Mercurial > docs > unix-phil
comparison unix-phil.ms @ 45:ade392f024aa
a lot of rework throughout the whole document
author | meillo@marmaro.de |
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date | Mon, 12 Apr 2010 09:33:01 +0200 |
parents | 46e34e433231 |
children | 98a1446744c7 |
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20 .if '\\$1'1' .nr PS +2 | 20 .if '\\$1'1' .nr PS +2 |
21 ._N \\$1 | 21 ._N \\$1 |
22 .if '\\$1'1' .nr PS -2 | 22 .if '\\$1'1' .nr PS -2 |
23 .. | 23 .. |
24 | 24 |
25 .am QP | |
26 .ps -1 | |
27 .. | |
28 | |
25 .\"---------------------------------------- | 29 .\"---------------------------------------- |
26 | 30 |
27 .TL | 31 .TL |
28 .ps +4 | 32 .ps +4 |
29 Why the Unix Philosophy still matters | 33 Why the Unix Philosophy still matters |
63 .[ | 67 .[ |
64 wikipedia | 68 wikipedia |
65 unix philosophy | 69 unix philosophy |
66 .] | 70 .] |
67 .QP | 71 .QP |
68 .ps -1 | |
69 The \fIUnix philosophy\fP is a set of cultural norms and philosophical | 72 The \fIUnix philosophy\fP is a set of cultural norms and philosophical |
70 approaches to developing software based on the experience of leading | 73 approaches to developing software based on the experience of leading |
71 developers of the Unix operating system. | 74 developers of the Unix operating system. |
72 .PP | 75 .PP |
73 As there is no single definition of the Unix Philosophy, | 76 As there is no single definition of the Unix Philosophy, |
96 Especially, the main concepts are similar in all of them. | 99 Especially, the main concepts are similar in all of them. |
97 McIlroy's definition can surely be called the core of the Unix Philosophy, | 100 McIlroy's definition can surely be called the core of the Unix Philosophy, |
98 but the fundamental idea behind it all, is ``small is beautiful''. | 101 but the fundamental idea behind it all, is ``small is beautiful''. |
99 | 102 |
100 .PP | 103 .PP |
101 The Unix Philosophy tells how to design and write good software for Unix. | 104 The Unix Philosophy explains how to design good software for Unix. |
102 Many concepts described here base on facilities of Unix. | 105 Many concepts described here, base on facilities of Unix. |
103 Other operating systems may not offer such facilities, | 106 Other operating systems may not offer such facilities, |
104 hence it may not be possible to design software in the way of the | 107 hence it may not be possible to design software in the way of the |
105 Unix Philosophy for them. | 108 Unix Philosophy for them. |
106 .PP | 109 .PP |
107 The Unix Philosophy has an idea of how the process of software development | 110 The Unix Philosophy has an idea of how the process of software development |
108 should look like, but large parts of the philosophy are quite independent | 111 should look like, but large parts of the philosophy are quite independent |
109 from the development process used. | 112 from a concrete development process. |
110 However, one will soon recognize that some development processes work well | 113 However, one will soon recognize that some development processes work well |
111 with the ideas of the Unix Philosophy and support them, while others are | 114 with the ideas of the Unix Philosophy and support them, while others are |
112 at cross-purposes. | 115 at cross-purposes. |
113 Kent Beck's books about Extreme Programming are valuable supplimental | 116 Kent Beck's books about Extreme Programming are valuable supplemental |
114 resources. | 117 resources on this topic. |
115 .PP | 118 .PP |
116 The question of how to actually write code and how the code should looks | 119 The question of how to actually write code and how the code should looks |
117 like internally, are out of focus here. | 120 like in detail, are out of focus here. |
118 ``The Practice of Programming'' by Kernighan and Pike, | 121 ``The Practice of Programming'' by Kernighan and Pike, |
119 .[ | 122 .[ |
120 kernighan pike | 123 kernighan pike |
121 practice of programming | 124 practice of programming |
122 .] | 125 .] |
133 Software design is the planning of how the internal structure | 136 Software design is the planning of how the internal structure |
134 and external interfaces of a software should look like. | 137 and external interfaces of a software should look like. |
135 It has nothing to do with visual appearance. | 138 It has nothing to do with visual appearance. |
136 If we take a program as a car, then its color is of no matter. | 139 If we take a program as a car, then its color is of no matter. |
137 Its design would be the car's size, its shape, the locations of doors, | 140 Its design would be the car's size, its shape, the locations of doors, |
138 the passenger/space ratio, the luggage capacity, and so forth. | 141 the passenger/space ratio, the available controls and instruments, |
142 and so forth. | |
139 .PP | 143 .PP |
140 Why should software get designed at all? | 144 Why should software get designed at all? |
141 It is general knowledge, that even a bad plan is better than no plan. | 145 It is general knowledge, that even a bad plan is better than no plan. |
142 Not designing software means programming without plan. | 146 Not designing software means programming without plan. |
143 This will pretty sure lead to horrible results. | 147 This will pretty sure lead to horrible results. |
144 Horrible to use and horrible to maintain. | 148 Software that is horrible to use and horrible to maintain. |
145 These two aspects are the visible ones. | 149 These two aspects are the visible ones. |
146 Often invisible are the wasted possible gains. | 150 Often invisible though, are the wasted possible gains. |
147 Good software design can make these gains available. | 151 Good software design can make these gains available. |
148 .PP | 152 .PP |
149 A software's design deals with quality properties. | 153 A software's design deals with quality properties. |
150 Good design leads to good quality, and quality is important. | 154 Good design leads to good quality, and quality is important. |
151 Any car may be able to drive from A to B, | 155 Any car may be able to drive from A to B, |
164 Someone has a problem and needs a tool to solve it. | 168 Someone has a problem and needs a tool to solve it. |
165 Being able to solve the problem is the main functional goal. | 169 Being able to solve the problem is the main functional goal. |
166 It is the driving force behind all programming effort. | 170 It is the driving force behind all programming effort. |
167 Functional requirements are easier to define and to verify. | 171 Functional requirements are easier to define and to verify. |
168 .IP \(bu | 172 .IP \(bu |
169 Non-functional requirements are also called \fIquality\fP requirements. | 173 Non-functional requirements are called \fIquality\fP requirements, too. |
170 The quality of a software are the properties that are not directly related to | 174 The quality of a software are the properties that are not directly related to |
171 the software's basic functions. | 175 the software's basic functions. |
172 Tools of bad quality often solve the problems they were written for, | 176 Tools of bad quality often do solve the problems they were written for, |
173 but introduce problems and difficulties for usage and development, later on. | 177 but introduce problems and difficulties for usage and development, later on. |
174 Quality aspects are often overlooked at first sight, | 178 Quality aspects are often overlooked at first sight, |
175 and they are often difficult to define clearly and to verify. | 179 and are often difficult to define clearly and to verify. |
176 .PP | 180 .PP |
177 Quality is of few matter when the software gets built initially, | 181 Quality is hardly interesting when the software gets built initially, |
178 but it is of matter for usage and maintenance of the software. | 182 but it has a high impact on usability and maintenance of the software, later. |
179 A short-sighted might see in developing a software mainly building something up. | 183 A short-sighted might see in developing a software, mainly building something up. |
180 But experience shows, that building the software the first time is | 184 But experience shows, that building the software the first time is |
181 only a small amount of the overall work. | 185 only a small amount of the overall work. |
182 Bug fixing, extending, rebuilding of parts | 186 Bug fixing, extending, rebuilding of parts \(en maintenance work \(en |
183 \(en maintenance work, for short \(en | |
184 does soon take over the major part of the time spent on a software. | 187 does soon take over the major part of the time spent on a software. |
185 Not to forget the usage of the software. | 188 And of course, the time spent actually using the software. |
186 These processes are highly influenced by the software's quality. | 189 These processes are highly influenced by the software's quality. |
187 Thus, quality must not be neglected. | 190 Thus, quality must not be neglected. |
188 The problem with quality is that you hardly ``stumble over'' | 191 However, the problem with quality is that you hardly ``stumble over'' |
189 bad quality during the first build, | 192 bad quality during the first build, |
190 but this is the time when you should care about good quality most. | 193 although this is the time when you should care about good quality most. |
191 .PP | 194 .PP |
192 Software design is less the basic function of a software \(en | 195 Software design has little to do with the basic function of a software \(en |
