annotate @ 44:46e34e433231

moved bibliography to external file
date Sat, 10 Apr 2010 15:00:38 +0200
parents 303e8f449e77
children ade392f024aa
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meillo@0 4 .de CW
meillo@0 5 .nr PQ \\n(.f
meillo@0 6 .if t .ft CW
meillo@17 7 .ie ^\\$1^^ .if n .ul 999
meillo@0 8 .el .if n .ul 1
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meillo@0 10 .if n .if \\n(.$=1 \&\\$1
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meillo@0 13 ..
meillo@0 14 .ds [. \ [
meillo@0 15 .ds .] ]
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meillo@42 17 .rn NH _N
meillo@42 18 .de NH
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meillo@42 23 ..
meillo@42 24
meillo@1 25 .\"----------------------------------------
meillo@42 26
meillo@0 27 .TL
meillo@42 28 .ps +4
meillo@6 29 Why the Unix Philosophy still matters
meillo@0 30 .AU
meillo@0 31 markus schnalke <>
meillo@0 32 .AB
meillo@1 33 .ti \n(.iu
meillo@39 34 This paper explains the importance of the Unix Philosophy for software design.
meillo@0 35 Today, few software designers are aware of these concepts,
meillo@39 36 and thus a lot of modern software is more limited than necessary
meillo@39 37 and makes less use of software leverage than possible.
meillo@38 38 Knowing and following the guidelines of the Unix Philosophy makes software more valuable.
meillo@0 39 .AE
meillo@0 40
meillo@2 41 .FS
meillo@2 42 .ps -1
meillo@39 43 This paper was prepared for the ``Software Analysis'' seminar at University Ulm.
meillo@39 44 Mentor was professor Schweiggert. 2010-04-05
meillo@2 45 .br
meillo@39 46 You may retrieve this document from
meillo@39 47 .CW \s-1 \ .
meillo@2 48 .FE
meillo@2 49
meillo@0 50 .NH 1
meillo@0 51 Introduction
meillo@42 52 .XS
meillo@42 53 \*(SN Introduction
meillo@42 54 .XE
meillo@0 55 .LP
meillo@40 56 The Unix Philosophy is the essence of how the Unix operating system,
meillo@40 57 especially its toolchest, was designed.
meillo@40 58 It is no limited set of fixed rules,
meillo@40 59 but a loose set of guidelines which tell how to write software that
meillo@40 60 suites well into Unix.
meillo@40 61 Actually, the Unix Philosophy describes what is common to typical Unix software.
meillo@40 62 The Wikipedia has an accurate definition:
meillo@40 63 .[
meillo@44 64 wikipedia
meillo@44 65 unix philosophy
meillo@40 66 .]
meillo@40 67 .QP
meillo@41 68 .ps -1
meillo@40 69 The \fIUnix philosophy\fP is a set of cultural norms and philosophical
meillo@40 70 approaches to developing software based on the experience of leading
meillo@40 71 developers of the Unix operating system.
meillo@1 72 .PP
meillo@40 73 As there is no single definition of the Unix Philosophy,
meillo@40 74 several people have stated their view on what it comprises.
meillo@1 75 Best known are:
meillo@1 76 .IP \(bu
meillo@1 77 Doug McIlroy's summary: ``Write programs that do one thing and do it well.''
meillo@1 78 .[
meillo@44 79 mahoney
meillo@44 80 oral history
meillo@1 81 .]
meillo@1 82 .IP \(bu
meillo@1 83 Mike Gancarz' book ``The UNIX Philosophy''.
meillo@1 84 .[
meillo@44 85 gancarz
meillo@44 86 unix philosophy
meillo@1 87 .]
meillo@1 88 .IP \(bu
meillo@1 89 Eric S. Raymond's book ``The Art of UNIX Programming''.
meillo@1 90 .[
meillo@44 91 raymond
meillo@44 92 art of unix programming
meillo@1 93 .]
meillo@0 94 .LP
meillo@1 95 These different views on the Unix Philosophy have much in common.
meillo@40 96 Especially, the main concepts are similar in all of them.
meillo@40 97 McIlroy's definition can surely be called the core of the Unix Philosophy,
meillo@40 98 but the fundamental idea behind it all, is ``small is beautiful''.
meillo@40 99
meillo@40 100 .PP
meillo@40 101 The Unix Philosophy tells how to design and write good software for Unix.
meillo@40 102 Many concepts described here base on facilities of Unix.
meillo@40 103 Other operating systems may not offer such facilities,
meillo@41 104 hence it may not be possible to design software in the way of the
meillo@41 105 Unix Philosophy for them.
meillo@40 106 .PP
meillo@41 107 The Unix Philosophy has an idea of how the process of software development
meillo@41 108 should look like, but large parts of the philosophy are quite independent
meillo@41 109 from the development process used.
meillo@41 110 However, one will soon recognize that some development processes work well
meillo@41 111 with the ideas of the Unix Philosophy and support them, while others are
meillo@41 112 at cross-purposes.
meillo@41 113 Kent Beck's books about Extreme Programming are valuable supplimental
meillo@41 114 resources.
meillo@1 115 .PP
meillo@41 116 The question of how to actually write code and how the code should looks
meillo@41 117 like internally, are out of focus here.
meillo@41 118 ``The Practice of Programming'' by Kernighan and Pike,
meillo@41 119 .[
meillo@44 120 kernighan pike
meillo@44 121 practice of programming
meillo@41 122 .]
meillo@41 123 is a good book that covers this topic.
meillo@41 124 Its point of view matches to the one of this paper.
meillo@0 125
meillo@0 126 .NH 1
meillo@6 127 Importance of software design in general
meillo@42 128 .XS
meillo@42 129 .sp .5v
meillo@42 130 \*(SN Importance of software design in general
meillo@42 131 .XE
meillo@0 132 .LP
meillo@40 133 Software design is the planning of how the internal structure
meillo@40 134 and external interfaces of a software should look like.
meillo@39 135 It has nothing to do with visual appearance.
meillo@39 136 If we take a program as a car, then its color is of no matter.
meillo@39 137 Its design would be the car's size, its shape, the locations of doors,
meillo@39 138 the passenger/space ratio, the luggage capacity, and so forth.
meillo@39 139 .PP
meillo@39 140 Why should software get designed at all?
meillo@6 141 It is general knowledge, that even a bad plan is better than no plan.
meillo@39 142 Not designing software means programming without plan.
meillo@39 143 This will pretty sure lead to horrible results.
meillo@39 144 Horrible to use and horrible to maintain.
meillo@39 145 These two aspects are the visible ones.
meillo@39 146 Often invisible are the wasted possible gains.
meillo@39 147 Good software design can make these gains available.
meillo@2 148 .PP
meillo@39 149 A software's design deals with quality properties.
meillo@39 150 Good design leads to good quality, and quality is important.
meillo@39 151 Any car may be able to drive from A to B,
meillo@39 152 but it depends on the car's properties whether it is a good choice
meillo@39 153 for passenger transport or not.
meillo@39 154 It depends on its properties if it is a good choice
meillo@39 155 for a rough mountain area.
meillo@39 156 And it depends on its properties if the ride will be fun.
meillo@39 157
meillo@2 158 .PP
meillo@39 159 Requirements for a software are twofold:
meillo@39 160 functional and non-functional.
meillo@39 161 .IP \(bu
meillo@39 162 Functional requirements define directly the software's functions.
meillo@39 163 They are the reason why software gets written.
meillo@39 164 Someone has a problem and needs a tool to solve it.
meillo@39 165 Being able to solve the problem is the main functional goal.
meillo@39 166 It is the driving force behind all programming effort.
meillo@39 167 Functional requirements are easier to define and to verify.
meillo@39 168 .IP \(bu
meillo@39 169 Non-functional requirements are also called \fIquality\fP requirements.
meillo@39 170 The quality of a software are the properties that are not directly related to
meillo@39 171 the software's basic functions.
meillo@39 172 Tools of bad quality often solve the problems they were written for,
meillo@39 173 but introduce problems and difficulties for usage and development, later on.
meillo@39 174 Quality aspects are often overlooked at first sight,
meillo@39 175 and they are often difficult to define clearly and to verify.
meillo@2 176 .PP
meillo@39 177 Quality is of few matter when the software gets built initially,
meillo@39 178 but it is of matter for usage and maintenance of the software.
meillo@6 179 A short-sighted might see in developing a software mainly building something up.
meillo@39 180 But experience shows, that building the software the first time is
meillo@39 181 only a small amount of the overall work.
meillo@39 182 Bug fixing, extending, rebuilding of parts
meillo@39 183 \(en maintenance work, for short \(en
meillo@6 184 does soon take over the major part of the time spent on a software.
meillo@6 185 Not to forget the usage of the software.
meillo@6 186 These processes are highly influenced by the software's quality.
meillo@39 187 Thus, quality must not be neglected.
meillo@39 188 The problem with quality is that you hardly ``stumble over''
meillo@39 189 bad quality during the first build,
meillo@6 190 but this is the time when you should care about good quality most.
meillo@6 191 .PP
meillo@39 192 Software design is less the basic function of a software \(en
meillo@39 193 this requirement will get satisfied anyway.
meillo@39 194 Software design is more about quality aspects of the software.
meillo@39 195 Good design leads to good quality, bad design to bad quality.
meillo@6 196 The primary functions of the software will be affected modestly by bad quality,
meillo@39 197 but good quality can provide a lot of additional gain,
meillo@6 198 even at places where one never expected it.
meillo@6 199 .PP
meillo@6 200 The ISO/IEC 9126-1 standard, part 1,
meillo@6 201 .[
meillo@44 202 iso product quality
meillo@6 203 .]
