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author meillo@marmaro.de
date Mon, 12 Apr 2010 10:52:59 +0200
parents ade392f024aa
children b6ae4a8ab1d3
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meillo@45 26 .ps -1
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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@46 375 .[ [
meillo@44 376 gancarz unix philosophy
meillo@46 377 .], page 88 ff.]
meillo@11 378 .PP
meillo@11 379 Non-interactive use is, during development, also an advantage for testing.
meillo@11 380 Testing of interactive programs is much more complicated,
meillo@11 381 than testing of non-interactive programs.
meillo@5 382
meillo@16 383 .NH 2
meillo@8 384 The toolchest approach
meillo@42 385 .XS
meillo@42 386 \*(SN The toolchest approach
meillo@42 387 .XE
meillo@5 388 .LP
meillo@5 389 A toolchest is a set of tools.
meillo@5 390 Instead of having one big tool for all tasks, one has many small tools,
meillo@5 391 each for one task.
meillo@5 392 Difficult tasks are solved by combining several of the small, simple tools.
meillo@5 393 .PP
meillo@11 394 The Unix toolchest \fIis\fP a set of small, (mostly) non-interactive programs
meillo@11 395 that are filters on byte streams.
meillo@11 396 They are, to a large extend, unrelated in their function.
meillo@11 397 Hence, the Unix toolchest provides a large set of functions
meillo@11 398 that can be accessed by combining the programs in the desired way.
meillo@11 399 .PP
meillo@11 400 There are also advantages for developing small toolchest programs.
meillo@5 401 It is easier and less error-prone to write small programs.
meillo@5 402 It is also easier and less error-prone to write a large set of small programs,
meillo@5 403 than to write one large program with all the functionality included.
meillo@5 404 If the small programs are combinable, then they offer even a larger set
meillo@5 405 of functions than the single large program.
meillo@45 406 Hence, one gets two advantages out of writing small, combinable programs:
meillo@45 407 They are easier to write and they offer a greater set of functions through
meillo@45 408 combination.
meillo@5 409 .PP
meillo@45 410 But there are also two main drawbacks of the toolchest approach.
meillo@45 411 First, one simple, standardized interface has to be sufficient.
meillo@5 412 If one feels the need for more ``logic'' than a stream of bytes,
meillo@8 413 then a different approach might be of need.
meillo@13 414 But it is also possible, that he just can not imagine a design where
meillo@8 415 a stream of bytes is sufficient.
meillo@8 416 By becoming more familiar with the ``Unix style of thinking'',
meillo@8 417 developers will more often and easier find simple designs where
meillo@8 418 a stream of bytes is a sufficient interface.
meillo@8 419 .PP
meillo@8 420 The second drawback of a toolchest affects the users.
meillo@45 421 A toolchest is often more difficult to use.
meillo@9 422 It is necessary to become familiar with each of the tools,
meillo@5 423 to be able to use the right one in a given situation.
meillo@45 424 Additionally, one needs to combine the tools in a senseful way himself.
meillo@45 425 This is like a sharp knife \(en it is a powerful tool in the hand of a
meillo@45 426 master, but of no good value in the hand of an unskilled.
meillo@45 427 However, learning single, small tools of a toolchest is easier than
meillo@45 428 learning a complex tool.
meillo@45 429 And the user will already have a basic understanding of a yet unknown tool,
meillo@45 430 if the tools of a toolchest have a common, consistent style.
meillo@45 431 He will be able to transfer knowledge over from one tool to another.
meillo@5 432 .PP
meillo@45 433 Moreover, the second drawback can be removed to a large extend
meillo@45 434 by adding wrappers around the basic tools.
meillo@45 435 Novice users do not need to learn several tools, if a professional wraps
meillo@45 436 complete command lines into a higher-level script.
meillo@5 437 Note that the wrapper script still calls the small tools;
meillo@45 438 it is just like a skin around them.
meillo@45 439 No complexity is added this way.
meillo@45 440 But new programs can get created out of existing one with very low effort.
meillo@5 441 .PP
meillo@5 442 A wrapper script for finding the five largest entries in the current directory
meillo@5 443 could look like this:
meillo@41 444 .DS
meillo@5 445 .CW
meillo@9 446 .ps -1
meillo@5 447 #!/bin/sh
meillo@5 448 du -s * | sort -nr | sed 5q
meillo@5 449 .DE
meillo@45 450 The script itself is just a text file that calls the command line,
meillo@45 451 which a professional user would type in directly.
meillo@45 452 It is probably worth to make the program flexible on the number of
meillo@45 453 entries it prints:
meillo@41 454 .DS
meillo@8 455 .CW
meillo@9 456 .ps -1
meillo@8 457 #!/bin/sh
meillo@8 458 num=5
meillo@8 459 [ $# -eq 1 ] && num="$1"
meillo@8 460 du -sh * | sort -nr | sed "${num}q"
meillo@8 461 .DE
meillo@8 462 This script acts like the one before, when called without an argument.
meillo@8 463 But one can also specify a numerical argument to define the number of lines to print.
meillo@45 464 One can surely imagine even more flexible versions, however,
meillo@45 465 they will still relay on the external programs,
meillo@45 466 which do the actual work.
meillo@5 467
meillo@16 468 .NH 2
meillo@8 469 A powerful shell
meillo@42 470 .XS
meillo@42 471 \*(SN A powerful shell
meillo@42 472 .XE
meillo@8 473 .LP
meillo@45 474 The Unix shell provides the possibility to combine small programs into large ones.
meillo@45 475 But a powerful shell is a great feature in other ways, too.
meillo@45 476 For instance by being scriptable.
meillo@45 477 Control statements are build into the shell.
meillo@45 478 The functions, however, are the normal programs of the system.
meillo@45 479 Thus, as the programs are already known,
meillo@45 480 learning to program in the shell becomes easy.
meillo@8 481 Using normal programs as functions in the shell programming language
meillo@10 482 is only possible because they are small and combinable tools in a toolchest style.
meillo@8 483 .PP
meillo@45 484 The Unix shell encourages to write small scripts,
meillo@45 485 by combining existing programs, because it is so easy to do.
meillo@8 486 This is a great step towards automation.
meillo@8 487 It is wonderful if the effort to automate a task equals the effort
meillo@45 488 to do the task a second time by hand.
meillo@45 489 If this holds,
meillo@45 490 then the user will be happy to automate everything he does more than once.
meillo@8 491 .PP
meillo@8 492 Small programs that do one job well, standardized interfaces between them,
meillo@8 493 a mechanism to combine parts to larger parts, and an easy way to automate tasks,
meillo@8 494 this will inevitably produce software leverage.
meillo@8 495 Getting multiple times the benefit of an investment is a great offer.
meillo@10 496 .PP
meillo@10 497 The shell also encourages rapid prototyping.
meillo@10 498 Many well known programs started as quickly hacked shell scripts,
meillo@10 499 and turned into ``real'' programs, written in C, later.
meillo@45 500 Building a prototype first, is a way to avoid the biggest problems
meillo@10 501 in application development.
meillo@45 502 Fred Brooks explains in ``No Silver Bullet'':
meillo@10 503 .[
meillo@44 504 brooks
meillo@44 505 no silver bullet
meillo@10 506 .]
meillo@10 507 .QP
meillo@10 508 The hardest single part of building a software system is deciding precisely what to build.
meillo@10 509 No other part of the conceptual work is so difficult as establishing the detailed
meillo@10 510 technical requirements, [...].
meillo@10 511 No other part of the work so cripples the resulting system if done wrong.
meillo@10 512 No other part is more difficult to rectify later.
meillo@10 513 .PP
meillo@45 514 Writing a prototype is a great method for becoming familiar with the requirements
meillo@45 515 and to run into real problems early.
meillo@45 516 .PP
meillo@45 517 Prototyping is often seen as a first step in building a software.
