annotate @ 47:b6ae4a8ab1d3

improved references and some minor design issues
date Mon, 12 Apr 2010 14:11:39 +0200
parents 98a1446744c7
children 40caeb9e9b25
rev   line source
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meillo@1 36 .\"----------------------------------------
meillo@42 37
meillo@0 38 .TL
meillo@42 39 .ps +4
meillo@6 40 Why the Unix Philosophy still matters
meillo@0 41 .AU
meillo@0 42 markus schnalke <>
meillo@0 43 .AB
meillo@1 44 .ti \n(.iu
meillo@39 45 This paper explains the importance of the Unix Philosophy for software design.
meillo@0 46 Today, few software designers are aware of these concepts,
meillo@39 47 and thus a lot of modern software is more limited than necessary
meillo@39 48 and makes less use of software leverage than possible.
meillo@38 49 Knowing and following the guidelines of the Unix Philosophy makes software more valuable.
meillo@0 50 .AE
meillo@0 51
meillo@2 52 .FS
meillo@2 53 .ps -1
meillo@39 54 This paper was prepared for the ``Software Analysis'' seminar at University Ulm.
meillo@47 55 Mentor was professor Franz Schweiggert.
meillo@47 56 Handed in on 2010-04-12.
meillo@39 57 You may retrieve this document from
meillo@39 58 .CW \s-1 \ .
meillo@2 59 .FE
meillo@2 60
meillo@0 61 .NH 1
meillo@0 62 Introduction
meillo@42 63 .XS
meillo@47 64 .sp .5v
meillo@47 65 .B
meillo@42 66 \*(SN Introduction
meillo@42 67 .XE
meillo@0 68 .LP
meillo@40 69 The Unix Philosophy is the essence of how the Unix operating system,
meillo@40 70 especially its toolchest, was designed.
meillo@40 71 It is no limited set of fixed rules,
meillo@40 72 but a loose set of guidelines which tell how to write software that
meillo@40 73 suites well into Unix.
meillo@40 74 Actually, the Unix Philosophy describes what is common to typical Unix software.
meillo@40 75 The Wikipedia has an accurate definition:
meillo@40 76 .[
meillo@44 77 wikipedia
meillo@44 78 unix philosophy
meillo@40 79 .]
meillo@40 80 .QP
meillo@40 81 The \fIUnix philosophy\fP is a set of cultural norms and philosophical
meillo@40 82 approaches to developing software based on the experience of leading
meillo@40 83 developers of the Unix operating system.
meillo@1 84 .PP
meillo@40 85 As there is no single definition of the Unix Philosophy,
meillo@40 86 several people have stated their view on what it comprises.
meillo@1 87 Best known are:
meillo@1 88 .IP \(bu
meillo@1 89 Doug McIlroy's summary: ``Write programs that do one thing and do it well.''
meillo@1 90 .[
meillo@44 91 mahoney
meillo@44 92 oral history
meillo@1 93 .]
meillo@1 94 .IP \(bu
meillo@1 95 Mike Gancarz' book ``The UNIX Philosophy''.
meillo@1 96 .[
meillo@44 97 gancarz
meillo@44 98 unix philosophy
meillo@1 99 .]
meillo@1 100 .IP \(bu
meillo@1 101 Eric S. Raymond's book ``The Art of UNIX Programming''.
meillo@1 102 .[
meillo@44 103 raymond
meillo@44 104 art of unix programming
meillo@1 105 .]
meillo@0 106 .LP
meillo@1 107 These different views on the Unix Philosophy have much in common.
meillo@40 108 Especially, the main concepts are similar in all of them.
meillo@40 109 McIlroy's definition can surely be called the core of the Unix Philosophy,
meillo@40 110 but the fundamental idea behind it all, is ``small is beautiful''.
meillo@40 111
meillo@40 112 .PP
meillo@45 113 The Unix Philosophy explains how to design good software for Unix.
meillo@45 114 Many concepts described here, base on facilities of Unix.
meillo@40 115 Other operating systems may not offer such facilities,
meillo@41 116 hence it may not be possible to design software in the way of the
meillo@41 117 Unix Philosophy for them.
meillo@40 118 .PP
meillo@41 119 The Unix Philosophy has an idea of how the process of software development
meillo@41 120 should look like, but large parts of the philosophy are quite independent
meillo@45 121 from a concrete development process.
meillo@41 122 However, one will soon recognize that some development processes work well
meillo@41 123 with the ideas of the Unix Philosophy and support them, while others are
meillo@41 124 at cross-purposes.
meillo@45 125 Kent Beck's books about Extreme Programming are valuable supplemental
meillo@45 126 resources on this topic.
meillo@1 127 .PP
meillo@41 128 The question of how to actually write code and how the code should looks
meillo@45 129 like in detail, are out of focus here.
meillo@41 130 ``The Practice of Programming'' by Kernighan and Pike,
meillo@41 131 .[
meillo@44 132 kernighan pike
meillo@44 133 practice of programming
meillo@41 134 .]
meillo@41 135 is a good book that covers this topic.
meillo@41 136 Its point of view matches to the one of this paper.
meillo@0 137
meillo@0 138 .NH 1
meillo@6 139 Importance of software design in general
meillo@42 140 .XS
meillo@42 141 .sp .5v
meillo@47 142 .B
meillo@42 143 \*(SN Importance of software design in general
meillo@42 144 .XE
meillo@0 145 .LP
meillo@40 146 Software design is the planning of how the internal structure
meillo@40 147 and external interfaces of a software should look like.
meillo@39 148 It has nothing to do with visual appearance.
meillo@39 149 If we take a program as a car, then its color is of no matter.
meillo@39 150 Its design would be the car's size, its shape, the locations of doors,
meillo@45 151 the passenger/space ratio, the available controls and instruments,
meillo@45 152 and so forth.
meillo@39 153 .PP
meillo@39 154 Why should software get designed at all?
meillo@6 155 It is general knowledge, that even a bad plan is better than no plan.
meillo@39 156 Not designing software means programming without plan.
meillo@39 157 This will pretty sure lead to horrible results.
meillo@45 158 Software that is horrible to use and horrible to maintain.
meillo@39 159 These two aspects are the visible ones.
meillo@45 160 Often invisible though, are the wasted possible gains.
meillo@39 161 Good software design can make these gains available.
meillo@2 162 .PP
meillo@39 163 A software's design deals with quality properties.
meillo@39 164 Good design leads to good quality, and quality is important.
meillo@39 165 Any car may be able to drive from A to B,
meillo@39 166 but it depends on the car's properties whether it is a good choice
meillo@39 167 for passenger transport or not.
meillo@39 168 It depends on its properties if it is a good choice
meillo@39 169 for a rough mountain area.
meillo@39 170 And it depends on its properties if the ride will be fun.
meillo@39 171
meillo@2 172 .PP
meillo@39 173 Requirements for a software are twofold:
meillo@39 174 functional and non-functional.
meillo@39 175 .IP \(bu
meillo@39 176 Functional requirements define directly the software's functions.
meillo@39 177 They are the reason why software gets written.
meillo@39 178 Someone has a problem and needs a tool to solve it.
meillo@39 179 Being able to solve the problem is the main functional goal.
meillo@39 180 It is the driving force behind all programming effort.
meillo@39 181 Functional requirements are easier to define and to verify.
meillo@39 182 .IP \(bu
meillo@45 183 Non-functional requirements are called \fIquality\fP requirements, too.
meillo@39 184 The quality of a software are the properties that are not directly related to
meillo@39 185 the software's basic functions.
meillo@45 186 Tools of bad quality often do solve the problems they were written for,
meillo@39 187 but introduce problems and difficulties for usage and development, later on.
meillo@39 188 Quality aspects are often overlooked at first sight,
meillo@45 189 and are often difficult to define clearly and to verify.
meillo@2 190 .PP
meillo@45 191 Quality is hardly interesting when the software gets built initially,
meillo@45 192 but it has a high impact on usability and maintenance of the software, later.
meillo@45 193 A short-sighted might see in developing a software, mainly building something up.
meillo@39 194 But experience shows, that building the software the first time is
meillo@39 195 only a small amount of the overall work.
meillo@45 196 Bug fixing, extending, rebuilding of parts \(en maintenance work \(en
meillo@6 197 does soon take over the major part of the time spent on a software.
meillo@45 198 And of course, the time spent actually using the software.
meillo@6 199 These processes are highly influenced by the software's quality.
meillo@39 200 Thus, quality must not be neglected.
meillo@45 201 However, the problem with quality is that you hardly ``stumble over''
meillo@39 202 bad quality during the first build,
meillo@45 203 although this is the time when you should care about good quality most.
meillo@6 204 .PP
meillo@45 205 Software design has little to do with the basic function of a software \(en
meillo@39 206 this requirement will get satisfied anyway.
meillo@39 207 Software design is more about quality aspects of the software.
meillo@39 208 Good design leads to good quality, bad design to bad quality.
meillo@6 209 The primary functions of the software will be affected modestly by bad quality,
meillo@39 210 but good quality can provide a lot of additional gain,
meillo@6 211 even at places where one never expected it.
meillo@6 212 .PP
meillo@45 213 The ISO/IEC\|9126-1 standard, part\|1,
meillo@6 214 .[
meillo@44 215 iso product quality
meillo@6 216 .]
meillo@6 217 defines the quality model as consisting out of:
meillo@6 218 .IP \(bu
meillo@6 219 .I Functionality
meillo@6 220 (suitability, accuracy, inter\%operability, security)
meillo@6 221 .IP \(bu
meillo@6 222 .I Reliability
meillo@6 223 (maturity, fault tolerance, recoverability)
meillo@6 224 .IP \(bu
meillo@6 225 .I Usability
meillo@6 226 (understandability, learnability, operability, attractiveness)
meillo@6 227 .IP \(bu
meillo@6 228 .I Efficiency
meillo@9 229 (time behavior, resource utilization)
meillo@6 230 .IP \(bu
meillo@6 231 .I Maintainability
meillo@23 232 (analyzability, changeability, stability, testability)
meillo@6 233 .IP \(bu
meillo@6 234 .I Portability
meillo@6 235 (adaptability, installability, co-existence, replaceability)
meillo@6 236 .LP
meillo@39 237 Good design can improve these properties of a software,
meillo@45 238 bad designed software likely suffers in these points.
