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author meillo@marmaro.de
date Thu, 15 Apr 2010 23:03:39 +0200
parents 0a435d76b868
children 840cbc667009
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meillo@49 1 .so style
meillo@42 2
meillo@0 3 .TL
meillo@42 4 .ps +4
meillo@6 5 Why the Unix Philosophy still matters
meillo@0 6 .AU
meillo@0 7 markus schnalke <meillo@marmaro.de>
meillo@0 8 .AB
meillo@1 9 .ti \n(.iu
meillo@39 10 This paper explains the importance of the Unix Philosophy for software design.
meillo@0 11 Today, few software designers are aware of these concepts,
meillo@39 12 and thus a lot of modern software is more limited than necessary
meillo@39 13 and makes less use of software leverage than possible.
meillo@38 14 Knowing and following the guidelines of the Unix Philosophy makes software more valuable.
meillo@0 15 .AE
meillo@0 16
meillo@2 17 .FS
meillo@2 18 .ps -1
meillo@39 19 This paper was prepared for the ``Software Analysis'' seminar at University Ulm.
meillo@47 20 Mentor was professor Franz Schweiggert.
meillo@55 21 Handed in on 2010-04-16.
meillo@39 22 You may retrieve this document from
meillo@39 23 .CW \s-1http://marmaro.de/docs \ .
meillo@2 24 .FE
meillo@2 25
meillo@48 26 .H 1 Introduction
meillo@0 27 .LP
meillo@40 28 The Unix Philosophy is the essence of how the Unix operating system,
meillo@40 29 especially its toolchest, was designed.
meillo@40 30 It is no limited set of fixed rules,
meillo@40 31 but a loose set of guidelines which tell how to write software that
meillo@40 32 suites well into Unix.
meillo@40 33 Actually, the Unix Philosophy describes what is common to typical Unix software.
meillo@40 34 The Wikipedia has an accurate definition:
meillo@40 35 .[
meillo@44 36 wikipedia
meillo@44 37 unix philosophy
meillo@40 38 .]
meillo@40 39 .QP
meillo@40 40 The \fIUnix philosophy\fP is a set of cultural norms and philosophical
meillo@40 41 approaches to developing software based on the experience of leading
meillo@40 42 developers of the Unix operating system.
meillo@1 43 .PP
meillo@40 44 As there is no single definition of the Unix Philosophy,
meillo@40 45 several people have stated their view on what it comprises.
meillo@1 46 Best known are:
meillo@1 47 .IP \(bu
meillo@1 48 Doug McIlroy's summary: ``Write programs that do one thing and do it well.''
meillo@1 49 .[
meillo@44 50 mahoney
meillo@44 51 oral history
meillo@1 52 .]
meillo@1 53 .IP \(bu
meillo@1 54 Mike Gancarz' book ``The UNIX Philosophy''.
meillo@1 55 .[
meillo@44 56 gancarz
meillo@44 57 unix philosophy
meillo@1 58 .]
meillo@1 59 .IP \(bu
meillo@1 60 Eric S. Raymond's book ``The Art of UNIX Programming''.
meillo@1 61 .[
meillo@44 62 raymond
meillo@44 63 art of unix programming
meillo@1 64 .]
meillo@0 65 .LP
meillo@1 66 These different views on the Unix Philosophy have much in common.
meillo@40 67 Especially, the main concepts are similar in all of them.
meillo@40 68 McIlroy's definition can surely be called the core of the Unix Philosophy,
meillo@40 69 but the fundamental idea behind it all, is ``small is beautiful''.
meillo@40 70
meillo@40 71 .PP
meillo@45 72 The Unix Philosophy explains how to design good software for Unix.
meillo@45 73 Many concepts described here, base on facilities of Unix.
meillo@40 74 Other operating systems may not offer such facilities,
meillo@41 75 hence it may not be possible to design software in the way of the
meillo@41 76 Unix Philosophy for them.
meillo@40 77 .PP
meillo@41 78 The Unix Philosophy has an idea of how the process of software development
meillo@41 79 should look like, but large parts of the philosophy are quite independent
meillo@45 80 from a concrete development process.
meillo@41 81 However, one will soon recognize that some development processes work well
meillo@41 82 with the ideas of the Unix Philosophy and support them, while others are
meillo@41 83 at cross-purposes.
meillo@45 84 Kent Beck's books about Extreme Programming are valuable supplemental
meillo@45 85 resources on this topic.
meillo@1 86 .PP
meillo@41 87 The question of how to actually write code and how the code should looks
meillo@45 88 like in detail, are out of focus here.
meillo@41 89 ``The Practice of Programming'' by Kernighan and Pike,
meillo@41 90 .[
meillo@44 91 kernighan pike
meillo@44 92 practice of programming
meillo@41 93 .]
meillo@41 94 is a good book that covers this topic.
meillo@41 95 Its point of view matches to the one of this paper.
meillo@0 96
meillo@48 97 .H 1 "Importance of software design in general
meillo@0 98 .LP
meillo@40 99 Software design is the planning of how the internal structure
meillo@54 100 and external interfaces of software should look like.
meillo@39 101 It has nothing to do with visual appearance.
meillo@39 102 If we take a program as a car, then its color is of no matter.
meillo@39 103 Its design would be the car's size, its shape, the locations of doors,
meillo@45 104 the passenger/space ratio, the available controls and instruments,
meillo@45 105 and so forth.
meillo@39 106 .PP
meillo@39 107 Why should software get designed at all?
meillo@6 108 It is general knowledge, that even a bad plan is better than no plan.
meillo@39 109 Not designing software means programming without plan.
meillo@39 110 This will pretty sure lead to horrible results.
meillo@45 111 Software that is horrible to use and horrible to maintain.
meillo@39 112 These two aspects are the visible ones.
meillo@45 113 Often invisible though, are the wasted possible gains.
meillo@39 114 Good software design can make these gains available.
meillo@2 115 .PP
meillo@54 116 Software design deals with quality properties.
meillo@39 117 Good design leads to good quality, and quality is important.
meillo@39 118 Any car may be able to drive from A to B,
meillo@39 119 but it depends on the car's properties whether it is a good choice
meillo@39 120 for passenger transport or not.
meillo@39 121 It depends on its properties if it is a good choice
meillo@39 122 for a rough mountain area.
meillo@39 123 And it depends on its properties if the ride will be fun.
meillo@39 124
meillo@2 125 .PP
meillo@54 126 Requirements for software are twofold:
meillo@39 127 functional and non-functional.
meillo@39 128 .IP \(bu
meillo@39 129 Functional requirements define directly the software's functions.
meillo@39 130 They are the reason why software gets written.
meillo@39 131 Someone has a problem and needs a tool to solve it.
meillo@39 132 Being able to solve the problem is the main functional goal.
meillo@39 133 It is the driving force behind all programming effort.
meillo@39 134 Functional requirements are easier to define and to verify.
meillo@39 135 .IP \(bu
meillo@45 136 Non-functional requirements are called \fIquality\fP requirements, too.
meillo@54 137 The quality of software are the properties that are not directly related to
meillo@39 138 the software's basic functions.
meillo@45 139 Tools of bad quality often do solve the problems they were written for,
meillo@39 140 but introduce problems and difficulties for usage and development, later on.
meillo@39 141 Quality aspects are often overlooked at first sight,
meillo@45 142 and are often difficult to define clearly and to verify.
meillo@2 143 .PP
meillo@54 144 Quality is hardly interesting when software gets built initially,
meillo@54 145 but it has a high impact on usability and maintenance, later.
meillo@54 146 A short-sighted might see in developing software, mainly building something up.
meillo@54 147 But experience shows, that building software the first time is
meillo@39 148 only a small amount of the overall work.
meillo@45 149 Bug fixing, extending, rebuilding of parts \(en maintenance work \(en
meillo@54 150 does soon take over the major part of the time spent on a software project.
meillo@45 151 And of course, the time spent actually using the software.
meillo@6 152 These processes are highly influenced by the software's quality.
meillo@39 153 Thus, quality must not be neglected.
meillo@45 154 However, the problem with quality is that you hardly ``stumble over''
meillo@39 155 bad quality during the first build,
meillo@45 156 although this is the time when you should care about good quality most.
meillo@6 157 .PP
meillo@54 158 Software design has little to do with the basic function of software \(en
meillo@39 159 this requirement will get satisfied anyway.
meillo@54 160 Software design is more about quality aspects of software.
meillo@39 161 Good design leads to good quality, bad design to bad quality.
meillo@54 162 The primary functions of software will be affected modestly by bad quality,
meillo@39 163 but good quality can provide a lot of additional gain,
meillo@6 164 even at places where one never expected it.
meillo@6 165 .PP
meillo@45 166 The ISO/IEC\|9126-1 standard, part\|1,
meillo@6 167 .[
meillo@44 168 iso product quality
meillo@6 169 .]
meillo@6 170 defines the quality model as consisting out of:
meillo@6 171 .IP \(bu
meillo@6 172 .I Functionality
meillo@6 173 (suitability, accuracy, inter\%operability, security)
meillo@6 174 .IP \(bu
meillo@6 175 .I Reliability
meillo@6 176 (maturity, fault tolerance, recoverability)
meillo@6 177 .IP \(bu
meillo@6 178 .I Usability
meillo@6 179 (understandability, learnability, operability, attractiveness)
meillo@6 180 .IP \(bu
meillo@6 181 .I Efficiency
meillo@9 182 (time behavior, resource utilization)
meillo@6 183 .IP \(bu
meillo@6 184 .I Maintainability
meillo@23 185 (analyzability, changeability, stability, testability)
meillo@6 186 .IP \(bu
meillo@6 187 .I Portability
meillo@6 188 (adaptability, installability, co-existence, replaceability)
meillo@6 189 .LP
meillo@54 190 Good design can improve these properties of software,
meillo@45 191 bad designed software likely suffers in these points.
