docs/unix-phil

annotate unix-phil.ms @ 45:ade392f024aa

find changesets by author, revision, files, or words in the commit message
a lot of rework throughout the whole document
author meillo@marmaro.de
date Mon, 12 Apr 2010 09:33:01 +0200
parents 46e34e433231
children 98a1446744c7
rev   line source
meillo@36 1 .nr PS 11
meillo@36 2 .nr VS 13
meillo@0 3 .nr lu 0
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
meillo@17 9 .if t .if !^\\$1^^ \&\\$1\f\\n(PQ\\$2
meillo@0 10 .if n .if \\n(.$=1 \&\\$1
meillo@0 11 .if n .if \\n(.$>1 \&\\$1\c
meillo@0 12 .if n .if \\n(.$>1 \&\\$2
meillo@0 13 ..
meillo@0 14 .ds [. \ [
meillo@0 15 .ds .] ]
meillo@42 16
meillo@42 17 .rn NH _N
meillo@42 18 .de NH
meillo@42 19 .if '\\$1'1' .sp 2v
meillo@42 20 .if '\\$1'1' .nr PS +2
meillo@42 21 ._N \\$1
meillo@42 22 .if '\\$1'1' .nr PS -2
meillo@42 23 ..
meillo@42 24
meillo@45 25 .am QP
meillo@45 26 .ps -1
meillo@45 27 ..
meillo@45 28
meillo@1 29 .\"----------------------------------------
meillo@42 30
meillo@0 31 .TL
meillo@42 32 .ps +4
meillo@6 33 Why the Unix Philosophy still matters
meillo@0 34 .AU
meillo@0 35 markus schnalke <meillo@marmaro.de>
meillo@0 36 .AB
meillo@1 37 .ti \n(.iu
meillo@39 38 This paper explains the importance of the Unix Philosophy for software design.
meillo@0 39 Today, few software designers are aware of these concepts,
meillo@39 40 and thus a lot of modern software is more limited than necessary
meillo@39 41 and makes less use of software leverage than possible.
meillo@38 42 Knowing and following the guidelines of the Unix Philosophy makes software more valuable.
meillo@0 43 .AE
meillo@0 44
meillo@2 45 .FS
meillo@2 46 .ps -1
meillo@39 47 This paper was prepared for the ``Software Analysis'' seminar at University Ulm.
meillo@39 48 Mentor was professor Schweiggert. 2010-04-05
meillo@2 49 .br
meillo@39 50 You may retrieve this document from
meillo@39 51 .CW \s-1http://marmaro.de/docs \ .
meillo@2 52 .FE
meillo@2 53
meillo@0 54 .NH 1
meillo@0 55 Introduction
meillo@42 56 .XS
meillo@42 57 \*(SN Introduction
meillo@42 58 .XE
meillo@0 59 .LP
meillo@40 60 The Unix Philosophy is the essence of how the Unix operating system,
meillo@40 61 especially its toolchest, was designed.
meillo@40 62 It is no limited set of fixed rules,
meillo@40 63 but a loose set of guidelines which tell how to write software that
meillo@40 64 suites well into Unix.
meillo@40 65 Actually, the Unix Philosophy describes what is common to typical Unix software.
meillo@40 66 The Wikipedia has an accurate definition:
meillo@40 67 .[
meillo@44 68 wikipedia
meillo@44 69 unix philosophy
meillo@40 70 .]
meillo@40 71 .QP
meillo@40 72 The \fIUnix philosophy\fP is a set of cultural norms and philosophical
meillo@40 73 approaches to developing software based on the experience of leading
meillo@40 74 developers of the Unix operating system.
meillo@1 75 .PP
meillo@40 76 As there is no single definition of the Unix Philosophy,
meillo@40 77 several people have stated their view on what it comprises.
meillo@1 78 Best known are:
meillo@1 79 .IP \(bu
meillo@1 80 Doug McIlroy's summary: ``Write programs that do one thing and do it well.''
meillo@1 81 .[
meillo@44 82 mahoney
meillo@44 83 oral history
meillo@1 84 .]
meillo@1 85 .IP \(bu
meillo@1 86 Mike Gancarz' book ``The UNIX Philosophy''.
meillo@1 87 .[
meillo@44 88 gancarz
meillo@44 89 unix philosophy
meillo@1 90 .]
meillo@1 91 .IP \(bu
meillo@1 92 Eric S. Raymond's book ``The Art of UNIX Programming''.
meillo@1 93 .[
meillo@44 94 raymond
meillo@44 95 art of unix programming
meillo@1 96 .]
meillo@0 97 .LP
meillo@1 98 These different views on the Unix Philosophy have much in common.
meillo@40 99 Especially, the main concepts are similar in all of them.
meillo@40 100 McIlroy's definition can surely be called the core of the Unix Philosophy,
meillo@40 101 but the fundamental idea behind it all, is ``small is beautiful''.
meillo@40 102
meillo@40 103 .PP
meillo@45 104 The Unix Philosophy explains how to design good software for Unix.
meillo@45 105 Many concepts described here, base on facilities of Unix.
meillo@40 106 Other operating systems may not offer such facilities,
meillo@41 107 hence it may not be possible to design software in the way of the
meillo@41 108 Unix Philosophy for them.
meillo@40 109 .PP
meillo@41 110 The Unix Philosophy has an idea of how the process of software development
meillo@41 111 should look like, but large parts of the philosophy are quite independent
meillo@45 112 from a concrete development process.
meillo@41 113 However, one will soon recognize that some development processes work well
meillo@41 114 with the ideas of the Unix Philosophy and support them, while others are
meillo@41 115 at cross-purposes.
meillo@45 116 Kent Beck's books about Extreme Programming are valuable supplemental
meillo@45 117 resources on this topic.
meillo@1 118 .PP
meillo@41 119 The question of how to actually write code and how the code should looks
meillo@45 120 like in detail, are out of focus here.
meillo@41 121 ``The Practice of Programming'' by Kernighan and Pike,
meillo@41 122 .[
meillo@44 123 kernighan pike
meillo@44 124 practice of programming
meillo@41 125 .]
meillo@41 126 is a good book that covers this topic.
meillo@41 127 Its point of view matches to the one of this paper.
meillo@0 128
meillo@0 129 .NH 1
meillo@6 130 Importance of software design in general
meillo@42 131 .XS
meillo@42 132 .sp .5v
meillo@42 133 \*(SN Importance of software design in general
meillo@42 134 .XE
meillo@0 135 .LP
meillo@40 136 Software design is the planning of how the internal structure
meillo@40 137 and external interfaces of a software should look like.
meillo@39 138 It has nothing to do with visual appearance.
meillo@39 139 If we take a program as a car, then its color is of no matter.
meillo@39 140 Its design would be the car's size, its shape, the locations of doors,
meillo@45 141 the passenger/space ratio, the available controls and instruments,
meillo@45 142 and so forth.
meillo@39 143 .PP
meillo@39 144 Why should software get designed at all?
meillo@6 145 It is general knowledge, that even a bad plan is better than no plan.
meillo@39 146 Not designing software means programming without plan.
meillo@39 147 This will pretty sure lead to horrible results.
meillo@45 148 Software that is horrible to use and horrible to maintain.
meillo@39 149 These two aspects are the visible ones.
meillo@45 150 Often invisible though, are the wasted possible gains.
meillo@39 151 Good software design can make these gains available.
meillo@2 152 .PP
meillo@39 153 A software's design deals with quality properties.
meillo@39 154 Good design leads to good quality, and quality is important.
meillo@39 155 Any car may be able to drive from A to B,
meillo@39 156 but it depends on the car's properties whether it is a good choice
meillo@39 157 for passenger transport or not.
meillo@39 158 It depends on its properties if it is a good choice
meillo@39 159 for a rough mountain area.
meillo@39 160 And it depends on its properties if the ride will be fun.
meillo@39 161
meillo@2 162 .PP
meillo@39 163 Requirements for a software are twofold:
meillo@39 164 functional and non-functional.
meillo@39 165 .IP \(bu
meillo@39 166 Functional requirements define directly the software's functions.
meillo@39 167 They are the reason why software gets written.
meillo@39 168 Someone has a problem and needs a tool to solve it.
meillo@39 169 Being able to solve the problem is the main functional goal.
meillo@39 170 It is the driving force behind all programming effort.
meillo@39 171 Functional requirements are easier to define and to verify.
meillo@39 172 .IP \(bu
meillo@45 173 Non-functional requirements are called \fIquality\fP requirements, too.
meillo@39 174 The quality of a software are the properties that are not directly related to
meillo@39 175 the software's basic functions.
meillo@45 176 Tools of bad quality often do solve the problems they were written for,
meillo@39 177 but introduce problems and difficulties for usage and development, later on.
meillo@39 178 Quality aspects are often overlooked at first sight,
meillo@45 179 and are often difficult to define clearly and to verify.
meillo@2 180 .PP
meillo@45 181 Quality is hardly interesting when the software gets built initially,
meillo@45 182 but it has a high impact on usability and maintenance of the software, later.
meillo@45 183 A short-sighted might see in developing a software, mainly building something up.
meillo@39 184 But experience shows, that building the software the first time is
meillo@39 185 only a small amount of the overall work.
meillo@45 186 Bug fixing, extending, rebuilding of parts \(en maintenance work \(en
meillo@6 187 does soon take over the major part of the time spent on a software.
meillo@45 188 And of course, the time spent actually using the software.
meillo@6 189 These processes are highly influenced by the software's quality.
meillo@39 190 Thus, quality must not be neglected.
meillo@45 191 However, the problem with quality is that you hardly ``stumble over''
meillo@39 192 bad quality during the first build,
meillo@45 193 although this is the time when you should care about good quality most.
meillo@6 194 .PP
meillo@45 195 Software design has little to do with the basic function of a software \(en
meillo@39 196 this requirement will get satisfied anyway.
meillo@39 197 Software design is more about quality aspects of the software.
meillo@39 198 Good design leads to good quality, bad design to bad quality.
meillo@6 199 The primary functions of the software will be affected modestly by bad quality,
meillo@39 200 but good quality can provide a lot of additional gain,
meillo@6 201 even at places where one never expected it.
