docs/master

annotate ch01.roff @ 49:d3a02f5e63b3

Various rework.
author markus schnalke <meillo@marmaro.de>
date Sat, 19 May 2012 17:56:15 +0200
parents eae5e50381ce
children a446f89cc5d9
rev   line source
meillo@39 1 .RN 1
meillo@39 2
meillo@0 3 .H0 "Introduction
meillo@0 4 .P
meillo@32 5 This chapter introduces MH, its history, concepts and how it is used.
meillo@47 6 It describes nmh's code base and community to give the reader
meillo@32 7 a better understanding of the state from which mmh started off.
meillo@47 8 Further more, this chapter outlines the mmh project itself,
meillo@47 9 describing the motivation for it and its goals.
meillo@8 10
meillo@0 11
meillo@28 12 .H1 "MH \(en the Mail Handler
meillo@0 13 .P
meillo@47 14 MH is a conceptual email system design and its concrete implementation.
meillo@47 15 Notably, MH had started as a design proposal at RAND Corporation,
meillo@47 16 where the first implementation followed later.
meillo@47 17 In spirit, MH is similar to Unix, which
meillo@42 18 influenced the world more in being a set of system design concepts
meillo@32 19 than in being a specific software product.
meillo@47 20 The ideas behind Unix are summarized in the \fIUnix philosophy\fP.
meillo@42 21 MH follows this philosophy.
meillo@2 22
meillo@11 23 .U2 "History
meillo@2 24 .P
meillo@32 25 In 1977 at RAND Corporation, Norman Shapiro and Stockton Gaines
meillo@32 26 had proposed the design
meillo@32 27 of a new mail handling system, called ``Mail Handler'' (MH),
meillo@32 28 to superseed RAND's old monolithic ``Mail System'' (MS).
meillo@27 29 Two years later, in 1979, Bruce Borden took the proposal and implemented a
meillo@32 30 prototype of MH.
meillo@32 31 Before the prototype had been available, the concept was
meillo@47 32 believed to be practically unusable.
meillo@47 33 But the prototype had proven successful and replaced MS thereafter.
meillo@47 34 In replacing MS, MH grew to an all-in-one mail system.
meillo@2 35 .P
meillo@47 36 In the early Eighties,
meillo@47 37 the University of California at Irvine (UCI) had started to use MH.
meillo@2 38 They also took over its development and pushed MH forward.
meillo@47 39 Marshall T. Rose and John L. Romine became the driving force then.
meillo@47 40 This was the time when the Internet appeared, when UCB implemented
meillo@47 41 the TCP/IP stack, and when Allman wrote Sendmail.
meillo@47 42 MH was extended as emailing became more featured.
meillo@32 43 The development of MH was closely related to the development of email
meillo@32 44 RFCs. In the advent of MIME, MH was the first implementation of this new
meillo@32 45 email standard.
meillo@2 46 .P
meillo@47 47 In the Nineties, MH had been moved into the public domain, making it
meillo@32 48 attractive to Free Software developers.
meillo@47 49 The Internet had became popular and in December 1996,
meillo@47 50 Richard Coleman initiated the ``New Mail Handler'' (nmh) project.
meillo@47 51 The project is a fork of MH 6.8.3 and bases strongly on the
meillo@47 52 \fILBL changes\fP by Van Jacobson, Mike Karels and Craig Leres.
meillo@32 53 Colman intended to modernize MH and improve its portability and
meillo@32 54 MIME handling capabilities.
meillo@32 55 This should be done openly within the Internet community.
meillo@47 56 The development of MH at UCI stopped after the 6.8.4 release in
meillo@47 57 February 1996, soon after the development of nmh had started.
meillo@32 58 Today, nmh almost completely replaced the original MH.
meillo@47 59 Some systems might still provide old MH, but mainly for historical reasons.
meillo@47 60 .P
meillo@47 61 In the last years, the work on nmh was mostly maintenance work.
meillo@47 62 However, the development revived in December 2011 and stayed busy since then.
meillo@0 63
meillo@11 64 .U2 "Concepts
meillo@0 65 .P
meillo@8 66 MH is a toolchest, modelled after the Unix toolchest. It consists of a
meillo@47 67 set of tools, each covering a specific task of email handling, like
meillo@47 68 composing a message, replying to a message, refiling a message to a
meillo@47 69 different folder, listing the messages in a folder.