meillo@7 192 .PP
meillo@7 193 One further goal of software design is consistency.
meillo@7 194 Consistency eases understanding, working on, and using things.
meillo@39 195 Consistent internal structure and consistent interfaces to the outside
meillo@39 196 can be provided by good design.
meillo@7 197 .PP
meillo@39 198 Software should be well designed because good design avoids many
meillo@54 199 problems during a software project's lifetime.
meillo@39 200 And software should be well designed because good design can offer
meillo@39 201 much additional gain.
meillo@39 202 Indeed, much effort should be spent into good design to make software more valuable.
meillo@39 203 The Unix Philosophy shows a way of how to design software well.
meillo@7 204 It offers guidelines to achieve good quality and high gain for the effort spent.
meillo@0 205
meillo@0 206
meillo@48 207 .H 1 "The Unix Philosophy
meillo@4 208 .LP
meillo@4 209 The origins of the Unix Philosophy were already introduced.
meillo@8 210 This chapter explains the philosophy, oriented on Gancarz,
meillo@55 211 .[
meillo@55 212 gancarz
meillo@55 213 unix philosophy
meillo@55 214 .]
meillo@8 215 and shows concrete examples of its application.
meillo@5 216
meillo@48 217 .H 2 Pipes
meillo@4 218 .LP
meillo@4 219 Following are some examples to demonstrate how applied Unix Philosophy feels like.
meillo@4 220 Knowledge of using the Unix shell is assumed.
meillo@4 221 .PP
meillo@4 222 Counting the number of files in the current directory:
meillo@41 223 .DS
meillo@4 224 ls | wc -l
meillo@4 225 .DE
meillo@4 226 The
meillo@4 227 .CW ls
meillo@4 228 command lists all files in the current directory, one per line,
meillo@4 229 and
meillo@4 230 .CW "wc -l
meillo@8 231 counts the number of lines.
meillo@4 232 .PP
meillo@8 233 Counting the number of files that do not contain ``foo'' in their name:
meillo@41 234 .DS
meillo@4 235 ls | grep -v foo | wc -l
meillo@4 236 .DE
meillo@4 237 Here, the list of files is filtered by
meillo@4 238 .CW grep
meillo@45 239 to remove all lines that contain ``foo''.
meillo@45 240 The rest equals the previous example.
meillo@4 241 .PP
meillo@4 242 Finding the five largest entries in the current directory.
meillo@41 243 .DS
meillo@4 244 du -s * | sort -nr | sed 5q
meillo@4 245 .DE
meillo@4 246 .CW "du -s *
meillo@45 247 returns the recursively summed sizes of all files in the current directory
meillo@8 248 \(en no matter if they are regular files or directories.
meillo@4 249 .CW "sort -nr
meillo@45 250 sorts the list numerically in reverse order (descending).
meillo@4 251 Finally,
meillo@4 252 .CW "sed 5q
meillo@4 253 quits after it has printed the fifth line.
meillo@4 254 .PP
meillo@4 255 The presented command lines are examples of what Unix people would use
meillo@4 256 to get the desired output.
meillo@4 257 There are also other ways to get the same output.
meillo@4 258 It's a user's decision which way to go.
meillo@14 259 .PP
meillo@8 260 The examples show that many tasks on a Unix system
meillo@4 261 are accomplished by combining several small programs.
meillo@4 262 The connection between the single programs is denoted by the pipe operator `|'.
meillo@4 263 .PP
meillo@4 264 Pipes, and their extensive and easy use, are one of the great
meillo@4 265 achievements of the Unix system.
meillo@4 266 Pipes between programs have been possible in earlier operating systems,
meillo@4 267 but it has never been a so central part of the concept.
meillo@45 268 When, in the early seventies, Doug McIlroy introduced pipes into the
meillo@4 269 Unix system,
meillo@4 270 ``it was this concept and notation for linking several programs together
meillo@4 271 that transformed Unix from a basic file-sharing system to an entirely new way of computing.''
meillo@4 272 .[
meillo@44 273 aughenbaugh
meillo@44 274 unix oral history
meillo@45 275 .]
meillo@4 276 .PP
meillo@4 277 Being able to specify pipelines in an easy way is,
meillo@4 278 however, not enough by itself.
meillo@5 279 It is only one half.
meillo@4 280 The other is the design of the programs that are used in the pipeline.
meillo@45 281 They need interfaces that allow them to be used in such a way.
meillo@5 282
meillo@48 283 .H 2 "Interface design
meillo@5 284 .LP
meillo@11 285 Unix is, first of all, simple \(en Everything is a file.
meillo@5 286 Files are sequences of bytes, without any special structure.
meillo@45 287 Programs should be filters, which read a stream of bytes from standard input (stdin)
meillo@45 288 and write a stream of bytes to standard output (stdout).
meillo@8 289 If the files \fIare\fP sequences of bytes,
meillo@8 290 and the programs \fIare\fP filters on byte streams,
meillo@45 291 then there is exactly one data interface.
meillo@45 292 Hence it is possible to combine programs in any desired way.
meillo@5 293 .PP
meillo@45 294 Even a handful of small programs yields a large set of combinations,
meillo@5 295 and thus a large set of different functions.
meillo@5 296 This is leverage!
meillo@5 297 If the programs are orthogonal to each other \(en the best case \(en
meillo@5 298 then the set of different functions is greatest.
meillo@5 299 .PP
meillo@45 300 Programs can also have a separate control interface,
meillo@11 301 besides their data interface.
meillo@11 302 The control interface is often called ``user interface'',
meillo@11 303 because it is usually designed to be used by humans.
meillo@11 304 The Unix Philosophy discourages to assume the user to be human.
meillo@11 305 Interactive use of software is slow use of software,
meillo@11 306 because the program waits for user input most of the time.
meillo@45 307 Interactive software requires the user to be in front of the computer.
meillo@11 308 Interactive software occupy the user's attention while they are running.
meillo@11 309 .PP
meillo@45 310 Now to come back to the idea of combining several small programs,
meillo@11 311 to have a more specific function.
meillo@11 312 If these single tools would all be interactive,
meillo@11 313 how would the user control them?
meillo@45 314 It is not only a problem to control several programs at once,
meillo@45 315 if they run at the same time,
meillo@11 316 it also very inefficient to have to control each of the single programs
meillo@45 317 that are intended to act as one large program.
meillo@11 318 Hence, the Unix Philosophy discourages programs to demand interactive use.
meillo@11 319 The behavior of programs should be defined at invocation.
meillo@45 320 This is done by specifying arguments to the program call
meillo@45 321 (command line switches).
meillo@11 322 Gancarz discusses this topic as ``avoid captive user interfaces''.
meillo@46 323 .[ [
meillo@44 324 gancarz unix philosophy
meillo@46 325 .], page 88 ff.]
meillo@11 326 .PP
meillo@11 327 Non-interactive use is, during development, also an advantage for testing.
meillo@11 328 Testing of interactive programs is much more complicated,
meillo@11 329 than testing of non-interactive programs.
meillo@5 330
meillo@48 331 .H 2 "The toolchest approach
meillo@5 332 .LP
meillo@5 333 A toolchest is a set of tools.
meillo@5 334 Instead of having one big tool for all tasks, one has many small tools,
meillo@5 335 each for one task.
meillo@5 336 Difficult tasks are solved by combining several of the small, simple tools.
meillo@5 337 .PP
meillo@11 338 The Unix toolchest \fIis\fP a set of small, (mostly) non-interactive programs
meillo@11 339 that are filters on byte streams.
meillo@54 340 They are, to a large extent, unrelated in their function.
meillo@11 341 Hence, the Unix toolchest provides a large set of functions
meillo@11 342 that can be accessed by combining the programs in the desired way.
meillo@11 343 .PP
meillo@11 344 There are also advantages for developing small toolchest programs.
meillo@5 345 It is easier and less error-prone to write small programs.
meillo@5 346 It is also easier and less error-prone to write a large set of small programs,
meillo@5 347 than to write one large program with all the functionality included.
meillo@5 348 If the small programs are combinable, then they offer even a larger set
meillo@5 349 of functions than the single large program.
meillo@45 350 Hence, one gets two advantages out of writing small, combinable programs:
meillo@45 351 They are easier to write and they offer a greater set of functions through
meillo@45 352 combination.
meillo@5 353 .PP
meillo@45 354 But there are also two main drawbacks of the toolchest approach.
meillo@45 355 First, one simple, standardized interface has to be sufficient.
meillo@5 356 If one feels the need for more ``logic'' than a stream of bytes,
meillo@8 357 then a different approach might be of need.
meillo@13 358 But it is also possible, that he just can not imagine a design where
meillo@8 359 a stream of bytes is sufficient.
meillo@8 360 By becoming more familiar with the ``Unix style of thinking'',
meillo@8 361 developers will more often and easier find simple designs where
meillo@8 362 a stream of bytes is a sufficient interface.
meillo@8 363 .PP
meillo@8 364 The second drawback of a toolchest affects the users.
meillo@45 365 A toolchest is often more difficult to use.
meillo@9 366 It is necessary to become familiar with each of the tools,
meillo@5 367 to be able to use the right one in a given situation.
meillo@54 368 Additionally, one needs to combine the tools in a sensible way himself.
meillo@45 369 This is like a sharp knife \(en it is a powerful tool in the hand of a
meillo@45 370 master, but of no good value in the hand of an unskilled.
meillo@45 371 However, learning single, small tools of a toolchest is easier than
meillo@45 372 learning a complex tool.
meillo@45 373 And the user will already have a basic understanding of a yet unknown tool,
meillo@45 374 if the tools of a toolchest have a common, consistent style.
meillo@45 375 He will be able to transfer knowledge over from one tool to another.