193 this requirement will get satisfied anyway. | 196 this requirement will get satisfied anyway. |
194 Software design is more about quality aspects of the software. | 197 Software design is more about quality aspects of the software. |
195 Good design leads to good quality, bad design to bad quality. | 198 Good design leads to good quality, bad design to bad quality. |
196 The primary functions of the software will be affected modestly by bad quality, | 199 The primary functions of the software will be affected modestly by bad quality, |
197 but good quality can provide a lot of additional gain, | 200 but good quality can provide a lot of additional gain, |
198 even at places where one never expected it. | 201 even at places where one never expected it. |
199 .PP | 202 .PP |
200 The ISO/IEC 9126-1 standard, part 1, | 203 The ISO/IEC\|9126-1 standard, part\|1, |
201 .[ | 204 .[ |
202 iso product quality | 205 iso product quality |
203 .] | 206 .] |
204 defines the quality model as consisting out of: | 207 defines the quality model as consisting out of: |
205 .IP \(bu | 208 .IP \(bu |
220 .IP \(bu | 223 .IP \(bu |
221 .I Portability | 224 .I Portability |
222 (adaptability, installability, co-existence, replaceability) | 225 (adaptability, installability, co-existence, replaceability) |
223 .LP | 226 .LP |
224 Good design can improve these properties of a software, | 227 Good design can improve these properties of a software, |
225 bad designed software probably suffers from not having them. | 228 bad designed software likely suffers in these points. |
226 .PP | 229 .PP |
227 One further goal of software design is consistency. | 230 One further goal of software design is consistency. |
228 Consistency eases understanding, working on, and using things. | 231 Consistency eases understanding, working on, and using things. |
229 Consistent internal structure and consistent interfaces to the outside | 232 Consistent internal structure and consistent interfaces to the outside |
230 can be provided by good design. | 233 can be provided by good design. |
231 .PP | 234 .PP |
232 Software should be well designed because good design avoids many | 235 Software should be well designed because good design avoids many |
233 problems during the software's lifetime. | 236 problems during a software's lifetime. |
234 And software should be well designed because good design can offer | 237 And software should be well designed because good design can offer |
235 much additional gain. | 238 much additional gain. |
236 Indeed, much effort should be spent into good design to make software more valuable. | 239 Indeed, much effort should be spent into good design to make software more valuable. |
237 The Unix Philosophy shows a way of how to design software well. | 240 The Unix Philosophy shows a way of how to design software well. |
238 It offers guidelines to achieve good quality and high gain for the effort spent. | 241 It offers guidelines to achieve good quality and high gain for the effort spent. |
277 .ps -1 | 280 .ps -1 |
278 ls | grep -v foo | wc -l | 281 ls | grep -v foo | wc -l |
279 .DE | 282 .DE |
280 Here, the list of files is filtered by | 283 Here, the list of files is filtered by |
281 .CW grep | 284 .CW grep |
282 to remove all that contain ``foo''. | 285 to remove all lines that contain ``foo''. |
283 The rest is the same as in the previous example. | 286 The rest equals the previous example. |
284 .PP | 287 .PP |
285 Finding the five largest entries in the current directory. | 288 Finding the five largest entries in the current directory. |
286 .DS | 289 .DS |
287 .CW | 290 .CW |
288 .ps -1 | 291 .ps -1 |
289 du -s * | sort -nr | sed 5q | 292 du -s * | sort -nr | sed 5q |
290 .DE | 293 .DE |
291 .CW "du -s * | 294 .CW "du -s * |
292 returns the recursively summed sizes of all files | 295 returns the recursively summed sizes of all files in the current directory |
293 \(en no matter if they are regular files or directories. | 296 \(en no matter if they are regular files or directories. |
294 .CW "sort -nr | 297 .CW "sort -nr |
295 sorts the list numerically in reverse order. | 298 sorts the list numerically in reverse order (descending). |
296 Finally, | 299 Finally, |
297 .CW "sed 5q | 300 .CW "sed 5q |
298 quits after it has printed the fifth line. | 301 quits after it has printed the fifth line. |
299 .PP | 302 .PP |
300 The presented command lines are examples of what Unix people would use | 303 The presented command lines are examples of what Unix people would use |
308 .PP | 311 .PP |
309 Pipes, and their extensive and easy use, are one of the great | 312 Pipes, and their extensive and easy use, are one of the great |
310 achievements of the Unix system. | 313 achievements of the Unix system. |
311 Pipes between programs have been possible in earlier operating systems, | 314 Pipes between programs have been possible in earlier operating systems, |
312 but it has never been a so central part of the concept. | 315 but it has never been a so central part of the concept. |
313 When, in the early seventies, Doug McIlroy introduced pipes for the | 316 When, in the early seventies, Doug McIlroy introduced pipes into the |
314 Unix system, | 317 Unix system, |
315 ``it was this concept and notation for linking several programs together | 318 ``it was this concept and notation for linking several programs together |
316 that transformed Unix from a basic file-sharing system to an entirely new way of computing.'' | 319 that transformed Unix from a basic file-sharing system to an entirely new way of computing.'' |
317 .[ | 320 .[ |
318 aughenbaugh | 321 aughenbaugh |
319 unix oral history | 322 unix oral history |
320 .] | 323 .] |
321 .PP | 324 .PP |
322 Being able to specify pipelines in an easy way is, | 325 Being able to specify pipelines in an easy way is, |
323 however, not enough by itself. | 326 however, not enough by itself. |
324 It is only one half. | 327 It is only one half. |
325 The other is the design of the programs that are used in the pipeline. | 328 The other is the design of the programs that are used in the pipeline. |
326 They have to interfaces that allows them to be used in such a way. | 329 They need interfaces that allow them to be used in such a way. |
327 | 330 |
328 .NH 2 | 331 .NH 2 |
329 Interface design | 332 Interface design |
330 .XS | 333 .XS |
331 \*(SN Interface design | 334 \*(SN Interface design |
332 .XE | 335 .XE |
333 .LP | 336 .LP |
334 Unix is, first of all, simple \(en Everything is a file. | 337 Unix is, first of all, simple \(en Everything is a file. |
335 Files are sequences of bytes, without any special structure. | 338 Files are sequences of bytes, without any special structure. |
336 Programs should be filters, which read a stream of bytes from ``standard input'' (stdin) | 339 Programs should be filters, which read a stream of bytes from standard input (stdin) |
337 and write a stream of bytes to ``standard output'' (stdout). | 340 and write a stream of bytes to standard output (stdout). |
338 .PP | |
339 If the files \fIare\fP sequences of bytes, | 341 If the files \fIare\fP sequences of bytes, |
340 and the programs \fIare\fP filters on byte streams, | 342 and the programs \fIare\fP filters on byte streams, |
341 then there is exactly one standardized data interface. | 343 then there is exactly one data interface. |
342 Thus it is possible to combine them in any desired way. | 344 Hence it is possible to combine programs in any desired way. |
343 .PP | 345 .PP |
344 Even a handful of small programs will yield a large set of combinations, | 346 Even a handful of small programs yields a large set of combinations, |
345 and thus a large set of different functions. | 347 and thus a large set of different functions. |
346 This is leverage! | 348 This is leverage! |
347 If the programs are orthogonal to each other \(en the best case \(en | 349 If the programs are orthogonal to each other \(en the best case \(en |
348 then the set of different functions is greatest. | 350 then the set of different functions is greatest. |
349 .PP | 351 .PP |
350 Programs might also have a separate control interface, | 352 Programs can also have a separate control interface, |
351 besides their data interface. | 353 besides their data interface. |
352 The control interface is often called ``user interface'', | 354 The control interface is often called ``user interface'', |
353 because it is usually designed to be used by humans. | 355 because it is usually designed to be used by humans. |
354 The Unix Philosophy discourages to assume the user to be human. | 356 The Unix Philosophy discourages to assume the user to be human. |
355 Interactive use of software is slow use of software, | 357 Interactive use of software is slow use of software, |
356 because the program waits for user input most of the time. | 358 because the program waits for user input most of the time. |
357 Interactive software requires the user to be in front of the computer | 359 Interactive software requires the user to be in front of the computer. |
358 all the time. | |
359 Interactive software occupy the user's attention while they are running. | 360 Interactive software occupy the user's attention while they are running. |
360 .PP | 361 .PP |
361 Now we come back to the idea of using several small programs, combined, | 362 Now to come back to the idea of combining several small programs, |
362 to have a more specific function. | 363 to have a more specific function. |
363 If these single tools would all be interactive, | 364 If these single tools would all be interactive, |
364 how would the user control them? | 365 how would the user control them? |