meillo@6 204 defines the quality model as consisting out of:
meillo@6 205 .IP \(bu
meillo@6 206 .I Functionality
meillo@6 207 (suitability, accuracy, inter\%operability, security)
meillo@6 208 .IP \(bu
meillo@6 209 .I Reliability
meillo@6 210 (maturity, fault tolerance, recoverability)
meillo@6 211 .IP \(bu
meillo@6 212 .I Usability
meillo@6 213 (understandability, learnability, operability, attractiveness)
meillo@6 214 .IP \(bu
meillo@6 215 .I Efficiency
meillo@9 216 (time behavior, resource utilization)
meillo@6 217 .IP \(bu
meillo@6 218 .I Maintainability
meillo@23 219 (analyzability, changeability, stability, testability)
meillo@6 220 .IP \(bu
meillo@6 221 .I Portability
meillo@6 222 (adaptability, installability, co-existence, replaceability)
meillo@6 223 .LP
meillo@39 224 Good design can improve these properties of a software,
meillo@39 225 bad designed software probably suffers from not having them.
meillo@7 226 .PP
meillo@7 227 One further goal of software design is consistency.
meillo@7 228 Consistency eases understanding, working on, and using things.
meillo@39 229 Consistent internal structure and consistent interfaces to the outside
meillo@39 230 can be provided by good design.
meillo@7 231 .PP
meillo@39 232 Software should be well designed because good design avoids many
meillo@39 233 problems during the software's lifetime.
meillo@39 234 And software should be well designed because good design can offer
meillo@39 235 much additional gain.
meillo@39 236 Indeed, much effort should be spent into good design to make software more valuable.
meillo@39 237 The Unix Philosophy shows a way of how to design software well.
meillo@7 238 It offers guidelines to achieve good quality and high gain for the effort spent.
meillo@0 239
meillo@0 240
meillo@0 241 .NH 1
meillo@0 242 The Unix Philosophy
meillo@42 243 .XS
meillo@42 244 .sp .5v
meillo@42 245 \*(SN The Unix Philosophy
meillo@42 246 .XE
meillo@4 247 .LP
meillo@4 248 The origins of the Unix Philosophy were already introduced.
meillo@8 249 This chapter explains the philosophy, oriented on Gancarz,
meillo@8 250 and shows concrete examples of its application.
meillo@5 251
meillo@16 252 .NH 2
meillo@14 253 Pipes
meillo@42 254 .XS
meillo@42 255 \*(SN Pipes
meillo@42 256 .XE
meillo@4 257 .LP
meillo@4 258 Following are some examples to demonstrate how applied Unix Philosophy feels like.
meillo@4 259 Knowledge of using the Unix shell is assumed.
meillo@4 260 .PP
meillo@4 261 Counting the number of files in the current directory:
meillo@41 262 .DS
meillo@4 263 .CW
meillo@9 264 .ps -1
meillo@4 265 ls | wc -l
meillo@4 266 .DE
meillo@4 267 The
meillo@4 268 .CW ls
meillo@4 269 command lists all files in the current directory, one per line,
meillo@4 270 and
meillo@4 271 .CW "wc -l
meillo@8 272 counts the number of lines.
meillo@4 273 .PP
meillo@8 274 Counting the number of files that do not contain ``foo'' in their name:
meillo@41 275 .DS
meillo@4 276 .CW
meillo@9 277 .ps -1
meillo@4 278 ls | grep -v foo | wc -l
meillo@4 279 .DE
meillo@4 280 Here, the list of files is filtered by
meillo@4 281 .CW grep
meillo@4 282 to remove all that contain ``foo''.
meillo@4 283 The rest is the same as in the previous example.
meillo@4 284 .PP
meillo@4 285 Finding the five largest entries in the current directory.
meillo@41 286 .DS
meillo@4 287 .CW
meillo@9 288 .ps -1
meillo@4 289 du -s * | sort -nr | sed 5q
meillo@4 290 .DE
meillo@4 291 .CW "du -s *
meillo@4 292 returns the recursively summed sizes of all files
meillo@8 293 \(en no matter if they are regular files or directories.
meillo@4 294 .CW "sort -nr
meillo@4 295 sorts the list numerically in reverse order.
meillo@4 296 Finally,
meillo@4 297 .CW "sed 5q
meillo@4 298 quits after it has printed the fifth line.
meillo@4 299 .PP
meillo@4 300 The presented command lines are examples of what Unix people would use
meillo@4 301 to get the desired output.
meillo@4 302 There are also other ways to get the same output.
meillo@4 303 It's a user's decision which way to go.
meillo@14 304 .PP
meillo@8 305 The examples show that many tasks on a Unix system
meillo@4 306 are accomplished by combining several small programs.
meillo@4 307 The connection between the single programs is denoted by the pipe operator `|'.
meillo@4 308 .PP
meillo@4 309 Pipes, and their extensive and easy use, are one of the great
meillo@4 310 achievements of the Unix system.
meillo@4 311 Pipes between programs have been possible in earlier operating systems,
meillo@4 312 but it has never been a so central part of the concept.
meillo@4 313 When, in the early seventies, Doug McIlroy introduced pipes for the
meillo@4 314 Unix system,
meillo@4 315 ``it was this concept and notation for linking several programs together
meillo@4 316 that transformed Unix from a basic file-sharing system to an entirely new way of computing.''
meillo@4 317 .[
meillo@44 318 aughenbaugh
meillo@44 319 unix oral history
meillo@4 320 .]
meillo@4 321 .PP
meillo@4 322 Being able to specify pipelines in an easy way is,
meillo@4 323 however, not enough by itself.
meillo@5 324 It is only one half.
meillo@4 325 The other is the design of the programs that are used in the pipeline.
meillo@8 326 They have to interfaces that allows them to be used in such a way.
meillo@5 327
meillo@16 328 .NH 2
meillo@14 329 Interface design
meillo@42 330 .XS
meillo@42 331 \*(SN Interface design
meillo@42 332 .XE
meillo@5 333 .LP
meillo@11 334 Unix is, first of all, simple \(en Everything is a file.
meillo@5 335 Files are sequences of bytes, without any special structure.
meillo@5 336 Programs should be filters, which read a stream of bytes from ``standard input'' (stdin)
meillo@5 337 and write a stream of bytes to ``standard output'' (stdout).
meillo@5 338 .PP
meillo@8 339 If the files \fIare\fP sequences of bytes,
meillo@8 340 and the programs \fIare\fP filters on byte streams,
meillo@11 341 then there is exactly one standardized data interface.
meillo@5 342 Thus it is possible to combine them in any desired way.
meillo@5 343 .PP
meillo@5 344 Even a handful of small programs will yield a large set of combinations,
meillo@5 345 and thus a large set of different functions.
meillo@5 346 This is leverage!
meillo@5 347 If the programs are orthogonal to each other \(en the best case \(en
meillo@5 348 then the set of different functions is greatest.
meillo@5 349 .PP
meillo@11 350 Programs might also have a separate control interface,
meillo@11 351 besides their data interface.
meillo@11 352 The control interface is often called ``user interface'',
meillo@11 353 because it is usually designed to be used by humans.
meillo@11 354 The Unix Philosophy discourages to assume the user to be human.
meillo@11 355 Interactive use of software is slow use of software,
meillo@11 356 because the program waits for user input most of the time.
meillo@11 357 Interactive software requires the user to be in front of the computer
meillo@11 358 all the time.
meillo@11 359 Interactive software occupy the user's attention while they are running.
meillo@11 360 .PP
meillo@11 361 Now we come back to the idea of using several small programs, combined,
meillo@11 362 to have a more specific function.
meillo@11 363 If these single tools would all be interactive,
meillo@11 364 how would the user control them?
meillo@11 365 It is not only a problem to control several programs at once if they run at the same time,
meillo@11 366 it also very inefficient to have to control each of the single programs
meillo@11 367 that are intended to work as one large program.
meillo@11 368 Hence, the Unix Philosophy discourages programs to demand interactive use.
meillo@11 369 The behavior of programs should be defined at invocation.
meillo@11 370 This is done by specifying arguments (``command line switches'') to the program call.
meillo@11 371 Gancarz discusses this topic as ``avoid captive user interfaces''.
meillo@11 372 .[
meillo@44 373 gancarz unix philosophy
meillo@11 374 %P 88 ff.
meillo@11 375 .]
meillo@44 376 .ds _p ", p. 88 ff.
meillo@11 377 .PP
meillo@11 378 Non-interactive use is, during development, also an advantage for testing.
meillo@11 379 Testing of interactive programs is much more complicated,
meillo@11 380 than testing of non-interactive programs.
meillo@5 381
meillo@16 382 .NH 2
meillo@8 383 The toolchest approach
meillo@42 384 .XS
meillo@42 385 \*(SN The toolchest approach
meillo@42 386 .XE
meillo@5 387 .LP
meillo@5 388 A toolchest is a set of tools.
meillo@5 389 Instead of having one big tool for all tasks, one has many small tools,
meillo@5 390 each for one task.
meillo@5 391 Difficult tasks are solved by combining several of the small, simple tools.
meillo@5 392 .PP
meillo@11 393 The Unix toolchest \fIis\fP a set of small, (mostly) non-interactive programs
meillo@11 394 that are filters on byte streams.
meillo@11 395 They are, to a large extend, unrelated in their function.
meillo@11 396 Hence, the Unix toolchest provides a large set of functions
meillo@11 397 that can be accessed by combining the programs in the desired way.
meillo@11 398 .PP
meillo@11 399 There are also advantages for developing small toolchest programs.
meillo@5 400 It is easier and less error-prone to write small programs.
meillo@5 401 It is also easier and less error-prone to write a large set of small programs,
meillo@5 402 than to write one large program with all the functionality included.
meillo@5 403 If the small programs are combinable, then they offer even a larger set
meillo@5 404 of functions than the single large program.
meillo@5 405 Hence, one gets two advantages out of writing small, combinable programs.
meillo@5 406 .PP
meillo@5 407 There are two drawbacks of the toolchest approach.
meillo@8 408 First, one simple, standardized, unidirectional interface has to be sufficient.
meillo@5 409 If one feels the need for more ``logic'' than a stream of bytes,
meillo@8 410 then a different approach might be of need.
meillo@13 411 But it is also possible, that he just can not imagine a design where
meillo@8 412 a stream of bytes is sufficient.