meillo@10 518 This is, of course, good.
meillo@10 519 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping:
meillo@10 520 After having built the prototype, one might notice, that the prototype is already
meillo@10 521 \fIgood enough\fP.
meillo@45 522 Hence, no reimplementation, in a more sophisticated programming language,
meillo@45 523 might be of need, at least for the moment.
meillo@23 524 Maybe later, it might be necessary to rewrite the software, but not now.
meillo@45 525 By delaying further work, one keeps the flexibility to react on
meillo@10 526 changing requirements.
meillo@10 527 Software parts that are not written will not miss the requirements.
meillo@10 528
meillo@16 529 .NH 2
meillo@10 530 Worse is better
meillo@42 531 .XS
meillo@42 532 \*(SN Worse is better
meillo@42 533 .XE
meillo@10 534 .LP
meillo@45 535 The Unix Philosophy aims for the 90% solution;
meillo@10 536 others call it the ``Worse is better'' approach.
meillo@45 537 Practical experience shows, that:
meillo@10 538 .PP
meillo@45 539 (1) It is almost never possible to define the
meillo@10 540 requirements completely and correctly the first time.
meillo@45 541 Hence one should not try to; one will fail anyway.
meillo@45 542 .PP
meillo@45 543 (2) Requirements change during time.
meillo@10 544 Hence it is best to delay requirement-based design decisions as long as possible.
meillo@45 545 The software should be small and flexible as long as possible
meillo@10 546 to react on changing requirements.
meillo@10 547 Shell scripts, for example, are more easily adjusted as C programs.
meillo@45 548 .PP
meillo@45 549 (3) Maintenance work is hard work.
meillo@45 550 Hence, one should keep the amount of code as small as possible;
meillo@10 551 it should just fulfill the \fIcurrent\fP requirements.
meillo@45 552 Software parts that will be written in future,
meillo@45 553 do not need maintenance till then.
meillo@10 554 .PP
meillo@10 555 Starting with a prototype in a scripting language has several advantages:
meillo@10 556 .IP \(bu
meillo@10 557 As the initial effort is low, one will likely start right away.
meillo@10 558 .IP \(bu
meillo@10 559 As working parts are available soon, the real requirements can get identified soon.
meillo@10 560 .IP \(bu
meillo@45 561 When a software is usable and valuable, it gets used, and thus tested.
meillo@10 562 Hence problems will be found at early stages of the development.
meillo@10 563 .IP \(bu
meillo@10 564 The prototype might be enough for the moment,
meillo@45 565 thus further work on the software can get delayed to a time
meillo@10 566 when one knows better about the requirements and problems,
meillo@10 567 than now.
meillo@10 568 .IP \(bu
meillo@45 569 Implementing now only the parts that are actually needed at the moment,
meillo@45 570 introduces fewer programming and maintenance work.
meillo@10 571 .IP \(bu
meillo@10 572 If the global situation changes so that the software is not needed anymore,
meillo@10 573 then less effort was spent into the project, than it would have be
meillo@10 574 when a different approach had been used.
meillo@10 575
meillo@16 576 .NH 2
meillo@11 577 Upgrowth and survival of software
meillo@42 578 .XS
meillo@42 579 \*(SN Upgrowth and survival of software
meillo@42 580 .XE
meillo@11 581 .LP
meillo@12 582 So far it was talked about \fIwriting\fP or \fIbuilding\fP software.
meillo@13 583 Although these are just verbs, they do imply a specific view on the work process
meillo@13 584 they describe.
meillo@12 585 The better verb, however, is to \fIgrow\fP.
meillo@12 586 Creating software in the sense of the Unix Philosophy is an incremental process.
meillo@12 587 It starts with a first prototype, which evolves as requirements change.
meillo@12 588 A quickly hacked shell script might become a large, sophisticated,
meillo@13 589 compiled program this way.
meillo@13 590 Its lifetime begins with the initial prototype and ends when the software is not used anymore.
meillo@45 591 While being alive it will get extended, rearranged, rebuilt.
meillo@12 592 Growing software matches the view that ``software is never finished. It is only released.''
meillo@46 593 .[ [
meillo@44 594 gancarz
meillo@44 595 unix philosophy
meillo@46 596 .], page 26]
meillo@12 597 .PP
meillo@13 598 Software can be seen as being controlled by evolutionary processes.
meillo@13 599 Successful software is software that is used by many for a long time.
meillo@12 600 This implies that the software is needed, useful, and better than alternatives.
meillo@12 601 Darwin talks about: ``The survival of the fittest.''
meillo@12 602 .[
meillo@44 603 darwin
meillo@44 604 origin of species
meillo@12 605 .]
meillo@12 606 Transferred to software: The most successful software, is the fittest,
meillo@12 607 is the one that survives.
meillo@13 608 (This may be at the level of one creature, or at the level of one species.)
meillo@13 609 The fitness of software is affected mainly by four properties:
meillo@15 610 portability of code, portability of data, range of usability, and reusability of parts.
meillo@15 611 .\" .IP \(bu
meillo@15 612 .\" portability of code
meillo@15 613 .\" .IP \(bu
meillo@15 614 .\" portability of data
meillo@15 615 .\" .IP \(bu
meillo@15 616 .\" range of usability
meillo@15 617 .\" .IP \(bu
meillo@15 618 .\" reuseability of parts
meillo@13 619 .PP
meillo@15 620 (1)
meillo@15 621 .I "Portability of code
meillo@15 622 means, using high-level programming languages,
meillo@13 623 sticking to the standard,
meillo@13 624 and avoiding optimizations that introduce dependencies on specific hardware.
meillo@13 625 Hardware has a much lower lifetime than software.
meillo@13 626 By chaining software to a specific hardware,
meillo@13 627 the software's lifetime gets shortened to that of this hardware.
meillo@13 628 In contrast, software should be easy to port \(en
meillo@23 629 adaptation is the key to success.
meillo@13 630 .\" cf. practice of prog: ch08
meillo@13 631 .PP
meillo@15 632 (2)
meillo@15 633 .I "Portability of data
meillo@15 634 is best achieved by avoiding binary representations
meillo@13 635 to store data, because binary representations differ from machine to machine.
meillo@23 636 Textual representation is favored.
meillo@45 637 Historically, \s-1ASCII\s0 was the charset of choice.
meillo@45 638 For the future, \s-1UTF\s0-8 might be the better choice.
meillo@13 639 Important is that it is a plain text representation in a
meillo@13 640 very common charset encoding.
meillo@13 641 Apart from being able to transfer data between machines,
meillo@45 642 readable data has the great advantage, that humans are able to directly
meillo@45 643 read and edit it with text editors and other tools from the Unix toolchest.
meillo@13 644 .\" gancarz tenet 5
meillo@13 645 .PP
meillo@15 646 (3)
meillo@15 647 A large
meillo@15 648 .I "range of usability
meillo@23 649 ensures good adaptation, and thus good survival.
meillo@13 650 It is a special distinction if a software becomes used in fields of action,
meillo@13 651 the original authors did never imagine.
meillo@13 652 Software that solves problems in a general way will likely be used
meillo@45 653 for many kinds of similar problems.
meillo@45 654 Being too specific limits the range of usability.
meillo@13 655 Requirements change through time, thus use cases change or even vanish.
meillo@45 656 As a good example in this point,
meillo@13 657 Allman identifies flexibility to be one major reason for sendmail's success:
meillo@13 658 .[
meillo@44 659 allman
meillo@44 660 sendmail
meillo@13 661 .]
meillo@13 662 .QP
meillo@13 663 Second, I limited myself to the routing function [...].
meillo@13 664 This was a departure from the dominant thought of the time, [...].
meillo@13 665 .QP
meillo@45 666 Third, the sendmail configuration file was flexible enough to adapt
meillo@13 667 to a rapidly changing world [...].