meillo@6 202 .PP
meillo@45 203 The ISO/IEC\|9126-1 standard, part\|1,
meillo@6 204 .[
meillo@44 205 iso product quality
meillo@6 206 .]
meillo@6 207 defines the quality model as consisting out of:
meillo@6 208 .IP \(bu
meillo@6 209 .I Functionality
meillo@6 210 (suitability, accuracy, inter\%operability, security)
meillo@6 211 .IP \(bu
meillo@6 212 .I Reliability
meillo@6 213 (maturity, fault tolerance, recoverability)
meillo@6 214 .IP \(bu
meillo@6 215 .I Usability
meillo@6 216 (understandability, learnability, operability, attractiveness)
meillo@6 217 .IP \(bu
meillo@6 218 .I Efficiency
meillo@9 219 (time behavior, resource utilization)
meillo@6 220 .IP \(bu
meillo@6 221 .I Maintainability
meillo@23 222 (analyzability, changeability, stability, testability)
meillo@6 223 .IP \(bu
meillo@6 224 .I Portability
meillo@6 225 (adaptability, installability, co-existence, replaceability)
meillo@6 226 .LP
meillo@39 227 Good design can improve these properties of a software,
meillo@45 228 bad designed software likely suffers in these points.
meillo@7 229 .PP
meillo@7 230 One further goal of software design is consistency.
meillo@7 231 Consistency eases understanding, working on, and using things.
meillo@39 232 Consistent internal structure and consistent interfaces to the outside
meillo@39 233 can be provided by good design.
meillo@7 234 .PP
meillo@39 235 Software should be well designed because good design avoids many
meillo@45 236 problems during a software's lifetime.
meillo@39 237 And software should be well designed because good design can offer
meillo@39 238 much additional gain.
meillo@39 239 Indeed, much effort should be spent into good design to make software more valuable.
meillo@39 240 The Unix Philosophy shows a way of how to design software well.
meillo@7 241 It offers guidelines to achieve good quality and high gain for the effort spent.
meillo@0 242
meillo@0 243
meillo@0 244 .NH 1
meillo@0 245 The Unix Philosophy
meillo@42 246 .XS
meillo@42 247 .sp .5v
meillo@42 248 \*(SN The Unix Philosophy
meillo@42 249 .XE
meillo@4 250 .LP
meillo@4 251 The origins of the Unix Philosophy were already introduced.
meillo@8 252 This chapter explains the philosophy, oriented on Gancarz,
meillo@8 253 and shows concrete examples of its application.
meillo@5 254
meillo@16 255 .NH 2
meillo@14 256 Pipes
meillo@42 257 .XS
meillo@42 258 \*(SN Pipes
meillo@42 259 .XE
meillo@4 260 .LP
meillo@4 261 Following are some examples to demonstrate how applied Unix Philosophy feels like.
meillo@4 262 Knowledge of using the Unix shell is assumed.
meillo@4 263 .PP
meillo@4 264 Counting the number of files in the current directory:
meillo@41 265 .DS
meillo@4 266 .CW
meillo@9 267 .ps -1
meillo@4 268 ls | wc -l
meillo@4 269 .DE
meillo@4 270 The
meillo@4 271 .CW ls
meillo@4 272 command lists all files in the current directory, one per line,
meillo@4 273 and
meillo@4 274 .CW "wc -l
meillo@8 275 counts the number of lines.
meillo@4 276 .PP
meillo@8 277 Counting the number of files that do not contain ``foo'' in their name:
meillo@41 278 .DS
meillo@4 279 .CW
meillo@9 280 .ps -1
meillo@4 281 ls | grep -v foo | wc -l
meillo@4 282 .DE
meillo@4 283 Here, the list of files is filtered by
meillo@4 284 .CW grep
meillo@45 285 to remove all lines that contain ``foo''.
meillo@45 286 The rest equals the previous example.
meillo@4 287 .PP
meillo@4 288 Finding the five largest entries in the current directory.
meillo@41 289 .DS
meillo@4 290 .CW
meillo@9 291 .ps -1
meillo@4 292 du -s * | sort -nr | sed 5q
meillo@4 293 .DE
meillo@4 294 .CW "du -s *
meillo@45 295 returns the recursively summed sizes of all files in the current directory
meillo@8 296 \(en no matter if they are regular files or directories.
meillo@4 297 .CW "sort -nr
meillo@45 298 sorts the list numerically in reverse order (descending).
meillo@4 299 Finally,
meillo@4 300 .CW "sed 5q
meillo@4 301 quits after it has printed the fifth line.
meillo@4 302 .PP
meillo@4 303 The presented command lines are examples of what Unix people would use
meillo@4 304 to get the desired output.
meillo@4 305 There are also other ways to get the same output.
meillo@4 306 It's a user's decision which way to go.
meillo@14 307 .PP
meillo@8 308 The examples show that many tasks on a Unix system
meillo@4 309 are accomplished by combining several small programs.
meillo@4 310 The connection between the single programs is denoted by the pipe operator `|'.
meillo@4 311 .PP
meillo@4 312 Pipes, and their extensive and easy use, are one of the great
meillo@4 313 achievements of the Unix system.
meillo@4 314 Pipes between programs have been possible in earlier operating systems,
meillo@4 315 but it has never been a so central part of the concept.
meillo@45 316 When, in the early seventies, Doug McIlroy introduced pipes into the
meillo@4 317 Unix system,
meillo@4 318 ``it was this concept and notation for linking several programs together
meillo@4 319 that transformed Unix from a basic file-sharing system to an entirely new way of computing.''
meillo@4 320 .[
meillo@44 321 aughenbaugh
meillo@44 322 unix oral history
meillo@45 323 .]
meillo@4 324 .PP
meillo@4 325 Being able to specify pipelines in an easy way is,
meillo@4 326 however, not enough by itself.
meillo@5 327 It is only one half.
meillo@4 328 The other is the design of the programs that are used in the pipeline.
meillo@45 329 They need interfaces that allow them to be used in such a way.
meillo@5 330
meillo@16 331 .NH 2
meillo@14 332 Interface design
meillo@42 333 .XS
meillo@42 334 \*(SN Interface design
meillo@42 335 .XE
meillo@5 336 .LP
meillo@11 337 Unix is, first of all, simple \(en Everything is a file.
meillo@5 338 Files are sequences of bytes, without any special structure.
meillo@45 339 Programs should be filters, which read a stream of bytes from standard input (stdin)
meillo@45 340 and write a stream of bytes to standard output (stdout).
meillo@8 341 If the files \fIare\fP sequences of bytes,
meillo@8 342 and the programs \fIare\fP filters on byte streams,
meillo@45 343 then there is exactly one data interface.
meillo@45 344 Hence it is possible to combine programs in any desired way.
meillo@5 345 .PP
meillo@45 346 Even a handful of small programs yields a large set of combinations,
meillo@5 347 and thus a large set of different functions.
meillo@5 348 This is leverage!
meillo@5 349 If the programs are orthogonal to each other \(en the best case \(en
meillo@5 350 then the set of different functions is greatest.
meillo@5 351 .PP
meillo@45 352 Programs can also have a separate control interface,
meillo@11 353 besides their data interface.
meillo@11 354 The control interface is often called ``user interface'',
meillo@11 355 because it is usually designed to be used by humans.
meillo@11 356 The Unix Philosophy discourages to assume the user to be human.
meillo@11 357 Interactive use of software is slow use of software,
meillo@11 358 because the program waits for user input most of the time.
meillo@45 359 Interactive software requires the user to be in front of the computer.
meillo@11 360 Interactive software occupy the user's attention while they are running.
meillo@11 361 .PP
meillo@45 362 Now to come back to the idea of combining several small programs,
meillo@11 363 to have a more specific function.
meillo@11 364 If these single tools would all be interactive,
meillo@11 365 how would the user control them?
meillo@45 366 It is not only a problem to control several programs at once,
meillo@45 367 if they run at the same time,
meillo@11 368 it also very inefficient to have to control each of the single programs
meillo@45 369 that are intended to act as one large program.
meillo@11 370 Hence, the Unix Philosophy discourages programs to demand interactive use.
meillo@11 371 The behavior of programs should be defined at invocation.
meillo@45 372 This is done by specifying arguments to the program call
meillo@45 373 (command line switches).
meillo@11 374 Gancarz discusses this topic as ``avoid captive user interfaces''.
meillo@11 375 .[
meillo@44 376 gancarz unix philosophy
meillo@11 377 %P 88 ff.
meillo@11 378 .]
meillo@44 379 .ds _p ", p. 88 ff.
meillo@11 380 .PP
meillo@11 381 Non-interactive use is, during development, also an advantage for testing.
meillo@11 382 Testing of interactive programs is much more complicated,
meillo@11 383 than testing of non-interactive programs.
meillo@5 384
meillo@16 385 .NH 2
meillo@8 386 The toolchest approach
meillo@42 387 .XS
meillo@42 388 \*(SN The toolchest approach
meillo@42 389 .XE
meillo@5 390 .LP
meillo@5 391 A toolchest is a set of tools.
meillo@5 392 Instead of having one big tool for all tasks, one has many small tools,
meillo@5 393 each for one task.
meillo@5 394 Difficult tasks are solved by combining several of the small, simple tools.
meillo@5 395 .PP
meillo@11 396 The Unix toolchest \fIis\fP a set of small, (mostly) non-interactive programs
meillo@11 397 that are filters on byte streams.
meillo@11 398 They are, to a large extend, unrelated in their function.
meillo@11 399 Hence, the Unix toolchest provides a large set of functions
meillo@11 400 that can be accessed by combining the programs in the desired way.
meillo@11 401 .PP
meillo@11 402 There are also advantages for developing small toolchest programs.
meillo@5 403 It is easier and less error-prone to write small programs.
meillo@5 404 It is also easier and less error-prone to write a large set of small programs,
meillo@5 405 than to write one large program with all the functionality included.
meillo@5 406 If the small programs are combinable, then they offer even a larger set
meillo@5 407 of functions than the single large program.