meillo@8 413 By becoming more familiar with the ``Unix style of thinking'',
meillo@8 414 developers will more often and easier find simple designs where
meillo@8 415 a stream of bytes is a sufficient interface.
meillo@8 416 .PP
meillo@8 417 The second drawback of a toolchest affects the users.
meillo@5 418 A toolchest is often more difficult to use for novices.
meillo@9 419 It is necessary to become familiar with each of the tools,
meillo@5 420 to be able to use the right one in a given situation.
meillo@9 421 Additionally, one needs to combine the tools in a senseful way on its own.
meillo@9 422 This is like a sharp knife \(en it is a powerful tool in the hand of a master,
meillo@5 423 but of no good value in the hand of an unskilled.
meillo@5 424 .PP
meillo@8 425 However, learning single, small tool of the toolchest is easier than
meillo@8 426 learning a complex tool.
meillo@8 427 The user will have a basic understanding of a yet unknown tool,
meillo@8 428 if the several tools of the toolchest have a common style.
meillo@8 429 He will be able to transfer knowledge over one tool to another.
meillo@8 430 .PP
meillo@8 431 Moreover, the second drawback can be removed easily by adding wrappers
meillo@8 432 around the single tools.
meillo@5 433 Novice users do not need to learn several tools if a professional wraps
meillo@8 434 the single commands into a more high-level script.
meillo@5 435 Note that the wrapper script still calls the small tools;
meillo@5 436 the wrapper script is just like a skin around.
meillo@8 437 No complexity is added this way,
meillo@8 438 but new programs can get created out of existing one with very low effort.
meillo@5 439 .PP
meillo@5 440 A wrapper script for finding the five largest entries in the current directory
meillo@5 441 could look like this:
meillo@41 442 .DS
meillo@5 443 .CW
meillo@9 444 .ps -1
meillo@5 445 #!/bin/sh
meillo@5 446 du -s * | sort -nr | sed 5q
meillo@5 447 .DE
meillo@5 448 The script itself is just a text file that calls the command line
meillo@5 449 a professional user would type in directly.
meillo@8 450 Making the program flexible on the number of entries it prints,
meillo@8 451 is easily possible:
meillo@41 452 .DS
meillo@8 453 .CW
meillo@9 454 .ps -1
meillo@8 455 #!/bin/sh
meillo@8 456 num=5
meillo@8 457 [ $# -eq 1 ] && num="$1"
meillo@8 458 du -sh * | sort -nr | sed "${num}q"
meillo@8 459 .DE
meillo@8 460 This script acts like the one before, when called without an argument.
meillo@8 461 But one can also specify a numerical argument to define the number of lines to print.
meillo@5 462
meillo@16 463 .NH 2
meillo@8 464 A powerful shell
meillo@42 465 .XS
meillo@42 466 \*(SN A powerful shell
meillo@42 467 .XE
meillo@8 468 .LP
meillo@10 469 It was already said, that the Unix shell provides the possibility to
meillo@10 470 combine small programs into large ones easily.
meillo@10 471 A powerful shell is a great feature in other ways, too.
meillo@8 472 .PP
meillo@10 473 For instance by including a scripting language.
meillo@10 474 The control statements are build into the shell.
meillo@8 475 The functions, however, are the normal programs, everyone can use on the system.
meillo@10 476 Thus, the programs are known, so learning to program in the shell is easy.
meillo@8 477 Using normal programs as functions in the shell programming language
meillo@10 478 is only possible because they are small and combinable tools in a toolchest style.
meillo@8 479 .PP
meillo@8 480 The Unix shell encourages to write small scripts out of other programs,
meillo@8 481 because it is so easy to do.
meillo@8 482 This is a great step towards automation.
meillo@8 483 It is wonderful if the effort to automate a task equals the effort
meillo@8 484 it takes to do it the second time by hand.
meillo@8 485 If it is so, then the user will be happy to automate everything he does more than once.
meillo@8 486 .PP
meillo@8 487 Small programs that do one job well, standardized interfaces between them,
meillo@8 488 a mechanism to combine parts to larger parts, and an easy way to automate tasks,
meillo@8 489 this will inevitably produce software leverage.
meillo@8 490 Getting multiple times the benefit of an investment is a great offer.
meillo@10 491 .PP
meillo@10 492 The shell also encourages rapid prototyping.
meillo@10 493 Many well known programs started as quickly hacked shell scripts,
meillo@10 494 and turned into ``real'' programs, written in C, later.
meillo@10 495 Building a prototype first is a way to avoid the biggest problems
meillo@10 496 in application development.
meillo@10 497 Fred Brooks writes in ``No Silver Bullet'':
meillo@10 498 .[
meillo@44 499 brooks
meillo@44 500 no silver bullet
meillo@10 501 .]
meillo@10 502 .QP
meillo@41 503 .ps -1
meillo@10 504 The hardest single part of building a software system is deciding precisely what to build.
meillo@10 505 No other part of the conceptual work is so difficult as establishing the detailed
meillo@10 506 technical requirements, [...].
meillo@10 507 No other part of the work so cripples the resulting system if done wrong.
meillo@10 508 No other part is more difficult to rectify later.
meillo@10 509 .PP
meillo@10 510 Writing a prototype is a great method to become familiar with the requirements
meillo@10 511 and to actually run into real problems.
meillo@10 512 Today, prototyping is often seen as a first step in building a software.
meillo@10 513 This is, of course, good.
meillo@10 514 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping:
meillo@10 515 After having built the prototype, one might notice, that the prototype is already
meillo@10 516 \fIgood enough\fP.
meillo@10 517 Hence, no reimplementation, in a more sophisticated programming language, might be of need,
meillo@10 518 for the moment.
meillo@23 519 Maybe later, it might be necessary to rewrite the software, but not now.
meillo@10 520 .PP
meillo@10 521 By delaying further work, one keeps the flexibility to react easily on
meillo@10 522 changing requirements.
meillo@10 523 Software parts that are not written will not miss the requirements.
meillo@10 524
meillo@16 525 .NH 2
meillo@10 526 Worse is better
meillo@42 527 .XS
meillo@42 528 \*(SN Worse is better
meillo@42 529 .XE
meillo@10 530 .LP
meillo@10 531 The Unix Philosophy aims for the 80% solution;
meillo@10 532 others call it the ``Worse is better'' approach.
meillo@10 533 .PP
meillo@10 534 First, practical experience shows, that it is almost never possible to define the
meillo@10 535 requirements completely and correctly the first time.
meillo@10 536 Hence one should not try to; it will fail anyway.
meillo@10 537 Second, practical experience shows, that requirements change during time.
meillo@10 538 Hence it is best to delay requirement-based design decisions as long as possible.
meillo@10 539 Also, the software should be small and flexible as long as possible
meillo@10 540 to react on changing requirements.
meillo@10 541 Shell scripts, for example, are more easily adjusted as C programs.
meillo@10 542 Third, practical experience shows, that maintenance is hard work.
meillo@10 543 Hence, one should keep the amount of software as small as possible;
meillo@10 544 it should just fulfill the \fIcurrent\fP requirements.
meillo@10 545 Software parts that will be written later, do not need maintenance now.
meillo@10 546 .PP
meillo@10 547 Starting with a prototype in a scripting language has several advantages:
meillo@10 548 .IP \(bu
meillo@10 549 As the initial effort is low, one will likely start right away.
meillo@10 550 .IP \(bu
meillo@10 551 As working parts are available soon, the real requirements can get identified soon.
meillo@10 552 .IP \(bu
meillo@10 553 When a software is usable, it gets used, and thus tested.
meillo@10 554 Hence problems will be found at early stages of the development.
meillo@10 555 .IP \(bu
meillo@10 556 The prototype might be enough for the moment,
meillo@10 557 thus further work on the software can be delayed to a time
meillo@10 558 when one knows better about the requirements and problems,
meillo@10 559 than now.
meillo@10 560 .IP \(bu
meillo@10 561 Implementing now only the parts that are actually needed now,
meillo@10 562 requires fewer maintenance work.
meillo@10 563 .IP \(bu
meillo@10 564 If the global situation changes so that the software is not needed anymore,
meillo@10 565 then less effort was spent into the project, than it would have be
meillo@10 566 when a different approach had been used.
meillo@10 567
meillo@16 568 .NH 2
meillo@11 569 Upgrowth and survival of software
meillo@42 570 .XS
meillo@42 571 \*(SN Upgrowth and survival of software
meillo@42 572 .XE
meillo@11 573 .LP
meillo@12 574 So far it was talked about \fIwriting\fP or \fIbuilding\fP software.
meillo@13 575 Although these are just verbs, they do imply a specific view on the work process
meillo@13 576 they describe.
meillo@12 577 The better verb, however, is to \fIgrow\fP.
meillo@12 578 .PP
meillo@12 579 Creating software in the sense of the Unix Philosophy is an incremental process.
meillo@12 580 It starts with a first prototype, which evolves as requirements change.
meillo@12 581 A quickly hacked shell script might become a large, sophisticated,
meillo@13 582 compiled program this way.
meillo@13 583 Its lifetime begins with the initial prototype and ends when the software is not used anymore.
meillo@13 584 While being alive it will get extended, rearranged, rebuilt (from scratch).
meillo@12 585 Growing software matches the view that ``software is never finished. It is only released.''
meillo@12 586 .[
meillo@44 587 gancarz
meillo@44 588 unix philosophy
meillo@13 589 %P 26
meillo@12 590 .]
meillo@12 591 .PP
meillo@13 592 Software can be seen as being controlled by evolutionary processes.
meillo@13 593 Successful software is software that is used by many for a long time.
meillo@12 594 This implies that the software is needed, useful, and better than alternatives.
meillo@12 595 Darwin talks about: ``The survival of the fittest.''
meillo@12 596 .[
meillo@44 597 darwin
meillo@44 598 origin of species
meillo@12 599 .]
meillo@12 600 Transferred to software: The most successful software, is the fittest,
meillo@12 601 is the one that survives.
