docs/master

annotate ch01.roff @ 48:d28ff07dfc0f

Rework in the Intro, with new text.
author markus schnalke <meillo@marmaro.de>
date Sat, 19 May 2012 17:26:15 +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@8 156 In order to understand the state, goals and dynamics of a project,
meillo@42 157 one needs to know its history. MH predates the Internet,
meillo@42 158 it comes from times before networking was universal,
meillo@42 159 times when emailing was small, short and simple.
meillo@42 160 Then it grew, spread and adopted to the changes email went through.
meillo@42 161 The core-concepts, however, remained the same.
meillo@42 162 During the 80s a small group of students at the University of
meillo@8 163 California, actively worked on MH. They added features and optimized,
meillo@8 164 like it is common for scientific work. This is still in pre-ANSI C
meillo@8 165 times. The source code contains many ancient parts. Code constructs
meillo@8 166 specific to BSD or hardware of that time are usual.
meillo@2 167 .P
meillo@8 168 Nmh started eight years after the ANSI C standard had been
meillo@8 169 established. A more modern coding style entered the code base. Still
meillo@8 170 a part of the developers come from ``the old days''. The developer
meillo@42 171 base became more diverse and thus the code had different style.
meillo@42 172 Programming practices
meillo@8 173 from different decades merged into the project. Different coding
meillo@8 174 styles came together. It appears as if multiple peers added code
meillo@42 175 parts, resulting in a conclomeration rather than a homogenic
meillo@8 176 of-one-cast mail system. Still, the basic concepts hold it together.
meillo@8 177 They were mostly untouched throughout the years.
meillo@8 178 .P
meillo@8 179 Although, at the surface, nmh is a toolchest, meaning a collection
meillo@8 180 of completely modularized small programs, on the source code level,
meillo@8 181 it is much more interweaved. Parts of the basic functions are
meillo@8 182 collected in a MH standard library, which is good, but often
meillo@8 183 separate functions are compiled into programs, for effiency reasons.
meillo@8 184 This lead to intricate innards.
meillo@8 185 The advent of MIME rose the complexity of email by a magnitude. This
meillo@8 186 is visible in nmh. The MIME-related parts are the most complex ones.
meillo@8 187 It's also visible that MIME support had been added on top of the
meillo@32 188 old MH later. The MH style made this easily possible, but it
meillo@8 189 also lead to duplicated functions (e.g. \fLshow\fP, \fLmhshow\fP)
meillo@8 190 and had not been thoroughly included into the concepts (e.g. the
meillo@8 191 user-visible access to whole messages and MIME parts are inherently
meillo@8 192 different).
meillo@8 193 .P
meillo@47 194 For backward-compatibility's sake, it is a common understanding to have the
meillo@8 195 default settings to be compatible, requiring any new feature to be
meillo@47 196 explicitely enabled.
meillo@47 197 In consequence, the user needs to activate modern features explicitely
meillo@47 198 to be able to use them.
meillo@47 199 This puts a burden on new users, because nmh
meillo@8 200 out-of-the-box keeps staying in the same ancient style, where users
meillo@8 201 usually want to have it practical for modern emailing.
meillo@47 202 But of course, this depends if nmh is seen to be a front-end or a
meillo@8 203 back-end.
meillo@8 204
meillo@8 205
meillo@27 206 .H1 "mmh
meillo@28 207 .P
meillo@42 208 I started to work on my experimental version in Fall 2011.
meillo@42 209 In December, when I announced my work on the nmh-workers mailing list,
meillo@42 210 .[
meillo@42 211 nmh-workers mmh announce december
meillo@42 212 .]
meillo@42 213 the activity in nmh rose heavily.
meillo@42 214 Suddently the community started to move.
meillo@42 215 This movement was pushed much by Paul Vixie's ``edginess'' message.
meillo@42 216 .[
meillo@42 217 nmh-workers vixie edginess
meillo@42 218 .]
meillo@42 219 After long years of much stagnation, nmh became actively developed again.
meillo@42 220 Hence, while I was working on mmh, the community was working on nmh,
meillo@42 221 in parallel.
meillo@28 222 .P
meillo@42 223 The name \fImmh\fP stands for \fImeillo's mail handler\fP,
meillo@42 224 because mmh is my own version of MH.
meillo@42 225 (My login name is \fImeillo\fP.)
meillo@42 226 The project follows my personal considerations and preferences.
meillo@42 227 By calling it a personal project, I don't need to justify my decisions,
meillo@42 228 though, still I do.