365 It is not only a problem to control several programs at once if they run at the same time, | 366 It is not only a problem to control several programs at once, |
367 if they run at the same time, | |
366 it also very inefficient to have to control each of the single programs | 368 it also very inefficient to have to control each of the single programs |
367 that are intended to work as one large program. | 369 that are intended to act as one large program. |
368 Hence, the Unix Philosophy discourages programs to demand interactive use. | 370 Hence, the Unix Philosophy discourages programs to demand interactive use. |
369 The behavior of programs should be defined at invocation. | 371 The behavior of programs should be defined at invocation. |
370 This is done by specifying arguments (``command line switches'') to the program call. | 372 This is done by specifying arguments to the program call |
373 (command line switches). | |
371 Gancarz discusses this topic as ``avoid captive user interfaces''. | 374 Gancarz discusses this topic as ``avoid captive user interfaces''. |
372 .[ | 375 .[ |
373 gancarz unix philosophy | 376 gancarz unix philosophy |
374 %P 88 ff. | 377 %P 88 ff. |
375 .] | 378 .] |
400 It is easier and less error-prone to write small programs. | 403 It is easier and less error-prone to write small programs. |
401 It is also easier and less error-prone to write a large set of small programs, | 404 It is also easier and less error-prone to write a large set of small programs, |
402 than to write one large program with all the functionality included. | 405 than to write one large program with all the functionality included. |
403 If the small programs are combinable, then they offer even a larger set | 406 If the small programs are combinable, then they offer even a larger set |
404 of functions than the single large program. | 407 of functions than the single large program. |
405 Hence, one gets two advantages out of writing small, combinable programs. | 408 Hence, one gets two advantages out of writing small, combinable programs: |
406 .PP | 409 They are easier to write and they offer a greater set of functions through |
407 There are two drawbacks of the toolchest approach. | 410 combination. |
408 First, one simple, standardized, unidirectional interface has to be sufficient. | 411 .PP |
412 But there are also two main drawbacks of the toolchest approach. | |
413 First, one simple, standardized interface has to be sufficient. | |
409 If one feels the need for more ``logic'' than a stream of bytes, | 414 If one feels the need for more ``logic'' than a stream of bytes, |
410 then a different approach might be of need. | 415 then a different approach might be of need. |
411 But it is also possible, that he just can not imagine a design where | 416 But it is also possible, that he just can not imagine a design where |
412 a stream of bytes is sufficient. | 417 a stream of bytes is sufficient. |
413 By becoming more familiar with the ``Unix style of thinking'', | 418 By becoming more familiar with the ``Unix style of thinking'', |
414 developers will more often and easier find simple designs where | 419 developers will more often and easier find simple designs where |
415 a stream of bytes is a sufficient interface. | 420 a stream of bytes is a sufficient interface. |
416 .PP | 421 .PP |
417 The second drawback of a toolchest affects the users. | 422 The second drawback of a toolchest affects the users. |
418 A toolchest is often more difficult to use for novices. | 423 A toolchest is often more difficult to use. |
419 It is necessary to become familiar with each of the tools, | 424 It is necessary to become familiar with each of the tools, |
420 to be able to use the right one in a given situation. | 425 to be able to use the right one in a given situation. |
421 Additionally, one needs to combine the tools in a senseful way on its own. | 426 Additionally, one needs to combine the tools in a senseful way himself. |
422 This is like a sharp knife \(en it is a powerful tool in the hand of a master, | 427 This is like a sharp knife \(en it is a powerful tool in the hand of a |
423 but of no good value in the hand of an unskilled. | 428 master, but of no good value in the hand of an unskilled. |
424 .PP | 429 However, learning single, small tools of a toolchest is easier than |
425 However, learning single, small tool of the toolchest is easier than | |
426 learning a complex tool. | 430 learning a complex tool. |
427 The user will have a basic understanding of a yet unknown tool, | 431 And the user will already have a basic understanding of a yet unknown tool, |
428 if the several tools of the toolchest have a common style. | 432 if the tools of a toolchest have a common, consistent style. |
429 He will be able to transfer knowledge over one tool to another. | 433 He will be able to transfer knowledge over from one tool to another. |
430 .PP | 434 .PP |
431 Moreover, the second drawback can be removed easily by adding wrappers | 435 Moreover, the second drawback can be removed to a large extend |
432 around the single tools. | 436 by adding wrappers around the basic tools. |
433 Novice users do not need to learn several tools if a professional wraps | 437 Novice users do not need to learn several tools, if a professional wraps |
434 the single commands into a more high-level script. | 438 complete command lines into a higher-level script. |
435 Note that the wrapper script still calls the small tools; | 439 Note that the wrapper script still calls the small tools; |
436 the wrapper script is just like a skin around. | 440 it is just like a skin around them. |
437 No complexity is added this way, | 441 No complexity is added this way. |
438 but new programs can get created out of existing one with very low effort. | 442 But new programs can get created out of existing one with very low effort. |
439 .PP | 443 .PP |
440 A wrapper script for finding the five largest entries in the current directory | 444 A wrapper script for finding the five largest entries in the current directory |
441 could look like this: | 445 could look like this: |
442 .DS | 446 .DS |
443 .CW | 447 .CW |
444 .ps -1 | 448 .ps -1 |
445 #!/bin/sh | 449 #!/bin/sh |
446 du -s * | sort -nr | sed 5q | 450 du -s * | sort -nr | sed 5q |
447 .DE | 451 .DE |
448 The script itself is just a text file that calls the command line | 452 The script itself is just a text file that calls the command line, |
449 a professional user would type in directly. | 453 which a professional user would type in directly. |
450 Making the program flexible on the number of entries it prints, | 454 It is probably worth to make the program flexible on the number of |
451 is easily possible: | 455 entries it prints: |
452 .DS | 456 .DS |
453 .CW | 457 .CW |
454 .ps -1 | 458 .ps -1 |
455 #!/bin/sh | 459 #!/bin/sh |
456 num=5 | 460 num=5 |
457 [ $# -eq 1 ] && num="$1" | 461 [ $# -eq 1 ] && num="$1" |
458 du -sh * | sort -nr | sed "${num}q" | 462 du -sh * | sort -nr | sed "${num}q" |
459 .DE | 463 .DE |
460 This script acts like the one before, when called without an argument. | 464 This script acts like the one before, when called without an argument. |
461 But one can also specify a numerical argument to define the number of lines to print. | 465 But one can also specify a numerical argument to define the number of lines to print. |
466 One can surely imagine even more flexible versions, however, | |
467 they will still relay on the external programs, | |
468 which do the actual work. | |
462 | 469 |
463 .NH 2 | 470 .NH 2 |
464 A powerful shell | 471 A powerful shell |
465 .XS | 472 .XS |
466 \*(SN A powerful shell | 473 \*(SN A powerful shell |
467 .XE | 474 .XE |
468 .LP | 475 .LP |
469 It was already said, that the Unix shell provides the possibility to | 476 The Unix shell provides the possibility to combine small programs into large ones. |
470 combine small programs into large ones easily. | 477 But a powerful shell is a great feature in other ways, too. |
471 A powerful shell is a great feature in other ways, too. | 478 For instance by being scriptable. |
472 .PP | 479 Control statements are build into the shell. |
473 For instance by including a scripting language. | 480 The functions, however, are the normal programs of the system. |
474 The control statements are build into the shell. | 481 Thus, as the programs are already known, |
475 The functions, however, are the normal programs, everyone can use on the system. | 482 learning to program in the shell becomes easy. |
476 Thus, the programs are known, so learning to program in the shell is easy. | |
477 Using normal programs as functions in the shell programming language | 483 Using normal programs as functions in the shell programming language |
478 is only possible because they are small and combinable tools in a toolchest style. | 484 is only possible because they are small and combinable tools in a toolchest style. |
479 .PP | 485 .PP |
480 The Unix shell encourages to write small scripts out of other programs, | 486 The Unix shell encourages to write small scripts, |
481 because it is so easy to do. | 487 by combining existing programs, because it is so easy to do. |
482 This is a great step towards automation. | 488 This is a great step towards automation. |
483 It is wonderful if the effort to automate a task equals the effort | 489 It is wonderful if the effort to automate a task equals the effort |
484 it takes to do it the second time by hand. | 490 to do the task a second time by hand. |