meillo@13 602 (This may be at the level of one creature, or at the level of one species.)
meillo@13 603 The fitness of software is affected mainly by four properties:
meillo@15 604 portability of code, portability of data, range of usability, and reusability of parts.
meillo@15 605 .\" .IP \(bu
meillo@15 606 .\" portability of code
meillo@15 607 .\" .IP \(bu
meillo@15 608 .\" portability of data
meillo@15 609 .\" .IP \(bu
meillo@15 610 .\" range of usability
meillo@15 611 .\" .IP \(bu
meillo@15 612 .\" reuseability of parts
meillo@13 613 .PP
meillo@15 614 (1)
meillo@15 615 .I "Portability of code
meillo@15 616 means, using high-level programming languages,
meillo@13 617 sticking to the standard,
meillo@13 618 and avoiding optimizations that introduce dependencies on specific hardware.
meillo@13 619 Hardware has a much lower lifetime than software.
meillo@13 620 By chaining software to a specific hardware,
meillo@13 621 the software's lifetime gets shortened to that of this hardware.
meillo@13 622 In contrast, software should be easy to port \(en
meillo@23 623 adaptation is the key to success.
meillo@13 624 .\" cf. practice of prog: ch08
meillo@13 625 .PP
meillo@15 626 (2)
meillo@15 627 .I "Portability of data
meillo@15 628 is best achieved by avoiding binary representations
meillo@13 629 to store data, because binary representations differ from machine to machine.
meillo@23 630 Textual representation is favored.
meillo@13 631 Historically, ASCII was the charset of choice.
meillo@13 632 In the future, UTF-8 might be the better choice, however.
meillo@13 633 Important is that it is a plain text representation in a
meillo@13 634 very common charset encoding.
meillo@13 635 Apart from being able to transfer data between machines,
meillo@13 636 readable data has the great advantage, that humans are able
meillo@13 637 to directly edit it with text editors and other tools from the Unix toolchest.
meillo@13 638 .\" gancarz tenet 5
meillo@13 639 .PP
meillo@15 640 (3)
meillo@15 641 A large
meillo@15 642 .I "range of usability
meillo@23 643 ensures good adaptation, and thus good survival.
meillo@13 644 It is a special distinction if a software becomes used in fields of action,
meillo@13 645 the original authors did never imagine.
meillo@13 646 Software that solves problems in a general way will likely be used
meillo@13 647 for all kinds of similar problems.
meillo@13 648 Being too specific limits the range of uses.
meillo@13 649 Requirements change through time, thus use cases change or even vanish.
meillo@13 650 A good example in this point is Allman's sendmail.
meillo@13 651 Allman identifies flexibility to be one major reason for sendmail's success:
meillo@13 652 .[
meillo@44 653 allman
meillo@44 654 sendmail
meillo@13 655 .]
meillo@13 656 .QP
meillo@41 657 .ps -1
meillo@13 658 Second, I limited myself to the routing function [...].
meillo@13 659 This was a departure from the dominant thought of the time, [...].
meillo@13 660 .QP
meillo@41 661 .ps -1
meillo@13 662 Third, the sendmail configuration file was flexible enough to adopt
meillo@13 663 to a rapidly changing world [...].
meillo@12 664 .LP
meillo@13 665 Successful software adopts itself to the changing world.
meillo@13 666 .PP
meillo@15 667 (4)
meillo@15 668 .I "Reuse of parts
meillo@15 669 is even one step further.
meillo@13 670 A software may completely lose its field of action,
meillo@13 671 but parts of which the software is build may be general and independent enough
meillo@13 672 to survive this death.
meillo@13 673 If software is build by combining small independent programs,
meillo@13 674 then there are parts readily available for reuse.
meillo@13 675 Who cares if the large program is a failure,
meillo@13 676 but parts of it become successful instead?
meillo@10 677
meillo@16 678 .NH 2
meillo@14 679 Summary
meillo@42 680 .XS
meillo@42 681 \*(SN Summary
meillo@42 682 .XE
meillo@0 683 .LP
meillo@14 684 This chapter explained the central ideas of the Unix Philosophy.
meillo@14 685 For each of the ideas, it was exposed what advantages they introduce.
meillo@14 686 The Unix Philosophy are guidelines that help to write valuable software.
meillo@14 687 From the view point of a software developer or software designer,
meillo@14 688 the Unix Philosophy provides answers to many software design problem.
meillo@14 689 .PP
meillo@14 690 The various ideas of the Unix Philosophy are very interweaved
meillo@14 691 and can hardly be applied independently.
meillo@14 692 However, the probably most important messages are:
meillo@14 693 .I "``Do one thing well!''" ,
meillo@14 694 .I "``Keep it simple!''" ,
meillo@14 695 and
meillo@14 696 .I "``Use software leverage!''
meillo@0 697
meillo@8 698
meillo@8 699
meillo@0 700 .NH 1
meillo@19 701 Case study: \s-1MH\s0
meillo@42 702 .XS
meillo@42 703 .sp .5v
meillo@42 704 \*(SN Case study: \s-1MH\s0
meillo@42 705 .XE
meillo@18 706 .LP
meillo@30 707 The previous chapter introduced and explained the Unix Philosophy
meillo@18 708 from a general point of view.
meillo@30 709 The driving force were the guidelines; references to
meillo@18 710 existing software were given only sparsely.
meillo@18 711 In this and the next chapter, concrete software will be
meillo@18 712 the driving force in the discussion.
meillo@18 713 .PP
meillo@23 714 This first case study is about the mail user agents (\s-1MUA\s0)
meillo@23 715 \s-1MH\s0 (``mail handler'') and its descendent \fInmh\fP
meillo@23 716 (``new mail handler'').
meillo@23 717 \s-1MUA\s0s provide functions to read, compose, and organize mail,
meillo@23 718 but (ideally) not to transfer.
meillo@19 719 In this document, the name \s-1MH\s0 will be used for both of them.
meillo@19 720 A distinction will only be made if differences between
meillo@19 721 them are described.
meillo@18 722
meillo@0 723
meillo@0 724 .NH 2
meillo@19 725 Historical background
meillo@42 726 .XS
meillo@42 727 \*(SN Historical background
meillo@42 728 .XE
meillo@0 729 .LP
meillo@19 730 Electronic mail was available in Unix very early.
meillo@30 731 The first \s-1MUA\s0 on Unix was \f(CWmail\fP,
meillo@30 732 which was already present in the First Edition.
meillo@30 733 .[
meillo@44 734 salus
meillo@44 735 quarter century of unix
meillo@30 736 %P 41 f.
meillo@30 737 .]
meillo@30 738 It was a small program that either prints the user's mailbox file
meillo@19 739 or appends text to someone elses mailbox file,
meillo@19 740 depending on the command line arguments.
meillo@19 741 .[
meillo@44 742 manual mail(1)
meillo@19 743 .]
meillo@19 744 It was a program that did one job well.
meillo@23 745 This job was emailing, which was very simple then.
meillo@19 746 .PP
meillo@23 747 Later, emailing became more powerful, and thus more complex.
meillo@19 748 The simple \f(CWmail\fP, which knew nothing of subjects,
meillo@19 749 independent handling of single messages,
meillo@19 750 and long-time storage of them, was not powerful enough anymore.
meillo@19 751 At Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
meillo@19 752 in 1978 to provide additional functions for emailing.
meillo@19 753 Mail was still one program, but now it was large and did
meillo@19 754 several jobs.
meillo@23 755 Its user interface is modeled after the one of \fIed\fP.
meillo@19 756 It is designed for humans, but is still scriptable.
meillo@23 757 \fImailx\fP is the adaptation of Berkeley Mail into System V.
meillo@19 758 .[
meillo@44 759 ritter
meillo@44 760 mailx history
meillo@19 761 .]
meillo@30 762 Elm, pine, mutt, and a whole bunch of graphical \s-1MUA\s0s
meillo@19 763 followed Mail's direction.
meillo@19 764 They are large, monolithic programs which include all emailing functions.
meillo@19 765 .PP
meillo@23 766 A different way was taken by the people of \s-1RAND\s0 Corporation.
meillo@38 767 In the beginning, they also had used a monolithic mail system,
meillo@30 768 called \s-1MS\s0 (for ``mail system'').
meillo@19 769 But in 1977, Stockton Gaines and Norman Shapiro
meillo@19 770 came up with a proposal of a new email system concept \(en
meillo@19 771 one that honors the Unix Philosophy.
meillo@19 772 The concept was implemented by Bruce Borden in 1978 and 1979.
meillo@19 773 This was the birth of \s-1MH\s0 \(en the ``mail handler''.
meillo@18 774 .PP
meillo@18 775 Since then, \s-1RAND\s0, the University of California at Irvine and
meillo@19 776 at Berkeley, and several others have contributed to the software.
meillo@18 777 However, it's core concepts remained the same.
meillo@23 778 In the late 90s, when development of \s-1MH\s0 slowed down,
meillo@19 779 Richard Coleman started with \fInmh\fP, the new mail handler.
meillo@19 780 His goal was to improve \s-1MH\s0, especially in regard of
meillo@23 781 the requirements of modern emailing.
meillo@19 782 Today, nmh is developed by various people on the Internet.
meillo@18 783 .[
meillo@44 784 ware
meillo@44 785 rand history
meillo@44 786 %P 128-137
meillo@18 787 .]
meillo@18 788 .[
meillo@44 789 peek
meillo@44 790 mh
meillo@18 791 .]
meillo@0 792
meillo@0 793 .NH 2
meillo@20 794 Contrasts to monolithic mail systems
meillo@42 795 .XS
meillo@42 796 \*(SN Contrasts to monolithic mail systems
meillo@42 797 .XE
meillo@0 798 .LP
meillo@19 799 All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
meillo@38 800 Although there might actually exist further, very little known,
meillo@30 801 toolchest \s-1MUA\s0s, this statement reflects the situation pretty well.
meillo@19 802 .PP
meillo@30 803 Monolithic \s-1MUA\s0s gather all their functions in one program.