meillo@7 239 .PP
meillo@7 240 One further goal of software design is consistency.
meillo@7 241 Consistency eases understanding, working on, and using things.
meillo@39 242 Consistent internal structure and consistent interfaces to the outside
meillo@39 243 can be provided by good design.
meillo@7 244 .PP
meillo@39 245 Software should be well designed because good design avoids many
meillo@45 246 problems during a software's lifetime.
meillo@39 247 And software should be well designed because good design can offer
meillo@39 248 much additional gain.
meillo@39 249 Indeed, much effort should be spent into good design to make software more valuable.
meillo@39 250 The Unix Philosophy shows a way of how to design software well.
meillo@7 251 It offers guidelines to achieve good quality and high gain for the effort spent.
meillo@0 252
meillo@0 253
meillo@0 254 .NH 1
meillo@0 255 The Unix Philosophy
meillo@42 256 .XS
meillo@42 257 .sp .5v
meillo@47 258 .B
meillo@42 259 \*(SN The Unix Philosophy
meillo@42 260 .XE
meillo@4 261 .LP
meillo@4 262 The origins of the Unix Philosophy were already introduced.
meillo@8 263 This chapter explains the philosophy, oriented on Gancarz,
meillo@8 264 and shows concrete examples of its application.
meillo@5 265
meillo@16 266 .NH 2
meillo@14 267 Pipes
meillo@42 268 .XS
meillo@42 269 \*(SN Pipes
meillo@42 270 .XE
meillo@4 271 .LP
meillo@4 272 Following are some examples to demonstrate how applied Unix Philosophy feels like.
meillo@4 273 Knowledge of using the Unix shell is assumed.
meillo@4 274 .PP
meillo@4 275 Counting the number of files in the current directory:
meillo@41 276 .DS
meillo@4 277 ls | wc -l
meillo@4 278 .DE
meillo@4 279 The
meillo@4 280 .CW ls
meillo@4 281 command lists all files in the current directory, one per line,
meillo@4 282 and
meillo@4 283 .CW "wc -l
meillo@8 284 counts the number of lines.
meillo@4 285 .PP
meillo@8 286 Counting the number of files that do not contain ``foo'' in their name:
meillo@41 287 .DS
meillo@4 288 ls | grep -v foo | wc -l
meillo@4 289 .DE
meillo@4 290 Here, the list of files is filtered by
meillo@4 291 .CW grep
meillo@45 292 to remove all lines that contain ``foo''.
meillo@45 293 The rest equals the previous example.
meillo@4 294 .PP
meillo@4 295 Finding the five largest entries in the current directory.
meillo@41 296 .DS
meillo@4 297 du -s * | sort -nr | sed 5q
meillo@4 298 .DE
meillo@4 299 .CW "du -s *
meillo@45 300 returns the recursively summed sizes of all files in the current directory
meillo@8 301 \(en no matter if they are regular files or directories.
meillo@4 302 .CW "sort -nr
meillo@45 303 sorts the list numerically in reverse order (descending).
meillo@4 304 Finally,
meillo@4 305 .CW "sed 5q
meillo@4 306 quits after it has printed the fifth line.
meillo@4 307 .PP
meillo@4 308 The presented command lines are examples of what Unix people would use
meillo@4 309 to get the desired output.
meillo@4 310 There are also other ways to get the same output.
meillo@4 311 It's a user's decision which way to go.
meillo@14 312 .PP
meillo@8 313 The examples show that many tasks on a Unix system
meillo@4 314 are accomplished by combining several small programs.
meillo@4 315 The connection between the single programs is denoted by the pipe operator `|'.
meillo@4 316 .PP
meillo@4 317 Pipes, and their extensive and easy use, are one of the great
meillo@4 318 achievements of the Unix system.
meillo@4 319 Pipes between programs have been possible in earlier operating systems,
meillo@4 320 but it has never been a so central part of the concept.
meillo@45 321 When, in the early seventies, Doug McIlroy introduced pipes into the
meillo@4 322 Unix system,
meillo@4 323 ``it was this concept and notation for linking several programs together
meillo@4 324 that transformed Unix from a basic file-sharing system to an entirely new way of computing.''
meillo@4 325 .[
meillo@44 326 aughenbaugh
meillo@44 327 unix oral history
meillo@45 328 .]
meillo@4 329 .PP
meillo@4 330 Being able to specify pipelines in an easy way is,
meillo@4 331 however, not enough by itself.
meillo@5 332 It is only one half.
meillo@4 333 The other is the design of the programs that are used in the pipeline.
meillo@45 334 They need interfaces that allow them to be used in such a way.
meillo@5 335
meillo@16 336 .NH 2
meillo@14 337 Interface design
meillo@42 338 .XS
meillo@42 339 \*(SN Interface design
meillo@42 340 .XE
meillo@5 341 .LP
meillo@11 342 Unix is, first of all, simple \(en Everything is a file.
meillo@5 343 Files are sequences of bytes, without any special structure.
meillo@45 344 Programs should be filters, which read a stream of bytes from standard input (stdin)
meillo@45 345 and write a stream of bytes to standard output (stdout).
meillo@8 346 If the files \fIare\fP sequences of bytes,
meillo@8 347 and the programs \fIare\fP filters on byte streams,
meillo@45 348 then there is exactly one data interface.
meillo@45 349 Hence it is possible to combine programs in any desired way.
meillo@5 350 .PP
meillo@45 351 Even a handful of small programs yields a large set of combinations,
meillo@5 352 and thus a large set of different functions.
meillo@5 353 This is leverage!
meillo@5 354 If the programs are orthogonal to each other \(en the best case \(en
meillo@5 355 then the set of different functions is greatest.
meillo@5 356 .PP
meillo@45 357 Programs can also have a separate control interface,
meillo@11 358 besides their data interface.
meillo@11 359 The control interface is often called ``user interface'',
meillo@11 360 because it is usually designed to be used by humans.
meillo@11 361 The Unix Philosophy discourages to assume the user to be human.
meillo@11 362 Interactive use of software is slow use of software,
meillo@11 363 because the program waits for user input most of the time.
meillo@45 364 Interactive software requires the user to be in front of the computer.
meillo@11 365 Interactive software occupy the user's attention while they are running.
meillo@11 366 .PP
meillo@45 367 Now to come back to the idea of combining several small programs,
meillo@11 368 to have a more specific function.
meillo@11 369 If these single tools would all be interactive,
meillo@11 370 how would the user control them?
meillo@45 371 It is not only a problem to control several programs at once,
meillo@45 372 if they run at the same time,
meillo@11 373 it also very inefficient to have to control each of the single programs
meillo@45 374 that are intended to act as one large program.
meillo@11 375 Hence, the Unix Philosophy discourages programs to demand interactive use.
meillo@11 376 The behavior of programs should be defined at invocation.
meillo@45 377 This is done by specifying arguments to the program call
meillo@45 378 (command line switches).
meillo@11 379 Gancarz discusses this topic as ``avoid captive user interfaces''.
meillo@46 380 .[ [
meillo@44 381 gancarz unix philosophy
meillo@46 382 .], page 88 ff.]
meillo@11 383 .PP
meillo@11 384 Non-interactive use is, during development, also an advantage for testing.
meillo@11 385 Testing of interactive programs is much more complicated,
meillo@11 386 than testing of non-interactive programs.
meillo@5 387
meillo@16 388 .NH 2
meillo@8 389 The toolchest approach
meillo@42 390 .XS
meillo@42 391 \*(SN The toolchest approach
meillo@42 392 .XE
meillo@5 393 .LP
meillo@5 394 A toolchest is a set of tools.
meillo@5 395 Instead of having one big tool for all tasks, one has many small tools,
meillo@5 396 each for one task.
meillo@5 397 Difficult tasks are solved by combining several of the small, simple tools.
meillo@5 398 .PP
meillo@11 399 The Unix toolchest \fIis\fP a set of small, (mostly) non-interactive programs
meillo@11 400 that are filters on byte streams.
meillo@11 401 They are, to a large extend, unrelated in their function.
meillo@11 402 Hence, the Unix toolchest provides a large set of functions
meillo@11 403 that can be accessed by combining the programs in the desired way.
meillo@11 404 .PP
meillo@11 405 There are also advantages for developing small toolchest programs.
meillo@5 406 It is easier and less error-prone to write small programs.
meillo@5 407 It is also easier and less error-prone to write a large set of small programs,
meillo@5 408 than to write one large program with all the functionality included.
meillo@5 409 If the small programs are combinable, then they offer even a larger set
meillo@5 410 of functions than the single large program.
meillo@45 411 Hence, one gets two advantages out of writing small, combinable programs:
meillo@45 412 They are easier to write and they offer a greater set of functions through
meillo@45 413 combination.
meillo@5 414 .PP
meillo@45 415 But there are also two main drawbacks of the toolchest approach.
meillo@45 416 First, one simple, standardized interface has to be sufficient.
meillo@5 417 If one feels the need for more ``logic'' than a stream of bytes,
meillo@8 418 then a different approach might be of need.
meillo@13 419 But it is also possible, that he just can not imagine a design where
meillo@8 420 a stream of bytes is sufficient.
meillo@8 421 By becoming more familiar with the ``Unix style of thinking'',
meillo@8 422 developers will more often and easier find simple designs where
meillo@8 423 a stream of bytes is a sufficient interface.
meillo@8 424 .PP
meillo@8 425 The second drawback of a toolchest affects the users.
meillo@45 426 A toolchest is often more difficult to use.
meillo@9 427 It is necessary to become familiar with each of the tools,
meillo@5 428 to be able to use the right one in a given situation.
meillo@45 429 Additionally, one needs to combine the tools in a senseful way himself.