meillo@45 408 Hence, one gets two advantages out of writing small, combinable programs:
meillo@45 409 They are easier to write and they offer a greater set of functions through
meillo@45 410 combination.
meillo@5 411 .PP
meillo@45 412 But there are also two main drawbacks of the toolchest approach.
meillo@45 413 First, one simple, standardized interface has to be sufficient.
meillo@5 414 If one feels the need for more ``logic'' than a stream of bytes,
meillo@8 415 then a different approach might be of need.
meillo@13 416 But it is also possible, that he just can not imagine a design where
meillo@8 417 a stream of bytes is sufficient.
meillo@8 418 By becoming more familiar with the ``Unix style of thinking'',
meillo@8 419 developers will more often and easier find simple designs where
meillo@8 420 a stream of bytes is a sufficient interface.
meillo@8 421 .PP
meillo@8 422 The second drawback of a toolchest affects the users.
meillo@45 423 A toolchest is often more difficult to use.
meillo@9 424 It is necessary to become familiar with each of the tools,
meillo@5 425 to be able to use the right one in a given situation.
meillo@45 426 Additionally, one needs to combine the tools in a senseful way himself.
meillo@45 427 This is like a sharp knife \(en it is a powerful tool in the hand of a
meillo@45 428 master, but of no good value in the hand of an unskilled.
meillo@45 429 However, learning single, small tools of a toolchest is easier than
meillo@45 430 learning a complex tool.
meillo@45 431 And the user will already have a basic understanding of a yet unknown tool,
meillo@45 432 if the tools of a toolchest have a common, consistent style.
meillo@45 433 He will be able to transfer knowledge over from one tool to another.
meillo@5 434 .PP
meillo@45 435 Moreover, the second drawback can be removed to a large extend
meillo@45 436 by adding wrappers around the basic tools.
meillo@45 437 Novice users do not need to learn several tools, if a professional wraps
meillo@45 438 complete command lines into a higher-level script.
meillo@5 439 Note that the wrapper script still calls the small tools;
meillo@45 440 it is just like a skin around them.
meillo@45 441 No complexity is added this way.
meillo@45 442 But new programs can get created out of existing one with very low effort.
meillo@5 443 .PP
meillo@5 444 A wrapper script for finding the five largest entries in the current directory
meillo@5 445 could look like this:
meillo@41 446 .DS
meillo@5 447 .CW
meillo@9 448 .ps -1
meillo@5 449 #!/bin/sh
meillo@5 450 du -s * | sort -nr | sed 5q
meillo@5 451 .DE
meillo@45 452 The script itself is just a text file that calls the command line,
meillo@45 453 which a professional user would type in directly.
meillo@45 454 It is probably worth to make the program flexible on the number of
meillo@45 455 entries it prints:
meillo@41 456 .DS
meillo@8 457 .CW
meillo@9 458 .ps -1
meillo@8 459 #!/bin/sh
meillo@8 460 num=5
meillo@8 461 [ $# -eq 1 ] && num="$1"
meillo@8 462 du -sh * | sort -nr | sed "${num}q"
meillo@8 463 .DE
meillo@8 464 This script acts like the one before, when called without an argument.
meillo@8 465 But one can also specify a numerical argument to define the number of lines to print.
meillo@45 466 One can surely imagine even more flexible versions, however,
meillo@45 467 they will still relay on the external programs,
meillo@45 468 which do the actual work.
meillo@5 469
meillo@16 470 .NH 2
meillo@8 471 A powerful shell
meillo@42 472 .XS
meillo@42 473 \*(SN A powerful shell
meillo@42 474 .XE
meillo@8 475 .LP
meillo@45 476 The Unix shell provides the possibility to combine small programs into large ones.
meillo@45 477 But a powerful shell is a great feature in other ways, too.
meillo@45 478 For instance by being scriptable.
meillo@45 479 Control statements are build into the shell.
meillo@45 480 The functions, however, are the normal programs of the system.
meillo@45 481 Thus, as the programs are already known,
meillo@45 482 learning to program in the shell becomes easy.
meillo@8 483 Using normal programs as functions in the shell programming language
meillo@10 484 is only possible because they are small and combinable tools in a toolchest style.
meillo@8 485 .PP
meillo@45 486 The Unix shell encourages to write small scripts,
meillo@45 487 by combining existing programs, because it is so easy to do.
meillo@8 488 This is a great step towards automation.
meillo@8 489 It is wonderful if the effort to automate a task equals the effort
meillo@45 490 to do the task a second time by hand.
meillo@45 491 If this holds,
meillo@45 492 then the user will be happy to automate everything he does more than once.
meillo@8 493 .PP
meillo@8 494 Small programs that do one job well, standardized interfaces between them,
meillo@8 495 a mechanism to combine parts to larger parts, and an easy way to automate tasks,
meillo@8 496 this will inevitably produce software leverage.
meillo@8 497 Getting multiple times the benefit of an investment is a great offer.
meillo@10 498 .PP
meillo@10 499 The shell also encourages rapid prototyping.
meillo@10 500 Many well known programs started as quickly hacked shell scripts,
meillo@10 501 and turned into ``real'' programs, written in C, later.
meillo@45 502 Building a prototype first, is a way to avoid the biggest problems
meillo@10 503 in application development.
meillo@45 504 Fred Brooks explains in ``No Silver Bullet'':
meillo@10 505 .[
meillo@44 506 brooks
meillo@44 507 no silver bullet
meillo@10 508 .]
meillo@10 509 .QP
meillo@10 510 The hardest single part of building a software system is deciding precisely what to build.
meillo@10 511 No other part of the conceptual work is so difficult as establishing the detailed
meillo@10 512 technical requirements, [...].
meillo@10 513 No other part of the work so cripples the resulting system if done wrong.
meillo@10 514 No other part is more difficult to rectify later.
meillo@10 515 .PP
meillo@45 516 Writing a prototype is a great method for becoming familiar with the requirements
meillo@45 517 and to run into real problems early.
meillo@45 518 .PP
meillo@45 519 Prototyping is often seen as a first step in building a software.
meillo@10 520 This is, of course, good.
meillo@10 521 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping:
meillo@10 522 After having built the prototype, one might notice, that the prototype is already
meillo@10 523 \fIgood enough\fP.
meillo@45 524 Hence, no reimplementation, in a more sophisticated programming language,
meillo@45 525 might be of need, at least for the moment.
meillo@23 526 Maybe later, it might be necessary to rewrite the software, but not now.
meillo@45 527 By delaying further work, one keeps the flexibility to react on
meillo@10 528 changing requirements.
meillo@10 529 Software parts that are not written will not miss the requirements.
meillo@10 530
meillo@16 531 .NH 2
meillo@10 532 Worse is better
meillo@42 533 .XS
meillo@42 534 \*(SN Worse is better
meillo@42 535 .XE
meillo@10 536 .LP
meillo@45 537 The Unix Philosophy aims for the 90% solution;
meillo@10 538 others call it the ``Worse is better'' approach.
meillo@45 539 Practical experience shows, that:
meillo@10 540 .PP
meillo@45 541 (1) It is almost never possible to define the
meillo@10 542 requirements completely and correctly the first time.
meillo@45 543 Hence one should not try to; one will fail anyway.
meillo@45 544 .PP
meillo@45 545 (2) Requirements change during time.
meillo@10 546 Hence it is best to delay requirement-based design decisions as long as possible.
meillo@45 547 The software should be small and flexible as long as possible
meillo@10 548 to react on changing requirements.
meillo@10 549 Shell scripts, for example, are more easily adjusted as C programs.
meillo@45 550 .PP
meillo@45 551 (3) Maintenance work is hard work.
meillo@45 552 Hence, one should keep the amount of code as small as possible;
meillo@10 553 it should just fulfill the \fIcurrent\fP requirements.
meillo@45 554 Software parts that will be written in future,
meillo@45 555 do not need maintenance till then.
meillo@10 556 .PP
meillo@10 557 Starting with a prototype in a scripting language has several advantages:
meillo@10 558 .IP \(bu
meillo@10 559 As the initial effort is low, one will likely start right away.
meillo@10 560 .IP \(bu
meillo@10 561 As working parts are available soon, the real requirements can get identified soon.
meillo@10 562 .IP \(bu
meillo@45 563 When a software is usable and valuable, it gets used, and thus tested.
meillo@10 564 Hence problems will be found at early stages of the development.
meillo@10 565 .IP \(bu
meillo@10 566 The prototype might be enough for the moment,
meillo@45 567 thus further work on the software can get delayed to a time
meillo@10 568 when one knows better about the requirements and problems,
meillo@10 569 than now.
meillo@10 570 .IP \(bu
meillo@45 571 Implementing now only the parts that are actually needed at the moment,
meillo@45 572 introduces fewer programming and maintenance work.
meillo@10 573 .IP \(bu
meillo@10 574 If the global situation changes so that the software is not needed anymore,
meillo@10 575 then less effort was spent into the project, than it would have be
meillo@10 576 when a different approach had been used.
meillo@10 577
meillo@16 578 .NH 2
meillo@11 579 Upgrowth and survival of software
meillo@42 580 .XS
meillo@42 581 \*(SN Upgrowth and survival of software
meillo@42 582 .XE
meillo@11 583 .LP
meillo@12 584 So far it was talked about \fIwriting\fP or \fIbuilding\fP software.
meillo@13 585 Although these are just verbs, they do imply a specific view on the work process
meillo@13 586 they describe.
meillo@12 587 The better verb, however, is to \fIgrow\fP.
meillo@12 588 Creating software in the sense of the Unix Philosophy is an incremental process.
meillo@12 589 It starts with a first prototype, which evolves as requirements change.
meillo@12 590 A quickly hacked shell script might become a large, sophisticated,
meillo@13 591 compiled program this way.
meillo@13 592 Its lifetime begins with the initial prototype and ends when the software is not used anymore.
meillo@45 593 While being alive it will get extended, rearranged, rebuilt.
meillo@12 594 Growing software matches the view that ``software is never finished. It is only released.''