meillo@12 668 .LP
meillo@45 669 Successful software adapts itself to the changing world.
meillo@13 670 .PP
meillo@15 671 (4)
meillo@15 672 .I "Reuse of parts
meillo@15 673 is even one step further.
meillo@13 674 A software may completely lose its field of action,
meillo@13 675 but parts of which the software is build may be general and independent enough
meillo@13 676 to survive this death.
meillo@13 677 If software is build by combining small independent programs,
meillo@45 678 then these parts are readily available for reuse.
meillo@13 679 Who cares if the large program is a failure,
meillo@13 680 but parts of it become successful instead?
meillo@10 681
meillo@16 682 .NH 2
meillo@14 683 Summary
meillo@42 684 .XS
meillo@42 685 \*(SN Summary
meillo@42 686 .XE
meillo@0 687 .LP
meillo@45 688 This chapter explained central ideas of the Unix Philosophy.
meillo@45 689 For each of the ideas, the advantages they introduce were explained.
meillo@45 690 The Unix Philosophy are guidelines that help to write more valuable software.
meillo@14 691 From the view point of a software developer or software designer,
meillo@14 692 the Unix Philosophy provides answers to many software design problem.
meillo@14 693 .PP
meillo@14 694 The various ideas of the Unix Philosophy are very interweaved
meillo@14 695 and can hardly be applied independently.
meillo@14 696 However, the probably most important messages are:
meillo@45 697 .I "``Keep it simple!''" ,
meillo@14 698 .I "``Do one thing well!''" ,
meillo@14 699 and
meillo@14 700 .I "``Use software leverage!''
meillo@0 701
meillo@8 702
meillo@8 703
meillo@0 704 .NH 1
meillo@19 705 Case study: \s-1MH\s0
meillo@42 706 .XS
meillo@42 707 .sp .5v
meillo@42 708 \*(SN Case study: \s-1MH\s0
meillo@42 709 .XE
meillo@18 710 .LP
meillo@30 711 The previous chapter introduced and explained the Unix Philosophy
meillo@18 712 from a general point of view.
meillo@30 713 The driving force were the guidelines; references to
meillo@18 714 existing software were given only sparsely.
meillo@18 715 In this and the next chapter, concrete software will be
meillo@18 716 the driving force in the discussion.
meillo@18 717 .PP
meillo@23 718 This first case study is about the mail user agents (\s-1MUA\s0)
meillo@23 719 \s-1MH\s0 (``mail handler'') and its descendent \fInmh\fP
meillo@23 720 (``new mail handler'').
meillo@23 721 \s-1MUA\s0s provide functions to read, compose, and organize mail,
meillo@45 722 but (ideally) not to transfer it.
meillo@45 723 In this document, the name \s-1MH\s0 will be used to include nmh.
meillo@19 724 A distinction will only be made if differences between
meillo@45 725 \s-1MH\s0 and nmh are described.
meillo@18 726
meillo@0 727
meillo@0 728 .NH 2
meillo@19 729 Historical background
meillo@42 730 .XS
meillo@42 731 \*(SN Historical background
meillo@42 732 .XE
meillo@0 733 .LP
meillo@19 734 Electronic mail was available in Unix very early.
meillo@30 735 The first \s-1MUA\s0 on Unix was \f(CWmail\fP,
meillo@30 736 which was already present in the First Edition.
meillo@46 737 .[ [
meillo@44 738 salus
meillo@44 739 quarter century of unix
meillo@46 740 .], page 41 f.]
meillo@45 741 It was a small program that either printed the user's mailbox file
meillo@45 742 or appended text to someone elses mailbox file,
meillo@19 743 depending on the command line arguments.
meillo@19 744 .[
meillo@44 745 manual mail(1)
meillo@19 746 .]
meillo@19 747 It was a program that did one job well.
meillo@23 748 This job was emailing, which was very simple then.
meillo@19 749 .PP
meillo@23 750 Later, emailing became more powerful, and thus more complex.
meillo@19 751 The simple \f(CWmail\fP, which knew nothing of subjects,
meillo@19 752 independent handling of single messages,
meillo@45 753 and long-time email storage, was not powerful enough anymore.
meillo@45 754 In 1978 at Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
meillo@45 755 to provide additional functions for emailing.
meillo@19 756 Mail was still one program, but now it was large and did
meillo@19 757 several jobs.
meillo@23 758 Its user interface is modeled after the one of \fIed\fP.
meillo@19 759 It is designed for humans, but is still scriptable.
meillo@23 760 \fImailx\fP is the adaptation of Berkeley Mail into System V.
meillo@19 761 .[
meillo@44 762 ritter
meillo@44 763 mailx history
meillo@19 764 .]
meillo@30 765 Elm, pine, mutt, and a whole bunch of graphical \s-1MUA\s0s
meillo@19 766 followed Mail's direction.
meillo@19 767 They are large, monolithic programs which include all emailing functions.
meillo@19 768 .PP
meillo@23 769 A different way was taken by the people of \s-1RAND\s0 Corporation.
meillo@38 770 In the beginning, they also had used a monolithic mail system,
meillo@30 771 called \s-1MS\s0 (for ``mail system'').
meillo@19 772 But in 1977, Stockton Gaines and Norman Shapiro
meillo@19 773 came up with a proposal of a new email system concept \(en
meillo@45 774 one that honored the Unix Philosophy.
meillo@19 775 The concept was implemented by Bruce Borden in 1978 and 1979.
meillo@19 776 This was the birth of \s-1MH\s0 \(en the ``mail handler''.
meillo@18 777 .PP
meillo@18 778 Since then, \s-1RAND\s0, the University of California at Irvine and
meillo@19 779 at Berkeley, and several others have contributed to the software.
meillo@18 780 However, it's core concepts remained the same.
meillo@23 781 In the late 90s, when development of \s-1MH\s0 slowed down,
meillo@19 782 Richard Coleman started with \fInmh\fP, the new mail handler.
meillo@45 783 His goal was to improve \s-1MH\s0 especially in regard of
meillo@23 784 the requirements of modern emailing.
meillo@19 785 Today, nmh is developed by various people on the Internet.
meillo@18 786 .[
meillo@44 787 ware
meillo@44 788 rand history
meillo@18 789 .]
meillo@18 790 .[
meillo@44 791 peek
meillo@44 792 mh
meillo@18 793 .]
meillo@0 794
meillo@0 795 .NH 2
meillo@20 796 Contrasts to monolithic mail systems
meillo@42 797 .XS
meillo@42 798 \*(SN Contrasts to monolithic mail systems
meillo@42 799 .XE
meillo@0 800 .LP
meillo@19 801 All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
meillo@38 802 Although there might actually exist further, very little known,
meillo@30 803 toolchest \s-1MUA\s0s, this statement reflects the situation pretty well.
meillo@19 804 .PP
meillo@30 805 Monolithic \s-1MUA\s0s gather all their functions in one program.
meillo@30 806 In contrast, \s-1MH\s0 is a toolchest of many small tools \(en one for each job.
meillo@23 807 Following is a list of important programs of \s-1MH\s0's toolchest
meillo@30 808 and their function.
meillo@30 809 It gives a feeling of how the toolchest looks like.