485 If it is so, then the user will be happy to automate everything he does more than once. | 491 If this holds, |
492 then the user will be happy to automate everything he does more than once. | |
486 .PP | 493 .PP |
487 Small programs that do one job well, standardized interfaces between them, | 494 Small programs that do one job well, standardized interfaces between them, |
488 a mechanism to combine parts to larger parts, and an easy way to automate tasks, | 495 a mechanism to combine parts to larger parts, and an easy way to automate tasks, |
489 this will inevitably produce software leverage. | 496 this will inevitably produce software leverage. |
490 Getting multiple times the benefit of an investment is a great offer. | 497 Getting multiple times the benefit of an investment is a great offer. |
491 .PP | 498 .PP |
492 The shell also encourages rapid prototyping. | 499 The shell also encourages rapid prototyping. |
493 Many well known programs started as quickly hacked shell scripts, | 500 Many well known programs started as quickly hacked shell scripts, |
494 and turned into ``real'' programs, written in C, later. | 501 and turned into ``real'' programs, written in C, later. |
495 Building a prototype first is a way to avoid the biggest problems | 502 Building a prototype first, is a way to avoid the biggest problems |
496 in application development. | 503 in application development. |
497 Fred Brooks writes in ``No Silver Bullet'': | 504 Fred Brooks explains in ``No Silver Bullet'': |
498 .[ | 505 .[ |
499 brooks | 506 brooks |
500 no silver bullet | 507 no silver bullet |
501 .] | 508 .] |
502 .QP | 509 .QP |
503 .ps -1 | |
504 The hardest single part of building a software system is deciding precisely what to build. | 510 The hardest single part of building a software system is deciding precisely what to build. |
505 No other part of the conceptual work is so difficult as establishing the detailed | 511 No other part of the conceptual work is so difficult as establishing the detailed |
506 technical requirements, [...]. | 512 technical requirements, [...]. |
507 No other part of the work so cripples the resulting system if done wrong. | 513 No other part of the work so cripples the resulting system if done wrong. |
508 No other part is more difficult to rectify later. | 514 No other part is more difficult to rectify later. |
509 .PP | 515 .PP |
510 Writing a prototype is a great method to become familiar with the requirements | 516 Writing a prototype is a great method for becoming familiar with the requirements |
511 and to actually run into real problems. | 517 and to run into real problems early. |
512 Today, prototyping is often seen as a first step in building a software. | 518 .PP |
519 Prototyping is often seen as a first step in building a software. | |
513 This is, of course, good. | 520 This is, of course, good. |
514 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping: | 521 However, the Unix Philosophy has an \fIadditional\fP perspective on prototyping: |
515 After having built the prototype, one might notice, that the prototype is already | 522 After having built the prototype, one might notice, that the prototype is already |
516 \fIgood enough\fP. | 523 \fIgood enough\fP. |
517 Hence, no reimplementation, in a more sophisticated programming language, might be of need, | 524 Hence, no reimplementation, in a more sophisticated programming language, |
518 for the moment. | 525 might be of need, at least for the moment. |
519 Maybe later, it might be necessary to rewrite the software, but not now. | 526 Maybe later, it might be necessary to rewrite the software, but not now. |
520 .PP | 527 By delaying further work, one keeps the flexibility to react on |
521 By delaying further work, one keeps the flexibility to react easily on | |
522 changing requirements. | 528 changing requirements. |
523 Software parts that are not written will not miss the requirements. | 529 Software parts that are not written will not miss the requirements. |
524 | 530 |
525 .NH 2 | 531 .NH 2 |
526 Worse is better | 532 Worse is better |
527 .XS | 533 .XS |
528 \*(SN Worse is better | 534 \*(SN Worse is better |
529 .XE | 535 .XE |
530 .LP | 536 .LP |
531 The Unix Philosophy aims for the 80% solution; | 537 The Unix Philosophy aims for the 90% solution; |
532 others call it the ``Worse is better'' approach. | 538 others call it the ``Worse is better'' approach. |
533 .PP | 539 Practical experience shows, that: |
534 First, practical experience shows, that it is almost never possible to define the | 540 .PP |
541 (1) It is almost never possible to define the | |
535 requirements completely and correctly the first time. | 542 requirements completely and correctly the first time. |
536 Hence one should not try to; it will fail anyway. | 543 Hence one should not try to; one will fail anyway. |
537 Second, practical experience shows, that requirements change during time. | 544 .PP |
545 (2) Requirements change during time. | |
538 Hence it is best to delay requirement-based design decisions as long as possible. | 546 Hence it is best to delay requirement-based design decisions as long as possible. |
539 Also, the software should be small and flexible as long as possible | 547 The software should be small and flexible as long as possible |
540 to react on changing requirements. | 548 to react on changing requirements. |
541 Shell scripts, for example, are more easily adjusted as C programs. | 549 Shell scripts, for example, are more easily adjusted as C programs. |
542 Third, practical experience shows, that maintenance is hard work. | 550 .PP |
543 Hence, one should keep the amount of software as small as possible; | 551 (3) Maintenance work is hard work. |
552 Hence, one should keep the amount of code as small as possible; | |
544 it should just fulfill the \fIcurrent\fP requirements. | 553 it should just fulfill the \fIcurrent\fP requirements. |
545 Software parts that will be written later, do not need maintenance now. | 554 Software parts that will be written in future, |
555 do not need maintenance till then. | |
546 .PP | 556 .PP |
547 Starting with a prototype in a scripting language has several advantages: | 557 Starting with a prototype in a scripting language has several advantages: |
548 .IP \(bu | 558 .IP \(bu |
549 As the initial effort is low, one will likely start right away. | 559 As the initial effort is low, one will likely start right away. |
550 .IP \(bu | 560 .IP \(bu |
551 As working parts are available soon, the real requirements can get identified soon. | 561 As working parts are available soon, the real requirements can get identified soon. |
552 .IP \(bu | 562 .IP \(bu |
553 When a software is usable, it gets used, and thus tested. | 563 When a software is usable and valuable, it gets used, and thus tested. |
554 Hence problems will be found at early stages of the development. | 564 Hence problems will be found at early stages of the development. |
555 .IP \(bu | 565 .IP \(bu |
556 The prototype might be enough for the moment, | 566 The prototype might be enough for the moment, |
557 thus further work on the software can be delayed to a time | 567 thus further work on the software can get delayed to a time |
558 when one knows better about the requirements and problems, | 568 when one knows better about the requirements and problems, |
559 than now. | 569 than now. |
560 .IP \(bu | 570 .IP \(bu |
561 Implementing now only the parts that are actually needed now, | 571 Implementing now only the parts that are actually needed at the moment, |
562 requires fewer maintenance work. | 572 introduces fewer programming and maintenance work. |
563 .IP \(bu | 573 .IP \(bu |
564 If the global situation changes so that the software is not needed anymore, | 574 If the global situation changes so that the software is not needed anymore, |
565 then less effort was spent into the project, than it would have be | 575 then less effort was spent into the project, than it would have be |
566 when a different approach had been used. | 576 when a different approach had been used. |
567 | 577 |
573 .LP | 583 .LP |
574 So far it was talked about \fIwriting\fP or \fIbuilding\fP software. | 584 So far it was talked about \fIwriting\fP or \fIbuilding\fP software. |
575 Although these are just verbs, they do imply a specific view on the work process | 585 Although these are just verbs, they do imply a specific view on the work process |
576 they describe. | 586 they describe. |
577 The better verb, however, is to \fIgrow\fP. | 587 The better verb, however, is to \fIgrow\fP. |
578 .PP | |
579 Creating software in the sense of the Unix Philosophy is an incremental process. | 588 Creating software in the sense of the Unix Philosophy is an incremental process. |
580 It starts with a first prototype, which evolves as requirements change. | 589 It starts with a first prototype, which evolves as requirements change. |
581 A quickly hacked shell script might become a large, sophisticated, | 590 A quickly hacked shell script might become a large, sophisticated, |
582 compiled program this way. | 591 compiled program this way. |
583 Its lifetime begins with the initial prototype and ends when the software is not used anymore. | 592 Its lifetime begins with the initial prototype and ends when the software is not used anymore. |
584 While being alive it will get extended, rearranged, rebuilt (from scratch). | 593 While being alive it will get extended, rearranged, rebuilt. |
585 Growing software matches the view that ``software is never finished. It is only released.'' | 594 Growing software matches the view that ``software is never finished. It is only released.'' |