meillo@5 376 .PP
meillo@54 377 Moreover, the second drawback can be removed to a large extent
meillo@45 378 by adding wrappers around the basic tools.
meillo@45 379 Novice users do not need to learn several tools, if a professional wraps
meillo@45 380 complete command lines into a higher-level script.
meillo@5 381 Note that the wrapper script still calls the small tools;
meillo@45 382 it is just like a skin around them.
meillo@45 383 No complexity is added this way.
meillo@45 384 But new programs can get created out of existing one with very low effort.
meillo@5 385 .PP
meillo@5 386 A wrapper script for finding the five largest entries in the current directory
meillo@5 387 could look like this:
meillo@41 388 .DS
meillo@5 389 #!/bin/sh
meillo@5 390 du -s * | sort -nr | sed 5q
meillo@5 391 .DE
meillo@45 392 The script itself is just a text file that calls the command line,
meillo@45 393 which a professional user would type in directly.
meillo@45 394 It is probably worth to make the program flexible on the number of
meillo@45 395 entries it prints:
meillo@41 396 .DS
meillo@8 397 #!/bin/sh
meillo@8 398 num=5
meillo@8 399 [ $# -eq 1 ] && num="$1"
meillo@8 400 du -sh * | sort -nr | sed "${num}q"
meillo@8 401 .DE
meillo@8 402 This script acts like the one before, when called without an argument.
meillo@8 403 But one can also specify a numerical argument to define the number of lines to print.
meillo@45 404 One can surely imagine even more flexible versions, however,
meillo@45 405 they will still relay on the external programs,
meillo@45 406 which do the actual work.
meillo@5 407
meillo@48 408 .H 2 "A powerful shell
meillo@8 409 .LP
meillo@45 410 The Unix shell provides the possibility to combine small programs into large ones.
meillo@45 411 But a powerful shell is a great feature in other ways, too.
meillo@45 412 For instance by being scriptable.
meillo@54 413 Control statements are built into the shell.
meillo@45 414 The functions, however, are the normal programs of the system.
meillo@45 415 Thus, as the programs are already known,
meillo@45 416 learning to program in the shell becomes easy.
meillo@8 417 Using normal programs as functions in the shell programming language
meillo@10 418 is only possible because they are small and combinable tools in a toolchest style.
meillo@8 419 .PP
meillo@45 420 The Unix shell encourages to write small scripts,
meillo@45 421 by combining existing programs, because it is so easy to do.
meillo@8 422 This is a great step towards automation.
meillo@8 423 It is wonderful if the effort to automate a task equals the effort
meillo@45 424 to do the task a second time by hand.
meillo@45 425 If this holds,
meillo@45 426 then the user will be happy to automate everything he does more than once.
meillo@8 427 .PP
meillo@8 428 Small programs that do one job well, standardized interfaces between them,
meillo@8 429 a mechanism to combine parts to larger parts, and an easy way to automate tasks,
meillo@8 430 this will inevitably produce software leverage.
meillo@8 431 Getting multiple times the benefit of an investment is a great offer.
meillo@10 432 .PP
meillo@10 433 The shell also encourages rapid prototyping.
meillo@10 434 Many well known programs started as quickly hacked shell scripts,
meillo@10 435 and turned into ``real'' programs, written in C, later.
meillo@45 436 Building a prototype first, is a way to avoid the biggest problems
meillo@10 437 in application development.
meillo@45 438 Fred Brooks explains in ``No Silver Bullet'':
meillo@10 439 .[
meillo@44 440 brooks
meillo@44 441 no silver bullet
meillo@10 442 .]
meillo@10 443 .QP
meillo@10 444 The hardest single part of building a software system is deciding precisely what to build.
meillo@10 445 No other part of the conceptual work is so difficult as establishing the detailed
meillo@10 446 technical requirements, [...].
meillo@10 447 No other part of the work so cripples the resulting system if done wrong.
meillo@10 448 No other part is more difficult to rectify later.
meillo@10 449 .PP
meillo@45 450 Writing a prototype is a great method for becoming familiar with the requirements
meillo@45 451 and to run into real problems early.
meillo@47 452 .[ [
meillo@47 453 gancarz
meillo@47 454 unix philosophy
meillo@47 455 .], page 28 f.]
meillo@45 456 .PP
meillo@54 457 Prototyping is often seen as a first step in building software.
meillo@10 458 This is, of course, good.
meillo@10 459 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping:
meillo@10 460 After having built the prototype, one might notice, that the prototype is already
meillo@10 461 \fIgood enough\fP.
meillo@45 462 Hence, no reimplementation, in a more sophisticated programming language,
meillo@45 463 might be of need, at least for the moment.
meillo@23 464 Maybe later, it might be necessary to rewrite the software, but not now.
meillo@45 465 By delaying further work, one keeps the flexibility to react on
meillo@10 466 changing requirements.
meillo@10 467 Software parts that are not written will not miss the requirements.
meillo@10 468
meillo@48 469 .H 2 "Worse is better
meillo@10 470 .LP
meillo@45 471 The Unix Philosophy aims for the 90% solution;
meillo@10 472 others call it the ``Worse is better'' approach.
meillo@47 473 Experience from real life projects shows:
meillo@10 474 .PP
meillo@45 475 (1) It is almost never possible to define the
meillo@10 476 requirements completely and correctly the first time.
meillo@45 477 Hence one should not try to; one will fail anyway.
meillo@45 478 .PP
meillo@45 479 (2) Requirements change during time.
meillo@10 480 Hence it is best to delay requirement-based design decisions as long as possible.
meillo@54 481 Software should be small and flexible as long as possible
meillo@10 482 to react on changing requirements.
meillo@10 483 Shell scripts, for example, are more easily adjusted as C programs.
meillo@45 484 .PP
meillo@45 485 (3) Maintenance work is hard work.
meillo@45 486 Hence, one should keep the amount of code as small as possible;
meillo@10 487 it should just fulfill the \fIcurrent\fP requirements.
meillo@45 488 Software parts that will be written in future,
meillo@45 489 do not need maintenance till then.
meillo@10 490 .PP
meillo@47 491 See Brooks' ``The Mythical Man-Month'' for reference.
meillo@47 492 .[ [
meillo@47 493 brooks
meillo@47 494 mythical man-month
meillo@47 495 .], page 115 ff.]
meillo@47 496 .PP
meillo@10 497 Starting with a prototype in a scripting language has several advantages:
meillo@10 498 .IP \(bu
meillo@10 499 As the initial effort is low, one will likely start right away.
meillo@10 500 .IP \(bu
meillo@10 501 As working parts are available soon, the real requirements can get identified soon.
meillo@10 502 .IP \(bu
meillo@54 503 When software is usable and valuable, it gets used, and thus tested.
meillo@10 504 Hence problems will be found at early stages of the development.
meillo@10 505 .IP \(bu
meillo@10 506 The prototype might be enough for the moment,
meillo@51 507 thus further work can get delayed to a time
meillo@10 508 when one knows better about the requirements and problems,
meillo@10 509 than now.
meillo@10 510 .IP \(bu
meillo@45 511 Implementing now only the parts that are actually needed at the moment,
meillo@45 512 introduces fewer programming and maintenance work.
meillo@10 513 .IP \(bu
meillo@10 514 If the global situation changes so that the software is not needed anymore,
meillo@10 515 then less effort was spent into the project, than it would have be
meillo@10 516 when a different approach had been used.
meillo@10 517
meillo@48 518 .H 2 "Upgrowth and survival of software
meillo@11 519 .LP
meillo@12 520 So far it was talked about \fIwriting\fP or \fIbuilding\fP software.
meillo@13 521 Although these are just verbs, they do imply a specific view on the work process
meillo@13 522 they describe.
meillo@12 523 The better verb, however, is to \fIgrow\fP.
meillo@12 524 Creating software in the sense of the Unix Philosophy is an incremental process.
meillo@12 525 It starts with a first prototype, which evolves as requirements change.
meillo@12 526 A quickly hacked shell script might become a large, sophisticated,
meillo@13 527 compiled program this way.
meillo@13 528 Its lifetime begins with the initial prototype and ends when the software is not used anymore.
meillo@45 529 While being alive it will get extended, rearranged, rebuilt.
meillo@12 530 Growing software matches the view that ``software is never finished. It is only released.''
meillo@46 531 .[ [
meillo@44 532 gancarz
meillo@44 533 unix philosophy
meillo@46 534 .], page 26]
meillo@12 535 .PP
meillo@13 536 Software can be seen as being controlled by evolutionary processes.
meillo@13 537 Successful software is software that is used by many for a long time.
meillo@12 538 This implies that the software is needed, useful, and better than alternatives.
meillo@12 539 Darwin talks about: ``The survival of the fittest.''
meillo@12 540 .[
meillo@44 541 darwin
meillo@44 542 origin of species
meillo@12 543 .]
meillo@12 544 Transferred to software: The most successful software, is the fittest,
meillo@12 545 is the one that survives.
meillo@13 546 (This may be at the level of one creature, or at the level of one species.)
meillo@13 547 The fitness of software is affected mainly by four properties:
meillo@15 548 portability of code, portability of data, range of usability, and reusability of parts.
meillo@13 549 .PP
meillo@15 550 (1)
meillo@15 551 .I "Portability of code
meillo@15 552 means, using high-level programming languages,
meillo@13 553 sticking to the standard,
meillo@47 554 .[ [
meillo@47 555 kernighan pike
meillo@47 556 practice of programming
meillo@47 557 .], chapter\|8]
meillo@13 558 and avoiding optimizations that introduce dependencies on specific hardware.
meillo@13 559 Hardware has a much lower lifetime than software.
meillo@13 560 By chaining software to a specific hardware,
meillo@54 561 its lifetime gets shortened to that of this hardware.