meillo@45 430 This is like a sharp knife \(en it is a powerful tool in the hand of a
meillo@45 431 master, but of no good value in the hand of an unskilled.
meillo@45 432 However, learning single, small tools of a toolchest is easier than
meillo@45 433 learning a complex tool.
meillo@45 434 And the user will already have a basic understanding of a yet unknown tool,
meillo@45 435 if the tools of a toolchest have a common, consistent style.
meillo@45 436 He will be able to transfer knowledge over from one tool to another.
meillo@5 437 .PP
meillo@45 438 Moreover, the second drawback can be removed to a large extend
meillo@45 439 by adding wrappers around the basic tools.
meillo@45 440 Novice users do not need to learn several tools, if a professional wraps
meillo@45 441 complete command lines into a higher-level script.
meillo@5 442 Note that the wrapper script still calls the small tools;
meillo@45 443 it is just like a skin around them.
meillo@45 444 No complexity is added this way.
meillo@45 445 But new programs can get created out of existing one with very low effort.
meillo@5 446 .PP
meillo@5 447 A wrapper script for finding the five largest entries in the current directory
meillo@5 448 could look like this:
meillo@41 449 .DS
meillo@5 450 #!/bin/sh
meillo@5 451 du -s * | sort -nr | sed 5q
meillo@5 452 .DE
meillo@45 453 The script itself is just a text file that calls the command line,
meillo@45 454 which a professional user would type in directly.
meillo@45 455 It is probably worth to make the program flexible on the number of
meillo@45 456 entries it prints:
meillo@41 457 .DS
meillo@8 458 #!/bin/sh
meillo@8 459 num=5
meillo@8 460 [ $# -eq 1 ] && num="$1"
meillo@8 461 du -sh * | sort -nr | sed "${num}q"
meillo@8 462 .DE
meillo@8 463 This script acts like the one before, when called without an argument.
meillo@8 464 But one can also specify a numerical argument to define the number of lines to print.
meillo@45 465 One can surely imagine even more flexible versions, however,
meillo@45 466 they will still relay on the external programs,
meillo@45 467 which do the actual work.
meillo@5 468
meillo@16 469 .NH 2
meillo@8 470 A powerful shell
meillo@42 471 .XS
meillo@42 472 \*(SN A powerful shell
meillo@42 473 .XE
meillo@8 474 .LP
meillo@45 475 The Unix shell provides the possibility to combine small programs into large ones.
meillo@45 476 But a powerful shell is a great feature in other ways, too.
meillo@45 477 For instance by being scriptable.
meillo@45 478 Control statements are build into the shell.
meillo@45 479 The functions, however, are the normal programs of the system.
meillo@45 480 Thus, as the programs are already known,
meillo@45 481 learning to program in the shell becomes easy.
meillo@8 482 Using normal programs as functions in the shell programming language
meillo@10 483 is only possible because they are small and combinable tools in a toolchest style.
meillo@8 484 .PP
meillo@45 485 The Unix shell encourages to write small scripts,
meillo@45 486 by combining existing programs, because it is so easy to do.
meillo@8 487 This is a great step towards automation.
meillo@8 488 It is wonderful if the effort to automate a task equals the effort
meillo@45 489 to do the task a second time by hand.
meillo@45 490 If this holds,
meillo@45 491 then the user will be happy to automate everything he does more than once.
meillo@8 492 .PP
meillo@8 493 Small programs that do one job well, standardized interfaces between them,
meillo@8 494 a mechanism to combine parts to larger parts, and an easy way to automate tasks,
meillo@8 495 this will inevitably produce software leverage.
meillo@8 496 Getting multiple times the benefit of an investment is a great offer.
meillo@10 497 .PP
meillo@10 498 The shell also encourages rapid prototyping.
meillo@10 499 Many well known programs started as quickly hacked shell scripts,
meillo@10 500 and turned into ``real'' programs, written in C, later.
meillo@45 501 Building a prototype first, is a way to avoid the biggest problems
meillo@10 502 in application development.
meillo@45 503 Fred Brooks explains in ``No Silver Bullet'':
meillo@10 504 .[
meillo@44 505 brooks
meillo@44 506 no silver bullet
meillo@10 507 .]
meillo@10 508 .QP
meillo@10 509 The hardest single part of building a software system is deciding precisely what to build.
meillo@10 510 No other part of the conceptual work is so difficult as establishing the detailed
meillo@10 511 technical requirements, [...].
meillo@10 512 No other part of the work so cripples the resulting system if done wrong.
meillo@10 513 No other part is more difficult to rectify later.
meillo@10 514 .PP
meillo@45 515 Writing a prototype is a great method for becoming familiar with the requirements
meillo@45 516 and to run into real problems early.
meillo@47 517 .[ [
meillo@47 518 gancarz
meillo@47 519 unix philosophy
meillo@47 520 .], page 28 f.]
meillo@45 521 .PP
meillo@45 522 Prototyping is often seen as a first step in building a software.
meillo@10 523 This is, of course, good.
meillo@10 524 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping:
meillo@10 525 After having built the prototype, one might notice, that the prototype is already
meillo@10 526 \fIgood enough\fP.
meillo@45 527 Hence, no reimplementation, in a more sophisticated programming language,
meillo@45 528 might be of need, at least for the moment.
meillo@23 529 Maybe later, it might be necessary to rewrite the software, but not now.
meillo@45 530 By delaying further work, one keeps the flexibility to react on
meillo@10 531 changing requirements.
meillo@10 532 Software parts that are not written will not miss the requirements.
meillo@10 533
meillo@16 534 .NH 2
meillo@10 535 Worse is better
meillo@42 536 .XS
meillo@42 537 \*(SN Worse is better
meillo@42 538 .XE
meillo@10 539 .LP
meillo@45 540 The Unix Philosophy aims for the 90% solution;
meillo@10 541 others call it the ``Worse is better'' approach.
meillo@47 542 Experience from real life projects shows:
meillo@10 543 .PP
meillo@45 544 (1) It is almost never possible to define the
meillo@10 545 requirements completely and correctly the first time.
meillo@45 546 Hence one should not try to; one will fail anyway.
meillo@45 547 .PP
meillo@45 548 (2) Requirements change during time.
meillo@10 549 Hence it is best to delay requirement-based design decisions as long as possible.
meillo@45 550 The software should be small and flexible as long as possible
meillo@10 551 to react on changing requirements.
meillo@10 552 Shell scripts, for example, are more easily adjusted as C programs.
meillo@45 553 .PP
meillo@45 554 (3) Maintenance work is hard work.
meillo@45 555 Hence, one should keep the amount of code as small as possible;
meillo@10 556 it should just fulfill the \fIcurrent\fP requirements.
meillo@45 557 Software parts that will be written in future,
meillo@45 558 do not need maintenance till then.
meillo@10 559 .PP
meillo@47 560 See Brooks' ``The Mythical Man-Month'' for reference.
meillo@47 561 .[ [
meillo@47 562 brooks
meillo@47 563 mythical man-month
meillo@47 564 .], page 115 ff.]
meillo@47 565 .PP
meillo@10 566 Starting with a prototype in a scripting language has several advantages:
meillo@10 567 .IP \(bu
meillo@10 568 As the initial effort is low, one will likely start right away.
meillo@10 569 .IP \(bu
meillo@10 570 As working parts are available soon, the real requirements can get identified soon.
meillo@10 571 .IP \(bu
meillo@45 572 When a software is usable and valuable, it gets used, and thus tested.
meillo@10 573 Hence problems will be found at early stages of the development.
meillo@10 574 .IP \(bu
meillo@10 575 The prototype might be enough for the moment,
meillo@45 576 thus further work on the software can get delayed to a time
meillo@10 577 when one knows better about the requirements and problems,
meillo@10 578 than now.
meillo@10 579 .IP \(bu
meillo@45 580 Implementing now only the parts that are actually needed at the moment,
meillo@45 581 introduces fewer programming and maintenance work.
meillo@10 582 .IP \(bu
meillo@10 583 If the global situation changes so that the software is not needed anymore,
meillo@10 584 then less effort was spent into the project, than it would have be
meillo@10 585 when a different approach had been used.
meillo@10 586
meillo@16 587 .NH 2
meillo@11 588 Upgrowth and survival of software
meillo@42 589 .XS
meillo@42 590 \*(SN Upgrowth and survival of software
meillo@42 591 .XE
meillo@11 592 .LP
meillo@12 593 So far it was talked about \fIwriting\fP or \fIbuilding\fP software.
meillo@13 594 Although these are just verbs, they do imply a specific view on the work process
meillo@13 595 they describe.
meillo@12 596 The better verb, however, is to \fIgrow\fP.
meillo@12 597 Creating software in the sense of the Unix Philosophy is an incremental process.
meillo@12 598 It starts with a first prototype, which evolves as requirements change.
meillo@12 599 A quickly hacked shell script might become a large, sophisticated,
meillo@13 600 compiled program this way.
meillo@13 601 Its lifetime begins with the initial prototype and ends when the software is not used anymore.
meillo@45 602 While being alive it will get extended, rearranged, rebuilt.
meillo@12 603 Growing software matches the view that ``software is never finished. It is only released.''
meillo@46 604 .[ [
meillo@44 605 gancarz
meillo@44 606 unix philosophy
meillo@46 607 .], page 26]
meillo@12 608 .PP
meillo@13 609 Software can be seen as being controlled by evolutionary processes.
meillo@13 610 Successful software is software that is used by many for a long time.
meillo@12 611 This implies that the software is needed, useful, and better than alternatives.
meillo@12 612 Darwin talks about: ``The survival of the fittest.''
meillo@12 613 .[
meillo@44 614 darwin
meillo@44 615 origin of species
meillo@12 616 .]
meillo@12 617 Transferred to software: The most successful software, is the fittest,
meillo@12 618 is the one that survives.
meillo@13 619 (This may be at the level of one creature, or at the level of one species.)
meillo@13 620 The fitness of software is affected mainly by four properties:
meillo@15 621 portability of code, portability of data, range of usability, and reusability of parts.