586 .[ | 595 .[ |
587 gancarz | 596 gancarz |
588 unix philosophy | 597 unix philosophy |
589 %P 26 | 598 %P 26 |
626 (2) | 635 (2) |
627 .I "Portability of data | 636 .I "Portability of data |
628 is best achieved by avoiding binary representations | 637 is best achieved by avoiding binary representations |
629 to store data, because binary representations differ from machine to machine. | 638 to store data, because binary representations differ from machine to machine. |
630 Textual representation is favored. | 639 Textual representation is favored. |
631 Historically, ASCII was the charset of choice. | 640 Historically, \s-1ASCII\s0 was the charset of choice. |
632 In the future, UTF-8 might be the better choice, however. | 641 For the future, \s-1UTF\s0-8 might be the better choice. |
633 Important is that it is a plain text representation in a | 642 Important is that it is a plain text representation in a |
634 very common charset encoding. | 643 very common charset encoding. |
635 Apart from being able to transfer data between machines, | 644 Apart from being able to transfer data between machines, |
636 readable data has the great advantage, that humans are able | 645 readable data has the great advantage, that humans are able to directly |
637 to directly edit it with text editors and other tools from the Unix toolchest. | 646 read and edit it with text editors and other tools from the Unix toolchest. |
638 .\" gancarz tenet 5 | 647 .\" gancarz tenet 5 |
639 .PP | 648 .PP |
640 (3) | 649 (3) |
641 A large | 650 A large |
642 .I "range of usability | 651 .I "range of usability |
643 ensures good adaptation, and thus good survival. | 652 ensures good adaptation, and thus good survival. |
644 It is a special distinction if a software becomes used in fields of action, | 653 It is a special distinction if a software becomes used in fields of action, |
645 the original authors did never imagine. | 654 the original authors did never imagine. |
646 Software that solves problems in a general way will likely be used | 655 Software that solves problems in a general way will likely be used |
647 for all kinds of similar problems. | 656 for many kinds of similar problems. |
648 Being too specific limits the range of uses. | 657 Being too specific limits the range of usability. |
649 Requirements change through time, thus use cases change or even vanish. | 658 Requirements change through time, thus use cases change or even vanish. |
650 A good example in this point is Allman's sendmail. | 659 As a good example in this point, |
651 Allman identifies flexibility to be one major reason for sendmail's success: | 660 Allman identifies flexibility to be one major reason for sendmail's success: |
652 .[ | 661 .[ |
653 allman | 662 allman |
654 sendmail | 663 sendmail |
655 .] | 664 .] |
656 .QP | 665 .QP |
657 .ps -1 | |
658 Second, I limited myself to the routing function [...]. | 666 Second, I limited myself to the routing function [...]. |
659 This was a departure from the dominant thought of the time, [...]. | 667 This was a departure from the dominant thought of the time, [...]. |
660 .QP | 668 .QP |
661 .ps -1 | 669 Third, the sendmail configuration file was flexible enough to adapt |
662 Third, the sendmail configuration file was flexible enough to adopt | |
663 to a rapidly changing world [...]. | 670 to a rapidly changing world [...]. |
664 .LP | 671 .LP |
665 Successful software adopts itself to the changing world. | 672 Successful software adapts itself to the changing world. |
666 .PP | 673 .PP |
667 (4) | 674 (4) |
668 .I "Reuse of parts | 675 .I "Reuse of parts |
669 is even one step further. | 676 is even one step further. |
670 A software may completely lose its field of action, | 677 A software may completely lose its field of action, |
671 but parts of which the software is build may be general and independent enough | 678 but parts of which the software is build may be general and independent enough |
672 to survive this death. | 679 to survive this death. |
673 If software is build by combining small independent programs, | 680 If software is build by combining small independent programs, |
674 then there are parts readily available for reuse. | 681 then these parts are readily available for reuse. |
675 Who cares if the large program is a failure, | 682 Who cares if the large program is a failure, |
676 but parts of it become successful instead? | 683 but parts of it become successful instead? |
677 | 684 |
678 .NH 2 | 685 .NH 2 |
679 Summary | 686 Summary |
680 .XS | 687 .XS |
681 \*(SN Summary | 688 \*(SN Summary |
682 .XE | 689 .XE |
683 .LP | 690 .LP |
684 This chapter explained the central ideas of the Unix Philosophy. | 691 This chapter explained central ideas of the Unix Philosophy. |
685 For each of the ideas, it was exposed what advantages they introduce. | 692 For each of the ideas, the advantages they introduce were explained. |
686 The Unix Philosophy are guidelines that help to write valuable software. | 693 The Unix Philosophy are guidelines that help to write more valuable software. |
687 From the view point of a software developer or software designer, | 694 From the view point of a software developer or software designer, |
688 the Unix Philosophy provides answers to many software design problem. | 695 the Unix Philosophy provides answers to many software design problem. |
689 .PP | 696 .PP |
690 The various ideas of the Unix Philosophy are very interweaved | 697 The various ideas of the Unix Philosophy are very interweaved |
691 and can hardly be applied independently. | 698 and can hardly be applied independently. |
692 However, the probably most important messages are: | 699 However, the probably most important messages are: |
700 .I "``Keep it simple!''" , | |
693 .I "``Do one thing well!''" , | 701 .I "``Do one thing well!''" , |
694 .I "``Keep it simple!''" , | |
695 and | 702 and |
696 .I "``Use software leverage!'' | 703 .I "``Use software leverage!'' |
697 | 704 |
698 | 705 |
699 | 706 |
713 .PP | 720 .PP |
714 This first case study is about the mail user agents (\s-1MUA\s0) | 721 This first case study is about the mail user agents (\s-1MUA\s0) |
715 \s-1MH\s0 (``mail handler'') and its descendent \fInmh\fP | 722 \s-1MH\s0 (``mail handler'') and its descendent \fInmh\fP |
716 (``new mail handler''). | 723 (``new mail handler''). |
717 \s-1MUA\s0s provide functions to read, compose, and organize mail, | 724 \s-1MUA\s0s provide functions to read, compose, and organize mail, |
718 but (ideally) not to transfer. | 725 but (ideally) not to transfer it. |
719 In this document, the name \s-1MH\s0 will be used for both of them. | 726 In this document, the name \s-1MH\s0 will be used to include nmh. |
720 A distinction will only be made if differences between | 727 A distinction will only be made if differences between |
721 them are described. | 728 \s-1MH\s0 and nmh are described. |
722 | 729 |
723 | 730 |
724 .NH 2 | 731 .NH 2 |
725 Historical background | 732 Historical background |
726 .XS | 733 .XS |
733 .[ | 740 .[ |
734 salus | 741 salus |
735 quarter century of unix | 742 quarter century of unix |
736 %P 41 f. | 743 %P 41 f. |
737 .] | 744 .] |
738 It was a small program that either prints the user's mailbox file | 745 It was a small program that either printed the user's mailbox file |
739 or appends text to someone elses mailbox file, | 746 or appended text to someone elses mailbox file, |
740 depending on the command line arguments. | 747 depending on the command line arguments. |
741 .[ | 748 .[ |
742 manual mail(1) | 749 manual mail(1) |
743 .] | 750 .] |
744 It was a program that did one job well. | 751 It was a program that did one job well. |
745 This job was emailing, which was very simple then. | 752 This job was emailing, which was very simple then. |
746 .PP | 753 .PP |
747 Later, emailing became more powerful, and thus more complex. | 754 Later, emailing became more powerful, and thus more complex. |
748 The simple \f(CWmail\fP, which knew nothing of subjects, | 755 The simple \f(CWmail\fP, which knew nothing of subjects, |
749 independent handling of single messages, | 756 independent handling of single messages, |
750 and long-time storage of them, was not powerful enough anymore. | 757 and long-time email storage, was not powerful enough anymore. |
751 At Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M') | 758 In 1978 at Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M') |
752 in 1978 to provide additional functions for emailing. | 759 to provide additional functions for emailing. |
753 Mail was still one program, but now it was large and did | 760 Mail was still one program, but now it was large and did |
754 several jobs. | 761 several jobs. |
755 Its user interface is modeled after the one of \fIed\fP. | 762 Its user interface is modeled after the one of \fIed\fP. |
756 It is designed for humans, but is still scriptable. | 763 It is designed for humans, but is still scriptable. |
757 \fImailx\fP is the adaptation of Berkeley Mail into System V. | 764 \fImailx\fP is the adaptation of Berkeley Mail into System V. |
766 A different way was taken by the people of \s-1RAND\s0 Corporation. | 773 A different way was taken by the people of \s-1RAND\s0 Corporation. |
767 In the beginning, they also had used a monolithic mail system, | 774 In the beginning, they also had used a monolithic mail system, |
768 called \s-1MS\s0 (for ``mail system''). | 775 called \s-1MS\s0 (for ``mail system''). |
769 But in 1977, Stockton Gaines and Norman Shapiro | 776 But in 1977, Stockton Gaines and Norman Shapiro |