meillo@13 562 In contrast, software should be easy to port \(en
meillo@23 563 adaptation is the key to success.
meillo@13 564 .PP
meillo@15 565 (2)
meillo@15 566 .I "Portability of data
meillo@15 567 is best achieved by avoiding binary representations
meillo@13 568 to store data, because binary representations differ from machine to machine.
meillo@23 569 Textual representation is favored.
meillo@45 570 Historically, \s-1ASCII\s0 was the charset of choice.
meillo@45 571 For the future, \s-1UTF\s0-8 might be the better choice.
meillo@13 572 Important is that it is a plain text representation in a
meillo@13 573 very common charset encoding.
meillo@13 574 Apart from being able to transfer data between machines,
meillo@45 575 readable data has the great advantage, that humans are able to directly
meillo@45 576 read and edit it with text editors and other tools from the Unix toolchest.
meillo@47 577 .[ [
meillo@47 578 gancarz
meillo@47 579 unix philosophy
meillo@47 580 .], page 56 ff.]
meillo@13 581 .PP
meillo@15 582 (3)
meillo@15 583 A large
meillo@15 584 .I "range of usability
meillo@23 585 ensures good adaptation, and thus good survival.
meillo@54 586 It is a special distinction if software becomes used in fields of action,
meillo@13 587 the original authors did never imagine.
meillo@13 588 Software that solves problems in a general way will likely be used
meillo@45 589 for many kinds of similar problems.
meillo@45 590 Being too specific limits the range of usability.
meillo@13 591 Requirements change through time, thus use cases change or even vanish.
meillo@45 592 As a good example in this point,
meillo@13 593 Allman identifies flexibility to be one major reason for sendmail's success:
meillo@13 594 .[
meillo@44 595 allman
meillo@44 596 sendmail
meillo@13 597 .]
meillo@13 598 .QP
meillo@13 599 Second, I limited myself to the routing function [...].
meillo@13 600 This was a departure from the dominant thought of the time, [...].
meillo@13 601 .QP
meillo@45 602 Third, the sendmail configuration file was flexible enough to adapt
meillo@13 603 to a rapidly changing world [...].
meillo@12 604 .LP
meillo@45 605 Successful software adapts itself to the changing world.
meillo@13 606 .PP
meillo@15 607 (4)
meillo@15 608 .I "Reuse of parts
meillo@15 609 is even one step further.
meillo@54 610 Software may completely lose its field of action,
meillo@54 611 but parts of which the software is built may be general and independent enough
meillo@13 612 to survive this death.
meillo@54 613 If software is built by combining small independent programs,
meillo@45 614 then these parts are readily available for reuse.
meillo@13 615 Who cares if the large program is a failure,
meillo@13 616 but parts of it become successful instead?
meillo@10 617
meillo@48 618 .H 2 "Summary
meillo@0 619 .LP
meillo@45 620 This chapter explained central ideas of the Unix Philosophy.
meillo@45 621 For each of the ideas, the advantages they introduce were explained.
meillo@45 622 The Unix Philosophy are guidelines that help to write more valuable software.
meillo@14 623 From the view point of a software developer or software designer,
meillo@14 624 the Unix Philosophy provides answers to many software design problem.
meillo@14 625 .PP
meillo@14 626 The various ideas of the Unix Philosophy are very interweaved
meillo@14 627 and can hardly be applied independently.
meillo@14 628 However, the probably most important messages are:
meillo@45 629 .I "``Keep it simple!''" ,
meillo@14 630 .I "``Do one thing well!''" ,
meillo@14 631 and
meillo@14 632 .I "``Use software leverage!''
meillo@0 633
meillo@8 634
meillo@8 635
meillo@48 636 .H 1 "Case study: \s-1MH\s0
meillo@18 637 .LP
meillo@30 638 The previous chapter introduced and explained the Unix Philosophy
meillo@18 639 from a general point of view.
meillo@30 640 The driving force were the guidelines; references to
meillo@18 641 existing software were given only sparsely.
meillo@18 642 In this and the next chapter, concrete software will be
meillo@18 643 the driving force in the discussion.
meillo@18 644 .PP
meillo@23 645 This first case study is about the mail user agents (\s-1MUA\s0)
meillo@54 646 \s-1MH\s0 (``mail handler'') and its descendant \fInmh\fP
meillo@23 647 (``new mail handler'').
meillo@47 648 .[
meillo@47 649 nmh website
meillo@47 650 .]
meillo@23 651 \s-1MUA\s0s provide functions to read, compose, and organize mail,
meillo@45 652 but (ideally) not to transfer it.
meillo@45 653 In this document, the name \s-1MH\s0 will be used to include nmh.
meillo@19 654 A distinction will only be made if differences between
meillo@45 655 \s-1MH\s0 and nmh are described.
meillo@18 656
meillo@0 657
meillo@48 658 .H 2 "Historical background
meillo@0 659 .LP
meillo@19 660 Electronic mail was available in Unix very early.
meillo@30 661 The first \s-1MUA\s0 on Unix was \f(CWmail\fP,
meillo@30 662 which was already present in the First Edition.
meillo@46 663 .[ [
meillo@44 664 salus
meillo@44 665 quarter century of unix
meillo@46 666 .], page 41 f.]
meillo@45 667 It was a small program that either printed the user's mailbox file
meillo@54 668 or appended text to someone else's mailbox file,
meillo@19 669 depending on the command line arguments.
meillo@19 670 .[
meillo@44 671 manual mail(1)
meillo@19 672 .]
meillo@19 673 It was a program that did one job well.
meillo@23 674 This job was emailing, which was very simple then.
meillo@19 675 .PP
meillo@23 676 Later, emailing became more powerful, and thus more complex.
meillo@19 677 The simple \f(CWmail\fP, which knew nothing of subjects,
meillo@19 678 independent handling of single messages,
meillo@45 679 and long-time email storage, was not powerful enough anymore.
meillo@45 680 In 1978 at Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
meillo@45 681 to provide additional functions for emailing.
meillo@19 682 Mail was still one program, but now it was large and did
meillo@19 683 several jobs.
meillo@23 684 Its user interface is modeled after the one of \fIed\fP.
meillo@19 685 It is designed for humans, but is still scriptable.
meillo@23 686 \fImailx\fP is the adaptation of Berkeley Mail into System V.
meillo@19 687 .[
meillo@44 688 ritter
meillo@44 689 mailx history
meillo@19 690 .]
meillo@30 691 Elm, pine, mutt, and a whole bunch of graphical \s-1MUA\s0s
meillo@19 692 followed Mail's direction.
meillo@19 693 They are large, monolithic programs which include all emailing functions.
meillo@19 694 .PP
meillo@23 695 A different way was taken by the people of \s-1RAND\s0 Corporation.
meillo@38 696 In the beginning, they also had used a monolithic mail system,
meillo@30 697 called \s-1MS\s0 (for ``mail system'').
meillo@19 698 But in 1977, Stockton Gaines and Norman Shapiro
meillo@19 699 came up with a proposal of a new email system concept \(en
meillo@45 700 one that honored the Unix Philosophy.
meillo@19 701 The concept was implemented by Bruce Borden in 1978 and 1979.
meillo@19 702 This was the birth of \s-1MH\s0 \(en the ``mail handler''.
meillo@18 703 .PP
meillo@18 704 Since then, \s-1RAND\s0, the University of California at Irvine and
meillo@19 705 at Berkeley, and several others have contributed to the software.
meillo@18 706 However, it's core concepts remained the same.
meillo@23 707 In the late 90s, when development of \s-1MH\s0 slowed down,
meillo@19 708 Richard Coleman started with \fInmh\fP, the new mail handler.
meillo@45 709 His goal was to improve \s-1MH\s0 especially in regard of
meillo@23 710 the requirements of modern emailing.
meillo@19 711 Today, nmh is developed by various people on the Internet.
meillo@18 712 .[
meillo@44 713 ware
meillo@44 714 rand history
meillo@18 715 .]
meillo@18 716 .[
meillo@44 717 peek
meillo@44 718 mh
meillo@18 719 .]
meillo@0 720
meillo@48 721 .H 2 "Contrasts to monolithic mail systems
meillo@0 722 .LP
meillo@19 723 All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
meillo@38 724 Although there might actually exist further, very little known,
meillo@30 725 toolchest \s-1MUA\s0s, this statement reflects the situation pretty well.
meillo@19 726 .PP
meillo@30 727 Monolithic \s-1MUA\s0s gather all their functions in one program.
meillo@30 728 In contrast, \s-1MH\s0 is a toolchest of many small tools \(en one for each job.
meillo@23 729 Following is a list of important programs of \s-1MH\s0's toolchest
meillo@30 730 and their function.
meillo@30 731 It gives a feeling of how the toolchest looks like.
meillo@19 732 .IP \(bu
meillo@19 733 .CW inc :
meillo@30 734 incorporate new mail (this is how mail enters the system)
meillo@19 735 .IP \(bu
meillo@19 736 .CW scan :
meillo@19 737 list messages in folder
meillo@19 738 .IP \(bu
meillo@19 739 .CW show :
meillo@19 740 show message
meillo@19 741 .IP \(bu
meillo@19 742 .CW next\fR/\fPprev :
meillo@19 743 show next/previous message
meillo@19 744 .IP \(bu
meillo@19 745 .CW folder :
meillo@19 746 change current folder
meillo@19 747 .IP \(bu
meillo@19 748 .CW refile :
meillo@45 749 refile message into different folder
meillo@19 750 .IP \(bu
meillo@19 751 .CW rmm :
meillo@19 752 remove message
meillo@19 753 .IP \(bu
meillo@19 754 .CW comp :
meillo@45 755 compose new message
meillo@19 756 .IP \(bu
meillo@19 757 .CW repl :
meillo@45 758 reply to message
meillo@19 759 .IP \(bu
meillo@19 760 .CW forw :
meillo@45 761 forward message
meillo@19 762 .IP \(bu
meillo@19 763 .CW send :
meillo@45 764 send prepared message (this is how mail leaves the system)
meillo@0 765 .LP
meillo@19 766 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
meillo@19 767 The user does not leave the shell to run \s-1MH\s0,
meillo@45 768 instead he uses the various \s-1MH\s0 programs within the shell.