meillo@13 622 .PP
meillo@15 623 (1)
meillo@15 624 .I "Portability of code
meillo@15 625 means, using high-level programming languages,
meillo@13 626 sticking to the standard,
meillo@47 627 .[ [
meillo@47 628 kernighan pike
meillo@47 629 practice of programming
meillo@47 630 .], chapter\|8]
meillo@13 631 and avoiding optimizations that introduce dependencies on specific hardware.
meillo@13 632 Hardware has a much lower lifetime than software.
meillo@13 633 By chaining software to a specific hardware,
meillo@13 634 the software's lifetime gets shortened to that of this hardware.
meillo@13 635 In contrast, software should be easy to port \(en
meillo@23 636 adaptation is the key to success.
meillo@13 637 .PP
meillo@15 638 (2)
meillo@15 639 .I "Portability of data
meillo@15 640 is best achieved by avoiding binary representations
meillo@13 641 to store data, because binary representations differ from machine to machine.
meillo@23 642 Textual representation is favored.
meillo@45 643 Historically, \s-1ASCII\s0 was the charset of choice.
meillo@45 644 For the future, \s-1UTF\s0-8 might be the better choice.
meillo@13 645 Important is that it is a plain text representation in a
meillo@13 646 very common charset encoding.
meillo@13 647 Apart from being able to transfer data between machines,
meillo@45 648 readable data has the great advantage, that humans are able to directly
meillo@45 649 read and edit it with text editors and other tools from the Unix toolchest.
meillo@47 650 .[ [
meillo@47 651 gancarz
meillo@47 652 unix philosophy
meillo@47 653 .], page 56 ff.]
meillo@13 654 .PP
meillo@15 655 (3)
meillo@15 656 A large
meillo@15 657 .I "range of usability
meillo@23 658 ensures good adaptation, and thus good survival.
meillo@13 659 It is a special distinction if a software becomes used in fields of action,
meillo@13 660 the original authors did never imagine.
meillo@13 661 Software that solves problems in a general way will likely be used
meillo@45 662 for many kinds of similar problems.
meillo@45 663 Being too specific limits the range of usability.
meillo@13 664 Requirements change through time, thus use cases change or even vanish.
meillo@45 665 As a good example in this point,
meillo@13 666 Allman identifies flexibility to be one major reason for sendmail's success:
meillo@13 667 .[
meillo@44 668 allman
meillo@44 669 sendmail
meillo@13 670 .]
meillo@13 671 .QP
meillo@13 672 Second, I limited myself to the routing function [...].
meillo@13 673 This was a departure from the dominant thought of the time, [...].
meillo@13 674 .QP
meillo@45 675 Third, the sendmail configuration file was flexible enough to adapt
meillo@13 676 to a rapidly changing world [...].
meillo@12 677 .LP
meillo@45 678 Successful software adapts itself to the changing world.
meillo@13 679 .PP
meillo@15 680 (4)
meillo@15 681 .I "Reuse of parts
meillo@15 682 is even one step further.
meillo@13 683 A software may completely lose its field of action,
meillo@13 684 but parts of which the software is build may be general and independent enough
meillo@13 685 to survive this death.
meillo@13 686 If software is build by combining small independent programs,
meillo@45 687 then these parts are readily available for reuse.
meillo@13 688 Who cares if the large program is a failure,
meillo@13 689 but parts of it become successful instead?
meillo@10 690
meillo@16 691 .NH 2
meillo@14 692 Summary
meillo@42 693 .XS
meillo@42 694 \*(SN Summary
meillo@42 695 .XE
meillo@0 696 .LP
meillo@45 697 This chapter explained central ideas of the Unix Philosophy.
meillo@45 698 For each of the ideas, the advantages they introduce were explained.
meillo@45 699 The Unix Philosophy are guidelines that help to write more valuable software.
meillo@14 700 From the view point of a software developer or software designer,
meillo@14 701 the Unix Philosophy provides answers to many software design problem.
meillo@14 702 .PP
meillo@14 703 The various ideas of the Unix Philosophy are very interweaved
meillo@14 704 and can hardly be applied independently.
meillo@14 705 However, the probably most important messages are:
meillo@45 706 .I "``Keep it simple!''" ,
meillo@14 707 .I "``Do one thing well!''" ,
meillo@14 708 and
meillo@14 709 .I "``Use software leverage!''
meillo@0 710
meillo@8 711
meillo@8 712
meillo@0 713 .NH 1
meillo@19 714 Case study: \s-1MH\s0
meillo@42 715 .XS
meillo@42 716 .sp .5v
meillo@47 717 .B
meillo@42 718 \*(SN Case study: \s-1MH\s0
meillo@42 719 .XE
meillo@18 720 .LP
meillo@30 721 The previous chapter introduced and explained the Unix Philosophy
meillo@18 722 from a general point of view.
meillo@30 723 The driving force were the guidelines; references to
meillo@18 724 existing software were given only sparsely.
meillo@18 725 In this and the next chapter, concrete software will be
meillo@18 726 the driving force in the discussion.
meillo@18 727 .PP
meillo@23 728 This first case study is about the mail user agents (\s-1MUA\s0)
meillo@23 729 \s-1MH\s0 (``mail handler'') and its descendent \fInmh\fP
meillo@23 730 (``new mail handler'').
meillo@47 731 .[
meillo@47 732 nmh website
meillo@47 733 .]
meillo@23 734 \s-1MUA\s0s provide functions to read, compose, and organize mail,
meillo@45 735 but (ideally) not to transfer it.
meillo@45 736 In this document, the name \s-1MH\s0 will be used to include nmh.
meillo@19 737 A distinction will only be made if differences between
meillo@45 738 \s-1MH\s0 and nmh are described.
meillo@18 739
meillo@0 740
meillo@0 741 .NH 2
meillo@19 742 Historical background
meillo@42 743 .XS
meillo@42 744 \*(SN Historical background
meillo@42 745 .XE
meillo@0 746 .LP
meillo@19 747 Electronic mail was available in Unix very early.
meillo@30 748 The first \s-1MUA\s0 on Unix was \f(CWmail\fP,
meillo@30 749 which was already present in the First Edition.
meillo@46 750 .[ [
meillo@44 751 salus
meillo@44 752 quarter century of unix
meillo@46 753 .], page 41 f.]
meillo@45 754 It was a small program that either printed the user's mailbox file
meillo@45 755 or appended text to someone elses mailbox file,
meillo@19 756 depending on the command line arguments.
meillo@19 757 .[
meillo@44 758 manual mail(1)
meillo@19 759 .]
meillo@19 760 It was a program that did one job well.
meillo@23 761 This job was emailing, which was very simple then.
meillo@19 762 .PP
meillo@23 763 Later, emailing became more powerful, and thus more complex.
meillo@19 764 The simple \f(CWmail\fP, which knew nothing of subjects,
meillo@19 765 independent handling of single messages,
meillo@45 766 and long-time email storage, was not powerful enough anymore.
meillo@45 767 In 1978 at Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
meillo@45 768 to provide additional functions for emailing.
meillo@19 769 Mail was still one program, but now it was large and did
meillo@19 770 several jobs.
meillo@23 771 Its user interface is modeled after the one of \fIed\fP.
meillo@19 772 It is designed for humans, but is still scriptable.
meillo@23 773 \fImailx\fP is the adaptation of Berkeley Mail into System V.
meillo@19 774 .[
meillo@44 775 ritter
meillo@44 776 mailx history
meillo@19 777 .]
meillo@30 778 Elm, pine, mutt, and a whole bunch of graphical \s-1MUA\s0s
meillo@19 779 followed Mail's direction.
meillo@19 780 They are large, monolithic programs which include all emailing functions.
meillo@19 781 .PP
meillo@23 782 A different way was taken by the people of \s-1RAND\s0 Corporation.
meillo@38 783 In the beginning, they also had used a monolithic mail system,
meillo@30 784 called \s-1MS\s0 (for ``mail system'').
meillo@19 785 But in 1977, Stockton Gaines and Norman Shapiro
meillo@19 786 came up with a proposal of a new email system concept \(en
meillo@45 787 one that honored the Unix Philosophy.
meillo@19 788 The concept was implemented by Bruce Borden in 1978 and 1979.
meillo@19 789 This was the birth of \s-1MH\s0 \(en the ``mail handler''.
meillo@18 790 .PP
meillo@18 791 Since then, \s-1RAND\s0, the University of California at Irvine and
meillo@19 792 at Berkeley, and several others have contributed to the software.
meillo@18 793 However, it's core concepts remained the same.
meillo@23 794 In the late 90s, when development of \s-1MH\s0 slowed down,
meillo@19 795 Richard Coleman started with \fInmh\fP, the new mail handler.
meillo@45 796 His goal was to improve \s-1MH\s0 especially in regard of
meillo@23 797 the requirements of modern emailing.
meillo@19 798 Today, nmh is developed by various people on the Internet.
meillo@18 799 .[
meillo@44 800 ware
meillo@44 801 rand history
meillo@18 802 .]
meillo@18 803 .[
meillo@44 804 peek
meillo@44 805 mh
meillo@18 806 .]
meillo@0 807
meillo@0 808 .NH 2
meillo@20 809 Contrasts to monolithic mail systems
meillo@42 810 .XS
meillo@42 811 \*(SN Contrasts to monolithic mail systems
meillo@42 812 .XE
meillo@0 813 .LP
meillo@19 814 All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
meillo@38 815 Although there might actually exist further, very little known,
meillo@30 816 toolchest \s-1MUA\s0s, this statement reflects the situation pretty well.
meillo@19 817 .PP
meillo@30 818 Monolithic \s-1MUA\s0s gather all their functions in one program.
meillo@30 819 In contrast, \s-1MH\s0 is a toolchest of many small tools \(en one for each job.
meillo@23 820 Following is a list of important programs of \s-1MH\s0's toolchest
meillo@30 821 and their function.
meillo@30 822 It gives a feeling of how the toolchest looks like.