meillo@47 70 All of the programs operate on a common mail storage.
meillo@42 71 .P
meillo@32 72 The mail storage consists of \fImail folders\fP (directories) and
meillo@32 73 \fPmessages\fP (regular files).
meillo@32 74 Each message is stored in a separate file in the format it had been
meillo@47 75 received (i.e. transfer format).
meillo@47 76 The files are named with ascending numbers in each folder.
meillo@47 77 The specific format of the mail storage characterizes MH in the same way
meillo@47 78 like the format of the file system characterizes Unix.
meillo@42 79 .P
meillo@47 80 MH tools maintain a \fIcontext\fP, which includes the current mail folder.
meillo@32 81 Processes in Unix have a similar context, containing the current working
meillo@32 82 directory, for instance. In contrast, the process context is maintained
meillo@32 83 by the Unix kernel automatically, whereas MH tools need to maintain the MH
meillo@32 84 context themselves.
meillo@32 85 The user can have one MH context or multiple ones, he can even share it
meillo@32 86 with other users.
meillo@42 87 .P
meillo@47 88 Messages are named by their numeric filename, but they can have symbolic names,
meillo@47 89 too. These are either automatically updated
meillo@32 90 position names like being the next or the last message,
meillo@32 91 or user-settable group names for arbitrary sets of messages.
meillo@32 92 These names are called sequences.
meillo@47 93 Sequences can be bound to the containing folder or to the context.
meillo@2 94 .P
meillo@47 95 The user's \fIprofile\fP is a file that contains his MH configuration.
meillo@47 96 Default switches for the individual tools can be specified to
meillo@47 97 adjust them to the user's personal preferences.
meillo@47 98 Multiple versions of the same command with different
meillo@47 99 default values can also be created very easily.
meillo@47 100 Form templates for new messages or for replies are easily changable,
meillo@47 101 and output is adjustable with format files.
meillo@47 102 Almost every part of the system can be adjusted to personal preference.
meillo@42 103 .P
meillo@32 104 The system is well scriptable and extendable.
meillo@47 105 New MH tools are built out of or on top of existing ones quickly.
meillo@47 106 Further more, MH encourages the user to taylor, extend and automate the system.
meillo@32 107 As the MH toolchest was modelled after the Unix toolchest, the
meillo@32 108 properties of the latter apply to the former as well.
meillo@8 109
meillo@8 110
meillo@27 111 .U2 "Example Session
meillo@27 112 .P
meillo@32 113 Following is an example mail handling session with mmh.
meillo@32 114 It should be mostly compatible with nmh and old MH.
meillo@32 115 Details might vary but the look'n'feel is the same.
meillo@42 116 .DS
meillo@42 117 $ \f(CBinc\fP
meillo@42 118 Incorporating new mail into inbox...
meillo@42 119
meillo@42 120 1+ 2012-05-16 11:16 meillo@dream.home Hello
meillo@42 121 2 2012-05-16 11:17 meillo@dream.home book
meillo@42 122
meillo@42 123 $ \f(CBshow\fP
meillo@42 124 Date: Wed, 16 May 2012 11:16:00 +0200
meillo@42 125 To: meillo
meillo@42 126 From: <meillo@dream.home.schnalke.org>
meillo@42 127 Subject: Hello
meillo@42 128
meillo@42 129 part text/plain 13
meillo@42 130 mmh is great
meillo@42 131
meillo@42 132 $ \f(CBnext\fP
meillo@42 133 Date: Wed, 16 May 2012 11:17:24 +0200
meillo@42 134 To: meillo
meillo@42 135 From: <meillo@dream.home.schnalke.org>
meillo@42 136 Subject: book
meillo@42 137
meillo@42 138 part text/plain 79
meillo@42 139 Hello meillo,
meillo@42 140
meillo@42 141 have a look at the ``Daemon book''. You need to read that!
meillo@42 142
meillo@42 143 foo
meillo@42 144
meillo@42 145 $ \f(CBrmm 1\fP
meillo@42 146
meillo@42 147 $ \f(CBscan\fP
meillo@42 148 2+ 2012-05-16 11:17 meillo@dream.home book
meillo@42 149
meillo@42 150 $
meillo@42 151 .DE
meillo@27 152
meillo@27 153
meillo@28 154 .H1 "nmh: Code and Community
meillo@2 155 .P
meillo@49 156 In order to understand the condition, goals and dynamics of a project,
meillo@49 157 one needs to know the reasons.