meillo@12 595 .[
meillo@44 596 gancarz
meillo@44 597 unix philosophy
meillo@13 598 %P 26
meillo@12 599 .]
meillo@12 600 .PP
meillo@13 601 Software can be seen as being controlled by evolutionary processes.
meillo@13 602 Successful software is software that is used by many for a long time.
meillo@12 603 This implies that the software is needed, useful, and better than alternatives.
meillo@12 604 Darwin talks about: ``The survival of the fittest.''
meillo@12 605 .[
meillo@44 606 darwin
meillo@44 607 origin of species
meillo@12 608 .]
meillo@12 609 Transferred to software: The most successful software, is the fittest,
meillo@12 610 is the one that survives.
meillo@13 611 (This may be at the level of one creature, or at the level of one species.)
meillo@13 612 The fitness of software is affected mainly by four properties:
meillo@15 613 portability of code, portability of data, range of usability, and reusability of parts.
meillo@15 614 .\" .IP \(bu
meillo@15 615 .\" portability of code
meillo@15 616 .\" .IP \(bu
meillo@15 617 .\" portability of data
meillo@15 618 .\" .IP \(bu
meillo@15 619 .\" range of usability
meillo@15 620 .\" .IP \(bu
meillo@15 621 .\" reuseability 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@13 627 and avoiding optimizations that introduce dependencies on specific hardware.
meillo@13 628 Hardware has a much lower lifetime than software.
meillo@13 629 By chaining software to a specific hardware,
meillo@13 630 the software's lifetime gets shortened to that of this hardware.
meillo@13 631 In contrast, software should be easy to port \(en
meillo@23 632 adaptation is the key to success.
meillo@13 633 .\" cf. practice of prog: ch08
meillo@13 634 .PP
meillo@15 635 (2)
meillo@15 636 .I "Portability of data
meillo@15 637 is best achieved by avoiding binary representations
meillo@13 638 to store data, because binary representations differ from machine to machine.
meillo@23 639 Textual representation is favored.
meillo@45 640 Historically, \s-1ASCII\s0 was the charset of choice.
meillo@45 641 For the future, \s-1UTF\s0-8 might be the better choice.
meillo@13 642 Important is that it is a plain text representation in a
meillo@13 643 very common charset encoding.
meillo@13 644 Apart from being able to transfer data between machines,
meillo@45 645 readable data has the great advantage, that humans are able to directly
meillo@45 646 read and edit it with text editors and other tools from the Unix toolchest.
meillo@13 647 .\" gancarz tenet 5
meillo@13 648 .PP
meillo@15 649 (3)
meillo@15 650 A large
meillo@15 651 .I "range of usability
meillo@23 652 ensures good adaptation, and thus good survival.
meillo@13 653 It is a special distinction if a software becomes used in fields of action,
meillo@13 654 the original authors did never imagine.
meillo@13 655 Software that solves problems in a general way will likely be used
meillo@45 656 for many kinds of similar problems.
meillo@45 657 Being too specific limits the range of usability.
meillo@13 658 Requirements change through time, thus use cases change or even vanish.
meillo@45 659 As a good example in this point,
meillo@13 660 Allman identifies flexibility to be one major reason for sendmail's success:
meillo@13 661 .[
meillo@44 662 allman
meillo@44 663 sendmail
meillo@13 664 .]
meillo@13 665 .QP
meillo@13 666 Second, I limited myself to the routing function [...].
meillo@13 667 This was a departure from the dominant thought of the time, [...].
meillo@13 668 .QP
meillo@45 669 Third, the sendmail configuration file was flexible enough to adapt
meillo@13 670 to a rapidly changing world [...].
meillo@12 671 .LP
meillo@45 672 Successful software adapts itself to the changing world.
meillo@13 673 .PP
meillo@15 674 (4)
meillo@15 675 .I "Reuse of parts
meillo@15 676 is even one step further.
meillo@13 677 A software may completely lose its field of action,
meillo@13 678 but parts of which the software is build may be general and independent enough
meillo@13 679 to survive this death.
meillo@13 680 If software is build by combining small independent programs,
meillo@45 681 then these parts are readily available for reuse.
meillo@13 682 Who cares if the large program is a failure,
meillo@13 683 but parts of it become successful instead?
meillo@10 684
meillo@16 685 .NH 2
meillo@14 686 Summary
meillo@42 687 .XS
meillo@42 688 \*(SN Summary
meillo@42 689 .XE
meillo@0 690 .LP
meillo@45 691 This chapter explained central ideas of the Unix Philosophy.
meillo@45 692 For each of the ideas, the advantages they introduce were explained.
meillo@45 693 The Unix Philosophy are guidelines that help to write more valuable software.
meillo@14 694 From the view point of a software developer or software designer,
meillo@14 695 the Unix Philosophy provides answers to many software design problem.
meillo@14 696 .PP
meillo@14 697 The various ideas of the Unix Philosophy are very interweaved
meillo@14 698 and can hardly be applied independently.
meillo@14 699 However, the probably most important messages are:
meillo@45 700 .I "``Keep it simple!''" ,
meillo@14 701 .I "``Do one thing well!''" ,
meillo@14 702 and
meillo@14 703 .I "``Use software leverage!''
meillo@0 704
meillo@8 705
meillo@8 706
meillo@0 707 .NH 1
meillo@19 708 Case study: \s-1MH\s0
meillo@42 709 .XS
meillo@42 710 .sp .5v
meillo@42 711 \*(SN Case study: \s-1MH\s0
meillo@42 712 .XE
meillo@18 713 .LP
meillo@30 714 The previous chapter introduced and explained the Unix Philosophy
meillo@18 715 from a general point of view.
meillo@30 716 The driving force were the guidelines; references to
meillo@18 717 existing software were given only sparsely.
meillo@18 718 In this and the next chapter, concrete software will be
meillo@18 719 the driving force in the discussion.
meillo@18 720 .PP
meillo@23 721 This first case study is about the mail user agents (\s-1MUA\s0)
meillo@23 722 \s-1MH\s0 (``mail handler'') and its descendent \fInmh\fP
meillo@23 723 (``new mail handler'').
meillo@23 724 \s-1MUA\s0s provide functions to read, compose, and organize mail,
meillo@45 725 but (ideally) not to transfer it.
meillo@45 726 In this document, the name \s-1MH\s0 will be used to include nmh.
meillo@19 727 A distinction will only be made if differences between
meillo@45 728 \s-1MH\s0 and nmh are described.
meillo@18 729
meillo@0 730
meillo@0 731 .NH 2
meillo@19 732 Historical background
meillo@42 733 .XS
meillo@42 734 \*(SN Historical background
meillo@42 735 .XE
meillo@0 736 .LP
meillo@19 737 Electronic mail was available in Unix very early.
meillo@30 738 The first \s-1MUA\s0 on Unix was \f(CWmail\fP,
meillo@30 739 which was already present in the First Edition.
meillo@30 740 .[
meillo@44 741 salus
meillo@44 742 quarter century of unix
meillo@30 743 %P 41 f.
meillo@30 744 .]
meillo@45 745 It was a small program that either printed the user's mailbox file
meillo@45 746 or appended text to someone elses mailbox file,
meillo@19 747 depending on the command line arguments.
meillo@19 748 .[
meillo@44 749 manual mail(1)
meillo@19 750 .]
meillo@19 751 It was a program that did one job well.
meillo@23 752 This job was emailing, which was very simple then.
meillo@19 753 .PP
meillo@23 754 Later, emailing became more powerful, and thus more complex.
meillo@19 755 The simple \f(CWmail\fP, which knew nothing of subjects,
meillo@19 756 independent handling of single messages,
meillo@45 757 and long-time email storage, was not powerful enough anymore.
meillo@45 758 In 1978 at Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
meillo@45 759 to provide additional functions for emailing.
meillo@19 760 Mail was still one program, but now it was large and did
meillo@19 761 several jobs.
meillo@23 762 Its user interface is modeled after the one of \fIed\fP.
meillo@19 763 It is designed for humans, but is still scriptable.
meillo@23 764 \fImailx\fP is the adaptation of Berkeley Mail into System V.
meillo@19 765 .[
meillo@44 766 ritter
meillo@44 767 mailx history
meillo@19 768 .]
meillo@30 769 Elm, pine, mutt, and a whole bunch of graphical \s-1MUA\s0s
meillo@19 770 followed Mail's direction.
meillo@19 771 They are large, monolithic programs which include all emailing functions.
meillo@19 772 .PP
meillo@23 773 A different way was taken by the people of \s-1RAND\s0 Corporation.
meillo@38 774 In the beginning, they also had used a monolithic mail system,
meillo@30 775 called \s-1MS\s0 (for ``mail system'').
meillo@19 776 But in 1977, Stockton Gaines and Norman Shapiro
meillo@19 777 came up with a proposal of a new email system concept \(en
meillo@45 778 one that honored the Unix Philosophy.
meillo@19 779 The concept was implemented by Bruce Borden in 1978 and 1979.
meillo@19 780 This was the birth of \s-1MH\s0 \(en the ``mail handler''.
meillo@18 781 .PP
meillo@18 782 Since then, \s-1RAND\s0, the University of California at Irvine and
meillo@19 783 at Berkeley, and several others have contributed to the software.
meillo@18 784 However, it's core concepts remained the same.
meillo@23 785 In the late 90s, when development of \s-1MH\s0 slowed down,
meillo@19 786 Richard Coleman started with \fInmh\fP, the new mail handler.
meillo@45 787 His goal was to improve \s-1MH\s0 especially in regard of
meillo@23 788 the requirements of modern emailing.
meillo@19 789 Today, nmh is developed by various people on the Internet.
meillo@18 790 .[
meillo@44 791 ware
meillo@44 792 rand history
meillo@44 793 %P 128-137
meillo@18 794 .]
meillo@18 795 .[
meillo@44 796 peek
meillo@44 797 mh
meillo@18 798 .]
meillo@0 799
meillo@0 800 .NH 2
meillo@20 801 Contrasts to monolithic mail systems
meillo@42 802 .XS
meillo@42 803 \*(SN Contrasts to monolithic mail systems
meillo@42 804 .XE
meillo@0 805 .LP
meillo@19 806 All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
meillo@38 807 Although there might actually exist further, very little known,
meillo@30 808 toolchest \s-1MUA\s0s, this statement reflects the situation pretty well.