meillo@30 804 In contrast, \s-1MH\s0 is a toolchest of many small tools \(en one for each job.
meillo@23 805 Following is a list of important programs of \s-1MH\s0's toolchest
meillo@30 806 and their function.
meillo@30 807 It gives a feeling of how the toolchest looks like.
meillo@19 808 .IP \(bu
meillo@19 809 .CW inc :
meillo@30 810 incorporate new mail (this is how mail enters the system)
meillo@19 811 .IP \(bu
meillo@19 812 .CW scan :
meillo@19 813 list messages in folder
meillo@19 814 .IP \(bu
meillo@19 815 .CW show :
meillo@19 816 show message
meillo@19 817 .IP \(bu
meillo@19 818 .CW next\fR/\fPprev :
meillo@19 819 show next/previous message
meillo@19 820 .IP \(bu
meillo@19 821 .CW folder :
meillo@19 822 change current folder
meillo@19 823 .IP \(bu
meillo@19 824 .CW refile :
meillo@19 825 refile message into folder
meillo@19 826 .IP \(bu
meillo@19 827 .CW rmm :
meillo@19 828 remove message
meillo@19 829 .IP \(bu
meillo@19 830 .CW comp :
meillo@19 831 compose a new message
meillo@19 832 .IP \(bu
meillo@19 833 .CW repl :
meillo@19 834 reply to a message
meillo@19 835 .IP \(bu
meillo@19 836 .CW forw :
meillo@19 837 forward a message
meillo@19 838 .IP \(bu
meillo@19 839 .CW send :
meillo@30 840 send a prepared message (this is how mail leaves the system)
meillo@0 841 .LP
meillo@19 842 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
meillo@19 843 The user does not leave the shell to run \s-1MH\s0,
meillo@30 844 but he uses the various \s-1MH\s0 programs within the shell.
meillo@23 845 Using a monolithic program with a captive user interface
meillo@23 846 means ``entering'' the program, using it, and ``exiting'' the program.
meillo@23 847 Using toolchests like \s-1MH\s0 means running programs,
meillo@38 848 alone or in combination with others, even from other toolchests,
meillo@23 849 without leaving the shell.
meillo@30 850
meillo@30 851 .NH 2
meillo@30 852 Data storage
meillo@42 853 .XS
meillo@42 854 \*(SN Data storage
meillo@42 855 .XE
meillo@30 856 .LP
meillo@34 857 \s-1MH\s0's mail storage is a directory tree under the user's
meillo@34 858 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP),
meillo@34 859 where mail folders are directories and mail messages are text files
meillo@34 860 within them.
meillo@34 861 Each mail folder contains a file \f(CW.mh_sequences\fP which lists
meillo@34 862 the public message sequences of that folder, for instance new messages.
meillo@34 863 Mail messages are text files located in a mail folder.
meillo@34 864 The files contain the messages as they were received.
meillo@34 865 They are numbered in ascending order in each folder.
meillo@19 866 .PP
meillo@30 867 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0.
meillo@30 868 Alternatives are \fImbox\fP and \fImaildir\fP.
meillo@30 869 In the mbox format all messages are stored within one file.
meillo@30 870 This was a good solution in the early days, when messages
meillo@30 871 were only a few lines of text and were deleted soon.
meillo@30 872 Today, when single messages often include several megabytes
meillo@30 873 of attachments, it is a bad solution.
meillo@30 874 Another disadvantage of the mbox format is that it is
meillo@30 875 more difficult to write tools that work on mail messages,
meillo@30 876 because it is always necessary to first find and extract
meillo@30 877 the relevant message in the mbox file.
meillo@30 878 With the \s-1MH\s0 mailbox format,
meillo@30 879 each message is a self-standing item, by definition.
meillo@30 880 Also, the problem of concurrent access to one mailbox is
meillo@30 881 reduced to the problem of concurrent access to one message.
meillo@30 882 Maildir is generally similar to \s-1MH\s0's format,
meillo@30 883 but modified towards guaranteed reliability.
meillo@30 884 This involves some complexity, unfortunately.
meillo@34 885 .PP
meillo@34 886 Working with \s-1MH\s0's toolchest on mailboxes is much like
meillo@34 887 working with Unix' toolchest on directory trees:
meillo@34 888 \f(CWscan\fP is like \f(CWls\fP,
meillo@34 889 \f(CWshow\fP is like \f(CWcat\fP,
meillo@34 890 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP,
meillo@34 891 \f(CWrefile\fP is like \f(CWmv\fP,
meillo@34 892 and \f(CWrmm\fP is like \f(CWrm\fP.
meillo@34 893 .PP
meillo@34 894 The context of tools in Unix consists mainly the current working directory,
meillo@34 895 the user identification, and the environment variables.
meillo@34 896 \s-1MH\s0 extends this context by two more items:
meillo@34 897 .IP \(bu
meillo@34 898 The current mail folder, which is similar to the current working directory.
meillo@34 899 For mail folders, \f(CWfolder\fP provides the corresponding functionality
meillo@34 900 of \f(CWcd\fP and \f(CWpwd\fP for directories.
meillo@34 901 .IP \(bu
meillo@34 902 Sequences, which are named sets of messages in a mail folder.
meillo@34 903 The current message, relative to a mail folder, is a special sequence.
meillo@34 904 It enables commands like \f(CWnext\fP and \f(CWprev\fP.
meillo@34 905 .LP
meillo@34 906 In contrast to Unix' context, which is chained to the shell session,
meillo@34 907 \s-1MH\s0's context is independent.
meillo@34 908 Usually there is one context for each user, but a user can have many
meillo@34 909 contexts.
meillo@34 910 Public sequences are an exception, as they belong to the mail folder.
meillo@34 911 .[
meillo@44 912 man page mh-profile mh-sequence
meillo@34 913 .]
meillo@20 914
meillo@0 915 .NH 2
meillo@20 916 Discussion of the design
meillo@42 917 .XS
meillo@42 918 \*(SN Discussion of the design
meillo@42 919 .XE
meillo@0 920 .LP
meillo@20 921 The following paragraphs discuss \s-1MH\s0 in regard to the tenets
meillo@23 922 of the Unix Philosophy which Gancarz identified.
meillo@20 923
meillo@20 924 .PP
meillo@33 925 .B "Small is beautiful
meillo@20 926 and
meillo@33 927 .B "do one thing well
meillo@20 928 are two design goals that are directly visible in \s-1MH\s0.
meillo@20 929 Gancarz actually presents \s-1MH\s0 as example under the headline
meillo@20 930 ``Making UNIX Do One Thing Well'':
meillo@41 931 .[
meillo@44 932 gancarz
meillo@44 933 unix philosophy
meillo@41 934 %P 125
meillo@41 935 .]
meillo@20 936 .QP
meillo@41 937 .ps -1
meillo@20 938 [\s-1MH\s0] consists of a series of programs which
meillo@20 939 when combined give the user an enormous ability
meillo@20 940 to manipulate electronic mail messages.
meillo@20 941 A complex application, it shows that not only is it
meillo@20 942 possible to build large applications from smaller
meillo@20 943 components, but also that such designs are actually preferable.
meillo@20 944 .LP
meillo@20 945 The various small programs of \s-1MH\s0 were relatively easy
meillo@23 946 to write, because each of them is small, limited to one function,
meillo@23 947 and has clear boundaries.
meillo@20 948 For the same reasons, they are also good to maintain.
meillo@20 949 Further more, the system can easily get extended.
meillo@20 950 One only needs to put a new program into the toolchest.
meillo@23 951 This was done, for instance, when \s-1MIME\s0 support was added
meillo@20 952 (e.g. \f(CWmhbuild\fP).
meillo@20 953 Also, different programs can exist to do the basically same job
meillo@20 954 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP).
meillo@20 955 If someone needs a mail system with some additionally
meillo@23 956 functions that are available nowhere yet, he best takes a
meillo@20 957 toolchest system like \s-1MH\s0 where he can add the
meillo@20 958 functionality with little work.
meillo@20 959
meillo@20 960 .PP
meillo@34 961 .B "Store data in flat text files
meillo@34 962 is followed by \s-1MH\s0.
meillo@34 963 This is not surprising, because email messages are already plain text.
meillo@34 964 \s-1MH\s0 stores the messages as it receives them,
meillo@34 965 thus any other tool that works on RFC 2822 mail messages can operate
meillo@34 966 on the messages in an \s-1MH\s0 mailbox.
meillo@34 967 All other files \s-1MH\s0 uses are plain text too.
meillo@34 968 It is therefore possible and encouraged to use the text processing
meillo@34 969 tools of Unix' toolchest to extend \s-1MH\s0's toolchest.
meillo@20 970
meillo@20 971 .PP
meillo@33 972 .B "Avoid captive user interfaces" .
meillo@19 973 \s-1MH\s0 is perfectly suited for non-interactive use.
meillo@19 974 It offers all functions directly and without captive user interfaces.
meillo@30 975 If, nonetheless, users want a graphical user interface,
meillo@20 976 they can have it with \fIxmh\fP or \fIexmh\fP, too.
meillo@19 977 These are graphical frontends for the \s-1MH\s0 toolchest.
meillo@19 978 This means, all email-related work is still done by \s-1MH\s0 tools,
meillo@20 979 but the frontend issues the appropriate calls when the user
meillo@30 980 clicks on buttons.
meillo@20 981 Providing easy-to-use user interfaces in form of frontends is a good
meillo@19 982 approach, because it does not limit the power of the backend itself.
meillo@20 983 The frontend will anyway only be able to make a subset of the
meillo@23 984 backend's power and flexibility available to the user.
meillo@20 985 But if it is a separate program,
meillo@20 986 then the missing parts can still be accessed at the backend directly.
meillo@19 987 If it is integrated, then this will hardly be possible.
meillo@30 988 Further more, it is possible to have different frontends to the same
meillo@30 989 backend.
meillo@19 990
meillo@19 991 .PP
meillo@33 992 .B "Choose portability over efficiency
meillo@20 993 and
meillo@33 994 .B "use shell scripts to increase leverage and portability" .