770 came up with a proposal of a new email system concept \(en | 777 came up with a proposal of a new email system concept \(en |
771 one that honors the Unix Philosophy. | 778 one that honored the Unix Philosophy. |
772 The concept was implemented by Bruce Borden in 1978 and 1979. | 779 The concept was implemented by Bruce Borden in 1978 and 1979. |
773 This was the birth of \s-1MH\s0 \(en the ``mail handler''. | 780 This was the birth of \s-1MH\s0 \(en the ``mail handler''. |
774 .PP | 781 .PP |
775 Since then, \s-1RAND\s0, the University of California at Irvine and | 782 Since then, \s-1RAND\s0, the University of California at Irvine and |
776 at Berkeley, and several others have contributed to the software. | 783 at Berkeley, and several others have contributed to the software. |
777 However, it's core concepts remained the same. | 784 However, it's core concepts remained the same. |
778 In the late 90s, when development of \s-1MH\s0 slowed down, | 785 In the late 90s, when development of \s-1MH\s0 slowed down, |
779 Richard Coleman started with \fInmh\fP, the new mail handler. | 786 Richard Coleman started with \fInmh\fP, the new mail handler. |
780 His goal was to improve \s-1MH\s0, especially in regard of | 787 His goal was to improve \s-1MH\s0 especially in regard of |
781 the requirements of modern emailing. | 788 the requirements of modern emailing. |
782 Today, nmh is developed by various people on the Internet. | 789 Today, nmh is developed by various people on the Internet. |
783 .[ | 790 .[ |
784 ware | 791 ware |
785 rand history | 792 rand history |
820 .IP \(bu | 827 .IP \(bu |
821 .CW folder : | 828 .CW folder : |
822 change current folder | 829 change current folder |
823 .IP \(bu | 830 .IP \(bu |
824 .CW refile : | 831 .CW refile : |
825 refile message into folder | 832 refile message into different folder |
826 .IP \(bu | 833 .IP \(bu |
827 .CW rmm : | 834 .CW rmm : |
828 remove message | 835 remove message |
829 .IP \(bu | 836 .IP \(bu |
830 .CW comp : | 837 .CW comp : |
831 compose a new message | 838 compose new message |
832 .IP \(bu | 839 .IP \(bu |
833 .CW repl : | 840 .CW repl : |
834 reply to a message | 841 reply to message |
835 .IP \(bu | 842 .IP \(bu |
836 .CW forw : | 843 .CW forw : |
837 forward a message | 844 forward message |
838 .IP \(bu | 845 .IP \(bu |
839 .CW send : | 846 .CW send : |
840 send a prepared message (this is how mail leaves the system) | 847 send prepared message (this is how mail leaves the system) |
841 .LP | 848 .LP |
842 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have. | 849 \s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have. |
843 The user does not leave the shell to run \s-1MH\s0, | 850 The user does not leave the shell to run \s-1MH\s0, |
844 but he uses the various \s-1MH\s0 programs within the shell. | 851 instead he uses the various \s-1MH\s0 programs within the shell. |
845 Using a monolithic program with a captive user interface | 852 Using a monolithic program with a captive user interface |
846 means ``entering'' the program, using it, and ``exiting'' the program. | 853 means ``entering'' the program, using it, and ``exiting'' the program. |
847 Using toolchests like \s-1MH\s0 means running programs, | 854 Using toolchests like \s-1MH\s0 means running programs, |
848 alone or in combination with others, even from other toolchests, | 855 alone or in combination with others, also from other toolchests, |
849 without leaving the shell. | 856 without leaving the shell. |
850 | 857 |
851 .NH 2 | 858 .NH 2 |
852 Data storage | 859 Data storage |
853 .XS | 860 .XS |
857 \s-1MH\s0's mail storage is a directory tree under the user's | 864 \s-1MH\s0's mail storage is a directory tree under the user's |
858 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP), | 865 \s-1MH\s0 directory (usually \f(CW$HOME/Mail\fP), |
859 where mail folders are directories and mail messages are text files | 866 where mail folders are directories and mail messages are text files |
860 within them. | 867 within them. |
861 Each mail folder contains a file \f(CW.mh_sequences\fP which lists | 868 Each mail folder contains a file \f(CW.mh_sequences\fP which lists |
862 the public message sequences of that folder, for instance new messages. | 869 the public message sequences of that folder, |
870 for instance the \fIunseen\fP sequence for new messages. | |
863 Mail messages are text files located in a mail folder. | 871 Mail messages are text files located in a mail folder. |
864 The files contain the messages as they were received. | 872 The files contain the messages as they were received. |
865 They are numbered in ascending order in each folder. | 873 They are named by ascending numbers in each folder. |
866 .PP | 874 .PP |
867 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0. | 875 This mailbox format is called ``\s-1MH\s0'' after the \s-1MUA\s0. |
868 Alternatives are \fImbox\fP and \fImaildir\fP. | 876 Alternatives are \fImbox\fP and \fImaildir\fP. |
869 In the mbox format all messages are stored within one file. | 877 In the mbox format all messages are stored within one file. |
870 This was a good solution in the early days, when messages | 878 This was a good solution in the early days, when messages |
873 of attachments, it is a bad solution. | 881 of attachments, it is a bad solution. |
874 Another disadvantage of the mbox format is that it is | 882 Another disadvantage of the mbox format is that it is |
875 more difficult to write tools that work on mail messages, | 883 more difficult to write tools that work on mail messages, |
876 because it is always necessary to first find and extract | 884 because it is always necessary to first find and extract |
877 the relevant message in the mbox file. | 885 the relevant message in the mbox file. |
878 With the \s-1MH\s0 mailbox format, | 886 With the \s-1MH\s0 mailbox format, each message is a separate file. |
879 each message is a self-standing item, by definition. | |
880 Also, the problem of concurrent access to one mailbox is | 887 Also, the problem of concurrent access to one mailbox is |
881 reduced to the problem of concurrent access to one message. | 888 reduced to the problem of concurrent access to one message. |
882 Maildir is generally similar to \s-1MH\s0's format, | 889 The maildir format is generally similar to the \s-1MH\s0 format, |
883 but modified towards guaranteed reliability. | 890 but modified towards guaranteed reliability. |
884 This involves some complexity, unfortunately. | 891 This involves some complexity, unfortunately. |
885 .PP | 892 .PP |
886 Working with \s-1MH\s0's toolchest on mailboxes is much like | 893 Working with \s-1MH\s0's toolchest on mailboxes is much like |
887 working with Unix' toolchest on directory trees: | 894 working with Unix' toolchest on directory trees: |
889 \f(CWshow\fP is like \f(CWcat\fP, | 896 \f(CWshow\fP is like \f(CWcat\fP, |
890 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP, | 897 \f(CWfolder\fP is like \f(CWcd\fP and \f(CWpwd\fP, |
891 \f(CWrefile\fP is like \f(CWmv\fP, | 898 \f(CWrefile\fP is like \f(CWmv\fP, |
892 and \f(CWrmm\fP is like \f(CWrm\fP. | 899 and \f(CWrmm\fP is like \f(CWrm\fP. |
893 .PP | 900 .PP |
894 The context of tools in Unix consists mainly the current working directory, | 901 \s-1MH\s0 extends the context of processes in Unix by two more items, |
895 the user identification, and the environment variables. | 902 for its tools: |
896 \s-1MH\s0 extends this context by two more items: | |
897 .IP \(bu | 903 .IP \(bu |
898 The current mail folder, which is similar to the current working directory. | 904 The current mail folder, which is similar to the current working directory. |
899 For mail folders, \f(CWfolder\fP provides the corresponding functionality | 905 For mail folders, \f(CWfolder\fP provides the corresponding functionality |
900 of \f(CWcd\fP and \f(CWpwd\fP for directories. | 906 of \f(CWcd\fP and \f(CWpwd\fP for directories. |
901 .IP \(bu | 907 .IP \(bu |
902 Sequences, which are named sets of messages in a mail folder. | 908 Sequences, which are named sets of messages in a mail folder. |
903 The current message, relative to a mail folder, is a special sequence. | 909 The current message, relative to a mail folder, is a special sequence. |
904 It enables commands like \f(CWnext\fP and \f(CWprev\fP. | 910 It enables commands like \f(CWnext\fP and \f(CWprev\fP. |
905 .LP | 911 .LP |
906 In contrast to Unix' context, which is chained to the shell session, | 912 In contrast to Unix' context, which is maintained by the kernel, |
907 \s-1MH\s0's context is independent. | 913 \s-1MH\s0's context must be maintained by the tools themselves. |
908 Usually there is one context for each user, but a user can have many | 914 Usually there is one context per user, which resides in his |
909 contexts. | 915 \f(CWcontext\fP file in the \s-1MH\s0 directory, |
910 Public sequences are an exception, as they belong to the mail folder. | 916 but a user can have several contexts, too. |
917 Public sequences are an exception, as they belong to a mail folder, | |
918 and reside in the \f(CW.mh_sequences\fP file there. | |
911 .[ | 919 .[ |
912 man page mh-profile mh-sequence | 920 man page mh-profile mh-sequence |
913 .] | 921 .] |
914 | 922 |
915 .NH 2 | 923 .NH 2 |
916 Discussion of the design | 924 Discussion of the design |
917 .XS | 925 .XS |
918 \*(SN Discussion of the design | 926 \*(SN Discussion of the design |
919 .XE | 927 .XE |
920 .LP | 928 .LP |
921 The following paragraphs discuss \s-1MH\s0 in regard to the tenets | 929 This section discusses \s-1MH\s0 in regard to the tenets |