meillo@19 810 .IP \(bu
meillo@19 811 .CW inc :
meillo@30 812 incorporate new mail (this is how mail enters the system)
meillo@19 813 .IP \(bu
meillo@19 814 .CW scan :
meillo@19 815 list messages in folder
meillo@19 816 .IP \(bu
meillo@19 817 .CW show :
meillo@19 818 show message
meillo@19 819 .IP \(bu
meillo@19 820 .CW next\fR/\fPprev :
meillo@19 821 show next/previous message
meillo@19 822 .IP \(bu
meillo@19 823 .CW folder :
meillo@19 824 change current folder
meillo@19 825 .IP \(bu
meillo@19 826 .CW refile :
meillo@45 827 refile message into different folder
meillo@19 828 .IP \(bu
meillo@19 829 .CW rmm :
meillo@19 830 remove message
meillo@19 831 .IP \(bu
meillo@19 832 .CW comp :
meillo@45 833 compose new message
meillo@19 834 .IP \(bu
meillo@19 835 .CW repl :
meillo@45 836 reply to message
meillo@19 837 .IP \(bu
meillo@19 838 .CW forw :
meillo@45 839 forward message
meillo@19 840 .IP \(bu
meillo@19 841 .CW send :
meillo@45 842 send prepared message (this is how mail leaves the system)
meillo@0 843 .LP
meillo@19 844 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
meillo@19 845 The user does not leave the shell to run \s-1MH\s0,
meillo@45 846 instead he uses the various \s-1MH\s0 programs within the shell.
meillo@23 847 Using a monolithic program with a captive user interface
meillo@23 848 means ``entering'' the program, using it, and ``exiting'' the program.
meillo@23 849 Using toolchests like \s-1MH\s0 means running programs,
meillo@45 850 alone or in combination with others, also from other toolchests,
meillo@23 851 without leaving the shell.
meillo@30 852
meillo@30 853 .NH 2
meillo@30 854 Data storage
meillo@42 855 .XS
meillo@42 856 \*(SN Data storage
meillo@42 857 .XE
meillo@30 858 .LP
meillo@34 859 \s-1MH\s0's mail storage is a directory tree under the user's
meillo@34 860 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP),
meillo@34 861 where mail folders are directories and mail messages are text files
meillo@34 862 within them.
meillo@34 863 Each mail folder contains a file \f(CW.mh_sequences\fP which lists
meillo@45 864 the public message sequences of that folder,
meillo@45 865 for instance the \fIunseen\fP sequence for new messages.
meillo@34 866 Mail messages are text files located in a mail folder.
meillo@34 867 The files contain the messages as they were received.
meillo@45 868 They are named by ascending numbers in each folder.
meillo@19 869 .PP
meillo@30 870 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0.
meillo@30 871 Alternatives are \fImbox\fP and \fImaildir\fP.
meillo@30 872 In the mbox format all messages are stored within one file.
meillo@30 873 This was a good solution in the early days, when messages
meillo@30 874 were only a few lines of text and were deleted soon.
meillo@30 875 Today, when single messages often include several megabytes
meillo@30 876 of attachments, it is a bad solution.
meillo@30 877 Another disadvantage of the mbox format is that it is
meillo@30 878 more difficult to write tools that work on mail messages,
meillo@30 879 because it is always necessary to first find and extract
meillo@30 880 the relevant message in the mbox file.
meillo@45 881 With the \s-1MH\s0 mailbox format, each message is a separate file.
meillo@30 882 Also, the problem of concurrent access to one mailbox is
meillo@30 883 reduced to the problem of concurrent access to one message.
meillo@45 884 The maildir format is generally similar to the \s-1MH\s0 format,
meillo@30 885 but modified towards guaranteed reliability.
meillo@30 886 This involves some complexity, unfortunately.
meillo@34 887 .PP
meillo@34 888 Working with \s-1MH\s0's toolchest on mailboxes is much like
meillo@34 889 working with Unix' toolchest on directory trees:
meillo@34 890 \f(CWscan\fP is like \f(CWls\fP,
meillo@34 891 \f(CWshow\fP is like \f(CWcat\fP,
meillo@34 892 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP,
meillo@34 893 \f(CWrefile\fP is like \f(CWmv\fP,
meillo@34 894 and \f(CWrmm\fP is like \f(CWrm\fP.
meillo@34 895 .PP
meillo@45 896 \s-1MH\s0 extends the context of processes in Unix by two more items,
meillo@45 897 for its tools:
meillo@34 898 .IP \(bu
meillo@34 899 The current mail folder, which is similar to the current working directory.
meillo@34 900 For mail folders, \f(CWfolder\fP provides the corresponding functionality
meillo@34 901 of \f(CWcd\fP and \f(CWpwd\fP for directories.
meillo@34 902 .IP \(bu
meillo@34 903 Sequences, which are named sets of messages in a mail folder.
meillo@34 904 The current message, relative to a mail folder, is a special sequence.
meillo@34 905 It enables commands like \f(CWnext\fP and \f(CWprev\fP.
meillo@34 906 .LP
meillo@45 907 In contrast to Unix' context, which is maintained by the kernel,
meillo@45 908 \s-1MH\s0's context must be maintained by the tools themselves.
meillo@45 909 Usually there is one context per user, which resides in his
meillo@45 910 \f(CWcontext\fP file in the \s-1MH\s0 directory,
meillo@45 911 but a user can have several contexts, too.
meillo@45 912 Public sequences are an exception, as they belong to a mail folder,
meillo@45 913 and reside in the \f(CW.mh_sequences\fP file there.
meillo@34 914 .[
meillo@44 915 man page mh-profile mh-sequence
meillo@34 916 .]
meillo@20 917
meillo@0 918 .NH 2
meillo@20 919 Discussion of the design
meillo@42 920 .XS
meillo@42 921 \*(SN Discussion of the design
meillo@42 922 .XE
meillo@0 923 .LP
meillo@45 924 This section discusses \s-1MH\s0 in regard to the tenets
meillo@45 925 of the Unix Philosophy that Gancarz identified.
meillo@20 926
meillo@20 927 .PP
meillo@33 928 .B "Small is beautiful
meillo@20 929 and
meillo@33 930 .B "do one thing well
meillo@20 931 are two design goals that are directly visible in \s-1MH\s0.
meillo@45 932 Gancarz actually presents \s-1MH\s0 in his book as example under the
meillo@45 933 headline ``Making \s-1UNIX\s0 Do One Thing Well'':
meillo@46 934 .[ [
meillo@44 935 gancarz
meillo@44 936 unix philosophy
meillo@46 937 .], page 125 ff.]
meillo@20 938 .QP
meillo@20 939 [\s-1MH\s0] consists of a series of programs which
meillo@20 940 when combined give the user an enormous ability
meillo@20 941 to manipulate electronic mail messages.
meillo@20 942 A complex application, it shows that not only is it
meillo@20 943 possible to build large applications from smaller
meillo@20 944 components, but also that such designs are actually preferable.
meillo@20 945 .LP
meillo@45 946 The various programs of \s-1MH\s0 were relatively easy to write,
meillo@45 947 because each of them is small, limited to one function,
meillo@23 948 and has clear boundaries.
meillo@20 949 For the same reasons, they are also good to maintain.
meillo@20 950 Further more, the system can easily get extended.
meillo@20 951 One only needs to put a new program into the toolchest.
meillo@23 952 This was done, for instance, when \s-1MIME\s0 support was added
meillo@20 953 (e.g. \f(CWmhbuild\fP).
meillo@20 954 Also, different programs can exist to do the basically same job
meillo@20 955 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP).
meillo@45 956 .PP
meillo@20 957 If someone needs a mail system with some additionally
meillo@45 958 functions that are not available anywhere yet, he best expands a
meillo@45 959 toolchest system like \s-1MH\s0.
meillo@45 960 There he can add new functionality by simply adding additional
meillo@45 961 programs to the toolchest.
meillo@45 962 There he does not risk to break existing functionality by doing so.
meillo@20 963
meillo@20 964 .PP
meillo@34 965 .B "Store data in flat text files
meillo@34 966 is followed by \s-1MH\s0.
meillo@34 967 This is not surprising, because email messages are already plain text.
meillo@34 968 \s-1MH\s0 stores the messages as it receives them,
meillo@45 969 thus any other tool that works on \s-1RFC\s0\|2822 mail messages can operate
meillo@34 970 on the messages in an \s-1MH\s0 mailbox.
meillo@45 971 All other files \s-1MH\s0 uses are plain text, too.