meillo@42 229 This enabled me to follow my vision staightly and thus produce
meillo@42 230 a result of greater pureness.
meillo@42 231 This project model was inspired by the window manager \fIdwm\fP,
meillo@42 232 which is Anselm Garbe's personal window manager \(en
meillo@42 233 targeted to satisfy Garbe's personal needs whenever conflicts appear.
meillo@42 234 dwm had remained much more focused on its original goals,
meillo@42 235 whereas its community-driven predecessor \fIwmii\fP had
meillo@42 236 grown large and lost it's leanness.
meillo@42 237 This should not happen to mmh.
meillo@42 238 .P
meillo@47 239 Mmh can also stand for \fImodern mail handler\fP, and this is
meillo@42 240 the variant chosen as titel for this document. One main focus of the
meillo@42 241 project was to modernize nmh. Another main goal is resembled in the
meillo@42 242 name \fIminimized mail handler\fP: Drop any parts that don't add
meillo@42 243 to the main task of mmh, being a MUA.
meillo@42 244 .P
meillo@42 245 It should also be noted that \fLstrcmp("mmh","nmh")<0\fP is true.
meillo@42 246 Although mmh bases on nmh, it is likely seen as a step backward.
meillo@42 247 I agree.
meillo@42 248 However, this step backward actually is a step forward,
meillo@42 249 although in another direction.
meillo@27 250
meillo@45 251
meillo@45 252 .H1 "This Thesis
meillo@45 253
meillo@27 254 .U2 "Motivation
meillo@27 255 .P
meillo@43 256 MH is the most important of very few command line toolchest email systems.
meillo@43 257 (There's also \fIim\fP by Tatsuya Kinoshita,
meillo@43 258 which operates on an MH mail storage.)
meillo@43 259 Toolchests are powerful because they can be perfectly automated and
meillo@43 260 extended. Toolchests are good back-ends for various sorts of front-ends.
meillo@43 261 They allow multiple front-ends for different special needs
meillo@43 262 to be implemented quickly and withough internal knowledge on emailing.
meillo@43 263 Further more, toolchests are much better to maintain than large monolithic
meillo@43 264 programs.
meillo@43 265 As there are few toolchests for emailing and MH-like ones are the most
meillo@43 266 popular amoung them, they should be developed further to keep their
meillo@43 267 conceptional elegance and unique scripting qualities available to users.
meillo@43 268 mmh will create a modern and convenient entry point for new, interested
meillo@43 269 users to MH-like systems.
meillo@43 270 .P
meillo@45 271 The mmh project is motivated by deficites of nmh and
meillo@45 272 my wish for general changes, combined
meillo@45 273 with the nmh community's reluctancy to change.
meillo@45 274 .P
meillo@45 275 nmh hadn't adjusted to modern emailing needs well enough.
meillo@45 276 The default setup was completely unusable for modern emailing.
meillo@45 277 Too much setup work was required.
meillo@45 278 Several modern features were already available but the community
meillo@45 279 didn't wanted to have them as default.
meillo@45 280 mmh is a way to change this.
meillo@45 281 .P
meillo@45 282 In my eyes, MH's concepts could be exploited even better and
meillo@45 283 the style of the tools could be improved. Both would simplify
meillo@45 284 and generalize the system, providing cleaner interfaces and more
meillo@45 285 software leverage, at the same time.
meillo@45 286 mmh is a way to demonstrate this.
meillo@45 287 .P
meillo@45 288 In providing several parts of an email system, nmh can hardly
meillo@45 289 compete with the large specialized projects that focus
meillo@45 290 on only one of the components.
meillo@45 291 The situation can be improved by concentrating the development power
meillo@45 292 on the most unique part of MH and letting the user pick his prefered
meillo@45 293 set of other mail components.
meillo@45 294 Today's pre-packaged software components encourage this model.
meillo@45 295 mmh is a way to go for this approach.
meillo@45 296 .P
meillo@43 297 It's worthwhile to fork nmh for the development of mmh, because
meillo@43 298 the two projects focus on different goals and differ in fundamental questions.
meillo@43 299 The nmh community's reluctance to change conflicts
meillo@43 300 with my strong will to change.
meillo@43 301 In developing a separate experimental version new approaches can
meillo@43 302 easily be tried out without the need to discuss changes beforehand.
meillo@43 303 In fact, revolutionary changes are hardly possible otherwise.
meillo@45 304 These reasons support the decision to start mmh as a fork of nmh.
meillo@43 305 .P
meillo@45 306 The mmh project provides the basis to implemented and demonstrated
meillo@45 307 the listed ideas without the need to change nmh or its community.
