computer life was a first indicator to
meillo@12 45 drop it, but I also asked others and searched the literature for modern
meillo@12 46 usage of the feature. If it appeared to be truly ancient, I dropped it.
meillo@12 47 The reason for dropping is always part of the commit message in the
meillo@12 48 version control system. Thus, it is easy for others to check their
meillo@12 49 view on the topic with mine and possibly to argue for reinclusion.
meillo@12 50
meillo@12 51 .U2 "MMDF maildrop support
meillo@12 52 .P
meillo@12 53 I did drop any support for the MMDF maildrop format. This type of format
meillo@12 54 is conceptionally similar to the mbox format, but uses four bytes with
meillo@12 55 value 1 (\fL^A^A^A^A\fP) as message delimiter,
meillo@18 56 instead of the string ``\fLFrom\ \fP''.
meillo@12 57 Due to the similarity and mbox being the de-facto standard maildrop
meillo@12 58 format on Unix, but also due to the larger influence of Sendmail than MMDF,
meillo@12 59 the MMDF maildrop format had vanished.
meillo@12 60 .P
meillo@12 61 The simplifications within the code were only moderate. Switches could
meillo@12 62 be removed from tools like
meillo@12 63 .L packf ,
meillo@12 64 which generate packed mailboxes. Only one packed mailbox format remained:
meillo@12 65 mbox.
meillo@12 66 The most important changes affect the equally named mail parsing routine in
meillo@12 67 .L sbr/m_getfld.c .
meillo@12 68 The direct MMDF code had been removed, but as now only one packed mailbox
meillo@12 69 format is left, code structure simplifications are likely possible.
meillo@12 70 The reason why they are still outstanding is the heavily optimized code
meillo@18 71 of
meillo@18 72 .Fu m_getfld() .
meillo@18 73 Changes beyond a small local scope \(en
meillo@12 74 which restructuring in its core is \(en cause a high risk of damaging
meillo@12 75 the intricate workings of the optimized code. This problem is know
meillo@12 76 to the developers of nmh, too. They also avoid touching this minefield
meillo@12 77 if possible.
meillo@12 78
meillo@12 79 .U2 "UUCP Bang Paths
meillo@12 80 .P
meillo@12 81 More questionably than the former topic is the removal of support for the
meillo@12 82 UUCP bang path address style. However, the user may translate the bang
meillo@12 83 paths on retrieval to Internet addresses and the other way on posting
meillo@12 84 messages. The former can be done my an MDA like procmail; the latter
meillo@12 85 by a sendmail wrapper. This would ensure that any address handling would
meillo@12 86 work as expected. However, it might just work well without any
meillo@12 87 such modifications, as mmh does not touch addresses much, in general.
meillo@12 88 But I can't ensure as I have never used an environment with bang paths.
meillo@12 89 Also, the behavior might break at any point in further development.
meillo@12 90
meillo@12 91 .U2 "Hardcopy terminal support
meillo@12 92 .P
meillo@12 93 More of a funny anecdote is the remaining of a check for printing to a
meillo@12 94 hardcopy terminal until Spring 2012, when I finally removed it.
meillo@12 95 I surely would be very happy to see such a terminal in action, maybe
meillo@12 96 actually being able to work on it, but I fear my chances are null.
meillo@12 97 .P
meillo@12 98 The check only prevented a pager to be placed between the outputting
meillo@18 99 program (\c
meillo@18 100 .Pn mhl )
meillo@18 101 and the terminal. This could have been ensured with
meillo@18 102 the
meillo@18 103 .Sw \-nomoreproc
meillo@18 104 at the command line statically, too.
meillo@12 105
meillo@12 106 .U2 "Removed support for header fields
meillo@12 107 .P
meillo@12 108 The `Encrypted' header had been introduced by RFC\^822, but already
meillo@12 109 marked legacy in RFC 2822. It was superseded by FIXME.
meillo@12 110 Mmh does no more support this header.
meillo@12 111 .P
meillo@12 112 `Content-MD5' headers were introduced by RFC\^1864. They provide only
meillo@12 113 a verification of data corruption during the transfer. By no means can
meillo@12 114 they ensure verbatim end-to-end delivery of the contents. This is clearly
meillo@12 115 stated in the RFC. The proper approach to provide verificationability
meillo@12 116 of content in an end-to-end relationship is the use of digital cryptography
meillo@12 117 (RFCs FIXME). On the other hand, transfer protocols should ensure the
meillo@12 118 integrity of the transmission. In combinations these two approaches
meillo@12 119 make the `Content-MD5' header field useless. In consequence, I removed
meillo@12 120 the support for it. By this removal, MD5 computation is not needed
meillo@12 121 anywhere in mmh. Hence, over 500 lines of code were removed by this one
meillo@12 122 change. Even if the `Content-MD5' header field is useful sometimes,
meillo@12 123 I value its usefulnes less than the improvement in maintainability, caused
meillo@12 124 by the removal.