meillo@34 972 It is therefore possible and encouraged to use the text processing
meillo@34 973 tools of Unix' toolchest to extend \s-1MH\s0's toolchest.
meillo@20 974
meillo@20 975 .PP
meillo@33 976 .B "Avoid captive user interfaces" .
meillo@19 977 \s-1MH\s0 is perfectly suited for non-interactive use.
meillo@19 978 It offers all functions directly and without captive user interfaces.
meillo@30 979 If, nonetheless, users want a graphical user interface,
meillo@45 980 they can have it with \fIxmh\fP or \fIexmh\fP.
meillo@19 981 These are graphical frontends for the \s-1MH\s0 toolchest.
meillo@19 982 This means, all email-related work is still done by \s-1MH\s0 tools,
meillo@45 983 but the frontend calls the appropriate commands when the user
meillo@30 984 clicks on buttons.
meillo@45 985 .PP
meillo@20 986 Providing easy-to-use user interfaces in form of frontends is a good
meillo@19 987 approach, because it does not limit the power of the backend itself.
meillo@20 988 The frontend will anyway only be able to make a subset of the
meillo@23 989 backend's power and flexibility available to the user.
meillo@20 990 But if it is a separate program,
meillo@20 991 then the missing parts can still be accessed at the backend directly.
meillo@19 992 If it is integrated, then this will hardly be possible.
meillo@45 993 An additional advantage is the possibility to have different frontends
meillo@45 994 to the same backend.
meillo@19 995
meillo@19 996 .PP
meillo@33 997 .B "Choose portability over efficiency
meillo@20 998 and
meillo@33 999 .B "use shell scripts to increase leverage and portability" .
meillo@20 1000 These two tenets are indirectly, but nicely, demonstrated by
meillo@30 1001 Bolsky and Korn in their book about the Korn Shell.
meillo@20 1002 .[
meillo@44 1003 bolsky korn
meillo@44 1004 korn shell
meillo@20 1005 .]
meillo@45 1006 Chapter\|18 of the book shows a basic implementation
meillo@20 1007 of a subset of \s-1MH\s0 in ksh scripts.
meillo@45 1008 Of course, this is just a demonstration, but a brilliant one.
meillo@20 1009 It shows how quickly one can implement such a prototype with shell scripts,
meillo@20 1010 and how readable they are.
meillo@20 1011 The implementation in the scripting language may not be very fast,
meillo@20 1012 but it can be fast enough though, and this is all that matters.
meillo@20 1013 By having the code in an interpreted language, like the shell,
meillo@20 1014 portability becomes a minor issue, if we assume the interpreter
meillo@20 1015 to be widespread.
meillo@45 1016 .PP
meillo@20 1017 This demonstration also shows how easy it is to create single programs
meillo@20 1018 of a toolchest software.
meillo@45 1019 Eight tools (two of them have multiple names) and 16 functions
meillo@45 1020 with supporting code are presented to the reader.
meillo@45 1021 The tools comprise less than 40 lines of ksh each,
meillo@30 1022 in total about 200 lines.
meillo@45 1023 The functions comprise less than 80 lines of ksh each,
meillo@30 1024 in total about 450 lines.
meillo@20 1025 Such small software is easy to write, easy to understand,
meillo@20 1026 and thus easy to maintain.
meillo@23 1027 A toolchest improves the possibility to only write some parts
meillo@20 1028 and though create a working result.
meillo@45 1029 Expanding the toolchest, even without global changes,
meillo@45 1030 will likely be possible.
meillo@20 1031
meillo@20 1032 .PP
meillo@33 1033 .B "Use software leverage to your advantage
meillo@20 1034 and the lesser tenet
meillo@33 1035 .B "allow the user to tailor the environment
meillo@20 1036 are ideally followed in the design of \s-1MH\s0.
meillo@21 1037 Tailoring the environment is heavily encouraged by the ability to
meillo@30 1038 directly define default options to programs.
meillo@30 1039 It is even possible to define different default options
meillo@45 1040 depending on the name under which a program is called.
meillo@45 1041 Software leverage is heavily encouraged by the ease of
meillo@45 1042 creating shell scripts that run a specific command line,
meillo@30 1043 built of several \s-1MH\s0 programs.
meillo@21 1044 There is few software that so much wants users to tailor their
meillo@21 1045 environment and to leverage the use of the software, like \s-1MH\s0.
meillo@45 1046 .PP
meillo@21 1047 Just to make one example:
meillo@23 1048 One might prefer a different listing format for the \f(CWscan\fP
meillo@21 1049 program.
meillo@30 1050 It is possible to take one of the distributed format files
meillo@21 1051 or to write one yourself.
meillo@21 1052 To use the format as default for \f(CWscan\fP, a single line,
meillo@21 1053 reading
meillo@21 1054 .DS
meillo@21 1055 .CW
meillo@21 1056 scan: -form FORMATFILE
meillo@21 1057 .DE
meillo@21 1058 must be added to \f(CW.mh_profile\fP.
meillo@21 1059 If one wants this different format as an additional command,
meillo@23 1060 instead of changing the default, he needs to create a link to
meillo@23 1061 \f(CWscan\fP, for instance titled \f(CWscan2\fP.
meillo@21 1062 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP,
meillo@45 1063 as the option should only be in effect for a program that is called as
meillo@21 1064 \f(CWscan2\fP.
meillo@20 1065
meillo@20 1066 .PP
meillo@33 1067 .B "Make every program a filter
meillo@21 1068 is hard to find in \s-1MH\s0.
meillo@21 1069 The reason therefore is that most of \s-1MH\s0's tools provide
meillo@45 1070 basic file system operations for mailboxes.
meillo@45 1071 It is the same reason because of which \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP,
meillo@45 1072 and \f(CWrm\fP aren't filters neither.
meillo@23 1073 \s-1MH\s0 does not provide many filters itself, but it is a basis
meillo@23 1074 to write filters for.
meillo@45 1075 An example would be a mail text highlighter,
meillo@30 1076 that means a program that makes use of a color terminal to display
meillo@30 1077 header lines, quotations, and signatures in distinct colors.
meillo@45 1078 The author's version of such a program is an awk script with 25 lines.
meillo@21 1079
meillo@21 1080 .PP
meillo@33 1081 .B "Build a prototype as soon as possible
meillo@21 1082 was again well followed by \s-1MH\s0.
meillo@21 1083 This tenet, of course, focuses on early development, which is
meillo@21 1084 long time ago for \s-1MH\s0.
meillo@21 1085 But without following this guideline at the very beginning,
meillo@23 1086 Bruce Borden may have not convinced the management of \s-1RAND\s0
meillo@23 1087 to ever create \s-1MH\s0.
meillo@23 1088 In Bruce' own words:
meillo@46 1089 .[ [
meillo@44 1090 ware rand history
meillo@46 1091 .], page 132]
meillo@21 1092 .QP
meillo@45 1093 [...] but [Stockton Gaines and Norm Shapiro] were not able
meillo@23 1094 to convince anyone that such a system would be fast enough to be usable.
meillo@21 1095 I proposed a very short project to prove the basic concepts,
meillo@21 1096 and my management agreed.
meillo@21 1097 Looking back, I realize that I had been very lucky with my first design.
meillo@21 1098 Without nearly enough design work,
meillo@21 1099 I built a working environment and some header files
meillo@21 1100 with key structures and wrote the first few \s-1MH\s0 commands:
meillo@21 1101 inc, show/next/prev, and comp.
meillo@21 1102 [...]
meillo@21 1103 With these three, I was able to convince people that the structure was viable.
meillo@21 1104 This took about three weeks.
meillo@0 1105
meillo@0 1106 .NH 2
meillo@0 1107 Problems
meillo@42 1108 .XS
meillo@42 1109 \*(SN Problems
meillo@42 1110 .XE
meillo@0 1111 .LP
meillo@45 1112 \s-1MH\s0 is not without problems.