meillo@19 823 .IP \(bu
meillo@19 824 .CW inc :
meillo@30 825 incorporate new mail (this is how mail enters the system)
meillo@19 826 .IP \(bu
meillo@19 827 .CW scan :
meillo@19 828 list messages in folder
meillo@19 829 .IP \(bu
meillo@19 830 .CW show :
meillo@19 831 show message
meillo@19 832 .IP \(bu
meillo@19 833 .CW next\fR/\fPprev :
meillo@19 834 show next/previous message
meillo@19 835 .IP \(bu
meillo@19 836 .CW folder :
meillo@19 837 change current folder
meillo@19 838 .IP \(bu
meillo@19 839 .CW refile :
meillo@45 840 refile message into different folder
meillo@19 841 .IP \(bu
meillo@19 842 .CW rmm :
meillo@19 843 remove message
meillo@19 844 .IP \(bu
meillo@19 845 .CW comp :
meillo@45 846 compose new message
meillo@19 847 .IP \(bu
meillo@19 848 .CW repl :
meillo@45 849 reply to message
meillo@19 850 .IP \(bu
meillo@19 851 .CW forw :
meillo@45 852 forward message
meillo@19 853 .IP \(bu
meillo@19 854 .CW send :
meillo@45 855 send prepared message (this is how mail leaves the system)
meillo@0 856 .LP
meillo@19 857 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
meillo@19 858 The user does not leave the shell to run \s-1MH\s0,
meillo@45 859 instead he uses the various \s-1MH\s0 programs within the shell.
meillo@23 860 Using a monolithic program with a captive user interface
meillo@23 861 means ``entering'' the program, using it, and ``exiting'' the program.
meillo@23 862 Using toolchests like \s-1MH\s0 means running programs,
meillo@45 863 alone or in combination with others, also from other toolchests,
meillo@23 864 without leaving the shell.
meillo@30 865
meillo@30 866 .NH 2
meillo@30 867 Data storage
meillo@42 868 .XS
meillo@42 869 \*(SN Data storage
meillo@42 870 .XE
meillo@30 871 .LP
meillo@34 872 \s-1MH\s0's mail storage is a directory tree under the user's
meillo@34 873 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP),
meillo@34 874 where mail folders are directories and mail messages are text files
meillo@34 875 within them.
meillo@34 876 Each mail folder contains a file \f(CW.mh_sequences\fP which lists
meillo@45 877 the public message sequences of that folder,
meillo@45 878 for instance the \fIunseen\fP sequence for new messages.
meillo@34 879 Mail messages are text files located in a mail folder.
meillo@34 880 The files contain the messages as they were received.
meillo@45 881 They are named by ascending numbers in each folder.
meillo@19 882 .PP
meillo@30 883 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0.
meillo@30 884 Alternatives are \fImbox\fP and \fImaildir\fP.
meillo@30 885 In the mbox format all messages are stored within one file.
meillo@30 886 This was a good solution in the early days, when messages
meillo@30 887 were only a few lines of text and were deleted soon.
meillo@30 888 Today, when single messages often include several megabytes
meillo@30 889 of attachments, it is a bad solution.
meillo@30 890 Another disadvantage of the mbox format is that it is
meillo@30 891 more difficult to write tools that work on mail messages,
meillo@30 892 because it is always necessary to first find and extract
meillo@30 893 the relevant message in the mbox file.
meillo@45 894 With the \s-1MH\s0 mailbox format, each message is a separate file.
meillo@30 895 Also, the problem of concurrent access to one mailbox is
meillo@30 896 reduced to the problem of concurrent access to one message.
meillo@45 897 The maildir format is generally similar to the \s-1MH\s0 format,
meillo@30 898 but modified towards guaranteed reliability.
meillo@30 899 This involves some complexity, unfortunately.
meillo@34 900 .PP
meillo@34 901 Working with \s-1MH\s0's toolchest on mailboxes is much like
meillo@34 902 working with Unix' toolchest on directory trees:
meillo@34 903 \f(CWscan\fP is like \f(CWls\fP,
meillo@34 904 \f(CWshow\fP is like \f(CWcat\fP,
meillo@34 905 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP,
meillo@34 906 \f(CWrefile\fP is like \f(CWmv\fP,
meillo@34 907 and \f(CWrmm\fP is like \f(CWrm\fP.
meillo@34 908 .PP
meillo@45 909 \s-1MH\s0 extends the context of processes in Unix by two more items,
meillo@45 910 for its tools:
meillo@34 911 .IP \(bu
meillo@34 912 The current mail folder, which is similar to the current working directory.
meillo@34 913 For mail folders, \f(CWfolder\fP provides the corresponding functionality
meillo@34 914 of \f(CWcd\fP and \f(CWpwd\fP for directories.
meillo@34 915 .IP \(bu
meillo@34 916 Sequences, which are named sets of messages in a mail folder.
meillo@34 917 The current message, relative to a mail folder, is a special sequence.
meillo@34 918 It enables commands like \f(CWnext\fP and \f(CWprev\fP.
meillo@34 919 .LP
meillo@45 920 In contrast to Unix' context, which is maintained by the kernel,
meillo@45 921 \s-1MH\s0's context must be maintained by the tools themselves.
meillo@45 922 Usually there is one context per user, which resides in his
meillo@45 923 \f(CWcontext\fP file in the \s-1MH\s0 directory,
meillo@45 924 but a user can have several contexts, too.
meillo@45 925 Public sequences are an exception, as they belong to a mail folder,
meillo@45 926 and reside in the \f(CW.mh_sequences\fP file there.
meillo@34 927 .[
meillo@44 928 man page mh-profile mh-sequence
meillo@34 929 .]
meillo@20 930
meillo@0 931 .NH 2
meillo@20 932 Discussion of the design
meillo@42 933 .XS
meillo@42 934 \*(SN Discussion of the design
meillo@42 935 .XE
meillo@0 936 .LP
meillo@45 937 This section discusses \s-1MH\s0 in regard to the tenets
meillo@45 938 of the Unix Philosophy that Gancarz identified.
meillo@20 939
meillo@20 940 .PP
meillo@33 941 .B "Small is beautiful
meillo@20 942 and
meillo@33 943 .B "do one thing well
meillo@20 944 are two design goals that are directly visible in \s-1MH\s0.
meillo@45 945 Gancarz actually presents \s-1MH\s0 in his book as example under the
meillo@45 946 headline ``Making \s-1UNIX\s0 Do One Thing Well'':
meillo@46 947 .[ [
meillo@44 948 gancarz
meillo@44 949 unix philosophy
meillo@46 950 .], page 125 ff.]
meillo@20 951 .QP
meillo@20 952 [\s-1MH\s0] consists of a series of programs which
meillo@20 953 when combined give the user an enormous ability
meillo@20 954 to manipulate electronic mail messages.
meillo@20 955 A complex application, it shows that not only is it
meillo@20 956 possible to build large applications from smaller
meillo@20 957 components, but also that such designs are actually preferable.
meillo@20 958 .LP
meillo@45 959 The various programs of \s-1MH\s0 were relatively easy to write,
meillo@45 960 because each of them is small, limited to one function,
meillo@23 961 and has clear boundaries.
meillo@20 962 For the same reasons, they are also good to maintain.
meillo@20 963 Further more, the system can easily get extended.
meillo@20 964 One only needs to put a new program into the toolchest.
meillo@23 965 This was done, for instance, when \s-1MIME\s0 support was added
meillo@20 966 (e.g. \f(CWmhbuild\fP).
meillo@20 967 Also, different programs can exist to do the basically same job
meillo@20 968 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP).
meillo@45 969 .PP
meillo@20 970 If someone needs a mail system with some additionally
meillo@45 971 functions that are not available anywhere yet, he best expands a
meillo@45 972 toolchest system like \s-1MH\s0.
meillo@45 973 There he can add new functionality by simply adding additional
meillo@45 974 programs to the toolchest.
meillo@45 975 There he does not risk to break existing functionality by doing so.
meillo@20 976
meillo@20 977 .PP
meillo@34 978 .B "Store data in flat text files
meillo@34 979 is followed by \s-1MH\s0.
meillo@34 980 This is not surprising, because email messages are already plain text.
meillo@34 981 \s-1MH\s0 stores the messages as it receives them,
meillo@45 982 thus any other tool that works on \s-1RFC\s0\|2822 mail messages can operate
meillo@34 983 on the messages in an \s-1MH\s0 mailbox.
meillo@45 984 All other files \s-1MH\s0 uses are plain text, too.
meillo@34 985 It is therefore possible and encouraged to use the text processing
meillo@34 986 tools of Unix' toolchest to extend \s-1MH\s0's toolchest.
meillo@20 987
meillo@20 988 .PP
meillo@33 989 .B "Avoid captive user interfaces" .
meillo@19 990 \s-1MH\s0 is perfectly suited for non-interactive use.
meillo@19 991 It offers all functions directly and without captive user interfaces.
meillo@30 992 If, nonetheless, users want a graphical user interface,
meillo@45 993 they can have it with \fIxmh\fP or \fIexmh\fP.
meillo@19 994 These are graphical frontends for the \s-1MH\s0 toolchest.
meillo@19 995 This means, all email-related work is still done by \s-1MH\s0 tools,
meillo@45 996 but the frontend calls the appropriate commands when the user
meillo@30 997 clicks on buttons.
meillo@45 998 .PP
meillo@20 999 Providing easy-to-use user interfaces in form of frontends is a good
meillo@19 1000 approach, because it does not limit the power of the backend itself.
meillo@20 1001 The frontend will anyway only be able to make a subset of the
meillo@23 1002 backend's power and flexibility available to the user.
meillo@20 1003 But if it is a separate program,
meillo@20 1004 then the missing parts can still be accessed at the backend directly.
meillo@19 1005 If it is integrated, then this will hardly be possible.
meillo@45 1006 An additional advantage is the possibility to have different frontends
meillo@45 1007 to the same backend.
meillo@19 1008
meillo@19 1009 .PP
meillo@33 1010 .B "Choose portability over efficiency
meillo@20 1011 and
meillo@33 1012 .B "use shell scripts to increase leverage and portability" .