meillo@23 769 Using a monolithic program with a captive user interface
meillo@23 770 means ``entering'' the program, using it, and ``exiting'' the program.
meillo@23 771 Using toolchests like \s-1MH\s0 means running programs,
meillo@45 772 alone or in combination with others, also from other toolchests,
meillo@23 773 without leaving the shell.
meillo@30 774
meillo@48 775 .H 2 "Data storage
meillo@30 776 .LP
meillo@34 777 \s-1MH\s0's mail storage is a directory tree under the user's
meillo@34 778 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP),
meillo@34 779 where mail folders are directories and mail messages are text files
meillo@34 780 within them.
meillo@34 781 Each mail folder contains a file \f(CW.mh_sequences\fP which lists
meillo@45 782 the public message sequences of that folder,
meillo@45 783 for instance the \fIunseen\fP sequence for new messages.
meillo@34 784 Mail messages are text files located in a mail folder.
meillo@34 785 The files contain the messages as they were received.
meillo@45 786 They are named by ascending numbers in each folder.
meillo@19 787 .PP
meillo@30 788 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0.
meillo@30 789 Alternatives are \fImbox\fP and \fImaildir\fP.
meillo@30 790 In the mbox format all messages are stored within one file.
meillo@30 791 This was a good solution in the early days, when messages
meillo@30 792 were only a few lines of text and were deleted soon.
meillo@30 793 Today, when single messages often include several megabytes
meillo@30 794 of attachments, it is a bad solution.
meillo@30 795 Another disadvantage of the mbox format is that it is
meillo@30 796 more difficult to write tools that work on mail messages,
meillo@30 797 because it is always necessary to first find and extract
meillo@30 798 the relevant message in the mbox file.
meillo@45 799 With the \s-1MH\s0 mailbox format, each message is a separate file.
meillo@30 800 Also, the problem of concurrent access to one mailbox is
meillo@30 801 reduced to the problem of concurrent access to one message.
meillo@45 802 The maildir format is generally similar to the \s-1MH\s0 format,
meillo@30 803 but modified towards guaranteed reliability.
meillo@30 804 This involves some complexity, unfortunately.
meillo@34 805 .PP
meillo@34 806 Working with \s-1MH\s0's toolchest on mailboxes is much like
meillo@34 807 working with Unix' toolchest on directory trees:
meillo@34 808 \f(CWscan\fP is like \f(CWls\fP,
meillo@34 809 \f(CWshow\fP is like \f(CWcat\fP,
meillo@34 810 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP,
meillo@34 811 \f(CWrefile\fP is like \f(CWmv\fP,
meillo@34 812 and \f(CWrmm\fP is like \f(CWrm\fP.
meillo@34 813 .PP
meillo@45 814 \s-1MH\s0 extends the context of processes in Unix by two more items,
meillo@45 815 for its tools:
meillo@34 816 .IP \(bu
meillo@34 817 The current mail folder, which is similar to the current working directory.
meillo@34 818 For mail folders, \f(CWfolder\fP provides the corresponding functionality
meillo@34 819 of \f(CWcd\fP and \f(CWpwd\fP for directories.
meillo@34 820 .IP \(bu
meillo@34 821 Sequences, which are named sets of messages in a mail folder.
meillo@34 822 The current message, relative to a mail folder, is a special sequence.
meillo@34 823 It enables commands like \f(CWnext\fP and \f(CWprev\fP.
meillo@34 824 .LP
meillo@45 825 In contrast to Unix' context, which is maintained by the kernel,
meillo@45 826 \s-1MH\s0's context must be maintained by the tools themselves.
meillo@45 827 Usually there is one context per user, which resides in his
meillo@45 828 \f(CWcontext\fP file in the \s-1MH\s0 directory,
meillo@45 829 but a user can have several contexts, too.
meillo@45 830 Public sequences are an exception, as they belong to a mail folder,
meillo@45 831 and reside in the \f(CW.mh_sequences\fP file there.
meillo@34 832 .[
meillo@44 833 man page mh-profile mh-sequence
meillo@34 834 .]
meillo@20 835
meillo@48 836 .H 2 "Discussion of the design
meillo@0 837 .LP
meillo@45 838 This section discusses \s-1MH\s0 in regard to the tenets
meillo@45 839 of the Unix Philosophy that Gancarz identified.
meillo@20 840
meillo@20 841 .PP
meillo@33 842 .B "Small is beautiful
meillo@20 843 and
meillo@33 844 .B "do one thing well
meillo@20 845 are two design goals that are directly visible in \s-1MH\s0.
meillo@45 846 Gancarz actually presents \s-1MH\s0 in his book as example under the
meillo@45 847 headline ``Making \s-1UNIX\s0 Do One Thing Well'':
meillo@46 848 .[ [
meillo@44 849 gancarz
meillo@44 850 unix philosophy
meillo@46 851 .], page 125 ff.]
meillo@20 852 .QP
meillo@20 853 [\s-1MH\s0] consists of a series of programs which
meillo@20 854 when combined give the user an enormous ability
meillo@20 855 to manipulate electronic mail messages.
meillo@20 856 A complex application, it shows that not only is it
meillo@20 857 possible to build large applications from smaller
meillo@20 858 components, but also that such designs are actually preferable.
meillo@20 859 .LP
meillo@45 860 The various programs of \s-1MH\s0 were relatively easy to write,
meillo@45 861 because each of them is small, limited to one function,
meillo@23 862 and has clear boundaries.
meillo@20 863 For the same reasons, they are also good to maintain.
meillo@20 864 Further more, the system can easily get extended.
meillo@20 865 One only needs to put a new program into the toolchest.
meillo@23 866 This was done, for instance, when \s-1MIME\s0 support was added
meillo@20 867 (e.g. \f(CWmhbuild\fP).
meillo@20 868 Also, different programs can exist to do the basically same job
meillo@20 869 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP).
meillo@45 870 .PP
meillo@20 871 If someone needs a mail system with some additionally
meillo@45 872 functions that are not available anywhere yet, he best expands a
meillo@45 873 toolchest system like \s-1MH\s0.
meillo@45 874 There he can add new functionality by simply adding additional
meillo@45 875 programs to the toolchest.
meillo@45 876 There he does not risk to break existing functionality by doing so.
meillo@20 877
meillo@20 878 .PP
meillo@34 879 .B "Store data in flat text files
meillo@34 880 is followed by \s-1MH\s0.
meillo@34 881 This is not surprising, because email messages are already plain text.
meillo@34 882 \s-1MH\s0 stores the messages as it receives them,
meillo@45 883 thus any other tool that works on \s-1RFC\s0\|2822 mail messages can operate
meillo@34 884 on the messages in an \s-1MH\s0 mailbox.
meillo@45 885 All other files \s-1MH\s0 uses are plain text, too.
meillo@34 886 It is therefore possible and encouraged to use the text processing
meillo@34 887 tools of Unix' toolchest to extend \s-1MH\s0's toolchest.
meillo@20 888
meillo@20 889 .PP
meillo@33 890 .B "Avoid captive user interfaces" .
meillo@19 891 \s-1MH\s0 is perfectly suited for non-interactive use.
meillo@19 892 It offers all functions directly and without captive user interfaces.
meillo@30 893 If, nonetheless, users want a graphical user interface,
meillo@53 894 they can have it with \fIxmh\fP, \fIexmh\fP,
meillo@53 895 or with the Emacs interface \fImh-e\fP.
meillo@53 896 These are frontends for the \s-1MH\s0 toolchest.
meillo@19 897 This means, all email-related work is still done by \s-1MH\s0 tools,
meillo@45 898 but the frontend calls the appropriate commands when the user
meillo@53 899 clicks on buttons or pushes a key.
meillo@45 900 .PP
meillo@20 901 Providing easy-to-use user interfaces in form of frontends is a good
meillo@19 902 approach, because it does not limit the power of the backend itself.
meillo@20 903 The frontend will anyway only be able to make a subset of the
meillo@23 904 backend's power and flexibility available to the user.
meillo@20 905 But if it is a separate program,
meillo@20 906 then the missing parts can still be accessed at the backend directly.
meillo@19 907 If it is integrated, then this will hardly be possible.
meillo@45 908 An additional advantage is the possibility to have different frontends
meillo@45 909 to the same backend.
meillo@19 910
meillo@19 911 .PP
meillo@33 912 .B "Choose portability over efficiency
meillo@20 913 and
meillo@33 914 .B "use shell scripts to increase leverage and portability" .
meillo@20 915 These two tenets are indirectly, but nicely, demonstrated by
meillo@30 916 Bolsky and Korn in their book about the Korn Shell.
meillo@20 917 .[
meillo@44 918 bolsky korn
meillo@44 919 korn shell
meillo@20 920 .]
meillo@45 921 Chapter\|18 of the book shows a basic implementation
meillo@20 922 of a subset of \s-1MH\s0 in ksh scripts.
meillo@45 923 Of course, this is just a demonstration, but a brilliant one.
meillo@20 924 It shows how quickly one can implement such a prototype with shell scripts,
meillo@20 925 and how readable they are.
meillo@20 926 The implementation in the scripting language may not be very fast,
meillo@20 927 but it can be fast enough though, and this is all that matters.
meillo@20 928 By having the code in an interpreted language, like the shell,
meillo@20 929 portability becomes a minor issue, if we assume the interpreter
meillo@20 930 to be widespread.