meillo@19 809 .PP
meillo@30 810 Monolithic \s-1MUA\s0s gather all their functions in one program.
meillo@30 811 In contrast, \s-1MH\s0 is a toolchest of many small tools \(en one for each job.
meillo@23 812 Following is a list of important programs of \s-1MH\s0's toolchest
meillo@30 813 and their function.
meillo@30 814 It gives a feeling of how the toolchest looks like.
meillo@19 815 .IP \(bu
meillo@19 816 .CW inc :
meillo@30 817 incorporate new mail (this is how mail enters the system)
meillo@19 818 .IP \(bu
meillo@19 819 .CW scan :
meillo@19 820 list messages in folder
meillo@19 821 .IP \(bu
meillo@19 822 .CW show :
meillo@19 823 show message
meillo@19 824 .IP \(bu
meillo@19 825 .CW next\fR/\fPprev :
meillo@19 826 show next/previous message
meillo@19 827 .IP \(bu
meillo@19 828 .CW folder :
meillo@19 829 change current folder
meillo@19 830 .IP \(bu
meillo@19 831 .CW refile :
meillo@45 832 refile message into different folder
meillo@19 833 .IP \(bu
meillo@19 834 .CW rmm :
meillo@19 835 remove message
meillo@19 836 .IP \(bu
meillo@19 837 .CW comp :
meillo@45 838 compose new message
meillo@19 839 .IP \(bu
meillo@19 840 .CW repl :
meillo@45 841 reply to message
meillo@19 842 .IP \(bu
meillo@19 843 .CW forw :
meillo@45 844 forward message
meillo@19 845 .IP \(bu
meillo@19 846 .CW send :
meillo@45 847 send prepared message (this is how mail leaves the system)
meillo@0 848 .LP
meillo@19 849 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
meillo@19 850 The user does not leave the shell to run \s-1MH\s0,
meillo@45 851 instead he uses the various \s-1MH\s0 programs within the shell.
meillo@23 852 Using a monolithic program with a captive user interface
meillo@23 853 means ``entering'' the program, using it, and ``exiting'' the program.
meillo@23 854 Using toolchests like \s-1MH\s0 means running programs,
meillo@45 855 alone or in combination with others, also from other toolchests,
meillo@23 856 without leaving the shell.
meillo@30 857
meillo@30 858 .NH 2
meillo@30 859 Data storage
meillo@42 860 .XS
meillo@42 861 \*(SN Data storage
meillo@42 862 .XE
meillo@30 863 .LP
meillo@34 864 \s-1MH\s0's mail storage is a directory tree under the user's
meillo@34 865 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP),
meillo@34 866 where mail folders are directories and mail messages are text files
meillo@34 867 within them.
meillo@34 868 Each mail folder contains a file \f(CW.mh_sequences\fP which lists
meillo@45 869 the public message sequences of that folder,
meillo@45 870 for instance the \fIunseen\fP sequence for new messages.
meillo@34 871 Mail messages are text files located in a mail folder.
meillo@34 872 The files contain the messages as they were received.
meillo@45 873 They are named by ascending numbers in each folder.
meillo@19 874 .PP
meillo@30 875 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0.
meillo@30 876 Alternatives are \fImbox\fP and \fImaildir\fP.
meillo@30 877 In the mbox format all messages are stored within one file.
meillo@30 878 This was a good solution in the early days, when messages
meillo@30 879 were only a few lines of text and were deleted soon.
meillo@30 880 Today, when single messages often include several megabytes
meillo@30 881 of attachments, it is a bad solution.
meillo@30 882 Another disadvantage of the mbox format is that it is
meillo@30 883 more difficult to write tools that work on mail messages,
meillo@30 884 because it is always necessary to first find and extract
meillo@30 885 the relevant message in the mbox file.
meillo@45 886 With the \s-1MH\s0 mailbox format, each message is a separate file.
meillo@30 887 Also, the problem of concurrent access to one mailbox is
meillo@30 888 reduced to the problem of concurrent access to one message.
meillo@45 889 The maildir format is generally similar to the \s-1MH\s0 format,
meillo@30 890 but modified towards guaranteed reliability.
meillo@30 891 This involves some complexity, unfortunately.
meillo@34 892 .PP
meillo@34 893 Working with \s-1MH\s0's toolchest on mailboxes is much like
meillo@34 894 working with Unix' toolchest on directory trees:
meillo@34 895 \f(CWscan\fP is like \f(CWls\fP,
meillo@34 896 \f(CWshow\fP is like \f(CWcat\fP,
meillo@34 897 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP,
meillo@34 898 \f(CWrefile\fP is like \f(CWmv\fP,
meillo@34 899 and \f(CWrmm\fP is like \f(CWrm\fP.
meillo@34 900 .PP
meillo@45 901 \s-1MH\s0 extends the context of processes in Unix by two more items,
meillo@45 902 for its tools:
meillo@34 903 .IP \(bu
meillo@34 904 The current mail folder, which is similar to the current working directory.
meillo@34 905 For mail folders, \f(CWfolder\fP provides the corresponding functionality
meillo@34 906 of \f(CWcd\fP and \f(CWpwd\fP for directories.
meillo@34 907 .IP \(bu
meillo@34 908 Sequences, which are named sets of messages in a mail folder.
meillo@34 909 The current message, relative to a mail folder, is a special sequence.
meillo@34 910 It enables commands like \f(CWnext\fP and \f(CWprev\fP.
meillo@34 911 .LP
meillo@45 912 In contrast to Unix' context, which is maintained by the kernel,
meillo@45 913 \s-1MH\s0's context must be maintained by the tools themselves.
meillo@45 914 Usually there is one context per user, which resides in his
meillo@45 915 \f(CWcontext\fP file in the \s-1MH\s0 directory,
meillo@45 916 but a user can have several contexts, too.
meillo@45 917 Public sequences are an exception, as they belong to a mail folder,
meillo@45 918 and reside in the \f(CW.mh_sequences\fP file there.
meillo@34 919 .[
meillo@44 920 man page mh-profile mh-sequence
meillo@34 921 .]
meillo@20 922
meillo@0 923 .NH 2
meillo@20 924 Discussion of the design
meillo@42 925 .XS
meillo@42 926 \*(SN Discussion of the design
meillo@42 927 .XE
meillo@0 928 .LP
meillo@45 929 This section discusses \s-1MH\s0 in regard to the tenets
meillo@45 930 of the Unix Philosophy that Gancarz identified.
meillo@20 931
meillo@20 932 .PP
meillo@33 933 .B "Small is beautiful
meillo@20 934 and
meillo@33 935 .B "do one thing well
meillo@20 936 are two design goals that are directly visible in \s-1MH\s0.
meillo@45 937 Gancarz actually presents \s-1MH\s0 in his book as example under the
meillo@45 938 headline ``Making \s-1UNIX\s0 Do One Thing Well'':
meillo@41 939 .[
meillo@44 940 gancarz
meillo@44 941 unix philosophy
meillo@41 942 %P 125
meillo@41 943 .]
meillo@20 944 .QP
meillo@20 945 [\s-1MH\s0] consists of a series of programs which
meillo@20 946 when combined give the user an enormous ability
meillo@20 947 to manipulate electronic mail messages.
meillo@20 948 A complex application, it shows that not only is it
meillo@20 949 possible to build large applications from smaller
meillo@20 950 components, but also that such designs are actually preferable.
meillo@20 951 .LP
meillo@45 952 The various programs of \s-1MH\s0 were relatively easy to write,
meillo@45 953 because each of them is small, limited to one function,
meillo@23 954 and has clear boundaries.
meillo@20 955 For the same reasons, they are also good to maintain.
meillo@20 956 Further more, the system can easily get extended.
meillo@20 957 One only needs to put a new program into the toolchest.
meillo@23 958 This was done, for instance, when \s-1MIME\s0 support was added
meillo@20 959 (e.g. \f(CWmhbuild\fP).
meillo@20 960 Also, different programs can exist to do the basically same job
meillo@20 961 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP).
meillo@45 962 .PP
meillo@20 963 If someone needs a mail system with some additionally
meillo@45 964 functions that are not available anywhere yet, he best expands a
meillo@45 965 toolchest system like \s-1MH\s0.
meillo@45 966 There he can add new functionality by simply adding additional
meillo@45 967 programs to the toolchest.
meillo@45 968 There he does not risk to break existing functionality by doing so.
meillo@20 969
meillo@20 970 .PP
meillo@34 971 .B "Store data in flat text files
meillo@34 972 is followed by \s-1MH\s0.
meillo@34 973 This is not surprising, because email messages are already plain text.
meillo@34 974 \s-1MH\s0 stores the messages as it receives them,
meillo@45 975 thus any other tool that works on \s-1RFC\s0\|2822 mail messages can operate
meillo@34 976 on the messages in an \s-1MH\s0 mailbox.
meillo@45 977 All other files \s-1MH\s0 uses are plain text, too.
meillo@34 978 It is therefore possible and encouraged to use the text processing
meillo@34 979 tools of Unix' toolchest to extend \s-1MH\s0's toolchest.
meillo@20 980
meillo@20 981 .PP
meillo@33 982 .B "Avoid captive user interfaces" .
meillo@19 983 \s-1MH\s0 is perfectly suited for non-interactive use.
meillo@19 984 It offers all functions directly and without captive user interfaces.
meillo@30 985 If, nonetheless, users want a graphical user interface,
meillo@45 986 they can have it with \fIxmh\fP or \fIexmh\fP.
meillo@19 987 These are graphical frontends for the \s-1MH\s0 toolchest.
meillo@19 988 This means, all email-related work is still done by \s-1MH\s0 tools,
meillo@45 989 but the frontend calls the appropriate commands when the user
meillo@30 990 clicks on buttons.
meillo@45 991 .PP
meillo@20 992 Providing easy-to-use user interfaces in form of frontends is a good
meillo@19 993 approach, because it does not limit the power of the backend itself.