meillo@30 1113 There are two main problems: one is technical, the other is about human behavior.
meillo@22 1114 .PP
meillo@22 1115 \s-1MH\s0 is old and email today is very different to email in the time
meillo@22 1116 when \s-1MH\s0 was designed.
meillo@45 1117 \s-1MH\s0 adapted to the changes pretty well, but it is limited, though.
meillo@22 1118 \s-1MIME\s0 support and support for different character encodings
meillo@22 1119 is available, but only on a moderate level.
meillo@45 1120 This comes from limited development resources.
meillo@45 1121 More active developers could quickly change this.
meillo@45 1122 But \s-1MH\s0 is also limited by design, which is the larger problem.
meillo@22 1123 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extend.
meillo@22 1124 These design conflicts are not easily solvable.
meillo@22 1125 Possibly, they require a redesign.
meillo@45 1126 \s-1IMAP\s0 may be too different to the classic mail model,
meillo@45 1127 which \s-1MH\s0 covers, so that \s-1MH\s0 may never support it well.
meillo@22 1128 .PP
meillo@45 1129 The other kind of problem are human habits.
meillo@45 1130 In this world, where almost all \s-1MUA\s0s are monolithic,
meillo@22 1131 it is very difficult to convince people to use a toolbox style \s-1MUA\s0
meillo@22 1132 like \s-1MH\s0.
meillo@45 1133 The habits are so strong, that even people who understand the concept
meillo@30 1134 and advantages of \s-1MH\s0 do not like to switch,
meillo@30 1135 simply because \s-1MH\s0 is different.
meillo@30 1136 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel,
meillo@45 1137 are quite outdated and thus not very appealing, compared to the modern interfaces
meillo@45 1138 of many monolithic \s-1MUA\s0s.
meillo@20 1139
meillo@20 1140 .NH 2
meillo@20 1141 Summary \s-1MH\s0
meillo@42 1142 .XS
meillo@42 1143 \*(SN Summary \s-1MH\s0
meillo@42 1144 .XE
meillo@20 1145 .LP
meillo@45 1146 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design.
meillo@31 1147 It consists of a toolchest of small tools, each of them does one job well.
meillo@31 1148 The toolchest approach offers great flexibility to the user.
meillo@45 1149 It is possible to utilize the complete power of the Unix shell with \s-1MH\s0.
meillo@31 1150 This makes \s-1MH\s0 a very powerful mail system.
meillo@45 1151 Extending and customizing \s-1MH\s0 is easy and encouraged.
meillo@31 1152 .PP
meillo@31 1153 Apart from the user's perspective, \s-1MH\s0 is development-friendly.
meillo@31 1154 Its overall design follows clear rules.
meillo@31 1155 The single tools do only one job, thus they are easy to understand,
meillo@31 1156 easy to write, and good to maintain.
meillo@31 1157 They are all independent and do not interfere with the others.
meillo@31 1158 Automated testing of their function is a straight forward task.
meillo@31 1159 .PP
meillo@31 1160 It is sad, that \s-1MH\s0's differentness is its largest problem,
meillo@31 1161 as its differentness is also its largest advantage.
meillo@31 1162 Unfortunately, for most people their habits are stronger
meillo@31 1163 than the attraction of the clear design and the power, \s-1MH\s0 offers.
meillo@0 1164
meillo@8 1165
meillo@8 1166
meillo@0 1167 .NH 1
meillo@0 1168 Case study: uzbl
meillo@42 1169 .XS
meillo@42 1170 .sp .5v
meillo@42 1171 \*(SN Case study: uzbl
meillo@42 1172 .XE
meillo@32 1173 .LP
meillo@32 1174 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0,
meillo@45 1175 which is an old and established software.
meillo@45 1176 This chapter covers uzbl, a fresh new project.
meillo@45 1177 Uzbl is a web browser that adheres to the Unix Philosophy.
meillo@45 1178 Its name comes from the \fILolspeak\fP word for ``usable'';
meillo@45 1179 it is pronounced identical.
meillo@0 1180
meillo@0 1181 .NH 2
meillo@32 1182 Historical background
meillo@42 1183 .XS
meillo@42 1184 \*(SN Historical background
meillo@42 1185 .XE
meillo@0 1186 .LP
meillo@32 1187 Uzbl was started by Dieter Plaetinck in April 2009.
meillo@44 1188 The idea was born in a thread in the Arch Linux Forums.
meillo@32 1189 .[
meillo@44 1190 arch linux forums
meillo@44 1191 browser
meillo@32 1192 .]
meillo@32 1193 After some discussion about failures of well known web browsers,
meillo@32 1194 Plaetinck (alias Dieter@be) came up with a very sketchy proposal
meillo@32 1195 of how a better web browser could look like.
meillo@32 1196 To the question of another member, if Plaetinck would write that program,
meillo@32 1197 because it would sound fantastic, Plaetinck replied:
meillo@32 1198 ``Maybe, if I find the time ;-)''.
meillo@32 1199 .PP
meillo@32 1200 Fortunately, he found the time.
meillo@32 1201 One day later, the first prototype was out.
meillo@32 1202 One week later, uzbl had an own website.
meillo@32 1203 One month after the first code showed up,
meillo@32 1204 a mailing list was installed to coordinate and discuss further development.
meillo@45 1205 Then a wiki followed to store documentation and scripts that showed up on the
meillo@32 1206 mailing list and elsewhere.
meillo@32 1207 .PP
meillo@45 1208 In the, now, one year of uzbl's existence, it was heavily developed on various branches.
meillo@32 1209 Plaetinck's task became more and more to only merge the best code from the
meillo@32 1210 different branches into his main branch, and to apply patches.
meillo@32 1211 About once a month, Plaetinck released a new version.
meillo@32 1212 In September 2009, he presented several forks of uzbl.
meillo@38 1213 Uzbl, actually, opened the field for a whole family of web browsers with similar shape.
meillo@32 1214 .PP
meillo@32 1215 In July 2009, \fILinux Weekly News\fP published an interview with Plaetinck about uzbl.
meillo@32 1216 In September 2009, the uzbl web browser was on \fISlashdot\fP.
meillo@0 1217
meillo@0 1218 .NH 2
meillo@32 1219 Contrasts to other web browsers
meillo@42 1220 .XS
meillo@42 1221 \*(SN Contrasts to other web browsers
meillo@42 1222 .XE
meillo@0 1223 .LP
meillo@32 1224 Like most \s-1MUA\s0s are monolithic, but \s-1MH\s0 is a toolchest,
meillo@32 1225 most web browsers are monolithic, but uzbl is a frontend to a toolchest.
meillo@32 1226 .PP
meillo@32 1227 Today, uzbl is divided into uzbl-core and uzbl-browser.
meillo@32 1228 Uzbl-core is, how its name already indicates, the core of uzbl.
meillo@32 1229 It handles commands and events to interface other programs,
meillo@45 1230 and also displays webpages by using \fIwebkit\fP as render engine.
meillo@32 1231 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar,
meillo@32 1232 an event manager, yanking, pasting, page searching, zooming, and more stuff,
meillo@32 1233 to form a ``complete'' web browser.
meillo@32 1234 In the following text, the term ``uzbl'' usually stands for uzbl-browser,
meillo@32 1235 so uzbl-core is included.
meillo@32 1236 .PP
meillo@32 1237 Unlike most other web browsers, uzbl is mainly the mediator between the
meillo@45 1238 various tools that cover single jobs.
meillo@35 1239 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket,
meillo@35 1240 and on stdin, and it writes events to a Unix socket and to stdout.
meillo@35 1241 Loading a webpage in a running uzbl instance requires only:
meillo@32 1242 .DS
meillo@32 1243 .CW
meillo@32 1244 echo 'uri http://example.org' >/path/to/uzbl-fifo
meillo@32 1245 .DE
meillo@45 1246 The graphical rendering of the webpage is done by webkit,
meillo@45 1247 a web content engine.