meillo@20 995 These two tenets are indirectly, but nicely, demonstrated by
meillo@30 996 Bolsky and Korn in their book about the Korn Shell.
meillo@20 997 .[
meillo@44 998 bolsky korn
meillo@44 999 korn shell
meillo@20 1000 .]
meillo@30 1001 They demonstrated, in chapter 18 of the book, a basic implementation
meillo@20 1002 of a subset of \s-1MH\s0 in ksh scripts.
meillo@20 1003 Of course, this was just a demonstration, but a brilliant one.
meillo@20 1004 It shows how quickly one can implement such a prototype with shell scripts,
meillo@20 1005 and how readable they are.
meillo@20 1006 The implementation in the scripting language may not be very fast,
meillo@20 1007 but it can be fast enough though, and this is all that matters.
meillo@20 1008 By having the code in an interpreted language, like the shell,
meillo@20 1009 portability becomes a minor issue, if we assume the interpreter
meillo@20 1010 to be widespread.
meillo@20 1011 This demonstration also shows how easy it is to create single programs
meillo@20 1012 of a toolchest software.
meillo@30 1013 There are eight tools (two of them have multiple names) and 16 functions
meillo@30 1014 with supporting code.
meillo@30 1015 Each tool comprises between 12 and 38 lines of ksh,
meillo@30 1016 in total about 200 lines.
meillo@30 1017 The functions comprise between 3 and 78 lines of ksh,
meillo@30 1018 in total about 450 lines.
meillo@20 1019 Such small software is easy to write, easy to understand,
meillo@20 1020 and thus easy to maintain.
meillo@23 1021 A toolchest improves the possibility to only write some parts
meillo@20 1022 and though create a working result.
meillo@20 1023 Expanding the toolchest without global changes will likely be
meillo@20 1024 possible, too.
meillo@20 1025
meillo@20 1026 .PP
meillo@33 1027 .B "Use software leverage to your advantage
meillo@20 1028 and the lesser tenet
meillo@33 1029 .B "allow the user to tailor the environment
meillo@20 1030 are ideally followed in the design of \s-1MH\s0.
meillo@21 1031 Tailoring the environment is heavily encouraged by the ability to
meillo@30 1032 directly define default options to programs.
meillo@30 1033 It is even possible to define different default options
meillo@21 1034 depending on the name under which the program was called.
meillo@21 1035 Software leverage is heavily encouraged by the ease it is to
meillo@21 1036 create shell scripts that run a specific command line,
meillo@30 1037 built of several \s-1MH\s0 programs.
meillo@21 1038 There is few software that so much wants users to tailor their
meillo@21 1039 environment and to leverage the use of the software, like \s-1MH\s0.
meillo@21 1040 Just to make one example:
meillo@23 1041 One might prefer a different listing format for the \f(CWscan\fP
meillo@21 1042 program.
meillo@30 1043 It is possible to take one of the distributed format files
meillo@21 1044 or to write one yourself.
meillo@21 1045 To use the format as default for \f(CWscan\fP, a single line,
meillo@21 1046 reading
meillo@21 1047 .DS
meillo@21 1048 .CW
meillo@21 1049 scan: -form FORMATFILE
meillo@21 1050 .DE
meillo@21 1051 must be added to \f(CW.mh_profile\fP.
meillo@21 1052 If one wants this different format as an additional command,
meillo@23 1053 instead of changing the default, he needs to create a link to
meillo@23 1054 \f(CWscan\fP, for instance titled \f(CWscan2\fP.
meillo@21 1055 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP,
meillo@30 1056 as the option should only be in effect when scan is called as
meillo@21 1057 \f(CWscan2\fP.
meillo@20 1058
meillo@20 1059 .PP
meillo@33 1060 .B "Make every program a filter
meillo@21 1061 is hard to find in \s-1MH\s0.
meillo@21 1062 The reason therefore is that most of \s-1MH\s0's tools provide
meillo@21 1063 basic file system operations for the mailboxes.
meillo@30 1064 The reason is the same because of which
meillo@21 1065 \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP, and \f(CWrm\fP
meillo@21 1066 aren't filters neither.
meillo@23 1067 However, they build a basis on which filters can operate.
meillo@23 1068 \s-1MH\s0 does not provide many filters itself, but it is a basis
meillo@23 1069 to write filters for.
meillo@30 1070 An example would be a mail message text highlighter,
meillo@30 1071 that means a program that makes use of a color terminal to display
meillo@30 1072 header lines, quotations, and signatures in distinct colors.
meillo@30 1073 The author's version of this program, for instance,
meillo@30 1074 is a 25 line awk script.
meillo@21 1075
meillo@21 1076 .PP
meillo@33 1077 .B "Build a prototype as soon as possible
meillo@21 1078 was again well followed by \s-1MH\s0.
meillo@21 1079 This tenet, of course, focuses on early development, which is
meillo@21 1080 long time ago for \s-1MH\s0.
meillo@21 1081 But without following this guideline at the very beginning,
meillo@23 1082 Bruce Borden may have not convinced the management of \s-1RAND\s0
meillo@23 1083 to ever create \s-1MH\s0.
meillo@23 1084 In Bruce' own words:
meillo@41 1085 .[
meillo@44 1086 ware rand history
meillo@44 1087 %P 132
meillo@41 1088 .]
meillo@21 1089 .QP
meillo@41 1090 .ps -1
meillo@30 1091 [...] but they [Stockton Gaines and Norm Shapiro] were not able
meillo@23 1092 to convince anyone that such a system would be fast enough to be usable.
meillo@21 1093 I proposed a very short project to prove the basic concepts,
meillo@21 1094 and my management agreed.
meillo@21 1095 Looking back, I realize that I had been very lucky with my first design.
meillo@21 1096 Without nearly enough design work,
meillo@21 1097 I built a working environment and some header files
meillo@21 1098 with key structures and wrote the first few \s-1MH\s0 commands:
meillo@21 1099 inc, show/next/prev, and comp.
meillo@21 1100 [...]
meillo@21 1101 With these three, I was able to convince people that the structure was viable.
meillo@21 1102 This took about three weeks.
meillo@0 1103
meillo@0 1104 .NH 2
meillo@0 1105 Problems
meillo@42 1106 .XS
meillo@42 1107 \*(SN Problems
meillo@42 1108 .XE
meillo@0 1109 .LP
meillo@22 1110 \s-1MH\s0, for sure is not without problems.
meillo@30 1111 There are two main problems: one is technical, the other is about human behavior.
meillo@22 1112 .PP
meillo@22 1113 \s-1MH\s0 is old and email today is very different to email in the time
meillo@22 1114 when \s-1MH\s0 was designed.
meillo@22 1115 \s-1MH\s0 adopted to the changes pretty well, but it is limited.
meillo@22 1116 For example in development resources.
meillo@22 1117 \s-1MIME\s0 support and support for different character encodings
meillo@22 1118 is available, but only on a moderate level.
meillo@22 1119 More active developers could quickly improve there.
meillo@22 1120 It is also limited by design, which is the larger problem.
meillo@22 1121 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extend.
meillo@22 1122 These design conflicts are not easily solvable.
meillo@22 1123 Possibly, they require a redesign.
meillo@30 1124 Maybe \s-1IMAP\s0 is too different to the classic mail model which \s-1MH\s0 covers,
meillo@30 1125 hence \s-1MH\s0 may never work well with \s-1IMAP\s0.
meillo@22 1126 .PP
meillo@22 1127 The other kind of problem is human habits.
meillo@22 1128 When in this world almost all \s-1MUA\s0s are monolithic,
meillo@22 1129 it is very difficult to convince people to use a toolbox style \s-1MUA\s0
meillo@22 1130 like \s-1MH\s0.
meillo@22 1131 The habits are so strong, that even people who understood the concept
meillo@30 1132 and advantages of \s-1MH\s0 do not like to switch,
meillo@30 1133 simply because \s-1MH\s0 is different.
meillo@30 1134 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel,
meillo@30 1135 are quite outdated and thus not very appealing compared to the modern interfaces
meillo@30 1136 which monolithic \s-1MUA\s0s offer.
meillo@20 1137
meillo@20 1138 .NH 2
meillo@20 1139 Summary \s-1MH\s0
meillo@42 1140 .XS
meillo@42 1141 \*(SN Summary \s-1MH\s0
meillo@42 1142 .XE
meillo@20 1143 .LP
meillo@31 1144 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design
meillo@31 1145 and implementation.
meillo@31 1146 It consists of a toolchest of small tools, each of them does one job well.
meillo@31 1147 The tools are orthogonal to each other, to a large extend.
meillo@31 1148 However, for historical reasons, there also exist distinct tools
meillo@31 1149 that cover the same task.
meillo@31 1150 .PP
meillo@31 1151 The toolchest approach offers great flexibility to the user.
meillo@31 1152 He can use the complete power of the Unix shell with \s-1MH\s0.
meillo@31 1153 This makes \s-1MH\s0 a very powerful mail system.
meillo@31 1154 Extending and customizing \s-1MH\s0 is easy and encouraged, too.
meillo@31 1155 .PP
meillo@31 1156 Apart from the user's perspective, \s-1MH\s0 is development-friendly.
meillo@31 1157 Its overall design follows clear rules.
meillo@31 1158 The single tools do only one job, thus they are easy to understand,
meillo@31 1159 easy to write, and good to maintain.
meillo@31 1160 They are all independent and do not interfere with the others.
meillo@31 1161 Automated testing of their function is a straight forward task.
meillo@31 1162 .PP
meillo@31 1163 It is sad, that \s-1MH\s0's differentness is its largest problem,
meillo@31 1164 as its differentness is also its largest advantage.
meillo@31 1165 Unfortunately, for most people their habits are stronger
meillo@31 1166 than the attraction of the clear design and the power, \s-1MH\s0 offers.