922 of the Unix Philosophy which Gancarz identified. | 930 of the Unix Philosophy that Gancarz identified. |
923 | 931 |
924 .PP | 932 .PP |
925 .B "Small is beautiful | 933 .B "Small is beautiful |
926 and | 934 and |
927 .B "do one thing well | 935 .B "do one thing well |
928 are two design goals that are directly visible in \s-1MH\s0. | 936 are two design goals that are directly visible in \s-1MH\s0. |
929 Gancarz actually presents \s-1MH\s0 as example under the headline | 937 Gancarz actually presents \s-1MH\s0 in his book as example under the |
930 ``Making UNIX Do One Thing Well'': | 938 headline ``Making \s-1UNIX\s0 Do One Thing Well'': |
931 .[ | 939 .[ |
932 gancarz | 940 gancarz |
933 unix philosophy | 941 unix philosophy |
934 %P 125 | 942 %P 125 |
935 .] | 943 .] |
936 .QP | 944 .QP |
937 .ps -1 | |
938 [\s-1MH\s0] consists of a series of programs which | 945 [\s-1MH\s0] consists of a series of programs which |
939 when combined give the user an enormous ability | 946 when combined give the user an enormous ability |
940 to manipulate electronic mail messages. | 947 to manipulate electronic mail messages. |
941 A complex application, it shows that not only is it | 948 A complex application, it shows that not only is it |
942 possible to build large applications from smaller | 949 possible to build large applications from smaller |
943 components, but also that such designs are actually preferable. | 950 components, but also that such designs are actually preferable. |
944 .LP | 951 .LP |
945 The various small programs of \s-1MH\s0 were relatively easy | 952 The various programs of \s-1MH\s0 were relatively easy to write, |
946 to write, because each of them is small, limited to one function, | 953 because each of them is small, limited to one function, |
947 and has clear boundaries. | 954 and has clear boundaries. |
948 For the same reasons, they are also good to maintain. | 955 For the same reasons, they are also good to maintain. |
949 Further more, the system can easily get extended. | 956 Further more, the system can easily get extended. |
950 One only needs to put a new program into the toolchest. | 957 One only needs to put a new program into the toolchest. |
951 This was done, for instance, when \s-1MIME\s0 support was added | 958 This was done, for instance, when \s-1MIME\s0 support was added |
952 (e.g. \f(CWmhbuild\fP). | 959 (e.g. \f(CWmhbuild\fP). |
953 Also, different programs can exist to do the basically same job | 960 Also, different programs can exist to do the basically same job |
954 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP). | 961 in different ways (e.g. in nmh: \f(CWshow\fP and \f(CWmhshow\fP). |
962 .PP | |
955 If someone needs a mail system with some additionally | 963 If someone needs a mail system with some additionally |
956 functions that are available nowhere yet, he best takes a | 964 functions that are not available anywhere yet, he best expands a |
957 toolchest system like \s-1MH\s0 where he can add the | 965 toolchest system like \s-1MH\s0. |
958 functionality with little work. | 966 There he can add new functionality by simply adding additional |
967 programs to the toolchest. | |
968 There he does not risk to break existing functionality by doing so. | |
959 | 969 |
960 .PP | 970 .PP |
961 .B "Store data in flat text files | 971 .B "Store data in flat text files |
962 is followed by \s-1MH\s0. | 972 is followed by \s-1MH\s0. |
963 This is not surprising, because email messages are already plain text. | 973 This is not surprising, because email messages are already plain text. |
964 \s-1MH\s0 stores the messages as it receives them, | 974 \s-1MH\s0 stores the messages as it receives them, |
965 thus any other tool that works on RFC 2822 mail messages can operate | 975 thus any other tool that works on \s-1RFC\s0\|2822 mail messages can operate |
966 on the messages in an \s-1MH\s0 mailbox. | 976 on the messages in an \s-1MH\s0 mailbox. |
967 All other files \s-1MH\s0 uses are plain text too. | 977 All other files \s-1MH\s0 uses are plain text, too. |
968 It is therefore possible and encouraged to use the text processing | 978 It is therefore possible and encouraged to use the text processing |
969 tools of Unix' toolchest to extend \s-1MH\s0's toolchest. | 979 tools of Unix' toolchest to extend \s-1MH\s0's toolchest. |
970 | 980 |
971 .PP | 981 .PP |
972 .B "Avoid captive user interfaces" . | 982 .B "Avoid captive user interfaces" . |
973 \s-1MH\s0 is perfectly suited for non-interactive use. | 983 \s-1MH\s0 is perfectly suited for non-interactive use. |
974 It offers all functions directly and without captive user interfaces. | 984 It offers all functions directly and without captive user interfaces. |
975 If, nonetheless, users want a graphical user interface, | 985 If, nonetheless, users want a graphical user interface, |
976 they can have it with \fIxmh\fP or \fIexmh\fP, too. | 986 they can have it with \fIxmh\fP or \fIexmh\fP. |
977 These are graphical frontends for the \s-1MH\s0 toolchest. | 987 These are graphical frontends for the \s-1MH\s0 toolchest. |
978 This means, all email-related work is still done by \s-1MH\s0 tools, | 988 This means, all email-related work is still done by \s-1MH\s0 tools, |
979 but the frontend issues the appropriate calls when the user | 989 but the frontend calls the appropriate commands when the user |
980 clicks on buttons. | 990 clicks on buttons. |
991 .PP | |
981 Providing easy-to-use user interfaces in form of frontends is a good | 992 Providing easy-to-use user interfaces in form of frontends is a good |
982 approach, because it does not limit the power of the backend itself. | 993 approach, because it does not limit the power of the backend itself. |
983 The frontend will anyway only be able to make a subset of the | 994 The frontend will anyway only be able to make a subset of the |
984 backend's power and flexibility available to the user. | 995 backend's power and flexibility available to the user. |
985 But if it is a separate program, | 996 But if it is a separate program, |
986 then the missing parts can still be accessed at the backend directly. | 997 then the missing parts can still be accessed at the backend directly. |
987 If it is integrated, then this will hardly be possible. | 998 If it is integrated, then this will hardly be possible. |
988 Further more, it is possible to have different frontends to the same | 999 An additional advantage is the possibility to have different frontends |
989 backend. | 1000 to the same backend. |
990 | 1001 |
991 .PP | 1002 .PP |
992 .B "Choose portability over efficiency | 1003 .B "Choose portability over efficiency |
993 and | 1004 and |
994 .B "use shell scripts to increase leverage and portability" . | 1005 .B "use shell scripts to increase leverage and portability" . |
996 Bolsky and Korn in their book about the Korn Shell. | 1007 Bolsky and Korn in their book about the Korn Shell. |
997 .[ | 1008 .[ |
998 bolsky korn | 1009 bolsky korn |
999 korn shell | 1010 korn shell |
1000 .] | 1011 .] |
1001 They demonstrated, in chapter 18 of the book, a basic implementation | 1012 Chapter\|18 of the book shows a basic implementation |
1002 of a subset of \s-1MH\s0 in ksh scripts. | 1013 of a subset of \s-1MH\s0 in ksh scripts. |
1003 Of course, this was just a demonstration, but a brilliant one. | 1014 Of course, this is just a demonstration, but a brilliant one. |
1004 It shows how quickly one can implement such a prototype with shell scripts, | 1015 It shows how quickly one can implement such a prototype with shell scripts, |
1005 and how readable they are. | 1016 and how readable they are. |
1006 The implementation in the scripting language may not be very fast, | 1017 The implementation in the scripting language may not be very fast, |
1007 but it can be fast enough though, and this is all that matters. | 1018 but it can be fast enough though, and this is all that matters. |
1008 By having the code in an interpreted language, like the shell, | 1019 By having the code in an interpreted language, like the shell, |
1009 portability becomes a minor issue, if we assume the interpreter | 1020 portability becomes a minor issue, if we assume the interpreter |
1010 to be widespread. | 1021 to be widespread. |
1022 .PP | |
1011 This demonstration also shows how easy it is to create single programs | 1023 This demonstration also shows how easy it is to create single programs |
1012 of a toolchest software. | 1024 of a toolchest software. |
1013 There are eight tools (two of them have multiple names) and 16 functions | 1025 Eight tools (two of them have multiple names) and 16 functions |
1014 with supporting code. | 1026 with supporting code are presented to the reader. |
1015 Each tool comprises between 12 and 38 lines of ksh, | 1027 The tools comprise less than 40 lines of ksh each, |
1016 in total about 200 lines. | 1028 in total about 200 lines. |
1017 The functions comprise between 3 and 78 lines of ksh, | 1029 The functions comprise less than 80 lines of ksh each, |
1018 in total about 450 lines. | 1030 in total about 450 lines. |
1019 Such small software is easy to write, easy to understand, | 1031 Such small software is easy to write, easy to understand, |
1020 and thus easy to maintain. | 1032 and thus easy to maintain. |
1021 A toolchest improves the possibility to only write some parts | 1033 A toolchest improves the possibility to only write some parts |
1022 and though create a working result. | 1034 and though create a working result. |