meillo@20 994 The frontend will anyway only be able to make a subset of the
meillo@23 995 backend's power and flexibility available to the user.
meillo@20 996 But if it is a separate program,
meillo@20 997 then the missing parts can still be accessed at the backend directly.
meillo@19 998 If it is integrated, then this will hardly be possible.
meillo@45 999 An additional advantage is the possibility to have different frontends
meillo@45 1000 to the same backend.
meillo@19 1001
meillo@19 1002 .PP
meillo@33 1003 .B "Choose portability over efficiency
meillo@20 1004 and
meillo@33 1005 .B "use shell scripts to increase leverage and portability" .
meillo@20 1006 These two tenets are indirectly, but nicely, demonstrated by
meillo@30 1007 Bolsky and Korn in their book about the Korn Shell.
meillo@20 1008 .[
meillo@44 1009 bolsky korn
meillo@44 1010 korn shell
meillo@20 1011 .]
meillo@45 1012 Chapter\|18 of the book shows a basic implementation
meillo@20 1013 of a subset of \s-1MH\s0 in ksh scripts.
meillo@45 1014 Of course, this is just a demonstration, but a brilliant one.
meillo@20 1015 It shows how quickly one can implement such a prototype with shell scripts,
meillo@20 1016 and how readable they are.
meillo@20 1017 The implementation in the scripting language may not be very fast,
meillo@20 1018 but it can be fast enough though, and this is all that matters.
meillo@20 1019 By having the code in an interpreted language, like the shell,
meillo@20 1020 portability becomes a minor issue, if we assume the interpreter
meillo@20 1021 to be widespread.
meillo@45 1022 .PP
meillo@20 1023 This demonstration also shows how easy it is to create single programs
meillo@20 1024 of a toolchest software.
meillo@45 1025 Eight tools (two of them have multiple names) and 16 functions
meillo@45 1026 with supporting code are presented to the reader.
meillo@45 1027 The tools comprise less than 40 lines of ksh each,
meillo@30 1028 in total about 200 lines.
meillo@45 1029 The functions comprise less than 80 lines of ksh each,
meillo@30 1030 in total about 450 lines.
meillo@20 1031 Such small software is easy to write, easy to understand,
meillo@20 1032 and thus easy to maintain.
meillo@23 1033 A toolchest improves the possibility to only write some parts
meillo@20 1034 and though create a working result.
meillo@45 1035 Expanding the toolchest, even without global changes,
meillo@45 1036 will likely be possible.
meillo@20 1037
meillo@20 1038 .PP
meillo@33 1039 .B "Use software leverage to your advantage
meillo@20 1040 and the lesser tenet
meillo@33 1041 .B "allow the user to tailor the environment
meillo@20 1042 are ideally followed in the design of \s-1MH\s0.
meillo@21 1043 Tailoring the environment is heavily encouraged by the ability to
meillo@30 1044 directly define default options to programs.
meillo@30 1045 It is even possible to define different default options
meillo@45 1046 depending on the name under which a program is called.
meillo@45 1047 Software leverage is heavily encouraged by the ease of
meillo@45 1048 creating shell scripts that run a specific command line,
meillo@30 1049 built of several \s-1MH\s0 programs.
meillo@21 1050 There is few software that so much wants users to tailor their
meillo@21 1051 environment and to leverage the use of the software, like \s-1MH\s0.
meillo@45 1052 .PP
meillo@21 1053 Just to make one example:
meillo@23 1054 One might prefer a different listing format for the \f(CWscan\fP
meillo@21 1055 program.
meillo@30 1056 It is possible to take one of the distributed format files
meillo@21 1057 or to write one yourself.
meillo@21 1058 To use the format as default for \f(CWscan\fP, a single line,
meillo@21 1059 reading
meillo@21 1060 .DS
meillo@21 1061 .CW
meillo@21 1062 scan: -form FORMATFILE
meillo@21 1063 .DE
meillo@21 1064 must be added to \f(CW.mh_profile\fP.
meillo@21 1065 If one wants this different format as an additional command,
meillo@23 1066 instead of changing the default, he needs to create a link to
meillo@23 1067 \f(CWscan\fP, for instance titled \f(CWscan2\fP.
meillo@21 1068 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP,
meillo@45 1069 as the option should only be in effect for a program that is called as
meillo@21 1070 \f(CWscan2\fP.
meillo@20 1071
meillo@20 1072 .PP
meillo@33 1073 .B "Make every program a filter
meillo@21 1074 is hard to find in \s-1MH\s0.
meillo@21 1075 The reason therefore is that most of \s-1MH\s0's tools provide
meillo@45 1076 basic file system operations for mailboxes.
meillo@45 1077 It is the same reason because of which \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP,
meillo@45 1078 and \f(CWrm\fP aren't filters neither.
meillo@23 1079 \s-1MH\s0 does not provide many filters itself, but it is a basis
meillo@23 1080 to write filters for.
meillo@45 1081 An example would be a mail text highlighter,
meillo@30 1082 that means a program that makes use of a color terminal to display
meillo@30 1083 header lines, quotations, and signatures in distinct colors.
meillo@45 1084 The author's version of such a program is an awk script with 25 lines.
meillo@21 1085
meillo@21 1086 .PP
meillo@33 1087 .B "Build a prototype as soon as possible
meillo@21 1088 was again well followed by \s-1MH\s0.
meillo@21 1089 This tenet, of course, focuses on early development, which is
meillo@21 1090 long time ago for \s-1MH\s0.
meillo@21 1091 But without following this guideline at the very beginning,
meillo@23 1092 Bruce Borden may have not convinced the management of \s-1RAND\s0
meillo@23 1093 to ever create \s-1MH\s0.
meillo@23 1094 In Bruce' own words:
meillo@41 1095 .[
meillo@44 1096 ware rand history
meillo@44 1097 %P 132
meillo@41 1098 .]
meillo@21 1099 .QP
meillo@45 1100 [...] but [Stockton Gaines and Norm Shapiro] were not able
meillo@23 1101 to convince anyone that such a system would be fast enough to be usable.
meillo@21 1102 I proposed a very short project to prove the basic concepts,
meillo@21 1103 and my management agreed.
meillo@21 1104 Looking back, I realize that I had been very lucky with my first design.
meillo@21 1105 Without nearly enough design work,
meillo@21 1106 I built a working environment and some header files
meillo@21 1107 with key structures and wrote the first few \s-1MH\s0 commands:
meillo@21 1108 inc, show/next/prev, and comp.
meillo@21 1109 [...]
meillo@21 1110 With these three, I was able to convince people that the structure was viable.
meillo@21 1111 This took about three weeks.
meillo@0 1112
meillo@0 1113 .NH 2
meillo@0 1114 Problems
meillo@42 1115 .XS
meillo@42 1116 \*(SN Problems
meillo@42 1117 .XE
meillo@0 1118 .LP
meillo@45 1119 \s-1MH\s0 is not without problems.
meillo@30 1120 There are two main problems: one is technical, the other is about human behavior.
meillo@22 1121 .PP
meillo@22 1122 \s-1MH\s0 is old and email today is very different to email in the time
meillo@22 1123 when \s-1MH\s0 was designed.
meillo@45 1124 \s-1MH\s0 adapted to the changes pretty well, but it is limited, though.
meillo@22 1125 \s-1MIME\s0 support and support for different character encodings
meillo@22 1126 is available, but only on a moderate level.
meillo@45 1127 This comes from limited development resources.
meillo@45 1128 More active developers could quickly change this.
meillo@45 1129 But \s-1MH\s0 is also limited by design, which is the larger problem.
meillo@22 1130 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extend.
meillo@22 1131 These design conflicts are not easily solvable.
meillo@22 1132 Possibly, they require a redesign.
meillo@45 1133 \s-1IMAP\s0 may be too different to the classic mail model,
meillo@45 1134 which \s-1MH\s0 covers, so that \s-1MH\s0 may never support it well.
meillo@22 1135 .PP
meillo@45 1136 The other kind of problem are human habits.
meillo@45 1137 In this world, where almost all \s-1MUA\s0s are monolithic,
meillo@22 1138 it is very difficult to convince people to use a toolbox style \s-1MUA\s0
meillo@22 1139 like \s-1MH\s0.
meillo@45 1140 The habits are so strong, that even people who understand the concept
meillo@30 1141 and advantages of \s-1MH\s0 do not like to switch,
meillo@30 1142 simply because \s-1MH\s0 is different.
meillo@30 1143 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel,
meillo@45 1144 are quite outdated and thus not very appealing, compared to the modern interfaces
meillo@45 1145 of many monolithic \s-1MUA\s0s.
meillo@20 1146
meillo@20 1147 .NH 2
meillo@20 1148 Summary \s-1MH\s0
meillo@42 1149 .XS
meillo@42 1150 \*(SN Summary \s-1MH\s0
meillo@42 1151 .XE
meillo@20 1152 .LP
meillo@45 1153 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design.
meillo@31 1154 It consists of a toolchest of small tools, each of them does one job well.
meillo@31 1155 The toolchest approach offers great flexibility to the user.
meillo@45 1156 It is possible to utilize the complete power of the Unix shell with \s-1MH\s0.
meillo@31 1157 This makes \s-1MH\s0 a very powerful mail system.
meillo@45 1158 Extending and customizing \s-1MH\s0 is easy and encouraged.
meillo@31 1159 .PP
meillo@31 1160 Apart from the user's perspective, \s-1MH\s0 is development-friendly.
meillo@31 1161 Its overall design follows clear rules.
meillo@31 1162 The single tools do only one job, thus they are easy to understand,
meillo@31 1163 easy to write, and good to maintain.
meillo@31 1164 They are all independent and do not interfere with the others.
meillo@31 1165 Automated testing of their function is a straight forward task.
meillo@31 1166 .PP
meillo@31 1167 It is sad, that \s-1MH\s0's differentness is its largest problem,
meillo@31 1168 as its differentness is also its largest advantage.
meillo@31 1169 Unfortunately, for most people their habits are stronger
meillo@31 1170 than the attraction of the clear design and the power, \s-1MH\s0 offers.