meillo@12 125
meillo@20 126 .U2 "Prompter's Control Keys
meillo@20 127 .P
meillo@20 128 The program
meillo@20 129 .Pn prompter
meillo@20 130 queries the user to fill in a message form. When used by
meillo@20 131 .Pn comp
meillo@20 132 as:
meillo@20 133 .DS
meillo@20 134 comp \-editor prompter
meillo@20 135 .DE
meillo@20 136 the resulting behavior is similar to
meillo@20 137 .Pn mailx .
meillo@20 138 Appearently,
meillo@20 139 .Pn prompter
meillo@20 140 hadn't been touched lately. Otherwise it's hardly explainable why it
meillo@20 141 still offered the switches
meillo@20 142 .Sn \-erase \fUchr\fP
meillo@20 143 and
meillo@20 144 .Sn \-kill \fUchr\fP
meillo@20 145 to name the characters for command line editing.
meillo@20 146 The times when this had been neccessary are long time gone.
meillo@20 147 Today these things work out-of-the-box, and if not, are configured
meillo@20 148 with the standard tool
meillo@20 149 .Pn stty .
meillo@20 150
meillo@12 151
meillo@14 152 .H1 "Draft and Trash Folders
meillo@16 153 .U2 "Draft Folder
meillo@14 154 .P
meillo@18 155 Historically, MH provided exactly one draft message, named
meillo@18 156 .Fn draft
meillo@18 157 and
meillo@14 158 being located in the MH directory. When starting to compose another message
meillo@14 159 before the former one was sent, the user had been questioned wether to use,
meillo@14 160 refile or replace the old draft. Working on multiple drafts at the same time
meillo@14 161 was impossible. One could only work on them in alteration by refiling the
meillo@14 162 previous one to some directory and fetching some other one for reediting.
meillo@14 163 This manual draft management needed to be done each time the user wanted
meillo@14 164 to switch between editing one draft to editing another.
meillo@14 165 .P
meillo@14 166 To allow true parallel editing of drafts, in a straight forward way, the
meillo@14 167 draft folder facility exists. It had been introduced already in July 1984
meillo@14 168 by Marshall T. Rose. The facility was deactivated by default.
meillo@14 169 Even in nmh, the draft folder facility remained deactivated by default.
meillo@18 170 At least, Richard Coleman added the man page
meillo@18 171 .Mp mh-draft(5)
meillo@18 172 to document
meillo@14 173 the feature well.
meillo@14 174 .P
meillo@14 175 The only advantage of not using the draft folder facility is the static
meillo@14 176 name of the draft file. This could be an issue for MH frontends like mh-e.
meillo@14 177 But as they likely want to provide working on multiple drafts in parallel,
meillo@14 178 the issue is only concerning compatibility. The aim of nmh to stay compatible
meillo@14 179 prevented the default activation of the draft folder facility.
meillo@14 180 .P
meillo@14 181 On the other hand, a draft folder is the much more natural concept than
meillo@14 182 a draft message. MH's mail storage consists of folders and messages,
meillo@14 183 the messages named with ascending numbers. A draft message breaks with this
meillo@18 184 concept by introducing a message in a file named
meillo@18 185 .Fn draft .
meillo@18 186 This draft
meillo@14 187 message is special. It can not be simply listed with the available tools,
meillo@17 188 but instead requires special switches. I.e. corner-cases were
meillo@14 189 introduced. A draft folder, in contrast, does not introduce such
meillo@14 190 corner-cases. The available tools can operate on the messages within that
meillo@14 191 folder like on any messages within any mail folders. The only difference
meillo@18 192 is the fact that the default folder for
meillo@18 193 .Pn send
meillo@18 194 is the draft folder,
meillo@14 195 instead of the current folder, like for all other tools.
meillo@14 196 .P
meillo@14 197 The trivial part of the change was activating the draft folder facility
meillo@14 198 by default and setting a default name for this folder. Obviously, I chose
meillo@18 199 the name
meillo@18 200 .Fn +drafts .