meillo@49 158 MH predates the Internet, it comes from times before networking was universal,
meillo@49 159 it comes from times when emailing was small, short and simple.
meillo@42 160 Then it grew, spread and adopted to the changes email went through.
meillo@49 161 Its core-concepts, however, remained the same.
meillo@49 162 During the Eighties students at UCI actively worked on MH.
meillo@49 163 They added new features and optimized the code for the then popular systems.
meillo@49 164 All this still was in times before POSIX and ANSI C.
meillo@49 165 As large parts of the code stem from this time, today's nmh source code
meillo@49 166 still contains many ancient parts.
meillo@49 167 BSD-specific code and constructs taylored for hardware of that time
meillo@49 168 are frequent.
meillo@2 169 .P
meillo@49 170 Nmh started about a decade after the POSIX and ANSI C standards had been
meillo@49 171 established. A more modern coding style entered the code base, but still
meillo@49 172 a part of the developers came from ``the old days''. The developer
meillo@49 173 base became more diverse and thus resulted in code of different style.
meillo@49 174 Programming practices from different decades merged in the project.
meillo@49 175 As several peers added code, the system became more a conclomeration
meillo@49 176 of single tools rather than a homogenic of-one-cast mail system.
meillo@49 177 Still, the existing basic concepts held it together.
meillo@8 178 They were mostly untouched throughout the years.
meillo@8 179 .P
meillo@49 180 Despite the toolchest approach at the surface \(en a collection
meillo@49 181 of separate small programs \(en on the source code level
meillo@49 182 it is much more interweaved.
meillo@49 183 Several separate components were compiled into one program
meillo@49 184 for effiency reasons.
meillo@8 185 This lead to intricate innards.
meillo@49 186 Unfortunately, the clear separation on the outside appeared as being
meillo@49 187 pretty interweaved inside.
meillo@8 188 .P
meillo@49 189 The advent of MIME rose the complexity of email by a magnitude.
meillo@49 190 This is visible in nmh. The MIME-related parts are the most complex ones.
meillo@49 191 It's also visible that MIME support had been added on top of the old MH core.
meillo@49 192 MH's toolchest style made this easily possible and encourages
meillo@49 193 such approaches, but unfortunately, it lead to duplicated functions
meillo@49 194 and half-hearted implementation of the concepts.
meillo@49 195 .P
meillo@49 196 To provide backward-compatibility, it is a common understanding to not
meillo@49 197 change the default settings.
meillo@47 198 In consequence, the user needs to activate modern features explicitely
meillo@47 199 to be able to use them.
meillo@49 200 This puts a burden on new users, because out-of-the-box nmh remains
meillo@49 201 in the same ancient style.
meillo@49 202 If nmh is seen to be a back-end, then this compatibility surely is important.
meillo@49 203 However, in the same go, new users have difficulties to use nmh for modern
meillo@49 204 emailing.
meillo@49 205 The small but matured community around nmh hardly needs much change
meillo@49 206 as they have their convenient setups since decades.
meillo@8 207
meillo@8 208
meillo@27 209 .H1 "mmh
meillo@28 210 .P
meillo@49 211 I started to work on my experimental version in October 2011,
meillo@49 212 when there were no more than three commits to nmh in the previous nine months..
meillo@42 213 In December, when I announced my work on the nmh-workers mailing list,
meillo@42 214 .[
meillo@42 215 nmh-workers mmh announce december
meillo@42 216 .]
meillo@49 217 the activity in nmh rose much.
meillo@42 218 Suddently the community started to move.
meillo@49 219 This movement was heavily pushed by Paul Vixie's ``edginess'' comment.
meillo@42 220 .[
meillo@42 221 nmh-workers vixie edginess
meillo@42 222 .]
meillo@42 223 After long years of much stagnation, nmh became actively developed again.
meillo@42 224 Hence, while I was working on mmh, the community was working on nmh,
meillo@42 225 in parallel.
meillo@28 226 .P
meillo@42 227 The name \fImmh\fP stands for \fImeillo's mail handler\fP,
meillo@42 228 because mmh is my own version of MH.