meillo@0 1171
meillo@8 1172
meillo@8 1173
meillo@0 1174 .NH 1
meillo@0 1175 Case study: uzbl
meillo@42 1176 .XS
meillo@42 1177 .sp .5v
meillo@42 1178 \*(SN Case study: uzbl
meillo@42 1179 .XE
meillo@32 1180 .LP
meillo@32 1181 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0,
meillo@45 1182 which is an old and established software.
meillo@45 1183 This chapter covers uzbl, a fresh new project.
meillo@45 1184 Uzbl is a web browser that adheres to the Unix Philosophy.
meillo@45 1185 Its name comes from the \fILolspeak\fP word for ``usable'';
meillo@45 1186 it is pronounced identical.
meillo@0 1187
meillo@0 1188 .NH 2
meillo@32 1189 Historical background
meillo@42 1190 .XS
meillo@42 1191 \*(SN Historical background
meillo@42 1192 .XE
meillo@0 1193 .LP
meillo@32 1194 Uzbl was started by Dieter Plaetinck in April 2009.
meillo@44 1195 The idea was born in a thread in the Arch Linux Forums.
meillo@32 1196 .[
meillo@44 1197 arch linux forums
meillo@44 1198 browser
meillo@32 1199 .]
meillo@32 1200 After some discussion about failures of well known web browsers,
meillo@32 1201 Plaetinck (alias Dieter@be) came up with a very sketchy proposal
meillo@32 1202 of how a better web browser could look like.
meillo@32 1203 To the question of another member, if Plaetinck would write that program,
meillo@32 1204 because it would sound fantastic, Plaetinck replied:
meillo@32 1205 ``Maybe, if I find the time ;-)''.
meillo@32 1206 .PP
meillo@32 1207 Fortunately, he found the time.
meillo@32 1208 One day later, the first prototype was out.
meillo@32 1209 One week later, uzbl had an own website.
meillo@32 1210 One month after the first code showed up,
meillo@32 1211 a mailing list was installed to coordinate and discuss further development.
meillo@45 1212 Then a wiki followed to store documentation and scripts that showed up on the
meillo@32 1213 mailing list and elsewhere.
meillo@32 1214 .PP
meillo@45 1215 In the, now, one year of uzbl's existence, it was heavily developed on various branches.
meillo@32 1216 Plaetinck's task became more and more to only merge the best code from the
meillo@32 1217 different branches into his main branch, and to apply patches.
meillo@32 1218 About once a month, Plaetinck released a new version.
meillo@32 1219 In September 2009, he presented several forks of uzbl.
meillo@38 1220 Uzbl, actually, opened the field for a whole family of web browsers with similar shape.
meillo@32 1221 .PP
meillo@32 1222 In July 2009, \fILinux Weekly News\fP published an interview with Plaetinck about uzbl.
meillo@32 1223 In September 2009, the uzbl web browser was on \fISlashdot\fP.
meillo@0 1224
meillo@0 1225 .NH 2
meillo@32 1226 Contrasts to other web browsers
meillo@42 1227 .XS
meillo@42 1228 \*(SN Contrasts to other web browsers
meillo@42 1229 .XE
meillo@0 1230 .LP
meillo@32 1231 Like most \s-1MUA\s0s are monolithic, but \s-1MH\s0 is a toolchest,
meillo@32 1232 most web browsers are monolithic, but uzbl is a frontend to a toolchest.
meillo@32 1233 .PP
meillo@32 1234 Today, uzbl is divided into uzbl-core and uzbl-browser.
meillo@32 1235 Uzbl-core is, how its name already indicates, the core of uzbl.
meillo@32 1236 It handles commands and events to interface other programs,
meillo@45 1237 and also displays webpages by using \fIwebkit\fP as render engine.
meillo@32 1238 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar,
meillo@32 1239 an event manager, yanking, pasting, page searching, zooming, and more stuff,
meillo@32 1240 to form a ``complete'' web browser.
meillo@32 1241 In the following text, the term ``uzbl'' usually stands for uzbl-browser,
meillo@32 1242 so uzbl-core is included.
meillo@32 1243 .PP
meillo@32 1244 Unlike most other web browsers, uzbl is mainly the mediator between the
meillo@45 1245 various tools that cover single jobs.
meillo@35 1246 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket,
meillo@35 1247 and on stdin, and it writes events to a Unix socket and to stdout.
meillo@35 1248 Loading a webpage in a running uzbl instance requires only:
meillo@32 1249 .DS
meillo@32 1250 .CW
meillo@32 1251 echo 'uri http://example.org' >/path/to/uzbl-fifo
meillo@32 1252 .DE
meillo@45 1253 The graphical rendering of the webpage is done by webkit,
meillo@45 1254 a web content engine.
meillo@45 1255 Uzbl-core is built around libwebkit.
meillo@32 1256 .PP
meillo@45 1257 Downloads, browsing history, bookmarks, and the like are not provided
meillo@45 1258 by the core itself, like they are in other web browsers.
meillo@35 1259 Uzbl-browser also only provides, so called, handler scripts that wrap
meillo@35 1260 external applications which provide the actual functionality.
meillo@32 1261 For instance, \fIwget\fP is used to download files and uzbl-browser
meillo@32 1262 includes a script that calls wget with appropriate options in
meillo@32 1263 a prepared environment.
meillo@32 1264 .PP
meillo@32 1265 Modern web browsers are proud to have addons, plugins, and modules, instead.
meillo@32 1266 This is their effort to achieve similar goals.
meillo@35 1267 But instead of using existing, external programs, modern web browsers
meillo@45 1268 include these functions.
meillo@0 1269
meillo@0 1270 .NH 2
meillo@32 1271 Discussion of the design
meillo@42 1272 .XS
meillo@42 1273 \*(SN Discussion of the design
meillo@42 1274 .XE
meillo@0 1275 .LP
meillo@32 1276 This section discusses uzbl in regard of the Unix Philosophy,
meillo@32 1277 as identified by Gancarz.
meillo@32 1278
meillo@32 1279 .PP
meillo@35 1280 .B "Make each program do one thing well" .
meillo@35 1281 Uzbl tries to be a web browser and nothing else.
meillo@36 1282 The common definition of a web browser is, of course, highly influenced by
meillo@36 1283 existing implementations of web browsers, although they are degenerated.
meillo@35 1284 Web browsers should be programs to browse the web, and nothing more.
meillo@45 1285 This is the one thing they should do.
meillo@36 1286 .PP
meillo@45 1287 Web browsers should not, for instance, manage downloads.
meillo@35 1288 This is the job download managers exist for.
meillo@35 1289 Download managers do primary care about being good in downloading files.
meillo@35 1290 Modern web browsers provide download management only as a secondary feature.
meillo@45 1291 How could they do this job better, than programs that exist only for
meillo@35 1292 this very job?
meillo@35 1293 And how could anyone want less than the best download manager available?
meillo@32 1294 .PP
meillo@35 1295 A web browser's job is to let the user browse the web.
meillo@35 1296 This means, navigating through websites by following links.
meillo@36 1297 Rendering the \s-1HTML\s0 sources is a different job, too.
meillo@36 1298 It is covered by the webkit render engine, in uzbl's case.
meillo@35 1299 Audio and video content and files like PostScript, \s-1PDF\s0, and the like,
meillo@36 1300 are also not the job of a web browser.
meillo@36 1301 They should be handled by external applications \(en
meillo@36 1302 ones which's job is to handle such data.
meillo@35 1303 Uzbl strives to do it this way.
meillo@36 1304 .PP
meillo@36 1305 Remember Doug McIlroy:
meillo@35 1306 .I
meillo@35 1307 ``Write programs that do one thing and do it well.
meillo@35 1308 Write programs to work together.''
meillo@35 1309 .R
meillo@35 1310 .PP
meillo@35 1311 The lesser tenet
meillo@35 1312 .B "allow the user to tailor the environment
meillo@35 1313 matches good here.
meillo@35 1314 There was the question, how anyone could want anything less than the
meillo@35 1315 best program for the job.
meillo@45 1316 But as personal preferences matter, it is probably more important to ask:
meillo@35 1317 How could anyone want something else than his preferred program for the job?
meillo@36 1318 .PP
meillo@45 1319 Usually users want one program for a specific job.
meillo@35 1320 Hence, whenever the task is, for instance, downloading,
meillo@45 1321 the same download manager should be used.
meillo@35 1322 More advanced users might want to have this download manager in this
meillo@35 1323 situation and that one in that situation.
meillo@35 1324 They should be able to configure it this way.
meillo@35 1325 With uzbl, one can use any download manager the user wants.
meillo@36 1326 To switch to a different one, only one line in a small handler script
meillo@35 1327 needs to be changed.
meillo@45 1328 Alternatively it would be possible to query the program to use by
meillo@45 1329 reading a global file or an environment variable, in the handler script.
meillo@36 1330 .PP
meillo@45 1331 Uzbl does neither have its own download manager nor depends on a
meillo@45 1332 specific one, hence uzbl's browsing abilities will not be lowered by having
meillo@35 1333 a bad download manager.
meillo@45 1334 Uzbl's download capabilities will be just as good as the ones of the best
meillo@36 1335 download manager available on the system.
meillo@38 1336 Of course, this applies to all of the other supplementary tools, too.
meillo@32 1337
meillo@32 1338 .PP
meillo@36 1339 .B "Use software leverage to your advantage" .
meillo@36 1340 Uzbl is designed to be extended by external tools.
meillo@36 1341 These external tools are usually wrapped by small handler shell scripts.
meillo@36 1342 Shell scripts are the glue in this approach.
meillo@36 1343 They make the various parts fit together.
meillo@36 1344 .PP
meillo@45 1345 The history mechanism of uzbl shall be presented as an example.
meillo@36 1346 Uzbl is configured to spawn a script to append an entry to the history
meillo@36 1347 whenever the event of a fully loaded page occurs.
meillo@45 1348 The script to append the entry to the history is not much more than:
meillo@36 1349 .DS
meillo@36 1350 .CW
meillo@36 1351 #!/bin/sh
meillo@36 1352 file=/path/to/uzbl-history
meillo@36 1353 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file
meillo@36 1354 .DE
meillo@36 1355 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title.