meillo@45 931 .PP
meillo@20 932 This demonstration also shows how easy it is to create single programs
meillo@20 933 of a toolchest software.
meillo@45 934 Eight tools (two of them have multiple names) and 16 functions
meillo@45 935 with supporting code are presented to the reader.
meillo@45 936 The tools comprise less than 40 lines of ksh each,
meillo@30 937 in total about 200 lines.
meillo@45 938 The functions comprise less than 80 lines of ksh each,
meillo@30 939 in total about 450 lines.
meillo@20 940 Such small software is easy to write, easy to understand,
meillo@20 941 and thus easy to maintain.
meillo@23 942 A toolchest improves the possibility to only write some parts
meillo@20 943 and though create a working result.
meillo@45 944 Expanding the toolchest, even without global changes,
meillo@45 945 will likely be possible.
meillo@20 946
meillo@20 947 .PP
meillo@33 948 .B "Use software leverage to your advantage
meillo@20 949 and the lesser tenet
meillo@33 950 .B "allow the user to tailor the environment
meillo@20 951 are ideally followed in the design of \s-1MH\s0.
meillo@21 952 Tailoring the environment is heavily encouraged by the ability to
meillo@30 953 directly define default options to programs.
meillo@30 954 It is even possible to define different default options
meillo@45 955 depending on the name under which a program is called.
meillo@45 956 Software leverage is heavily encouraged by the ease of
meillo@45 957 creating shell scripts that run a specific command line,
meillo@30 958 built of several \s-1MH\s0 programs.
meillo@21 959 There is few software that so much wants users to tailor their
meillo@21 960 environment and to leverage the use of the software, like \s-1MH\s0.
meillo@45 961 .PP
meillo@21 962 Just to make one example:
meillo@23 963 One might prefer a different listing format for the \f(CWscan\fP
meillo@21 964 program.
meillo@30 965 It is possible to take one of the distributed format files
meillo@21 966 or to write one yourself.
meillo@21 967 To use the format as default for \f(CWscan\fP, a single line,
meillo@21 968 reading
meillo@21 969 .DS
meillo@21 970 scan: -form FORMATFILE
meillo@21 971 .DE
meillo@21 972 must be added to \f(CW.mh_profile\fP.
meillo@21 973 If one wants this different format as an additional command,
meillo@23 974 instead of changing the default, he needs to create a link to
meillo@23 975 \f(CWscan\fP, for instance titled \f(CWscan2\fP.
meillo@21 976 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP,
meillo@45 977 as the option should only be in effect for a program that is called as
meillo@21 978 \f(CWscan2\fP.
meillo@20 979
meillo@20 980 .PP
meillo@33 981 .B "Make every program a filter
meillo@21 982 is hard to find in \s-1MH\s0.
meillo@21 983 The reason therefore is that most of \s-1MH\s0's tools provide
meillo@45 984 basic file system operations for mailboxes.
meillo@45 985 It is the same reason because of which \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP,
meillo@45 986 and \f(CWrm\fP aren't filters neither.
meillo@23 987 \s-1MH\s0 does not provide many filters itself, but it is a basis
meillo@23 988 to write filters for.
meillo@45 989 An example would be a mail text highlighter,
meillo@30 990 that means a program that makes use of a color terminal to display
meillo@30 991 header lines, quotations, and signatures in distinct colors.
meillo@45 992 The author's version of such a program is an awk script with 25 lines.
meillo@21 993
meillo@21 994 .PP
meillo@33 995 .B "Build a prototype as soon as possible
meillo@21 996 was again well followed by \s-1MH\s0.
meillo@21 997 This tenet, of course, focuses on early development, which is
meillo@21 998 long time ago for \s-1MH\s0.
meillo@21 999 But without following this guideline at the very beginning,
meillo@23 1000 Bruce Borden may have not convinced the management of \s-1RAND\s0
meillo@23 1001 to ever create \s-1MH\s0.
meillo@23 1002 In Bruce' own words:
meillo@46 1003 .[ [
meillo@44 1004 ware rand history
meillo@46 1005 .], page 132]
meillo@21 1006 .QP
meillo@45 1007 [...] but [Stockton Gaines and Norm Shapiro] were not able
meillo@23 1008 to convince anyone that such a system would be fast enough to be usable.
meillo@21 1009 I proposed a very short project to prove the basic concepts,
meillo@21 1010 and my management agreed.
meillo@21 1011 Looking back, I realize that I had been very lucky with my first design.
meillo@21 1012 Without nearly enough design work,
meillo@21 1013 I built a working environment and some header files
meillo@21 1014 with key structures and wrote the first few \s-1MH\s0 commands:
meillo@21 1015 inc, show/next/prev, and comp.
meillo@21 1016 [...]
meillo@21 1017 With these three, I was able to convince people that the structure was viable.
meillo@21 1018 This took about three weeks.
meillo@0 1019
meillo@48 1020 .H 2 "Problems
meillo@0 1021 .LP
meillo@45 1022 \s-1MH\s0 is not without problems.
meillo@30 1023 There are two main problems: one is technical, the other is about human behavior.
meillo@22 1024 .PP
meillo@22 1025 \s-1MH\s0 is old and email today is very different to email in the time
meillo@22 1026 when \s-1MH\s0 was designed.
meillo@45 1027 \s-1MH\s0 adapted to the changes pretty well, but it is limited, though.
meillo@22 1028 \s-1MIME\s0 support and support for different character encodings
meillo@22 1029 is available, but only on a moderate level.
meillo@45 1030 This comes from limited development resources.
meillo@45 1031 More active developers could quickly change this.
meillo@45 1032 But \s-1MH\s0 is also limited by design, which is the larger problem.
meillo@54 1033 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extent.
meillo@22 1034 These design conflicts are not easily solvable.
meillo@22 1035 Possibly, they require a redesign.
meillo@45 1036 \s-1IMAP\s0 may be too different to the classic mail model,
meillo@45 1037 which \s-1MH\s0 covers, so that \s-1MH\s0 may never support it well.
meillo@22 1038 .PP
meillo@45 1039 The other kind of problem are human habits.
meillo@45 1040 In this world, where almost all \s-1MUA\s0s are monolithic,
meillo@22 1041 it is very difficult to convince people to use a toolbox style \s-1MUA\s0
meillo@22 1042 like \s-1MH\s0.
meillo@45 1043 The habits are so strong, that even people who understand the concept
meillo@30 1044 and advantages of \s-1MH\s0 do not like to switch,
meillo@30 1045 simply because \s-1MH\s0 is different.
meillo@30 1046 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel,
meillo@45 1047 are quite outdated and thus not very appealing, compared to the modern interfaces
meillo@45 1048 of many monolithic \s-1MUA\s0s.
meillo@53 1049 One notable exception is \fImh-e\fP which provides an Emacs interface
meillo@53 1050 to \s-1MH\s0.
meillo@53 1051 \fIMh-e\fP looks much like \fImutt\fP or \fIpine\fP,
meillo@53 1052 but it has buttons, menus, and graphical display capabilities.
meillo@20 1053
meillo@53 1054 .H 2 "Summary
meillo@20 1055 .LP
meillo@45 1056 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design.
meillo@31 1057 It consists of a toolchest of small tools, each of them does one job well.
meillo@31 1058 The toolchest approach offers great flexibility to the user.
meillo@45 1059 It is possible to utilize the complete power of the Unix shell with \s-1MH\s0.
meillo@31 1060 This makes \s-1MH\s0 a very powerful mail system.
meillo@45 1061 Extending and customizing \s-1MH\s0 is easy and encouraged.
meillo@31 1062 .PP
meillo@31 1063 Apart from the user's perspective, \s-1MH\s0 is development-friendly.
meillo@31 1064 Its overall design follows clear rules.
meillo@31 1065 The single tools do only one job, thus they are easy to understand,
meillo@31 1066 easy to write, and good to maintain.
meillo@31 1067 They are all independent and do not interfere with the others.
meillo@31 1068 Automated testing of their function is a straight forward task.
meillo@31 1069 .PP
meillo@31 1070 It is sad, that \s-1MH\s0's differentness is its largest problem,
meillo@31 1071 as its differentness is also its largest advantage.
meillo@31 1072 Unfortunately, for most people their habits are stronger
meillo@31 1073 than the attraction of the clear design and the power, \s-1MH\s0 offers.
meillo@0 1074
meillo@8 1075
meillo@8 1076
meillo@48 1077 .H 1 "Case study: uzbl
meillo@32 1078 .LP
meillo@32 1079 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0,
meillo@45 1080 which is an old and established software.
meillo@45 1081 This chapter covers uzbl, a fresh new project.
meillo@45 1082 Uzbl is a web browser that adheres to the Unix Philosophy.
meillo@45 1083 Its name comes from the \fILolspeak\fP word for ``usable'';
meillo@45 1084 it is pronounced identical.
meillo@0 1085
meillo@48 1086 .H 2 "Historical background
meillo@0 1087 .LP
meillo@32 1088 Uzbl was started by Dieter Plaetinck in April 2009.
meillo@44 1089 The idea was born in a thread in the Arch Linux Forums.
meillo@32 1090 .[
meillo@44 1091 arch linux forums
meillo@44 1092 browser
meillo@32 1093 .]
meillo@32 1094 After some discussion about failures of well known web browsers,
meillo@32 1095 Plaetinck (alias Dieter@be) came up with a very sketchy proposal
meillo@32 1096 of how a better web browser could look like.
meillo@32 1097 To the question of another member, if Plaetinck would write that program,
meillo@32 1098 because it would sound fantastic, Plaetinck replied:
meillo@32 1099 ``Maybe, if I find the time ;-)''.
meillo@32 1100 .PP
meillo@32 1101 Fortunately, he found the time.