meillo@20 1013 These two tenets are indirectly, but nicely, demonstrated by
meillo@30 1014 Bolsky and Korn in their book about the Korn Shell.
meillo@20 1015 .[
meillo@44 1016 bolsky korn
meillo@44 1017 korn shell
meillo@20 1018 .]
meillo@45 1019 Chapter\|18 of the book shows a basic implementation
meillo@20 1020 of a subset of \s-1MH\s0 in ksh scripts.
meillo@45 1021 Of course, this is just a demonstration, but a brilliant one.
meillo@20 1022 It shows how quickly one can implement such a prototype with shell scripts,
meillo@20 1023 and how readable they are.
meillo@20 1024 The implementation in the scripting language may not be very fast,
meillo@20 1025 but it can be fast enough though, and this is all that matters.
meillo@20 1026 By having the code in an interpreted language, like the shell,
meillo@20 1027 portability becomes a minor issue, if we assume the interpreter
meillo@20 1028 to be widespread.
meillo@45 1029 .PP
meillo@20 1030 This demonstration also shows how easy it is to create single programs
meillo@20 1031 of a toolchest software.
meillo@45 1032 Eight tools (two of them have multiple names) and 16 functions
meillo@45 1033 with supporting code are presented to the reader.
meillo@45 1034 The tools comprise less than 40 lines of ksh each,
meillo@30 1035 in total about 200 lines.
meillo@45 1036 The functions comprise less than 80 lines of ksh each,
meillo@30 1037 in total about 450 lines.
meillo@20 1038 Such small software is easy to write, easy to understand,
meillo@20 1039 and thus easy to maintain.
meillo@23 1040 A toolchest improves the possibility to only write some parts
meillo@20 1041 and though create a working result.
meillo@45 1042 Expanding the toolchest, even without global changes,
meillo@45 1043 will likely be possible.
meillo@20 1044
meillo@20 1045 .PP
meillo@33 1046 .B "Use software leverage to your advantage
meillo@20 1047 and the lesser tenet
meillo@33 1048 .B "allow the user to tailor the environment
meillo@20 1049 are ideally followed in the design of \s-1MH\s0.
meillo@21 1050 Tailoring the environment is heavily encouraged by the ability to
meillo@30 1051 directly define default options to programs.
meillo@30 1052 It is even possible to define different default options
meillo@45 1053 depending on the name under which a program is called.
meillo@45 1054 Software leverage is heavily encouraged by the ease of
meillo@45 1055 creating shell scripts that run a specific command line,
meillo@30 1056 built of several \s-1MH\s0 programs.
meillo@21 1057 There is few software that so much wants users to tailor their
meillo@21 1058 environment and to leverage the use of the software, like \s-1MH\s0.
meillo@45 1059 .PP
meillo@21 1060 Just to make one example:
meillo@23 1061 One might prefer a different listing format for the \f(CWscan\fP
meillo@21 1062 program.
meillo@30 1063 It is possible to take one of the distributed format files
meillo@21 1064 or to write one yourself.
meillo@21 1065 To use the format as default for \f(CWscan\fP, a single line,
meillo@21 1066 reading
meillo@21 1067 .DS
meillo@21 1068 scan: -form FORMATFILE
meillo@21 1069 .DE
meillo@21 1070 must be added to \f(CW.mh_profile\fP.
meillo@21 1071 If one wants this different format as an additional command,
meillo@23 1072 instead of changing the default, he needs to create a link to
meillo@23 1073 \f(CWscan\fP, for instance titled \f(CWscan2\fP.
meillo@21 1074 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP,
meillo@45 1075 as the option should only be in effect for a program that is called as
meillo@21 1076 \f(CWscan2\fP.
meillo@20 1077
meillo@20 1078 .PP
meillo@33 1079 .B "Make every program a filter
meillo@21 1080 is hard to find in \s-1MH\s0.
meillo@21 1081 The reason therefore is that most of \s-1MH\s0's tools provide
meillo@45 1082 basic file system operations for mailboxes.
meillo@45 1083 It is the same reason because of which \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP,
meillo@45 1084 and \f(CWrm\fP aren't filters neither.
meillo@23 1085 \s-1MH\s0 does not provide many filters itself, but it is a basis
meillo@23 1086 to write filters for.
meillo@45 1087 An example would be a mail text highlighter,
meillo@30 1088 that means a program that makes use of a color terminal to display
meillo@30 1089 header lines, quotations, and signatures in distinct colors.
meillo@45 1090 The author's version of such a program is an awk script with 25 lines.
meillo@21 1091
meillo@21 1092 .PP
meillo@33 1093 .B "Build a prototype as soon as possible
meillo@21 1094 was again well followed by \s-1MH\s0.
meillo@21 1095 This tenet, of course, focuses on early development, which is
meillo@21 1096 long time ago for \s-1MH\s0.
meillo@21 1097 But without following this guideline at the very beginning,
meillo@23 1098 Bruce Borden may have not convinced the management of \s-1RAND\s0
meillo@23 1099 to ever create \s-1MH\s0.
meillo@23 1100 In Bruce' own words:
meillo@46 1101 .[ [
meillo@44 1102 ware rand history
meillo@46 1103 .], page 132]
meillo@21 1104 .QP
meillo@45 1105 [...] but [Stockton Gaines and Norm Shapiro] were not able
meillo@23 1106 to convince anyone that such a system would be fast enough to be usable.
meillo@21 1107 I proposed a very short project to prove the basic concepts,
meillo@21 1108 and my management agreed.
meillo@21 1109 Looking back, I realize that I had been very lucky with my first design.
meillo@21 1110 Without nearly enough design work,
meillo@21 1111 I built a working environment and some header files
meillo@21 1112 with key structures and wrote the first few \s-1MH\s0 commands:
meillo@21 1113 inc, show/next/prev, and comp.
meillo@21 1114 [...]
meillo@21 1115 With these three, I was able to convince people that the structure was viable.
meillo@21 1116 This took about three weeks.
meillo@0 1117
meillo@0 1118 .NH 2
meillo@0 1119 Problems
meillo@42 1120 .XS
meillo@42 1121 \*(SN Problems
meillo@42 1122 .XE
meillo@0 1123 .LP
meillo@45 1124 \s-1MH\s0 is not without problems.
meillo@30 1125 There are two main problems: one is technical, the other is about human behavior.
meillo@22 1126 .PP
meillo@22 1127 \s-1MH\s0 is old and email today is very different to email in the time
meillo@22 1128 when \s-1MH\s0 was designed.
meillo@45 1129 \s-1MH\s0 adapted to the changes pretty well, but it is limited, though.
meillo@22 1130 \s-1MIME\s0 support and support for different character encodings
meillo@22 1131 is available, but only on a moderate level.
meillo@45 1132 This comes from limited development resources.
meillo@45 1133 More active developers could quickly change this.
meillo@45 1134 But \s-1MH\s0 is also limited by design, which is the larger problem.
meillo@22 1135 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extend.
meillo@22 1136 These design conflicts are not easily solvable.
meillo@22 1137 Possibly, they require a redesign.
meillo@45 1138 \s-1IMAP\s0 may be too different to the classic mail model,
meillo@45 1139 which \s-1MH\s0 covers, so that \s-1MH\s0 may never support it well.
meillo@22 1140 .PP
meillo@45 1141 The other kind of problem are human habits.
meillo@45 1142 In this world, where almost all \s-1MUA\s0s are monolithic,
meillo@22 1143 it is very difficult to convince people to use a toolbox style \s-1MUA\s0
meillo@22 1144 like \s-1MH\s0.
meillo@45 1145 The habits are so strong, that even people who understand the concept
meillo@30 1146 and advantages of \s-1MH\s0 do not like to switch,
meillo@30 1147 simply because \s-1MH\s0 is different.
meillo@30 1148 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel,
meillo@45 1149 are quite outdated and thus not very appealing, compared to the modern interfaces
meillo@45 1150 of many monolithic \s-1MUA\s0s.
meillo@20 1151
meillo@20 1152 .NH 2
meillo@20 1153 Summary \s-1MH\s0
meillo@42 1154 .XS
meillo@42 1155 \*(SN Summary \s-1MH\s0
meillo@42 1156 .XE
meillo@20 1157 .LP
meillo@45 1158 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design.
meillo@31 1159 It consists of a toolchest of small tools, each of them does one job well.
meillo@31 1160 The toolchest approach offers great flexibility to the user.
meillo@45 1161 It is possible to utilize the complete power of the Unix shell with \s-1MH\s0.
meillo@31 1162 This makes \s-1MH\s0 a very powerful mail system.
meillo@45 1163 Extending and customizing \s-1MH\s0 is easy and encouraged.
meillo@31 1164 .PP
meillo@31 1165 Apart from the user's perspective, \s-1MH\s0 is development-friendly.
meillo@31 1166 Its overall design follows clear rules.
meillo@31 1167 The single tools do only one job, thus they are easy to understand,
meillo@31 1168 easy to write, and good to maintain.
meillo@31 1169 They are all independent and do not interfere with the others.
meillo@31 1170 Automated testing of their function is a straight forward task.
meillo@31 1171 .PP
meillo@31 1172 It is sad, that \s-1MH\s0's differentness is its largest problem,
meillo@31 1173 as its differentness is also its largest advantage.
meillo@31 1174 Unfortunately, for most people their habits are stronger
meillo@31 1175 than the attraction of the clear design and the power, \s-1MH\s0 offers.
meillo@0 1176
meillo@8 1177
meillo@8 1178
meillo@0 1179 .NH 1
meillo@0 1180 Case study: uzbl
meillo@42 1181 .XS
meillo@42 1182 .sp .5v
meillo@47 1183 .B
meillo@42 1184 \*(SN Case study: uzbl
meillo@42 1185 .XE
meillo@32 1186 .LP
meillo@32 1187 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0,
meillo@45 1188 which is an old and established software.
meillo@45 1189 This chapter covers uzbl, a fresh new project.
meillo@45 1190 Uzbl is a web browser that adheres to the Unix Philosophy.