meillo@18 201 This made the
meillo@18 202 .Sw \-draftfolder
meillo@18 203 and
meillo@18 204 .Sw \-draftmessage
meillo@18 205 switches useless, and I could remove them.
meillo@14 206 The more difficult but also the part that showed the real improvement,
meillo@18 207 was updating the tools to the new concept.
meillo@18 208 .Sw \-draft
meillo@18 209 switches could
meillo@14 210 be dropped, as operating on a draft message became indistinguishable to
meillo@18 211 operating on any other message for the tools.
meillo@18 212 .Pn comp
meillo@18 213 still has its
meillo@18 214 .Sw \-use
meillo@18 215 switch for switching between its two modes: (1) Compose a new
meillo@14 216 draft, possibly by taking some existing message as a form. (2) Modify
meillo@18 217 an existing draft. In either case, the behavior of
meillo@18 218 .Pn comp is
meillo@14 219 deterministic. There is no more need to query the user. I consider this
meillo@18 220 a major improvement. By making
meillo@18 221 .Pn send
meillo@18 222 simply operate on the current
meillo@17 223 message in the draft folder by default, with message and folder both
meillo@14 224 overridable by specifying them on the command line, it is now possible
meillo@17 225 to send a draft anywhere within the storage by simply specifying its folder
meillo@17 226 and name.
meillo@14 227 .P
meillo@14 228 All theses changes converted special cases to regular cases, thus
meillo@14 229 simplifying the tools and increasing the flexibility.
meillo@14 230
meillo@16 231 .U2 "Trash Folder
meillo@16 232 .P
meillo@16 233 Similar to the situation for drafts is the situation for removed messages.
meillo@16 234 Historically, a message was deleted by renaming. A specific
meillo@18 235 \fIbackup prefix\fP, often comma (\c
meillo@18 236 .Fn , )
meillo@18 237 or hash (\c
meillo@18 238 .Fn # ),
meillo@16 239 being prepended to the file name. Thus, MH wouldn't recognize the file
meillo@16 240 as a message anymore, as only files whose name consists of digits only
meillo@16 241 are treated as messages. The removed messages remained as files in the
meillo@16 242 same directory and needed some maintenance job to truly delete them after
meillo@16 243 some grace time. Usually, by running a command similar to
meillo@16 244 .DS
meillo@16 245 find /home/user/Mail \-ctime +7 \-name ',*' | xargs rm
meillo@16 246 .DE
meillo@16 247 in a cron job. Within the grace time interval
meillo@16 248 the original message could be restored by stripping the
meillo@16 249 the backup prefix from the file name. If however, the last message of
meillo@18 250 a folder is been removed \(en say message
meillo@18 251 .Fn 6
meillo@18 252 becomes file
meillo@18 253 .Fn ,6
meillo@18 254 \(en and a new message enters the same folder, thus the same
meillo@18 255 numbered being given again \(en in our case
meillo@18 256 .Fn 6
meillo@18 257 \(en, if that one
meillo@17 258 is removed too, then the backup of the former message gets overwritten.
meillo@16 259 Thus, the ability to restore removed messages does not only depend on
meillo@16 260 the ``sweeping cron job'' but also on the removing of further messages.
meillo@16 261 This is undesireable, because the real mechanism is hidden from the user
meillo@16 262 and the concequences of further removals are not always obvious.
meillo@16 263 Further more, the backup files are scattered within the whole mail
meillo@16 264 storage, instead of being collected at one place.
meillo@16 265 .P
meillo@18 266 To improve the situation, the profile entry
meillo@18 267 .Pe rmmproc
meillo@18 268 (previously named
meillo@18 269 .Pe Delete-Prog )
meillo@18 270 was introduced, very early.
meillo@16 271 It could be set to any command, which would care for the mail removal
meillo@16 272 instead of taking the default action, described above.
meillo@16 273 Refiling the to-be-removed files to some wastebin folder was a common
meillo@18 274 example. Nmh's man page
meillo@18 275 .Mp rmm(1)
meillo@18 276 proposes
meillo@18 277 .Cl "refile +d
meillo@18 278 to move messages to the wastebin and
meillo@18 279 .Cl "rm `mhpath +d all`
meillo@16 280 the empty the wastebin.
meillo@16 281 Managing the message removal this way is a sane approach. It keeps
meillo@16 282 the removed messages in one place, makes it easy to remove the backup
meillo@16 283 files, and, most important, enables the user to use the tools of MH
meillo@18 284 itself to operate on the removed messages. One can
meillo@18 285 .Pn scan
meillo@18 286 them,
meillo@18 287 .Pn show
meillo@18 288 them, and restore them with
meillo@18 289 .Pn refile .