meillo@43 308 Of course, the results of the mmh project shall improve nmh, in the end.
meillo@27 309
meillo@27 310 .U2 "Target Field
meillo@27 311 .P
meillo@45 312 Any effort needs to be targeted towards a specific goal
meillo@45 313 in order to be successful.
meillo@45 314 Following is a description of the imagined typical mmh user.
meillo@45 315 mmh should satisfy his needs.
meillo@48 316 Actually, as mmh is my personal version of MH, this is a description
meillo@48 317 of myself.
meillo@45 318 .P
meillo@43 319 The target user of mmh likes Unix and its philosophy.
meillo@27 320 He likes to use programs that are conceptionally appealing.
meillo@27 321 He's familiar with the command line and enjoys its power.
meillo@27 322 He is at least capable of shell scripting and wants to improve his
meillo@27 323 productivity by scripting the mail system.
meillo@43 324 He naturally uses modern email features, like attachments,
meillo@43 325 non-ASCII text, and digital cryptrography.
meillo@43 326 He is able to setup email system components besides mmh,
meillo@43 327 and actually likes the choice to pick the ones he preferes.
meillo@43 328 He has a reasonably modern system that complies to standards,
meillo@43 329 like POSIX and ANSI C.
meillo@27 330 .P
meillo@48 331 The typical user invokes mmh commands directly in an interactive
meillo@48 332 shell session, but as well, he uses them to automate mail handling tasks.
meillo@48 333 Likely, he runs his mail setup on a server machine, to which he connects
meillo@48 334 via ssh. He might also have local mmh installations on his workstations,
meillo@48 335 but does rather not rely on graphical frontends. He definitely wants
meillo@48 336 to be flexible and thus be able to change his setup to suite his needs.
meillo@8 337 .P
meillo@48 338 The typical mmh user is a programmer himself.
meillo@48 339 He likes to, occasionally, take the opportunity of Free Software to put
meillo@48 340 hands on and get involved in the software he uses.
meillo@48 341 Hence, he likes small and clean code bases and he cares for code quality.
meillo@48 342 In general, he believes that:
meillo@8 343 .BU
meillo@48 344 Elegance \(en i.e. simplicity, clarity and generality \(en
meillo@48 345 is most important.
meillo@8 346 .BU
meillo@48 347 Concepts are more important than the concrete implementation.
meillo@8 348 .BU
meillo@48 349 Code optimizations for anything but readability should be avoided
meillo@48 350 if possible.
meillo@8 351 .BU
meillo@45 352 Having a lot of choice is bad.
meillo@48 353 .BU
meillo@48 354 Removed code is debugged code.
meillo@8 355
meillo@48 356 .U2 "Goals
meillo@45 357 .P
meillo@45 358 The general goals for the mmh project are the following:
meillo@48 359 .IP "Stream-lining
meillo@48 360 Mmh should be stripped down to its core, which is the MUA part of emailing.
meillo@48 361 The feature set should be distilled to the ones really needed,
meillo@48 362 effectively removing corner-cases.
meillo@48 363 Functions that are not related to the main task should be removed.
meillo@48 364 This includes, the MTA and MRA facilities.
meillo@48 365 Choice should be reduced to the main options.
meillo@48 366 .IP "Modernizing
meillo@48 367 Mmh's feature set needs to become more modern.
meillo@48 368 Better support for attachment and digital cryptography needs to be added.
meillo@48 369 MIME support needs to be integrated deeper and more naturally.
meillo@48 370 The modern email features need to be readily available, out-of-the-box.
meillo@48 371 And on the other hand,
meillo@48 372 bulletin board support and similar obsolete facilities need to be dropped
meillo@48 373 out.
meillo@48 374 Likewise, ancient technologies, like hardcopy terminals, should not
meillo@48 375 be supported any further.
meillo@48 376 .IP "Code style
meillo@48 377 Mmh's source code needs to be updated to modern standards.
meillo@48 378 Standardized library functions should replace non-standard versions
meillo@48 379 whenever possible.
meillo@48 380 Code should be separated into distinct modules when possible.
meillo@48 381 Time and space optimizations should to be replaced by
meillo@48 382 clear and readable code.
meillo@48 383 A uniform programming style should prevail.
meillo@48 384 .IP "Homogenity
meillo@48 385 The available concepts need to be expanded as far as possible.
meillo@48 386 A small set of concepts should prevail thoroughly throughout the system.
meillo@48 387 The whole system should appear to be of-one-style.
meillo@48 388 It should feel like being cast as one.