meillo@45 1191 Its name comes from the \fILolspeak\fP word for ``usable'';
meillo@45 1192 it is pronounced identical.
meillo@0 1193
meillo@0 1194 .NH 2
meillo@32 1195 Historical background
meillo@42 1196 .XS
meillo@42 1197 \*(SN Historical background
meillo@42 1198 .XE
meillo@0 1199 .LP
meillo@32 1200 Uzbl was started by Dieter Plaetinck in April 2009.
meillo@44 1201 The idea was born in a thread in the Arch Linux Forums.
meillo@32 1202 .[
meillo@44 1203 arch linux forums
meillo@44 1204 browser
meillo@32 1205 .]
meillo@32 1206 After some discussion about failures of well known web browsers,
meillo@32 1207 Plaetinck (alias Dieter@be) came up with a very sketchy proposal
meillo@32 1208 of how a better web browser could look like.
meillo@32 1209 To the question of another member, if Plaetinck would write that program,
meillo@32 1210 because it would sound fantastic, Plaetinck replied:
meillo@32 1211 ``Maybe, if I find the time ;-)''.
meillo@32 1212 .PP
meillo@32 1213 Fortunately, he found the time.
meillo@32 1214 One day later, the first prototype was out.
meillo@32 1215 One week later, uzbl had an own website.
meillo@47 1216 .[
meillo@47 1217 uzbl website
meillo@47 1218 .]
meillo@32 1219 One month after the first code showed up,
meillo@47 1220 a mailing list was installed to coordinate and discuss further development,
meillo@47 1221 and a wiki was added to store documentation and scripts that showed up on the
meillo@32 1222 mailing list and elsewhere.
meillo@32 1223 .PP
meillo@45 1224 In the, now, one year of uzbl's existence, it was heavily developed on various branches.
meillo@32 1225 Plaetinck's task became more and more to only merge the best code from the
meillo@32 1226 different branches into his main branch, and to apply patches.
meillo@47 1227 .[
meillo@47 1228 lwn uzbl
meillo@47 1229 .]
meillo@32 1230 About once a month, Plaetinck released a new version.
meillo@32 1231 In September 2009, he presented several forks of uzbl.
meillo@47 1232 .[ [
meillo@47 1233 uzbl website
meillo@47 1234 .], news archive]
meillo@38 1235 Uzbl, actually, opened the field for a whole family of web browsers with similar shape.
meillo@32 1236 .PP
meillo@32 1237 In July 2009, \fILinux Weekly News\fP published an interview with Plaetinck about uzbl.
meillo@47 1238 .[
meillo@47 1239 lwn uzbl
meillo@47 1240 .]
meillo@32 1241 In September 2009, the uzbl web browser was on \fISlashdot\fP.
meillo@47 1242 .[
meillo@47 1243 slashdot uzbl
meillo@47 1244 .]
meillo@0 1245
meillo@0 1246 .NH 2
meillo@32 1247 Contrasts to other web browsers
meillo@42 1248 .XS
meillo@42 1249 \*(SN Contrasts to other web browsers
meillo@42 1250 .XE
meillo@0 1251 .LP
meillo@32 1252 Like most \s-1MUA\s0s are monolithic, but \s-1MH\s0 is a toolchest,
meillo@32 1253 most web browsers are monolithic, but uzbl is a frontend to a toolchest.
meillo@32 1254 .PP
meillo@32 1255 Today, uzbl is divided into uzbl-core and uzbl-browser.
meillo@32 1256 Uzbl-core is, how its name already indicates, the core of uzbl.
meillo@32 1257 It handles commands and events to interface other programs,
meillo@45 1258 and also displays webpages by using \fIwebkit\fP as render engine.
meillo@32 1259 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar,
meillo@32 1260 an event manager, yanking, pasting, page searching, zooming, and more stuff,
meillo@32 1261 to form a ``complete'' web browser.
meillo@32 1262 In the following text, the term ``uzbl'' usually stands for uzbl-browser,
meillo@32 1263 so uzbl-core is included.
meillo@32 1264 .PP
meillo@32 1265 Unlike most other web browsers, uzbl is mainly the mediator between the
meillo@45 1266 various tools that cover single jobs.
meillo@35 1267 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket,
meillo@35 1268 and on stdin, and it writes events to a Unix socket and to stdout.
meillo@35 1269 Loading a webpage in a running uzbl instance requires only:
meillo@32 1270 .DS
meillo@32 1271 echo 'uri' >/path/to/uzbl-fifo
meillo@32 1272 .DE
meillo@45 1273 The graphical rendering of the webpage is done by webkit,
meillo@45 1274 a web content engine.
meillo@45 1275 Uzbl-core is built around libwebkit.
meillo@32 1276 .PP
meillo@45 1277 Downloads, browsing history, bookmarks, and the like are not provided
meillo@45 1278 by the core itself, like they are in other web browsers.
meillo@35 1279 Uzbl-browser also only provides, so called, handler scripts that wrap
meillo@35 1280 external applications which provide the actual functionality.
meillo@32 1281 For instance, \fIwget\fP is used to download files and uzbl-browser
meillo@32 1282 includes a script that calls wget with appropriate options in
meillo@32 1283 a prepared environment.
meillo@32 1284 .PP
meillo@32 1285 Modern web browsers are proud to have addons, plugins, and modules, instead.
meillo@32 1286 This is their effort to achieve similar goals.
meillo@35 1287 But instead of using existing, external programs, modern web browsers
meillo@45 1288 include these functions.
meillo@0 1289
meillo@0 1290 .NH 2
meillo@32 1291 Discussion of the design
meillo@42 1292 .XS
meillo@42 1293 \*(SN Discussion of the design
meillo@42 1294 .XE
meillo@0 1295 .LP
meillo@32 1296 This section discusses uzbl in regard of the Unix Philosophy,
meillo@32 1297 as identified by Gancarz.
meillo@32 1298
meillo@32 1299 .PP
meillo@35 1300 .B "Make each program do one thing well" .
meillo@35 1301 Uzbl tries to be a web browser and nothing else.
meillo@36 1302 The common definition of a web browser is, of course, highly influenced by
meillo@36 1303 existing implementations of web browsers, although they are degenerated.
meillo@35 1304 Web browsers should be programs to browse the web, and nothing more.
meillo@45 1305 This is the one thing they should do.
meillo@36 1306 .PP
meillo@45 1307 Web browsers should not, for instance, manage downloads.
meillo@35 1308 This is the job download managers exist for.
meillo@35 1309 Download managers do primary care about being good in downloading files.
meillo@35 1310 Modern web browsers provide download management only as a secondary feature.
meillo@45 1311 How could they do this job better, than programs that exist only for
meillo@35 1312 this very job?
meillo@35 1313 And how could anyone want less than the best download manager available?
meillo@32 1314 .PP
meillo@35 1315 A web browser's job is to let the user browse the web.
meillo@35 1316 This means, navigating through websites by following links.
meillo@36 1317 Rendering the \s-1HTML\s0 sources is a different job, too.
meillo@36 1318 It is covered by the webkit render engine, in uzbl's case.
meillo@35 1319 Audio and video content and files like PostScript, \s-1PDF\s0, and the like,
meillo@36 1320 are also not the job of a web browser.
meillo@36 1321 They should be handled by external applications \(en
meillo@36 1322 ones which's job is to handle such data.
meillo@35 1323 Uzbl strives to do it this way.
meillo@36 1324 .PP
meillo@36 1325 Remember Doug McIlroy:
meillo@35 1326 .I
meillo@35 1327 ``Write programs that do one thing and do it well.
meillo@35 1328 Write programs to work together.''
meillo@35 1329 .R
meillo@35 1330 .PP
meillo@35 1331 The lesser tenet
meillo@35 1332 .B "allow the user to tailor the environment
meillo@35 1333 matches good here.
meillo@35 1334 There was the question, how anyone could want anything less than the
meillo@35 1335 best program for the job.
meillo@45 1336 But as personal preferences matter, it is probably more important to ask:
meillo@35 1337 How could anyone want something else than his preferred program for the job?
meillo@36 1338 .PP
meillo@45 1339 Usually users want one program for a specific job.
meillo@35 1340 Hence, whenever the task is, for instance, downloading,
meillo@45 1341 the same download manager should be used.
meillo@35 1342 More advanced users might want to have this download manager in this
meillo@35 1343 situation and that one in that situation.
meillo@35 1344 They should be able to configure it this way.
meillo@35 1345 With uzbl, one can use any download manager the user wants.
meillo@36 1346 To switch to a different one, only one line in a small handler script
meillo@35 1347 needs to be changed.
meillo@45 1348 Alternatively it would be possible to query the program to use by
meillo@45 1349 reading a global file or an environment variable, in the handler script.
meillo@36 1350 .PP
meillo@45 1351 Uzbl does neither have its own download manager nor depends on a
meillo@45 1352 specific one, hence uzbl's browsing abilities will not be lowered by having
meillo@35 1353 a bad download manager.
meillo@45 1354 Uzbl's download capabilities will be just as good as the ones of the best
meillo@36 1355 download manager available on the system.
meillo@38 1356 Of course, this applies to all of the other supplementary tools, too.
meillo@32 1357
meillo@32 1358 .PP
meillo@36 1359 .B "Use software leverage to your advantage" .
meillo@36 1360 Uzbl is designed to be extended by external tools.
meillo@36 1361 These external tools are usually wrapped by small handler shell scripts.
meillo@36 1362 Shell scripts are the glue in this approach.
meillo@36 1363 They make the various parts fit together.
meillo@36 1364 .PP
meillo@45 1365 The history mechanism of uzbl shall be presented as an example.
meillo@36 1366 Uzbl is configured to spawn a script to append an entry to the history
meillo@36 1367 whenever the event of a fully loaded page occurs.
meillo@45 1368 The script to append the entry to the history is not much more than:
meillo@36 1369 .DS
meillo@36 1370 #!/bin/sh
meillo@36 1371 file=/path/to/uzbl-history
meillo@36 1372 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file
meillo@36 1373 .DE
meillo@36 1374 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title.