meillo@0 1167
meillo@8 1168
meillo@8 1169
meillo@0 1170 .NH 1
meillo@0 1171 Case study: uzbl
meillo@42 1172 .XS
meillo@42 1173 .sp .5v
meillo@42 1174 \*(SN Case study: uzbl
meillo@42 1175 .XE
meillo@32 1176 .LP
meillo@32 1177 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0,
meillo@32 1178 this chapter is about uzbl, a web browser that adheres to the Unix Philosophy.
meillo@32 1179 ``uzbl'' is the \fIlolcat\fP's word for the English adjective ``usable''.
meillo@32 1180 It is pronounced the identical.
meillo@0 1181
meillo@0 1182 .NH 2
meillo@32 1183 Historical background
meillo@42 1184 .XS
meillo@42 1185 \*(SN Historical background
meillo@42 1186 .XE
meillo@0 1187 .LP
meillo@32 1188 Uzbl was started by Dieter Plaetinck in April 2009.
meillo@44 1189 The idea was born in a thread in the Arch Linux Forums.
meillo@32 1190 .[
meillo@44 1191 arch linux forums
meillo@44 1192 browser
meillo@32 1193 .]
meillo@32 1194 After some discussion about failures of well known web browsers,
meillo@32 1195 Plaetinck (alias Dieter@be) came up with a very sketchy proposal
meillo@32 1196 of how a better web browser could look like.
meillo@32 1197 To the question of another member, if Plaetinck would write that program,
meillo@32 1198 because it would sound fantastic, Plaetinck replied:
meillo@32 1199 ``Maybe, if I find the time ;-)''.
meillo@32 1200 .PP
meillo@32 1201 Fortunately, he found the time.
meillo@32 1202 One day later, the first prototype was out.
meillo@32 1203 One week later, uzbl had an own website.
meillo@32 1204 One month after the first code showed up,
meillo@32 1205 a mailing list was installed to coordinate and discuss further development.
meillo@32 1206 A wiki was set up to store documentation and scripts that showed up on the
meillo@32 1207 mailing list and elsewhere.
meillo@32 1208 .PP
meillo@38 1209 In the, now, one year of uzbl's existence, it was heavily developed in various branches.
meillo@32 1210 Plaetinck's task became more and more to only merge the best code from the
meillo@32 1211 different branches into his main branch, and to apply patches.
meillo@32 1212 About once a month, Plaetinck released a new version.
meillo@32 1213 In September 2009, he presented several forks of uzbl.
meillo@38 1214 Uzbl, actually, opened the field for a whole family of web browsers with similar shape.
meillo@32 1215 .PP
meillo@32 1216 In July 2009, \fILinux Weekly News\fP published an interview with Plaetinck about uzbl.
meillo@32 1217 In September 2009, the uzbl web browser was on \fISlashdot\fP.
meillo@0 1218
meillo@0 1219 .NH 2
meillo@32 1220 Contrasts to other web browsers
meillo@42 1221 .XS
meillo@42 1222 \*(SN Contrasts to other web browsers
meillo@42 1223 .XE
meillo@0 1224 .LP
meillo@32 1225 Like most \s-1MUA\s0s are monolithic, but \s-1MH\s0 is a toolchest,
meillo@32 1226 most web browsers are monolithic, but uzbl is a frontend to a toolchest.
meillo@32 1227 .PP
meillo@32 1228 Today, uzbl is divided into uzbl-core and uzbl-browser.
meillo@32 1229 Uzbl-core is, how its name already indicates, the core of uzbl.
meillo@32 1230 It handles commands and events to interface other programs,
meillo@32 1231 and also displays webpages by using webkit as render engine.
meillo@32 1232 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar,
meillo@32 1233 an event manager, yanking, pasting, page searching, zooming, and more stuff,
meillo@32 1234 to form a ``complete'' web browser.
meillo@32 1235 In the following text, the term ``uzbl'' usually stands for uzbl-browser,
meillo@32 1236 so uzbl-core is included.
meillo@32 1237 .PP
meillo@32 1238 Unlike most other web browsers, uzbl is mainly the mediator between the
meillo@32 1239 various tools that cover single jobs of web browsing.
meillo@35 1240 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket,
meillo@35 1241 and on stdin, and it writes events to a Unix socket and to stdout.
meillo@35 1242 The graphical rendering of the webpage is done by webkit, a web content engine.
meillo@35 1243 Uzbl-core is build around this library.
meillo@35 1244 Loading a webpage in a running uzbl instance requires only:
meillo@32 1245 .DS
meillo@32 1246 .CW
meillo@32 1247 echo 'uri' >/path/to/uzbl-fifo
meillo@32 1248 .DE
meillo@32 1249 .PP
meillo@32 1250 Downloads, browsing history, bookmarks, and thelike are not provided
meillo@32 1251 by uzbl-core itself, as they are in other web browsers.
meillo@35 1252 Uzbl-browser also only provides, so called, handler scripts that wrap
meillo@35 1253 external applications which provide the actual functionality.
meillo@32 1254 For instance, \fIwget\fP is used to download files and uzbl-browser
meillo@32 1255 includes a script that calls wget with appropriate options in
meillo@32 1256 a prepared environment.
meillo@32 1257 .PP
meillo@32 1258 Modern web browsers are proud to have addons, plugins, and modules, instead.
meillo@32 1259 This is their effort to achieve similar goals.
meillo@35 1260 But instead of using existing, external programs, modern web browsers
meillo@35 1261 include these functions, although they might be loaded at runtime.
meillo@0 1262
meillo@0 1263 .NH 2
meillo@32 1264 Discussion of the design
meillo@42 1265 .XS
meillo@42 1266 \*(SN Discussion of the design
meillo@42 1267 .XE
meillo@0 1268 .LP
meillo@32 1269 This section discusses uzbl in regard of the Unix Philosophy,
meillo@32 1270 as identified by Gancarz.
meillo@32 1271
meillo@32 1272 .PP
meillo@35 1273 .B "Make each program do one thing well" .
meillo@35 1274 Uzbl tries to be a web browser and nothing else.
meillo@36 1275 The common definition of a web browser is, of course, highly influenced by
meillo@36 1276 existing implementations of web browsers, although they are degenerated.
meillo@35 1277 Web browsers should be programs to browse the web, and nothing more.
meillo@35 1278 This is the one thing they should do, as demanded by the Unix Philosophy.
meillo@36 1279 .PP
meillo@36 1280 Web browsers should, for instance, not manage downloads.
meillo@35 1281 This is the job download managers exist for.
meillo@35 1282 Download managers do primary care about being good in downloading files.
meillo@35 1283 Modern web browsers provide download management only as a secondary feature.
meillo@35 1284 How could they perform this job better, than programs that exist only for
meillo@35 1285 this very job?
meillo@35 1286 And how could anyone want less than the best download manager available?
meillo@32 1287 .PP
meillo@35 1288 A web browser's job is to let the user browse the web.
meillo@35 1289 This means, navigating through websites by following links.
meillo@36 1290 Rendering the \s-1HTML\s0 sources is a different job, too.
meillo@36 1291 It is covered by the webkit render engine, in uzbl's case.
meillo@35 1292 Audio and video content and files like PostScript, \s-1PDF\s0, and the like,
meillo@36 1293 are also not the job of a web browser.
meillo@36 1294 They should be handled by external applications \(en
meillo@36 1295 ones which's job is to handle such data.
meillo@35 1296 Uzbl strives to do it this way.
meillo@36 1297 .PP
meillo@36 1298 Remember Doug McIlroy:
meillo@35 1299 .I
meillo@35 1300 ``Write programs that do one thing and do it well.
meillo@35 1301 Write programs to work together.''
meillo@35 1302 .R
meillo@35 1303 .PP
meillo@35 1304 The lesser tenet
meillo@35 1305 .B "allow the user to tailor the environment
meillo@35 1306 matches good here.
meillo@35 1307 There was the question, how anyone could want anything less than the
meillo@35 1308 best program for the job.
meillo@36 1309 But as personal preferences matter much,
meillo@36 1310 it is probably more important to ask:
meillo@35 1311 How could anyone want something else than his preferred program for the job?
meillo@36 1312 .PP
meillo@35 1313 Usually users want one program for one job.
meillo@35 1314 Hence, whenever the task is, for instance, downloading,
meillo@36 1315 exactly one download manager should be used.
meillo@35 1316 More advanced users might want to have this download manager in this
meillo@35 1317 situation and that one in that situation.
meillo@35 1318 They should be able to configure it this way.
meillo@35 1319 With uzbl, one can use any download manager the user wants.
meillo@36 1320 To switch to a different one, only one line in a small handler script
meillo@35 1321 needs to be changed.
meillo@36 1322 Alternatively it would be possible to query an entry in a global file
meillo@36 1323 or an environment variable, which specifies the download manager to use,
meillo@35 1324 in the handler script.
meillo@36 1325 .PP
meillo@35 1326 As uzbl does neither have its own download manager nor depends on a
meillo@35 1327 specific one, thus uzbl's browsing abilities will not be lowered by having
meillo@35 1328 a bad download manager.
meillo@36 1329 Uzbl's download capabilities will just as good as the ones of the best
meillo@36 1330 download manager available on the system.
meillo@38 1331 Of course, this applies to all of the other supplementary tools, too.
meillo@32 1332
meillo@32 1333 .PP
meillo@36 1334 .B "Use software leverage to your advantage" .
meillo@36 1335 Shell scripts are a good choice to extend uzbl.
meillo@36 1336 Uzbl is designed to be extended by external tools.
meillo@36 1337 These external tools are usually wrapped by small handler shell scripts.
meillo@36 1338 Shell scripts are the glue in this approach.
meillo@36 1339 They make the various parts fit together.
meillo@36 1340 .PP
meillo@36 1341 As an example, the history mechanism of uzbl shall be presented.
meillo@36 1342 Uzbl is configured to spawn a script to append an entry to the history
meillo@36 1343 whenever the event of a fully loaded page occurs.
meillo@36 1344 The script to append the entry to the history not much more than:
meillo@36 1345 .DS
meillo@36 1346 .CW
meillo@36 1347 #!/bin/sh
meillo@36 1348 file=/path/to/uzbl-history
meillo@36 1349 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file
meillo@36 1350 .DE
meillo@36 1351 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title.