meillo@32 1102 One day later, the first prototype was out.
meillo@32 1103 One week later, uzbl had an own website.
meillo@47 1104 .[
meillo@47 1105 uzbl website
meillo@47 1106 .]
meillo@32 1107 One month after the first code showed up,
meillo@47 1108 a mailing list was installed to coordinate and discuss further development,
meillo@47 1109 and a wiki was added to store documentation and scripts that showed up on the
meillo@32 1110 mailing list and elsewhere.
meillo@32 1111 .PP
meillo@45 1112 In the, now, one year of uzbl's existence, it was heavily developed on various branches.
meillo@32 1113 Plaetinck's task became more and more to only merge the best code from the
meillo@32 1114 different branches into his main branch, and to apply patches.
meillo@47 1115 .[
meillo@47 1116 lwn uzbl
meillo@47 1117 .]
meillo@32 1118 About once a month, Plaetinck released a new version.
meillo@32 1119 In September 2009, he presented several forks of uzbl.
meillo@47 1120 .[ [
meillo@47 1121 uzbl website
meillo@47 1122 .], news archive]
meillo@38 1123 Uzbl, actually, opened the field for a whole family of web browsers with similar shape.
meillo@32 1124 .PP
meillo@32 1125 In July 2009, \fILinux Weekly News\fP published an interview with Plaetinck about uzbl.
meillo@47 1126 .[
meillo@47 1127 lwn uzbl
meillo@47 1128 .]
meillo@32 1129 In September 2009, the uzbl web browser was on \fISlashdot\fP.
meillo@47 1130 .[
meillo@47 1131 slashdot uzbl
meillo@47 1132 .]
meillo@0 1133
meillo@48 1134 .H 2 "Contrasts to other web browsers
meillo@0 1135 .LP
meillo@32 1136 Like most \s-1MUA\s0s are monolithic, but \s-1MH\s0 is a toolchest,
meillo@32 1137 most web browsers are monolithic, but uzbl is a frontend to a toolchest.
meillo@32 1138 .PP
meillo@32 1139 Today, uzbl is divided into uzbl-core and uzbl-browser.
meillo@32 1140 Uzbl-core is, how its name already indicates, the core of uzbl.
meillo@32 1141 It handles commands and events to interface other programs,
meillo@45 1142 and also displays webpages by using \fIwebkit\fP as render engine.
meillo@32 1143 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar,
meillo@32 1144 an event manager, yanking, pasting, page searching, zooming, and more stuff,
meillo@32 1145 to form a ``complete'' web browser.
meillo@32 1146 In the following text, the term ``uzbl'' usually stands for uzbl-browser,
meillo@32 1147 so uzbl-core is included.
meillo@32 1148 .PP
meillo@32 1149 Unlike most other web browsers, uzbl is mainly the mediator between the
meillo@45 1150 various tools that cover single jobs.
meillo@35 1151 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket,
meillo@35 1152 and on stdin, and it writes events to a Unix socket and to stdout.
meillo@35 1153 Loading a webpage in a running uzbl instance requires only:
meillo@32 1154 .DS
meillo@32 1155 echo 'uri http://example.org' >/path/to/uzbl-fifo
meillo@32 1156 .DE
meillo@45 1157 The graphical rendering of the webpage is done by webkit,
meillo@45 1158 a web content engine.
meillo@45 1159 Uzbl-core is built around libwebkit.
meillo@32 1160 .PP
meillo@45 1161 Downloads, browsing history, bookmarks, and the like are not provided
meillo@45 1162 by the core itself, like they are in other web browsers.
meillo@35 1163 Uzbl-browser also only provides, so called, handler scripts that wrap
meillo@35 1164 external applications which provide the actual functionality.
meillo@32 1165 For instance, \fIwget\fP is used to download files and uzbl-browser
meillo@32 1166 includes a script that calls wget with appropriate options in
meillo@32 1167 a prepared environment.
meillo@32 1168 .PP
meillo@32 1169 Modern web browsers are proud to have addons, plugins, and modules, instead.
meillo@32 1170 This is their effort to achieve similar goals.
meillo@35 1171 But instead of using existing, external programs, modern web browsers
meillo@45 1172 include these functions.
meillo@0 1173
meillo@48 1174 .H 2 "Discussion of the design
meillo@0 1175 .LP
meillo@32 1176 This section discusses uzbl in regard of the Unix Philosophy,
meillo@32 1177 as identified by Gancarz.
meillo@32 1178
meillo@32 1179 .PP
meillo@35 1180 .B "Make each program do one thing well" .
meillo@35 1181 Uzbl tries to be a web browser and nothing else.
meillo@36 1182 The common definition of a web browser is, of course, highly influenced by
meillo@36 1183 existing implementations of web browsers, although they are degenerated.
meillo@35 1184 Web browsers should be programs to browse the web, and nothing more.
meillo@45 1185 This is the one thing they should do.
meillo@36 1186 .PP
meillo@45 1187 Web browsers should not, for instance, manage downloads.
meillo@35 1188 This is the job download managers exist for.
meillo@35 1189 Download managers do primary care about being good in downloading files.
meillo@35 1190 Modern web browsers provide download management only as a secondary feature.
meillo@45 1191 How could they do this job better, than programs that exist only for
meillo@35 1192 this very job?
meillo@35 1193 And how could anyone want less than the best download manager available?
meillo@32 1194 .PP
meillo@35 1195 A web browser's job is to let the user browse the web.
meillo@35 1196 This means, navigating through websites by following links.
meillo@36 1197 Rendering the \s-1HTML\s0 sources is a different job, too.
meillo@36 1198 It is covered by the webkit render engine, in uzbl's case.
meillo@54 1199 Audio and video content and files like PostScript, \s-1PDF\s0,
meillo@54 1200 and the like, are also not the job of a web browser.
meillo@54 1201 Such content should be handled by external programs \(en
meillo@54 1202 programs that were written to handle such data.
meillo@35 1203 Uzbl strives to do it this way.
meillo@36 1204 .PP
meillo@36 1205 Remember Doug McIlroy:
meillo@35 1206 .I
meillo@35 1207 ``Write programs that do one thing and do it well.
meillo@35 1208 Write programs to work together.''
meillo@35 1209 .R
meillo@35 1210 .PP
meillo@35 1211 The lesser tenet
meillo@35 1212 .B "allow the user to tailor the environment
meillo@35 1213 matches good here.
meillo@35 1214 There was the question, how anyone could want anything less than the
meillo@35 1215 best program for the job.
meillo@45 1216 But as personal preferences matter, it is probably more important to ask:
meillo@35 1217 How could anyone want something else than his preferred program for the job?
meillo@36 1218 .PP
meillo@45 1219 Usually users want one program for a specific job.
meillo@35 1220 Hence, whenever the task is, for instance, downloading,
meillo@45 1221 the same download manager should be used.
meillo@35 1222 More advanced users might want to have this download manager in this
meillo@35 1223 situation and that one in that situation.
meillo@35 1224 They should be able to configure it this way.
meillo@35 1225 With uzbl, one can use any download manager the user wants.
meillo@36 1226 To switch to a different one, only one line in a small handler script
meillo@35 1227 needs to be changed.
meillo@45 1228 Alternatively it would be possible to query the program to use by
meillo@45 1229 reading a global file or an environment variable, in the handler script.
meillo@54 1230 Of course, one can tell uzbl to use a different handler script, too.
meillo@54 1231 This requires a one line change in uzbl's config file.
meillo@36 1232 .PP
meillo@45 1233 Uzbl does neither have its own download manager nor depends on a
meillo@45 1234 specific one, hence uzbl's browsing abilities will not be lowered by having
meillo@35 1235 a bad download manager.
meillo@45 1236 Uzbl's download capabilities will be just as good as the ones of the best
meillo@36 1237 download manager available on the system.
meillo@38 1238 Of course, this applies to all of the other supplementary tools, too.
meillo@32 1239
meillo@32 1240 .PP
meillo@36 1241 .B "Use software leverage to your advantage" .
meillo@36 1242 Uzbl is designed to be extended by external tools.
meillo@36 1243 These external tools are usually wrapped by small handler shell scripts.
meillo@36 1244 Shell scripts are the glue in this approach.
meillo@36 1245 They make the various parts fit together.
meillo@36 1246 .PP
meillo@45 1247 The history mechanism of uzbl shall be presented as an example.
meillo@36 1248 Uzbl is configured to spawn a script to append an entry to the history
meillo@36 1249 whenever the event of a fully loaded page occurs.
meillo@45 1250 The script to append the entry to the history is not much more than:
meillo@36 1251 .DS
meillo@36 1252 #!/bin/sh
meillo@36 1253 file=/path/to/uzbl-history
meillo@36 1254 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file
meillo@36 1255 .DE
meillo@36 1256 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title.
meillo@45 1257 .PP
meillo@45 1258 For loading an entry, a key is bound to spawn a load-from-history script.
meillo@36 1259 The script reverses the history to have newer entries first,
meillo@45 1260 then displays \fIdmenu\fP to let the user select an item,
meillo@36 1261 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe.
meillo@45 1262 With error checking and corner case handling removed,
meillo@45 1263 the script looks like this:
meillo@36 1264 .DS
meillo@36 1265 #!/bin/sh
meillo@36 1266 file=/path/to/uzbl-history
meillo@36 1267 goto=`tac $file | dmenu | cut -d' ' -f 3`
meillo@36 1268 echo "uri $goto" > $4
meillo@36 1269 .DE
meillo@36 1270 \f(CW$4\fP expands to the path of the command input pipe of the current
meillo@36 1271 uzbl instance.
meillo@32 1272
meillo@32 1273 .PP
meillo@33 1274 .B "Avoid captive user interfaces" .