meillo@45 1375 .PP
meillo@45 1376 For loading an entry, a key is bound to spawn a load-from-history script.
meillo@36 1377 The script reverses the history to have newer entries first,
meillo@45 1378 then displays \fIdmenu\fP to let the user select an item,
meillo@36 1379 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe.
meillo@45 1380 With error checking and corner case handling removed,
meillo@45 1381 the script looks like this:
meillo@36 1382 .DS
meillo@36 1383 #!/bin/sh
meillo@36 1384 file=/path/to/uzbl-history
meillo@36 1385 goto=`tac $file | dmenu | cut -d' ' -f 3`
meillo@36 1386 echo "uri $goto" > $4
meillo@36 1387 .DE
meillo@36 1388 \f(CW$4\fP expands to the path of the command input pipe of the current
meillo@36 1389 uzbl instance.
meillo@32 1390
meillo@32 1391 .PP
meillo@33 1392 .B "Avoid captive user interfaces" .
meillo@36 1393 One could say, that uzbl, to a large extend, actually \fIis\fP
meillo@36 1394 a captive user interface.
meillo@37 1395 But the difference to most other web browsers is, that uzbl is only
meillo@45 1396 the captive user interface frontend (and the core of the backend).
meillo@38 1397 Many parts of the backend are independent of uzbl.
meillo@45 1398 Some are distributed with uzbl, for some external programs,
meillo@45 1399 handler scripts are distributed,
meillo@45 1400 but arbitrary additional functionality can be added if desired.
meillo@37 1401 .PP
meillo@37 1402 The frontend is captive \(en that is true.
meillo@37 1403 This is okay for the task of browsing the web, as this task is only relevant
meillo@37 1404 for humans.
meillo@37 1405 Automated programs would \fIcrawl\fP the web.
meillo@37 1406 That means, they read the source directly.
meillo@37 1407 The source includes all the semantics.
meillo@37 1408 The graphical representation is just for humans to transfer the semantics
meillo@37 1409 more intuitively.
meillo@32 1410
meillo@32 1411 .PP
meillo@33 1412 .B "Make every program a filter" .
meillo@37 1413 Graphical web browsers are almost dead ends in the chain of information flow.
meillo@37 1414 Thus it is difficult to see what graphical web browsers should filter.
meillo@45 1415 Graphical web browsers exist almost only to be interactively used by humans.
meillo@37 1416 The only case when one might want to automate the rendering function is
meillo@37 1417 to generate images of rendered webpages.
meillo@37 1418
meillo@37 1419 .PP
meillo@37 1420 .B "Small is beautiful"
meillo@45 1421 is not easy to apply to a web browser, because modern web technology
meillo@45 1422 is very complex, hence the rendering task is very complex.
meillo@45 1423 Modern web browsers have to consist of many thousand lines of code,
meillo@37 1424 unfortunately.
meillo@37 1425 Using the toolchest approach and wrappers can split the browser into
meillo@37 1426 several small parts, tough.
meillo@37 1427 .PP
meillo@45 1428 As of March 2010, uzbl-core consists of about 3\,500 lines of C code.
meillo@37 1429 The distribution includes another 3\,500 lines of Shell and Python code,
meillo@37 1430 which are the handler scripts and plugins like a modal interface.
meillo@38 1431 Further more, uzbl uses functionality of external tools like
meillo@38 1432 \fIwget\fP and \fInetcat\fP.
meillo@37 1433 Up to this point, uzbl looks pretty neat and small.
meillo@38 1434 The ugly part of uzbl is the web content renderer, webkit.
meillo@37 1435 Webkit consists of roughly 400\,000 (!) lines of code.
meillo@38 1436 Unfortunately, small web render engines are not possible anymore
meillo@38 1437 because of the modern web.
meillo@35 1438
meillo@35 1439 .PP
meillo@35 1440 .B "Build a prototype as soon as possible" .
meillo@35 1441 Plaetinck made his code public, right from the beginning.
meillo@38 1442 Discussion and development was, and still is, open to everyone interested.
meillo@38 1443 Development versions of uzbl can be obtained very simply from the code
meillo@38 1444 repository.
meillo@38 1445 Within the first year of uzbl's existence, a new version was released
meillo@35 1446 more often than once a month.
meillo@38 1447 Different forks and branches arose.
meillo@45 1448 They introduced new features, which were tested for suitability
meillo@45 1449 for the main branch.
meillo@35 1450 The experiences of using prototypes influenced further development.
meillo@35 1451 Actually, all development was community driven.
meillo@38 1452 Plaetinck says, three months after uzbl's birth:
meillo@35 1453 ``Right now I hardly code anything myself for Uzbl.
meillo@35 1454 I just merge in other people's code, ponder a lot, and lead the discussions.''
meillo@35 1455 .[
meillo@44 1456 lwn
meillo@44 1457 uzbl
meillo@35 1458 .]
meillo@32 1459
meillo@0 1460
meillo@0 1461 .NH 2
meillo@0 1462 Problems
meillo@42 1463 .XS
meillo@42 1464 \*(SN Problems
meillo@42 1465 .XE
meillo@0 1466 .LP
meillo@38 1467 Similar to \s-1MH\s0, uzbl, too suffers from being different.
meillo@38 1468 It is sad, but people use what they know.
meillo@38 1469 Fortunately, uzbl's user interface can look and feel very much the
meillo@38 1470 same as the one of the well known web browsers,
meillo@38 1471 hiding the internal differences.
meillo@38 1472 But uzbl has to provide this similar look and feel to be accepted
meillo@38 1473 as a ``normal'' browser by ``normal'' users.
meillo@37 1474 .PP
meillo@45 1475 Though, the more important problem is the modern web.
meillo@38 1476 The modern web is simply broken.
meillo@38 1477 It has state in a state-less protocol,
meillo@38 1478 it misuses technologies,
meillo@38 1479 and it is helplessly overloaded.
meillo@38 1480 The result are web content render engines that must consist
meillo@38 1481 of hundreds of thousands lines of code.
meillo@38 1482 They also must combine and integrate many different technologies,
meillo@45 1483 only to make our modern web accessible.
meillo@38 1484 Website to image converter are hardly possible to run without
meillo@38 1485 human interaction because of state in sessions, impossible
meillo@38 1486 deep-linking, and unautomatable technologies.
meillo@37 1487 .PP
meillo@38 1488 The web was misused to provide all kinds of imaginable wishes.
meillo@38 1489 Now web browsers, and eventually the users, suffer from it.
meillo@37 1490
meillo@8 1491
meillo@32 1492 .NH 2
meillo@32 1493 Summary uzbl
meillo@42 1494 .XS
meillo@42 1495 \*(SN Summary uzbl
meillo@42 1496 .XE
meillo@32 1497 .LP
meillo@38 1498 ``Uzbl is a browser that adheres to the Unix Philosophy'',
meillo@38 1499 that is how uzbl is seen by its authors.
meillo@38 1500 Indeed, uzbl follows the Unix Philosophy in many ways.
meillo@38 1501 It consists of independent parts that work together,
meillo@45 1502 while its core is mainly a mediator which glues the parts together.
meillo@38 1503 .PP
meillo@38 1504 Software leverage can excellently be seen in uzbl.
meillo@45 1505 External tools are used, independent tasks are separated
meillo@45 1506 in independent parts and glued together with small handler scripts.
meillo@38 1507 .PP
meillo@38 1508 As uzbl, more or less, consists of a set of tools and a bit
meillo@38 1509 of glue, anyone can put the parts together and expand it
meillo@38 1510 in any desired way.
meillo@38 1511 Uzbl is very flexible and customizable.
meillo@38 1512 These properties make it valuable for advanced users,
meillo@38 1513 but may keep novice users from using it.
meillo@38 1514 .PP
meillo@45 1515 But uzbl's main problem is the modern web, that makes it hard
meillo@38 1516 to design a sane web browser.
meillo@38 1517 Despite this bad situation, uzbl does a fairly good job.
meillo@32 1518
meillo@8 1519
meillo@0 1520 .NH 1
meillo@0 1521 Final thoughts
meillo@42 1522 .XS
meillo@42 1523 .sp .5v
meillo@47 1524 .B
meillo@42 1525 \*(SN Final thoughts
meillo@42 1526 .XE
meillo@0 1527
meillo@0 1528 .NH 2
meillo@0 1529 Quick summary
meillo@42 1530 .XS
meillo@42 1531 \*(SN Quick summary
meillo@42 1532 .XE
meillo@0 1533 .LP
meillo@0 1534 good design
meillo@0 1535 .LP
meillo@0 1536 unix phil
meillo@0 1537 .LP
meillo@0 1538 case studies
meillo@0 1539
meillo@0 1540 .NH 2
meillo@0 1541 Why people should choose
meillo@42 1542 .XS
meillo@42 1543 \*(SN Why people should choose
meillo@42 1544 .XE
meillo@0 1545 .LP
meillo@0 1546 Make the right choice!
meillo@0 1547
meillo@47 1548
meillo@47 1549 .bp
meillo@47 1550 .TL
meillo@47 1551 References
meillo@47 1552 .LP
meillo@47 1553 .XS
meillo@47 1554 .sp .5v
meillo@47 1555 .B
meillo@47 1556 References
meillo@47 1557 .XE
meillo@47 1558 .ev r
meillo@0 1559 .rm ]<
meillo@0 1560 .de ]<
meillo@0 1561 .LP
meillo@0 1562 .de FP
meillo@0 1563 .IP \\\\$1.
meillo@0 1564 \\..
meillo@0 1565 .rm FS FE
meillo@0 1566 ..
meillo@42 1567 .nr PS -1
meillo@42 1568 .nr VS -1
meillo@0 1569 .[
meillo@0 1570 $LIST$
meillo@0 1571 .]
meillo@47 1572 .nr PS +1
meillo@47 1573 .nr VS +1
meillo@47 1574 .ev
meillo@47 1575
meillo@42 1576 .bp
meillo@47 1577 .TL
meillo@47 1578 Table of Contents
meillo@47 1579 .LP
meillo@47 1580 .PX no