meillo@45 1248 Uzbl-core is built around libwebkit.
meillo@32 1249 .PP
meillo@45 1250 Downloads, browsing history, bookmarks, and the like are not provided
meillo@45 1251 by the core itself, like they are in other web browsers.
meillo@35 1252 Uzbl-browser also only provides, so called, handler scripts that wrap
meillo@35 1253 external applications which provide the actual functionality.
meillo@32 1254 For instance, \fIwget\fP is used to download files and uzbl-browser
meillo@32 1255 includes a script that calls wget with appropriate options in
meillo@32 1256 a prepared environment.
meillo@32 1257 .PP
meillo@32 1258 Modern web browsers are proud to have addons, plugins, and modules, instead.
meillo@32 1259 This is their effort to achieve similar goals.
meillo@35 1260 But instead of using existing, external programs, modern web browsers
meillo@45 1261 include these functions.
meillo@0 1262
meillo@0 1263 .NH 2
meillo@32 1264 Discussion of the design
meillo@42 1265 .XS
meillo@42 1266 \*(SN Discussion of the design
meillo@42 1267 .XE
meillo@0 1268 .LP
meillo@32 1269 This section discusses uzbl in regard of the Unix Philosophy,
meillo@32 1270 as identified by Gancarz.
meillo@32 1271
meillo@32 1272 .PP
meillo@35 1273 .B "Make each program do one thing well" .
meillo@35 1274 Uzbl tries to be a web browser and nothing else.
meillo@36 1275 The common definition of a web browser is, of course, highly influenced by
meillo@36 1276 existing implementations of web browsers, although they are degenerated.
meillo@35 1277 Web browsers should be programs to browse the web, and nothing more.
meillo@45 1278 This is the one thing they should do.
meillo@36 1279 .PP
meillo@45 1280 Web browsers should not, for instance, manage downloads.
meillo@35 1281 This is the job download managers exist for.
meillo@35 1282 Download managers do primary care about being good in downloading files.
meillo@35 1283 Modern web browsers provide download management only as a secondary feature.
meillo@45 1284 How could they do this job better, than programs that exist only for
meillo@35 1285 this very job?
meillo@35 1286 And how could anyone want less than the best download manager available?
meillo@32 1287 .PP
meillo@35 1288 A web browser's job is to let the user browse the web.
meillo@35 1289 This means, navigating through websites by following links.
meillo@36 1290 Rendering the \s-1HTML\s0 sources is a different job, too.
meillo@36 1291 It is covered by the webkit render engine, in uzbl's case.
meillo@35 1292 Audio and video content and files like PostScript, \s-1PDF\s0, and the like,
meillo@36 1293 are also not the job of a web browser.
meillo@36 1294 They should be handled by external applications \(en
meillo@36 1295 ones which's job is to handle such data.
meillo@35 1296 Uzbl strives to do it this way.
meillo@36 1297 .PP
meillo@36 1298 Remember Doug McIlroy:
meillo@35 1299 .I
meillo@35 1300 ``Write programs that do one thing and do it well.
meillo@35 1301 Write programs to work together.''
meillo@35 1302 .R
meillo@35 1303 .PP
meillo@35 1304 The lesser tenet
meillo@35 1305 .B "allow the user to tailor the environment
meillo@35 1306 matches good here.
meillo@35 1307 There was the question, how anyone could want anything less than the
meillo@35 1308 best program for the job.
meillo@45 1309 But as personal preferences matter, it is probably more important to ask:
meillo@35 1310 How could anyone want something else than his preferred program for the job?
meillo@36 1311 .PP
meillo@45 1312 Usually users want one program for a specific job.
meillo@35 1313 Hence, whenever the task is, for instance, downloading,
meillo@45 1314 the same download manager should be used.
meillo@35 1315 More advanced users might want to have this download manager in this
meillo@35 1316 situation and that one in that situation.
meillo@35 1317 They should be able to configure it this way.
meillo@35 1318 With uzbl, one can use any download manager the user wants.
meillo@36 1319 To switch to a different one, only one line in a small handler script
meillo@35 1320 needs to be changed.
meillo@45 1321 Alternatively it would be possible to query the program to use by
meillo@45 1322 reading a global file or an environment variable, in the handler script.
meillo@36 1323 .PP
meillo@45 1324 Uzbl does neither have its own download manager nor depends on a
meillo@45 1325 specific one, hence uzbl's browsing abilities will not be lowered by having
meillo@35 1326 a bad download manager.
meillo@45 1327 Uzbl's download capabilities will be just as good as the ones of the best
meillo@36 1328 download manager available on the system.
meillo@38 1329 Of course, this applies to all of the other supplementary tools, too.
meillo@32 1330
meillo@32 1331 .PP
meillo@36 1332 .B "Use software leverage to your advantage" .
meillo@36 1333 Uzbl is designed to be extended by external tools.
meillo@36 1334 These external tools are usually wrapped by small handler shell scripts.
meillo@36 1335 Shell scripts are the glue in this approach.
meillo@36 1336 They make the various parts fit together.
meillo@36 1337 .PP
meillo@45 1338 The history mechanism of uzbl shall be presented as an example.
meillo@36 1339 Uzbl is configured to spawn a script to append an entry to the history
meillo@36 1340 whenever the event of a fully loaded page occurs.
meillo@45 1341 The script to append the entry to the history is not much more than:
meillo@36 1342 .DS
meillo@36 1343 .CW
meillo@36 1344 #!/bin/sh
meillo@36 1345 file=/path/to/uzbl-history
meillo@36 1346 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file
meillo@36 1347 .DE
meillo@36 1348 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title.
meillo@45 1349 .PP
meillo@45 1350 For loading an entry, a key is bound to spawn a load-from-history script.
meillo@36 1351 The script reverses the history to have newer entries first,
meillo@45 1352 then displays \fIdmenu\fP to let the user select an item,
meillo@36 1353 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe.
meillo@45 1354 With error checking and corner case handling removed,
meillo@45 1355 the script looks like this:
meillo@36 1356 .DS
meillo@36 1357 .CW
meillo@36 1358 #!/bin/sh
meillo@36 1359 file=/path/to/uzbl-history
meillo@36 1360 goto=`tac $file | dmenu | cut -d' ' -f 3`
meillo@36 1361 echo "uri $goto" > $4
meillo@36 1362 .DE
meillo@36 1363 \f(CW$4\fP expands to the path of the command input pipe of the current
meillo@36 1364 uzbl instance.
meillo@32 1365
meillo@32 1366 .PP
meillo@33 1367 .B "Avoid captive user interfaces" .
meillo@36 1368 One could say, that uzbl, to a large extend, actually \fIis\fP
meillo@36 1369 a captive user interface.
meillo@37 1370 But the difference to most other web browsers is, that uzbl is only
meillo@45 1371 the captive user interface frontend (and the core of the backend).
meillo@38 1372 Many parts of the backend are independent of uzbl.
meillo@45 1373 Some are distributed with uzbl, for some external programs,
meillo@45 1374 handler scripts are distributed,
meillo@45 1375 but arbitrary additional functionality can be added if desired.
meillo@37 1376 .PP
meillo@37 1377 The frontend is captive \(en that is true.
meillo@37 1378 This is okay for the task of browsing the web, as this task is only relevant
meillo@37 1379 for humans.
meillo@37 1380 Automated programs would \fIcrawl\fP the web.
meillo@37 1381 That means, they read the source directly.
meillo@37 1382 The source includes all the semantics.
meillo@37 1383 The graphical representation is just for humans to transfer the semantics
meillo@37 1384 more intuitively.
meillo@32 1385
meillo@32 1386 .PP
meillo@33 1387 .B "Make every program a filter" .
meillo@37 1388 Graphical web browsers are almost dead ends in the chain of information flow.