meillo@18 290 There's no more
meillo@18 291 need to use
meillo@18 292 .Pn mhpath
meillo@18 293 to switch over from MH tools to Unix tools \(en MH can do it all itself.
meillo@16 294 .P
meillo@18 295 This apporach matches perfect with the concepts of MH, thus making
meillo@16 296 it powerful. Hence, I made it the default. And even more, I also
meillo@16 297 removed the old backup prefix approach, as it is clearly less powerful.
meillo@16 298 Keeping unused alternative in the code is a bad choice as they likely
meillo@16 299 gather bugs, by not being constantly tested. Also, the increased code
meillo@16 300 size and more conditions crease the maintenance costs. By strictly
meillo@16 301 converting to the trash folder approach, I simplified the code base.
meillo@18 302 .Pn rmm
meillo@18 303 calls
meillo@18 304 .Pn refile
meillo@18 305 internally to move the to-be-removed
meillo@18 306 message to the trash folder (\c
meillo@18 307 .Fn +trash
meillo@18 308 by default). Messages
meillo@16 309 there can be operated on like on any other message in the storage.
meillo@18 310 The sweep clean, one can use
meillo@18 311 .Cl "rmm \-unlink +trash a" ,
meillo@18 312 where the
meillo@18 313 .Sw \-unlink
meillo@18 314 switch causes the files to be truly unliked instead
meillo@16 315 of moved to the trash folder.
meillo@16 316
meillo@0 317
meillo@17 318 .H1 "MH Directory Split
meillo@0 319 .P
meillo@19 320 In MH and nmh, a personal setup had consisted of two parts:
meillo@19 321 The MH profile, named
meillo@19 322 .Fn \&.mh_profile
meillo@19 323 and being located directly in the user's home directory.
meillo@19 324 And the MH directory, where all his mail messages and also his personal
meillo@19 325 forms, scan formats, other configuration files are stored. The location
meillo@19 326 of this directory could be user-chosen. The default was to name it
meillo@19 327 .Fn Mail
meillo@19 328 and have it directly in the home directory.
meillo@19 329 .P
meillo@19 330 I've never liked the data storage and the configuration to be intermixed.
meillo@19 331 They are different kinds of data. One part, are the messages,
meillo@19 332 which are the data to operate on. The other part, are the personal
meillo@19 333 configuration files, which are able to change the behavior of the operations.
meillo@19 334 The actual operations are defined in the profile, however.
meillo@19 335 .P
meillo@19 336 When storing data, one should try to group data by its type.
meillo@19 337 There's sense in the Unix file system hierarchy, where configuration
meillo@19 338 file are stored separate (\c
meillo@19 339 .Fn /etc )
meillo@19 340 to the programs (\c
meillo@19 341 .Fn /bin
meillo@19 342 and
meillo@19 343 .Fn /usr/bin )
meillo@19 344 to their sources (\c
meillo@19 345 .Fn /usr/src ).
meillo@19 346 Such separation eases the backup management, for instance.
meillo@19 347 .P
meillo@19 348 In mmh, I've reorganized the file locations.
meillo@19 349 Still there are two places:
meillo@19 350 There's the mail storage directory, which, like in MH, contains all the
meillo@19 351 messages, but, unlike in MH, nothing else.
meillo@19 352 Its location still is user-chosen, with the default name
meillo@19 353 .Fn Mail ,
meillo@19 354 in the user's home directory. This is much similar to the case in nmh.
meillo@19 355 The configuration files, however, are grouped together in the new directory
meillo@19 356 .Fn \&.mmh
meillo@19 357 in the user's home directory.
meillo@19 358 The user's profile now is a file, named
meillo@19 359 .Fn profile ,
meillo@19 360 in this mmh directory.
meillo@19 361 Consistently, the context file and all the personal forms, scan formats,
meillo@19 362 and the like, are also there.
meillo@19 363 .P
meillo@19 364 The naming changed with the relocation.
meillo@19 365 The directory where everything, except the profile, had been stored (\c
meillo@19 366 .Fn $HOME/Mail ),
meillo@19 367 used to be called \fIMH directory\fP. Now, this directory is called the
meillo@19 368 user's \fImail storage\fP. The name \fImmh directory\fP is now given to
meillo@19 369 the new directory
meillo@19 370 (\c
meillo@19 371 .Fn $HOME/.mmh ),
meillo@19 372 containing all the personal configuration files.