meillo@42 229 (My login name is \fImeillo\fP.)
meillo@42 230 The project follows my personal considerations and preferences.
meillo@42 231 By calling it a personal project, I don't need to justify my decisions,
meillo@49 232 though, still I like to do.
meillo@42 233 This enabled me to follow my vision staightly and thus produce
meillo@42 234 a result of greater pureness.
meillo@42 235 This project model was inspired by the window manager \fIdwm\fP,
meillo@42 236 which is Anselm Garbe's personal window manager \(en
meillo@42 237 targeted to satisfy Garbe's personal needs whenever conflicts appear.
meillo@42 238 dwm had remained much more focused on its original goals,
meillo@42 239 whereas its community-driven predecessor \fIwmii\fP had
meillo@49 240 grown big and lost it's lean elegance.
meillo@42 241 This should not happen to mmh.
meillo@42 242 .P
meillo@49 243 Mmh also stands for \fImodern mail handler\fP, and this is
meillo@49 244 the variant chosen to entitel this document. One main focus of the
meillo@42 245 project was to modernize nmh. Another main goal is resembled in the
meillo@42 246 name \fIminimized mail handler\fP: Drop any parts that don't add
meillo@49 247 to the main task of mmh, being a conceptionally appealing MUA.
meillo@42 248 .P
meillo@42 249 It should also be noted that \fLstrcmp("mmh","nmh")<0\fP is true.
meillo@42 250 Although mmh bases on nmh, it is likely seen as a step backward.
meillo@42 251 I agree.
meillo@42 252 However, this step backward actually is a step forward,
meillo@49 253 although in a different direction.
meillo@27 254
meillo@45 255
meillo@45 256 .H1 "This Thesis
meillo@45 257
meillo@27 258 .U2 "Motivation
meillo@27 259 .P
meillo@43 260 MH is the most important of very few command line toolchest email systems.
meillo@43 261 (There's also \fIim\fP by Tatsuya Kinoshita,
meillo@43 262 which operates on an MH mail storage.)
meillo@43 263 Toolchests are powerful because they can be perfectly automated and
meillo@43 264 extended. Toolchests are good back-ends for various sorts of front-ends.
meillo@43 265 They allow multiple front-ends for different special needs
meillo@43 266 to be implemented quickly and withough internal knowledge on emailing.
meillo@43 267 Further more, toolchests are much better to maintain than large monolithic
meillo@43 268 programs.
meillo@43 269 As there are few toolchests for emailing and MH-like ones are the most
meillo@43 270 popular amoung them, they should be developed further to keep their
meillo@43 271 conceptional elegance and unique scripting qualities available to users.
meillo@43 272 mmh will create a modern and convenient entry point for new, interested
meillo@43 273 users to MH-like systems.
meillo@43 274 .P
meillo@45 275 The mmh project is motivated by deficites of nmh and
meillo@45 276 my wish for general changes, combined
meillo@45 277 with the nmh community's reluctancy to change.
meillo@45 278 .P
meillo@45 279 nmh hadn't adjusted to modern emailing needs well enough.
meillo@45 280 The default setup was completely unusable for modern emailing.
meillo@45 281 Too much setup work was required.
meillo@45 282 Several modern features were already available but the community
meillo@45 283 didn't wanted to have them as default.
meillo@45 284 mmh is a way to change this.
meillo@45 285 .P
meillo@45 286 In my eyes, MH's concepts could be exploited even better and
meillo@45 287 the style of the tools could be improved. Both would simplify
meillo@45 288 and generalize the system, providing cleaner interfaces and more
meillo@45 289 software leverage, at the same time.
meillo@45 290 mmh is a way to demonstrate this.
meillo@45 291 .P
meillo@45 292 In providing several parts of an email system, nmh can hardly
meillo@45 293 compete with the large specialized projects that focus
meillo@45 294 on only one of the components.
meillo@45 295 The situation can be improved by concentrating the development power
meillo@45 296 on the most unique part of MH and letting the user pick his prefered
meillo@45 297 set of other mail components.
meillo@45 298 Today's pre-packaged software components encourage this model.
meillo@45 299 mmh is a way to go for this approach.
meillo@45 300 .P
meillo@43 301 It's worthwhile to fork nmh for the development of mmh, because
meillo@43 302 the two projects focus on different goals and differ in fundamental questions.