meillo@45 1356 .PP
meillo@45 1357 For loading an entry, a key is bound to spawn a load-from-history script.
meillo@36 1358 The script reverses the history to have newer entries first,
meillo@45 1359 then displays \fIdmenu\fP to let the user select an item,
meillo@36 1360 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe.
meillo@45 1361 With error checking and corner case handling removed,
meillo@45 1362 the script looks like this:
meillo@36 1363 .DS
meillo@36 1364 .CW
meillo@36 1365 #!/bin/sh
meillo@36 1366 file=/path/to/uzbl-history
meillo@36 1367 goto=`tac $file | dmenu | cut -d' ' -f 3`
meillo@36 1368 echo "uri $goto" > $4
meillo@36 1369 .DE
meillo@36 1370 \f(CW$4\fP expands to the path of the command input pipe of the current
meillo@36 1371 uzbl instance.
meillo@32 1372
meillo@32 1373 .PP
meillo@33 1374 .B "Avoid captive user interfaces" .
meillo@36 1375 One could say, that uzbl, to a large extend, actually \fIis\fP
meillo@36 1376 a captive user interface.
meillo@37 1377 But the difference to most other web browsers is, that uzbl is only
meillo@45 1378 the captive user interface frontend (and the core of the backend).
meillo@38 1379 Many parts of the backend are independent of uzbl.
meillo@45 1380 Some are distributed with uzbl, for some external programs,
meillo@45 1381 handler scripts are distributed,
meillo@45 1382 but arbitrary additional functionality can be added if desired.
meillo@37 1383 .PP
meillo@37 1384 The frontend is captive \(en that is true.
meillo@37 1385 This is okay for the task of browsing the web, as this task is only relevant
meillo@37 1386 for humans.
meillo@37 1387 Automated programs would \fIcrawl\fP the web.
meillo@37 1388 That means, they read the source directly.
meillo@37 1389 The source includes all the semantics.
meillo@37 1390 The graphical representation is just for humans to transfer the semantics
meillo@37 1391 more intuitively.
meillo@32 1392
meillo@32 1393 .PP
meillo@33 1394 .B "Make every program a filter" .
meillo@37 1395 Graphical web browsers are almost dead ends in the chain of information flow.
meillo@37 1396 Thus it is difficult to see what graphical web browsers should filter.
meillo@45 1397 Graphical web browsers exist almost only to be interactively used by humans.
meillo@37 1398 The only case when one might want to automate the rendering function is
meillo@37 1399 to generate images of rendered webpages.
meillo@37 1400
meillo@37 1401 .PP
meillo@37 1402 .B "Small is beautiful"
meillo@45 1403 is not easy to apply to a web browser, because modern web technology
meillo@45 1404 is very complex, hence the rendering task is very complex.
meillo@45 1405 Modern web browsers have to consist of many thousand lines of code,
meillo@37 1406 unfortunately.
meillo@37 1407 Using the toolchest approach and wrappers can split the browser into
meillo@37 1408 several small parts, tough.
meillo@37 1409 .PP
meillo@45 1410 As of March 2010, uzbl-core consists of about 3\,500 lines of C code.
meillo@37 1411 The distribution includes another 3\,500 lines of Shell and Python code,
meillo@37 1412 which are the handler scripts and plugins like a modal interface.
meillo@38 1413 Further more, uzbl uses functionality of external tools like
meillo@38 1414 \fIwget\fP and \fInetcat\fP.
meillo@37 1415 Up to this point, uzbl looks pretty neat and small.
meillo@38 1416 The ugly part of uzbl is the web content renderer, webkit.
meillo@37 1417 Webkit consists of roughly 400\,000 (!) lines of code.
meillo@38 1418 Unfortunately, small web render engines are not possible anymore
meillo@38 1419 because of the modern web.
meillo@35 1420
meillo@35 1421 .PP
meillo@35 1422 .B "Build a prototype as soon as possible" .
meillo@35 1423 Plaetinck made his code public, right from the beginning.
meillo@38 1424 Discussion and development was, and still is, open to everyone interested.
meillo@38 1425 Development versions of uzbl can be obtained very simply from the code
meillo@38 1426 repository.
meillo@38 1427 Within the first year of uzbl's existence, a new version was released
meillo@35 1428 more often than once a month.
meillo@38 1429 Different forks and branches arose.
meillo@45 1430 They introduced new features, which were tested for suitability
meillo@45 1431 for the main branch.
meillo@35 1432 The experiences of using prototypes influenced further development.
meillo@35 1433 Actually, all development was community driven.
meillo@38 1434 Plaetinck says, three months after uzbl's birth:
meillo@35 1435 ``Right now I hardly code anything myself for Uzbl.
meillo@35 1436 I just merge in other people's code, ponder a lot, and lead the discussions.''
meillo@35 1437 .[
meillo@44 1438 lwn
meillo@44 1439 uzbl
meillo@35 1440 .]
meillo@32 1441
meillo@0 1442
meillo@0 1443 .NH 2
meillo@0 1444 Problems
meillo@42 1445 .XS
meillo@42 1446 \*(SN Problems
meillo@42 1447 .XE
meillo@0 1448 .LP
meillo@38 1449 Similar to \s-1MH\s0, uzbl, too suffers from being different.
meillo@38 1450 It is sad, but people use what they know.
meillo@38 1451 Fortunately, uzbl's user interface can look and feel very much the
meillo@38 1452 same as the one of the well known web browsers,
meillo@38 1453 hiding the internal differences.
meillo@38 1454 But uzbl has to provide this similar look and feel to be accepted
meillo@38 1455 as a ``normal'' browser by ``normal'' users.
meillo@37 1456 .PP
meillo@45 1457 Though, the more important problem is the modern web.
meillo@38 1458 The modern web is simply broken.
meillo@38 1459 It has state in a state-less protocol,
meillo@38 1460 it misuses technologies,
meillo@38 1461 and it is helplessly overloaded.
meillo@38 1462 The result are web content render engines that must consist
meillo@38 1463 of hundreds of thousands lines of code.
meillo@38 1464 They also must combine and integrate many different technologies,
meillo@45 1465 only to make our modern web accessible.
meillo@38 1466 Website to image converter are hardly possible to run without
meillo@38 1467 human interaction because of state in sessions, impossible
meillo@38 1468 deep-linking, and unautomatable technologies.
meillo@37 1469 .PP
meillo@38 1470 The web was misused to provide all kinds of imaginable wishes.
meillo@38 1471 Now web browsers, and eventually the users, suffer from it.
meillo@37 1472
meillo@8 1473
meillo@32 1474 .NH 2
meillo@32 1475 Summary uzbl
meillo@42 1476 .XS
meillo@42 1477 \*(SN Summary uzbl
meillo@42 1478 .XE
meillo@32 1479 .LP
meillo@38 1480 ``Uzbl is a browser that adheres to the Unix Philosophy'',
meillo@38 1481 that is how uzbl is seen by its authors.
meillo@38 1482 Indeed, uzbl follows the Unix Philosophy in many ways.
meillo@38 1483 It consists of independent parts that work together,
meillo@45 1484 while its core is mainly a mediator which glues the parts together.
meillo@38 1485 .PP
meillo@38 1486 Software leverage can excellently be seen in uzbl.
meillo@45 1487 External tools are used, independent tasks are separated
meillo@45 1488 in independent parts and glued together with small handler scripts.
meillo@38 1489 .PP
meillo@38 1490 As uzbl, more or less, consists of a set of tools and a bit
meillo@38 1491 of glue, anyone can put the parts together and expand it
meillo@38 1492 in any desired way.
meillo@38 1493 Uzbl is very flexible and customizable.
meillo@38 1494 These properties make it valuable for advanced users,
meillo@38 1495 but may keep novice users from using it.
meillo@38 1496 .PP
meillo@45 1497 But uzbl's main problem is the modern web, that makes it hard
meillo@38 1498 to design a sane web browser.
meillo@38 1499 Despite this bad situation, uzbl does a fairly good job.
meillo@32 1500
meillo@8 1501
meillo@0 1502 .NH 1
meillo@0 1503 Final thoughts
meillo@42 1504 .XS
meillo@42 1505 .sp .5v
meillo@42 1506 \*(SN Final thoughts
meillo@42 1507 .XE
meillo@0 1508
meillo@0 1509 .NH 2
meillo@0 1510 Quick summary
meillo@42 1511 .XS
meillo@42 1512 \*(SN Quick summary
meillo@42 1513 .XE
meillo@0 1514 .LP
meillo@0 1515 good design
meillo@0 1516 .LP
meillo@0 1517 unix phil
meillo@0 1518 .LP
meillo@0 1519 case studies
meillo@0 1520
meillo@0 1521 .NH 2
meillo@0 1522 Why people should choose
meillo@42 1523 .XS
meillo@42 1524 \*(SN Why people should choose
meillo@42 1525 .XE
meillo@0 1526 .LP
meillo@0 1527 Make the right choice!
meillo@0 1528
meillo@42 1529 .nr PI .3i
meillo@0 1530 .rm ]<
meillo@0 1531 .de ]<
meillo@0 1532 .LP
meillo@0 1533 .de FP
meillo@0 1534 .IP \\\\$1.
meillo@0 1535 \\..
meillo@0 1536 .rm FS FE
meillo@0 1537 ..
meillo@42 1538 .ds CH "
meillo@42 1539 .bp
meillo@42 1540 .rs
meillo@42 1541 .sp .3i
meillo@42 1542 .TL
meillo@0 1543 References
meillo@42 1544 .LP
meillo@42 1545 .XS
meillo@42 1546 .sp .5v
meillo@42 1547 References
meillo@42 1548 .XE
meillo@42 1549 .sp 2v
meillo@42 1550 .nr PS -1
meillo@42 1551 .nr VS -1
meillo@0 1552 .[
meillo@0 1553 $LIST$
meillo@0 1554 .]
meillo@42 1555 .\".wh -1p
meillo@42 1556 .bp
meillo@42 1557 .PX