meillo@36 1352 For loading an entry, a key is bound to spawn a load from history script.
meillo@36 1353 The script reverses the history to have newer entries first,
meillo@36 1354 then displays \fIdmenu\fP to select an item,
meillo@36 1355 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe.
meillo@36 1356 With error checking and corner cases removed, the script looks like this:
meillo@36 1357 .DS
meillo@36 1358 .CW
meillo@36 1359 #!/bin/sh
meillo@36 1360 file=/path/to/uzbl-history
meillo@36 1361 goto=`tac $file | dmenu | cut -d' ' -f 3`
meillo@36 1362 echo "uri $goto" > $4
meillo@36 1363 .DE
meillo@36 1364 \f(CW$4\fP expands to the path of the command input pipe of the current
meillo@36 1365 uzbl instance.
meillo@32 1366
meillo@32 1367 .PP
meillo@33 1368 .B "Avoid captive user interfaces" .
meillo@36 1369 One could say, that uzbl, to a large extend, actually \fIis\fP
meillo@36 1370 a captive user interface.
meillo@37 1371 But the difference to most other web browsers is, that uzbl is only
meillo@37 1372 the captive user interface frontend and the core of the backend.
meillo@38 1373 Many parts of the backend are independent of uzbl.
meillo@37 1374 Some are distributed with uzbl, for some external programs, handler scripts
meillo@37 1375 are distributed, arbitrary additional functionality can be added if desired.
meillo@37 1376 .PP
meillo@37 1377 The frontend is captive \(en that is true.
meillo@37 1378 This is okay for the task of browsing the web, as this task is only relevant
meillo@37 1379 for humans.
meillo@37 1380 Automated programs would \fIcrawl\fP the web.
meillo@37 1381 That means, they read the source directly.
meillo@37 1382 The source includes all the semantics.
meillo@37 1383 The graphical representation is just for humans to transfer the semantics
meillo@37 1384 more intuitively.
meillo@32 1385
meillo@32 1386 .PP
meillo@33 1387 .B "Make every program a filter" .
meillo@37 1388 Graphical web browsers are almost dead ends in the chain of information flow.
meillo@37 1389 Thus it is difficult to see what graphical web browsers should filter.
meillo@37 1390 Graphical web browsers exist almost only for interactive use by humans.
meillo@37 1391 The only case when one might want to automate the rendering function is
meillo@37 1392 to generate images of rendered webpages.
meillo@37 1393
meillo@37 1394 .PP
meillo@37 1395 .B "Small is beautiful"
meillo@38 1396 is not easy to apply to a web browser, primary because modern web technology
meillo@38 1397 is very complex; hence the rendering task is very complex.
meillo@37 1398 Modern web browsers will always consist of many thousand lines of code,
meillo@37 1399 unfortunately.
meillo@37 1400 Using the toolchest approach and wrappers can split the browser into
meillo@37 1401 several small parts, tough.
meillo@37 1402 .PP
meillo@37 1403 Uzbl-core consists of about 3\,500 lines of C code.
meillo@37 1404 The distribution includes another 3\,500 lines of Shell and Python code,
meillo@37 1405 which are the handler scripts and plugins like a modal interface.
meillo@38 1406 Further more, uzbl uses functionality of external tools like
meillo@38 1407 \fIwget\fP and \fInetcat\fP.
meillo@37 1408 Up to this point, uzbl looks pretty neat and small.
meillo@38 1409 The ugly part of uzbl is the web content renderer, webkit.
meillo@37 1410 Webkit consists of roughly 400\,000 (!) lines of code.
meillo@38 1411 Unfortunately, small web render engines are not possible anymore
meillo@38 1412 because of the modern web.
meillo@38 1413 The problems section will explain this in more detail.
meillo@35 1414
meillo@35 1415 .PP
meillo@35 1416 .B "Build a prototype as soon as possible" .
meillo@35 1417 Plaetinck made his code public, right from the beginning.
meillo@38 1418 Discussion and development was, and still is, open to everyone interested.
meillo@38 1419 Development versions of uzbl can be obtained very simply from the code
meillo@38 1420 repository.
meillo@38 1421 Within the first year of uzbl's existence, a new version was released
meillo@35 1422 more often than once a month.
meillo@38 1423 Different forks and branches arose.
meillo@38 1424 They introduced new features, which were tested for suitability.
meillo@35 1425 The experiences of using prototypes influenced further development.
meillo@35 1426 Actually, all development was community driven.
meillo@38 1427 Plaetinck says, three months after uzbl's birth:
meillo@35 1428 ``Right now I hardly code anything myself for Uzbl.
meillo@35 1429 I just merge in other people's code, ponder a lot, and lead the discussions.''
meillo@35 1430 .[
meillo@44 1431 lwn
meillo@44 1432 uzbl
meillo@35 1433 .]
meillo@32 1434
meillo@0 1435
meillo@0 1436 .NH 2
meillo@0 1437 Problems
meillo@42 1438 .XS
meillo@42 1439 \*(SN Problems
meillo@42 1440 .XE
meillo@0 1441 .LP
meillo@38 1442 Similar to \s-1MH\s0, uzbl, too suffers from being different.
meillo@38 1443 It is sad, but people use what they know.
meillo@38 1444 Fortunately, uzbl's user interface can look and feel very much the
meillo@38 1445 same as the one of the well known web browsers,
meillo@38 1446 hiding the internal differences.
meillo@38 1447 But uzbl has to provide this similar look and feel to be accepted
meillo@38 1448 as a ``normal'' browser by ``normal'' users.
meillo@37 1449 .PP
meillo@38 1450 The more important problem is the modern web.
meillo@38 1451 The modern web is simply broken.
meillo@38 1452 It has state in a state-less protocol,
meillo@38 1453 it misuses technologies,
meillo@38 1454 and it is helplessly overloaded.
meillo@38 1455 The result are web content render engines that must consist
meillo@38 1456 of hundreds of thousands lines of code.
meillo@38 1457 They also must combine and integrate many different technologies,
meillo@38 1458 only to make our modern web usable.
meillo@38 1459 Website to image converter are hardly possible to run without
meillo@38 1460 human interaction because of state in sessions, impossible
meillo@38 1461 deep-linking, and unautomatable technologies.
meillo@37 1462 .PP
meillo@38 1463 The web was misused to provide all kinds of imaginable wishes.
meillo@38 1464 Now web browsers, and eventually the users, suffer from it.
meillo@37 1465
meillo@8 1466
meillo@32 1467 .NH 2
meillo@32 1468 Summary uzbl
meillo@42 1469 .XS
meillo@42 1470 \*(SN Summary uzbl
meillo@42 1471 .XE
meillo@32 1472 .LP
meillo@38 1473 ``Uzbl is a browser that adheres to the Unix Philosophy'',
meillo@38 1474 that is how uzbl is seen by its authors.
meillo@38 1475 Indeed, uzbl follows the Unix Philosophy in many ways.
meillo@38 1476 It consists of independent parts that work together,
meillo@38 1477 its core is mainly a mediator which glues the parts together.
meillo@38 1478 .PP
meillo@38 1479 Software leverage can excellently be seen in uzbl.
meillo@38 1480 It makes use of external tools, separates independent tasks
meillo@38 1481 in independent parts, and glues them together with small
meillo@38 1482 handler scripts, around uzbl-core.
meillo@38 1483 .PP
meillo@38 1484 As uzbl, more or less, consists of a set of tools and a bit
meillo@38 1485 of glue, anyone can put the parts together and expand it
meillo@38 1486 in any desired way.
meillo@38 1487 Uzbl is very flexible and customizable.
meillo@38 1488 These properties make it valuable for advanced users,
meillo@38 1489 but may keep novice users from using it.
meillo@38 1490 .PP
meillo@38 1491 Uzbl's main problem is the modern web, that makes it hard
meillo@38 1492 to design a sane web browser.
meillo@38 1493 Despite this bad situation, uzbl does a fairly good job.
meillo@32 1494
meillo@8 1495
meillo@0 1496 .NH 1
meillo@0 1497 Final thoughts
meillo@42 1498 .XS
meillo@42 1499 .sp .5v
meillo@42 1500 \*(SN Final thoughts
meillo@42 1501 .XE
meillo@0 1502
meillo@0 1503 .NH 2
meillo@0 1504 Quick summary
meillo@42 1505 .XS
meillo@42 1506 \*(SN Quick summary
meillo@42 1507 .XE
meillo@0 1508 .LP
meillo@0 1509 good design
meillo@0 1510 .LP
meillo@0 1511 unix phil
meillo@0 1512 .LP
meillo@0 1513 case studies
meillo@0 1514
meillo@0 1515 .NH 2
meillo@0 1516 Why people should choose
meillo@42 1517 .XS
meillo@42 1518 \*(SN Why people should choose
meillo@42 1519 .XE
meillo@0 1520 .LP
meillo@0 1521 Make the right choice!
meillo@0 1522
meillo@42 1523 .nr PI .3i
meillo@0 1524 .rm ]<
meillo@0 1525 .de ]<
meillo@0 1526 .LP
meillo@0 1527 .de FP
meillo@0 1528 .IP \\\\$1.
meillo@0 1529 \\..
meillo@0 1530 .rm FS FE
meillo@0 1531 ..
meillo@42 1532 .ds CH "
meillo@42 1533 .bp
meillo@42 1534 .rs
meillo@42 1535 .sp .3i
meillo@42 1536 .TL
meillo@0 1537 References
meillo@42 1538 .LP
meillo@42 1539 .XS
meillo@42 1540 .sp .5v
meillo@42 1541 References
meillo@42 1542 .XE
meillo@42 1543 .sp 2v
meillo@42 1544 .nr PS -1
meillo@42 1545 .nr VS -1
meillo@0 1546 .[
meillo@0 1547 $LIST$
meillo@0 1548 .]
meillo@42 1549 .\".wh -1p
meillo@42 1550 .bp
meillo@42 1551 .PX