meillo@43 303 The nmh community's reluctance to change conflicts
meillo@43 304 with my strong will to change.
meillo@43 305 In developing a separate experimental version new approaches can
meillo@43 306 easily be tried out without the need to discuss changes beforehand.
meillo@43 307 In fact, revolutionary changes are hardly possible otherwise.
meillo@45 308 These reasons support the decision to start mmh as a fork of nmh.
meillo@43 309 .P
meillo@45 310 The mmh project provides the basis to implemented and demonstrated
meillo@45 311 the listed ideas without the need to change nmh or its community.
meillo@43 312 Of course, the results of the mmh project shall improve nmh, in the end.
meillo@27 313
meillo@27 314 .U2 "Target Field
meillo@27 315 .P
meillo@45 316 Any effort needs to be targeted towards a specific goal
meillo@45 317 in order to be successful.
meillo@45 318 Following is a description of the imagined typical mmh user.
meillo@45 319 mmh should satisfy his needs.
meillo@45 320 .P
meillo@43 321 The target user of mmh likes Unix and its philosophy.
meillo@27 322 He likes to use programs that are conceptionally appealing.
meillo@27 323 He's familiar with the command line and enjoys its power.
meillo@27 324 He is at least capable of shell scripting and wants to improve his
meillo@27 325 productivity by scripting the mail system.
meillo@43 326 He naturally uses modern email features, like attachments,
meillo@43 327 non-ASCII text, and digital cryptrography.
meillo@43 328 He is able to setup email system components besides mmh,
meillo@43 329 and actually likes the choice to pick the ones he preferes.
meillo@43 330 He has a reasonably modern system that complies to standards,
meillo@43 331 like POSIX and ANSI C.
meillo@27 332 .P
meillo@43 333 XXX common scenarios?
meillo@8 334 .P
meillo@45 335 General assumptions of the project are:
meillo@8 336 .BU
meillo@45 337 Elegance \(en being simplicity, clarity and generality \(en is most important.
meillo@8 338 .BU
meillo@45 339 Concepts are more important than concrete implementations.
meillo@8 340 .BU
meillo@45 341 Time and space optimizations are only useful if absolutely needed to make
meillo@45 342 the software usable.
meillo@8 343 .BU
meillo@45 344 Having a lot of choice is bad.
meillo@8 345
meillo@27 346 .U2 "Work to do
meillo@45 347 .P
meillo@45 348 The general goals for the mmh project are the following:
meillo@45 349 .BU
meillo@45 350 mmh should be perfectly suited for modern emailing, out-of-the-box.
meillo@45 351 This is a necessity to spread among new users.
meillo@45 352 .BU
meillo@45 353 The system shall be of-one-style. It should feel like cast as one.
meillo@45 354 .P
meillo@45 355 To do list:
meillo@8 356 .BU
meillo@27 357 Remove the MTA and MRA facilities. Mmh shall concentrate on the MUA
meillo@8 358 task. Mail shall enter mmh's mail storage via the system mail drop
meillo@8 359 and it shall leave mmh via the local \fLsendmail\fP command.
meillo@8 360 .BU
meillo@8 361 Remove any further functions that are not related to mmh's main task.
meillo@8 362 Bulletin board support is on example. Also remove support for ancient
meillo@8 363 technologies, like hardcopy terminals.
meillo@8 364 .BU
meillo@8 365 Refactor the source code to meet modern style criteria. Use
meillo@8 366 standardized library functions when possible.
meillo@8 367 .BU
meillo@8 368 Replace performance optimizations by clear and readable code.
meillo@8 369 .BU
meillo@8 370 Reduce the feature set to the commonly used one, removing
meillo@8 371 corner-cases. Set sane default values.
meillo@8 372 .BU
meillo@8 373 Add better attachment support. Add support for digital signatures and
meillo@8 374 encryption.
meillo@8 375 .BU
meillo@8 376 Merge \fLshow\fP and \fLmhshow\fP into one single mail display program.
meillo@8 377 Integrate MIME support deeper and more natural into MH.
meillo@8 378 .BU
meillo@8 379 Provide a ready-to-use setup out-of-the-box.
meillo@27 380
meillo@27 381 .U2 "Methods
meillo@27 382 .P
meillo@27 383 foo