meillo@19 373 .P
meillo@19 374 The separation of the files by type of content is logical and convenient.
meillo@19 375 There are no functional differences as any possible setup known to me
meillo@19 376 can be implemented with both approaches, although likely a bit easier
meillo@19 377 with the new approach. The main goal of the change had been to provide
meillo@19 378 sensible storage locations for any type of personal mmh file.
meillo@19 379 .P
meillo@19 380 In order for one user to have multiple MH setups, he can use the
meillo@19 381 environment variable
meillo@19 382 .Ev MH
meillo@19 383 the point to a different profile file.
meillo@19 384 The MH directory (mail storage plus personal configuration files) is
meillo@19 385 defined by the
meillo@19 386 .Pe Path
meillo@19 387 profile entry.
meillo@19 388 The context file could be defined by the
meillo@19 389 .Pe context
meillo@19 390 profile entry or by the
meillo@19 391 .Ev MHCONTEXT
meillo@19 392 environment variable.
meillo@19 393 The latter is useful to have a distinct context (e.g. current folders)
meillo@19 394 in each terminal window, for instance.
meillo@19 395 In mmh, there are three environment variables now.
meillo@19 396 .Ev MMH
meillo@19 397 may be used to change the location of the mmh directory.
meillo@19 398 .Ev MMHP
meillo@19 399 and
meillo@19 400 .Ev MMHC
meillo@19 401 change the profile and context files, respectively.
meillo@19 402 Besides providing a more consistent feel (which simply is the result
meillo@19 403 of being designed anew), the set of personal configuration files can
meillo@19 404 be chosen independently from the profile (including mail storage location)
meillo@19 405 and context, now. Being it relevant for practical use or not, it
meillo@19 406 de-facto is an improvement. However, the main achievement is the
meillo@19 407 split between mail storage and personal configuration files.
meillo@17 408
meillo@0 409
meillo@0 410 .H1 "Path Notations
meillo@0 411 .P
meillo@0 412 foo
meillo@0 413
meillo@0 414 .H1 "Attachments
meillo@0 415 .P
meillo@0 416 foo
meillo@0 417
meillo@20 418 .H1 "mhshow to show Transition
meillo@20 419 .P
meillo@20 420 Since the very beginning, already in the first concept paper,
meillo@20 421 .Pn show
meillo@20 422 had been MH's mail display program.
meillo@20 423 .Pn show
meillo@20 424 found out which pathnames the relevant messages had and invoked
meillo@20 425 .Pn mhl
meillo@20 426 then to let it render the content.
meillo@20 427 With the advent of MIME, this approach wasn't sufficient anymore.
meillo@20 428 MIME messages can consist of multiple parts, some of which aren't
meillo@20 429 directly displayable, and text content can be encoded in
meillo@20 430 foreign charsets.
meillo@20 431 .Pn show 's
meillo@20 432 simple approach and
meillo@20 433 .Pn mhl 's
meillo@20 434 limited display facilities couldn't cope with the task any longer.
meillo@20 435 Instead of extending these tools, new ones were written from scratch
meillo@20 436 and then added to the MH toolchest. Doing so is encouraged by the
meillo@20 437 toolchest approach. The new tools could be added without interfearing
meillo@20 438 with the existing ones. This is great. It allowed MH to be the
meillo@20 439 first MUA to implement MIME.
meillo@20 440 .P
meillo@20 441 The new MIME features were added in form of the single program
meillo@20 442 .Pn mhn .
meillo@20 443 The command
meillo@20 444 .DS
meillo@20 445 mhn \-show 42
meillo@20 446 .DE
meillo@20 447 would show the MIME message numbered 42.
meillo@20 448 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@20 449 the split of
meillo@20 450 .Pn mhn
meillo@20 451 into a set of specialized programs, which together covered the
meillo@20 452 aspects of MIME. One of these resulting tools was
meillo@20 453 .Pn mhshow .
meillo@20 454
meillo@20 455
meillo@0 456 .H1 "Blind Carbon Copies
meillo@0 457 .P
meillo@0 458 foo
meillo@0 459
meillo@0 460 .H1 "Good Defaults
meillo@0 461 .P
meillo@0 462 foo
meillo@0 463
meillo@0 464 .H1 "Modularization
meillo@0 465 .P
meillo@0 466 foo
meillo@0 467
meillo@0 468 .H1 "Code style
meillo@0 469 .P
meillo@0 470 foo