meillo@37 1389 Thus it is difficult to see what graphical web browsers should filter.
meillo@45 1390 Graphical web browsers exist almost only to be interactively used by humans.
meillo@37 1391 The only case when one might want to automate the rendering function is
meillo@37 1392 to generate images of rendered webpages.
meillo@37 1393
meillo@37 1394 .PP
meillo@37 1395 .B "Small is beautiful"
meillo@45 1396 is not easy to apply to a web browser, because modern web technology
meillo@45 1397 is very complex, hence the rendering task is very complex.
meillo@45 1398 Modern web browsers have to consist of many thousand lines of code,
meillo@37 1399 unfortunately.
meillo@37 1400 Using the toolchest approach and wrappers can split the browser into
meillo@37 1401 several small parts, tough.
meillo@37 1402 .PP
meillo@45 1403 As of March 2010, uzbl-core consists of about 3\,500 lines of C code.
meillo@37 1404 The distribution includes another 3\,500 lines of Shell and Python code,
meillo@37 1405 which are the handler scripts and plugins like a modal interface.
meillo@38 1406 Further more, uzbl uses functionality of external tools like
meillo@38 1407 \fIwget\fP and \fInetcat\fP.
meillo@37 1408 Up to this point, uzbl looks pretty neat and small.
meillo@38 1409 The ugly part of uzbl is the web content renderer, webkit.
meillo@37 1410 Webkit consists of roughly 400\,000 (!) lines of code.
meillo@38 1411 Unfortunately, small web render engines are not possible anymore
meillo@38 1412 because of the modern web.
meillo@35 1413
meillo@35 1414 .PP
meillo@35 1415 .B "Build a prototype as soon as possible" .
meillo@35 1416 Plaetinck made his code public, right from the beginning.
meillo@38 1417 Discussion and development was, and still is, open to everyone interested.
meillo@38 1418 Development versions of uzbl can be obtained very simply from the code
meillo@38 1419 repository.
meillo@38 1420 Within the first year of uzbl's existence, a new version was released
meillo@35 1421 more often than once a month.
meillo@38 1422 Different forks and branches arose.
meillo@45 1423 They introduced new features, which were tested for suitability
meillo@45 1424 for the main branch.
meillo@35 1425 The experiences of using prototypes influenced further development.
meillo@35 1426 Actually, all development was community driven.
meillo@38 1427 Plaetinck says, three months after uzbl's birth:
meillo@35 1428 ``Right now I hardly code anything myself for Uzbl.
meillo@35 1429 I just merge in other people's code, ponder a lot, and lead the discussions.''
meillo@35 1430 .[
meillo@44 1431 lwn
meillo@44 1432 uzbl
meillo@35 1433 .]
meillo@32 1434
meillo@0 1435
meillo@0 1436 .NH 2
meillo@0 1437 Problems
meillo@42 1438 .XS
meillo@42 1439 \*(SN Problems
meillo@42 1440 .XE
meillo@0 1441 .LP
meillo@38 1442 Similar to \s-1MH\s0, uzbl, too suffers from being different.
meillo@38 1443 It is sad, but people use what they know.
meillo@38 1444 Fortunately, uzbl's user interface can look and feel very much the
meillo@38 1445 same as the one of the well known web browsers,
meillo@38 1446 hiding the internal differences.
meillo@38 1447 But uzbl has to provide this similar look and feel to be accepted
meillo@38 1448 as a ``normal'' browser by ``normal'' users.
meillo@37 1449 .PP
meillo@45 1450 Though, the more important problem is the modern web.
meillo@38 1451 The modern web is simply broken.
meillo@38 1452 It has state in a state-less protocol,
meillo@38 1453 it misuses technologies,
meillo@38 1454 and it is helplessly overloaded.
meillo@38 1455 The result are web content render engines that must consist
meillo@38 1456 of hundreds of thousands lines of code.
meillo@38 1457 They also must combine and integrate many different technologies,
meillo@45 1458 only to make our modern web accessible.
meillo@38 1459 Website to image converter are hardly possible to run without
meillo@38 1460 human interaction because of state in sessions, impossible
meillo@38 1461 deep-linking, and unautomatable technologies.
meillo@37 1462 .PP
meillo@38 1463 The web was misused to provide all kinds of imaginable wishes.
meillo@38 1464 Now web browsers, and eventually the users, suffer from it.
meillo@37 1465
meillo@8 1466
meillo@32 1467 .NH 2
meillo@32 1468 Summary uzbl
meillo@42 1469 .XS
meillo@42 1470 \*(SN Summary uzbl
meillo@42 1471 .XE
meillo@32 1472 .LP
meillo@38 1473 ``Uzbl is a browser that adheres to the Unix Philosophy'',
meillo@38 1474 that is how uzbl is seen by its authors.
meillo@38 1475 Indeed, uzbl follows the Unix Philosophy in many ways.
meillo@38 1476 It consists of independent parts that work together,
meillo@45 1477 while its core is mainly a mediator which glues the parts together.
meillo@38 1478 .PP
meillo@38 1479 Software leverage can excellently be seen in uzbl.
meillo@45 1480 External tools are used, independent tasks are separated
meillo@45 1481 in independent parts and glued together with small handler scripts.
meillo@38 1482 .PP
meillo@38 1483 As uzbl, more or less, consists of a set of tools and a bit
meillo@38 1484 of glue, anyone can put the parts together and expand it
meillo@38 1485 in any desired way.
meillo@38 1486 Uzbl is very flexible and customizable.
meillo@38 1487 These properties make it valuable for advanced users,
meillo@38 1488 but may keep novice users from using it.
meillo@38 1489 .PP
meillo@45 1490 But uzbl's main problem is the modern web, that makes it hard
meillo@38 1491 to design a sane web browser.
meillo@38 1492 Despite this bad situation, uzbl does a fairly good job.
meillo@32 1493
meillo@8 1494
meillo@0 1495 .NH 1
meillo@0 1496 Final thoughts
meillo@42 1497 .XS
meillo@42 1498 .sp .5v
meillo@42 1499 \*(SN Final thoughts
meillo@42 1500 .XE
meillo@0 1501
meillo@0 1502 .NH 2
meillo@0 1503 Quick summary
meillo@42 1504 .XS
meillo@42 1505 \*(SN Quick summary
meillo@42 1506 .XE
meillo@0 1507 .LP
meillo@0 1508 good design
meillo@0 1509 .LP
meillo@0 1510 unix phil
meillo@0 1511 .LP
meillo@0 1512 case studies
meillo@0 1513
meillo@0 1514 .NH 2
meillo@0 1515 Why people should choose
meillo@42 1516 .XS
meillo@42 1517 \*(SN Why people should choose
meillo@42 1518 .XE
meillo@0 1519 .LP
meillo@0 1520 Make the right choice!
meillo@0 1521
meillo@42 1522 .nr PI .3i
meillo@0 1523 .rm ]<
meillo@0 1524 .de ]<
meillo@0 1525 .LP
meillo@0 1526 .de FP
meillo@0 1527 .IP \\\\$1.
meillo@0 1528 \\..
meillo@0 1529 .rm FS FE
meillo@0 1530 ..
meillo@42 1531 .ds CH "
meillo@42 1532 .bp
meillo@42 1533 .rs
meillo@42 1534 .sp .3i
meillo@42 1535 .TL
meillo@0 1536 References
meillo@42 1537 .LP
meillo@42 1538 .XS
meillo@42 1539 .sp .5v
meillo@42 1540 References
meillo@42 1541 .XE
meillo@42 1542 .sp 2v
meillo@42 1543 .nr PS -1
meillo@42 1544 .nr VS -1
meillo@0 1545 .[
meillo@0 1546 $LIST$
meillo@0 1547 .]
meillo@42 1548 .\".wh -1p
meillo@42 1549 .bp
meillo@42 1550 .PX