meillo@54 1275 One could say, that uzbl, to a large extent, actually \fIis\fP
meillo@36 1276 a captive user interface.
meillo@37 1277 But the difference to most other web browsers is, that uzbl is only
meillo@45 1278 the captive user interface frontend (and the core of the backend).
meillo@38 1279 Many parts of the backend are independent of uzbl.
meillo@45 1280 Some are distributed with uzbl, for some external programs,
meillo@45 1281 handler scripts are distributed,
meillo@45 1282 but arbitrary additional functionality can be added if desired.
meillo@37 1283 .PP
meillo@37 1284 The frontend is captive \(en that is true.
meillo@37 1285 This is okay for the task of browsing the web, as this task is only relevant
meillo@37 1286 for humans.
meillo@37 1287 Automated programs would \fIcrawl\fP the web.
meillo@37 1288 That means, they read the source directly.
meillo@37 1289 The source includes all the semantics.
meillo@37 1290 The graphical representation is just for humans to transfer the semantics
meillo@37 1291 more intuitively.
meillo@32 1292
meillo@32 1293 .PP
meillo@33 1294 .B "Make every program a filter" .
meillo@37 1295 Graphical web browsers are almost dead ends in the chain of information flow.
meillo@37 1296 Thus it is difficult to see what graphical web browsers should filter.
meillo@45 1297 Graphical web browsers exist almost only to be interactively used by humans.
meillo@37 1298 The only case when one might want to automate the rendering function is
meillo@37 1299 to generate images of rendered webpages.
meillo@37 1300
meillo@37 1301 .PP
meillo@37 1302 .B "Small is beautiful"
meillo@45 1303 is not easy to apply to a web browser, because modern web technology
meillo@45 1304 is very complex, hence the rendering task is very complex.
meillo@45 1305 Modern web browsers have to consist of many thousand lines of code,
meillo@37 1306 unfortunately.
meillo@37 1307 Using the toolchest approach and wrappers can split the browser into
meillo@37 1308 several small parts, tough.
meillo@37 1309 .PP
meillo@45 1310 As of March 2010, uzbl-core consists of about 3\,500 lines of C code.
meillo@37 1311 The distribution includes another 3\,500 lines of Shell and Python code,
meillo@37 1312 which are the handler scripts and plugins like a modal interface.
meillo@38 1313 Further more, uzbl uses functionality of external tools like
meillo@54 1314 \fIwget\fP and \fIsocat\fP.
meillo@37 1315 Up to this point, uzbl looks pretty neat and small.
meillo@54 1316 The ugly part of uzbl is the web content render engine, webkit.
meillo@37 1317 Webkit consists of roughly 400\,000 (!) lines of code.
meillo@38 1318 Unfortunately, small web render engines are not possible anymore
meillo@38 1319 because of the modern web.
meillo@35 1320
meillo@35 1321 .PP
meillo@35 1322 .B "Build a prototype as soon as possible" .
meillo@35 1323 Plaetinck made his code public, right from the beginning.
meillo@38 1324 Discussion and development was, and still is, open to everyone interested.
meillo@38 1325 Development versions of uzbl can be obtained very simply from the code
meillo@38 1326 repository.
meillo@38 1327 Within the first year of uzbl's existence, a new version was released
meillo@35 1328 more often than once a month.
meillo@38 1329 Different forks and branches arose.
meillo@45 1330 They introduced new features, which were tested for suitability
meillo@45 1331 for the main branch.
meillo@35 1332 The experiences of using prototypes influenced further development.
meillo@35 1333 Actually, all development was community driven.
meillo@38 1334 Plaetinck says, three months after uzbl's birth:
meillo@35 1335 ``Right now I hardly code anything myself for Uzbl.
meillo@35 1336 I just merge in other people's code, ponder a lot, and lead the discussions.''
meillo@35 1337 .[
meillo@44 1338 lwn
meillo@44 1339 uzbl
meillo@35 1340 .]
meillo@32 1341
meillo@0 1342
meillo@48 1343 .H 2 "Problems
meillo@0 1344 .LP
meillo@38 1345 Similar to \s-1MH\s0, uzbl, too suffers from being different.
meillo@38 1346 It is sad, but people use what they know.
meillo@38 1347 Fortunately, uzbl's user interface can look and feel very much the
meillo@38 1348 same as the one of the well known web browsers,
meillo@38 1349 hiding the internal differences.
meillo@38 1350 But uzbl has to provide this similar look and feel to be accepted
meillo@38 1351 as a ``normal'' browser by ``normal'' users.
meillo@37 1352 .PP
meillo@45 1353 Though, the more important problem is the modern web.
meillo@38 1354 The modern web is simply broken.
meillo@38 1355 It has state in a state-less protocol,
meillo@38 1356 it misuses technologies,
meillo@38 1357 and it is helplessly overloaded.
meillo@38 1358 The result are web content render engines that must consist
meillo@38 1359 of hundreds of thousands lines of code.
meillo@38 1360 They also must combine and integrate many different technologies,
meillo@45 1361 only to make our modern web accessible.
meillo@38 1362 Website to image converter are hardly possible to run without
meillo@38 1363 human interaction because of state in sessions, impossible
meillo@38 1364 deep-linking, and unautomatable technologies.
meillo@37 1365 .PP
meillo@38 1366 The web was misused to provide all kinds of imaginable wishes.
meillo@38 1367 Now web browsers, and eventually the users, suffer from it.
meillo@37 1368
meillo@8 1369
meillo@51 1370 .H 2 "Summary
meillo@32 1371 .LP
meillo@38 1372 ``Uzbl is a browser that adheres to the Unix Philosophy'',
meillo@38 1373 that is how uzbl is seen by its authors.
meillo@38 1374 Indeed, uzbl follows the Unix Philosophy in many ways.
meillo@38 1375 It consists of independent parts that work together,
meillo@45 1376 while its core is mainly a mediator which glues the parts together.
meillo@38 1377 .PP
meillo@38 1378 Software leverage can excellently be seen in uzbl.
meillo@45 1379 External tools are used, independent tasks are separated
meillo@45 1380 in independent parts and glued together with small handler scripts.
meillo@38 1381 .PP
meillo@38 1382 As uzbl, more or less, consists of a set of tools and a bit
meillo@38 1383 of glue, anyone can put the parts together and expand it
meillo@38 1384 in any desired way.
meillo@38 1385 Uzbl is very flexible and customizable.
meillo@38 1386 These properties make it valuable for advanced users,
meillo@38 1387 but may keep novice users from using it.
meillo@38 1388 .PP
meillo@45 1389 But uzbl's main problem is the modern web, that makes it hard
meillo@38 1390 to design a sane web browser.
meillo@38 1391 Despite this bad situation, uzbl does a fairly good job.
meillo@32 1392
meillo@8 1393
meillo@48 1394 .H 1 "Final thoughts
meillo@0 1395
meillo@0 1396 .LP
meillo@50 1397 This paper explained why good design is important.
meillo@50 1398 It introduced the Unix Philosophy as guidelines to good design,
meillo@50 1399 in order to create good quality software.
meillo@50 1400 Then, real life software, that was designed with the Unix Philosophy
meillo@50 1401 in mind, was discussed.
meillo@50 1402 .PP
meillo@50 1403 Throughout the paper, the aim was do explain \fIwhy\fP something
meillo@50 1404 should be done the Unix way.
meillo@50 1405 It was tried to give reasons that expose that the Unix Philosophy
meillo@54 1406 is a preferable way for designing software.
meillo@50 1407 .PP
meillo@50 1408 The Unix Philosophy is close to the software developer's point of view.
meillo@50 1409 Its main goal is taming the beast ``software complexity''.
meillo@50 1410 Hence it strives first and foremost for simplicity, of software.
meillo@50 1411 It might appear, that usability for people is a minor goal.
meillo@50 1412 Actually, the Unix Philosophy sees usability as a result of sound design.
meillo@50 1413 Sound design does not need to be most intuitive,
meillo@50 1414 but it will provide a consistent way to access the enormous power
meillo@50 1415 of software leverage.
meillo@50 1416 .PP
meillo@50 1417 Being able to solve some concrete problem becomes less and less important,
meillo@50 1418 as there is software available for nearly every possible task today.
meillo@50 1419 But the quality of software matters.
meillo@50 1420 It is important that we have \fIgood\fP software.
meillo@50 1421 .sp
meillo@0 1422 .LP
meillo@50 1423 .B "But why the Unix Philosophy?
meillo@50 1424 .PP
meillo@50 1425 The largest problem of software development is the complexity involved.
meillo@50 1426 It is the only part of the job that computers cannot take over.
meillo@50 1427 The Unix Philosophy fights complexity as main enemy.
meillo@50 1428 .PP
meillo@50 1429 On the other hand,
meillo@50 1430 the most unique gain of software is its ability to leverage.
meillo@50 1431 Current software still fails to make the best possible use of this ability.
meillo@50 1432 The Unix Philosophy concentrates much on exploiting this great opportunity.
meillo@0 1433
meillo@47 1434
meillo@47 1435 .bp
meillo@47 1436 .TL
meillo@47 1437 References
meillo@47 1438 .LP
meillo@47 1439 .XS
meillo@47 1440 .sp .5v
meillo@47 1441 .B
meillo@47 1442 References
meillo@47 1443 .XE
meillo@47 1444 .ev r
meillo@42 1445 .nr PS -1
meillo@42 1446 .nr VS -1
meillo@0 1447 .[
meillo@0 1448 $LIST$
meillo@0 1449 .]
meillo@47 1450 .nr PS +1
meillo@47 1451 .nr VS +1
meillo@47 1452 .ev
meillo@47 1453
meillo@42 1454 .bp
meillo@47 1455 .TL
meillo@47 1456 Table of Contents
meillo@47 1457 .LP
meillo@47 1458 .PX no