1023 Expanding the toolchest without global changes will likely be | 1035 Expanding the toolchest, even without global changes, |
1024 possible, too. | 1036 will likely be possible. |
1025 | 1037 |
1026 .PP | 1038 .PP |
1027 .B "Use software leverage to your advantage | 1039 .B "Use software leverage to your advantage |
1028 and the lesser tenet | 1040 and the lesser tenet |
1029 .B "allow the user to tailor the environment | 1041 .B "allow the user to tailor the environment |
1030 are ideally followed in the design of \s-1MH\s0. | 1042 are ideally followed in the design of \s-1MH\s0. |
1031 Tailoring the environment is heavily encouraged by the ability to | 1043 Tailoring the environment is heavily encouraged by the ability to |
1032 directly define default options to programs. | 1044 directly define default options to programs. |
1033 It is even possible to define different default options | 1045 It is even possible to define different default options |
1034 depending on the name under which the program was called. | 1046 depending on the name under which a program is called. |
1035 Software leverage is heavily encouraged by the ease it is to | 1047 Software leverage is heavily encouraged by the ease of |
1036 create shell scripts that run a specific command line, | 1048 creating shell scripts that run a specific command line, |
1037 built of several \s-1MH\s0 programs. | 1049 built of several \s-1MH\s0 programs. |
1038 There is few software that so much wants users to tailor their | 1050 There is few software that so much wants users to tailor their |
1039 environment and to leverage the use of the software, like \s-1MH\s0. | 1051 environment and to leverage the use of the software, like \s-1MH\s0. |
1052 .PP | |
1040 Just to make one example: | 1053 Just to make one example: |
1041 One might prefer a different listing format for the \f(CWscan\fP | 1054 One might prefer a different listing format for the \f(CWscan\fP |
1042 program. | 1055 program. |
1043 It is possible to take one of the distributed format files | 1056 It is possible to take one of the distributed format files |
1044 or to write one yourself. | 1057 or to write one yourself. |
1051 must be added to \f(CW.mh_profile\fP. | 1064 must be added to \f(CW.mh_profile\fP. |
1052 If one wants this different format as an additional command, | 1065 If one wants this different format as an additional command, |
1053 instead of changing the default, he needs to create a link to | 1066 instead of changing the default, he needs to create a link to |
1054 \f(CWscan\fP, for instance titled \f(CWscan2\fP. | 1067 \f(CWscan\fP, for instance titled \f(CWscan2\fP. |
1055 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP, | 1068 The line in \f(CW.mh_profile\fP would then start with \f(CWscan2\fP, |
1056 as the option should only be in effect when scan is called as | 1069 as the option should only be in effect for a program that is called as |
1057 \f(CWscan2\fP. | 1070 \f(CWscan2\fP. |
1058 | 1071 |
1059 .PP | 1072 .PP |
1060 .B "Make every program a filter | 1073 .B "Make every program a filter |
1061 is hard to find in \s-1MH\s0. | 1074 is hard to find in \s-1MH\s0. |
1062 The reason therefore is that most of \s-1MH\s0's tools provide | 1075 The reason therefore is that most of \s-1MH\s0's tools provide |
1063 basic file system operations for the mailboxes. | 1076 basic file system operations for mailboxes. |
1064 The reason is the same because of which | 1077 It is the same reason because of which \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP, |
1065 \f(CWls\fP, \f(CWcp\fP, \f(CWmv\fP, and \f(CWrm\fP | 1078 and \f(CWrm\fP aren't filters neither. |
1066 aren't filters neither. | |
1067 However, they build a basis on which filters can operate. | |
1068 \s-1MH\s0 does not provide many filters itself, but it is a basis | 1079 \s-1MH\s0 does not provide many filters itself, but it is a basis |
1069 to write filters for. | 1080 to write filters for. |
1070 An example would be a mail message text highlighter, | 1081 An example would be a mail text highlighter, |
1071 that means a program that makes use of a color terminal to display | 1082 that means a program that makes use of a color terminal to display |
1072 header lines, quotations, and signatures in distinct colors. | 1083 header lines, quotations, and signatures in distinct colors. |
1073 The author's version of this program, for instance, | 1084 The author's version of such a program is an awk script with 25 lines. |
1074 is a 25 line awk script. | |
1075 | 1085 |
1076 .PP | 1086 .PP |
1077 .B "Build a prototype as soon as possible | 1087 .B "Build a prototype as soon as possible |
1078 was again well followed by \s-1MH\s0. | 1088 was again well followed by \s-1MH\s0. |
1079 This tenet, of course, focuses on early development, which is | 1089 This tenet, of course, focuses on early development, which is |
1085 .[ | 1095 .[ |
1086 ware rand history | 1096 ware rand history |
1087 %P 132 | 1097 %P 132 |
1088 .] | 1098 .] |
1089 .QP | 1099 .QP |
1090 .ps -1 | 1100 [...] but [Stockton Gaines and Norm Shapiro] were not able |
1091 [...] but they [Stockton Gaines and Norm Shapiro] were not able | |
1092 to convince anyone that such a system would be fast enough to be usable. | 1101 to convince anyone that such a system would be fast enough to be usable. |
1093 I proposed a very short project to prove the basic concepts, | 1102 I proposed a very short project to prove the basic concepts, |
1094 and my management agreed. | 1103 and my management agreed. |
1095 Looking back, I realize that I had been very lucky with my first design. | 1104 Looking back, I realize that I had been very lucky with my first design. |
1096 Without nearly enough design work, | 1105 Without nearly enough design work, |
1105 Problems | 1114 Problems |
1106 .XS | 1115 .XS |
1107 \*(SN Problems | 1116 \*(SN Problems |
1108 .XE | 1117 .XE |
1109 .LP | 1118 .LP |
1110 \s-1MH\s0, for sure is not without problems. | 1119 \s-1MH\s0 is not without problems. |
1111 There are two main problems: one is technical, the other is about human behavior. | 1120 There are two main problems: one is technical, the other is about human behavior. |
1112 .PP | 1121 .PP |
1113 \s-1MH\s0 is old and email today is very different to email in the time | 1122 \s-1MH\s0 is old and email today is very different to email in the time |
1114 when \s-1MH\s0 was designed. | 1123 when \s-1MH\s0 was designed. |
1115 \s-1MH\s0 adopted to the changes pretty well, but it is limited. | 1124 \s-1MH\s0 adapted to the changes pretty well, but it is limited, though. |
1116 For example in development resources. | |
1117 \s-1MIME\s0 support and support for different character encodings | 1125 \s-1MIME\s0 support and support for different character encodings |
1118 is available, but only on a moderate level. | 1126 is available, but only on a moderate level. |
1119 More active developers could quickly improve there. | 1127 This comes from limited development resources. |
1120 It is also limited by design, which is the larger problem. | 1128 More active developers could quickly change this. |
1129 But \s-1MH\s0 is also limited by design, which is the larger problem. | |
1121 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extend. | 1130 \s-1IMAP\s0, for example, conflicts with \s-1MH\s0's design to a large extend. |
1122 These design conflicts are not easily solvable. | 1131 These design conflicts are not easily solvable. |
1123 Possibly, they require a redesign. | 1132 Possibly, they require a redesign. |
1124 Maybe \s-1IMAP\s0 is too different to the classic mail model which \s-1MH\s0 covers, | 1133 \s-1IMAP\s0 may be too different to the classic mail model, |
1125 hence \s-1MH\s0 may never work well with \s-1IMAP\s0. | 1134 which \s-1MH\s0 covers, so that \s-1MH\s0 may never support it well. |
1126 .PP | 1135 .PP |
1127 The other kind of problem is human habits. | 1136 The other kind of problem are human habits. |
1128 When in this world almost all \s-1MUA\s0s are monolithic, | 1137 In this world, where almost all \s-1MUA\s0s are monolithic, |
1129 it is very difficult to convince people to use a toolbox style \s-1MUA\s0 | 1138 it is very difficult to convince people to use a toolbox style \s-1MUA\s0 |
1130 like \s-1MH\s0. | 1139 like \s-1MH\s0. |
1131 The habits are so strong, that even people who understood the concept | 1140 The habits are so strong, that even people who understand the concept |
1132 and advantages of \s-1MH\s0 do not like to switch, | 1141 and advantages of \s-1MH\s0 do not like to switch, |
1133 simply because \s-1MH\s0 is different. | 1142 simply because \s-1MH\s0 is different. |
1134 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel, | 1143 Unfortunately, the frontends to \s-1MH\s0, which could provide familiar look'n'feel, |
1135 are quite outdated and thus not very appealing compared to the modern interfaces | 1144 are quite outdated and thus not very appealing, compared to the modern interfaces |
1136 which monolithic \s-1MUA\s0s offer. | 1145 of many monolithic \s-1MUA\s0s. |
1137 | 1146 |
1138 .NH 2 | 1147 .NH 2 |
1139 Summary \s-1MH\s0 | 1148 Summary \s-1MH\s0 |
1140 .XS | 1149 .XS |
1141 \*(SN Summary \s-1MH\s0 | 1150 \*(SN Summary \s-1MH\s0 |
1142 .XE | 1151 .XE |
1143 .LP | 1152 .LP |
1144 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design | 1153 \s-1MH\s0 is an \s-1MUA\s0 that follows the Unix Philosophy in its design. |
1145 and implementation. | |
1146 It consists of a toolchest of small tools, each of them does one job well. | 1154 It consists of a toolchest of small tools, each of them does one job well. |
1147 The tools are orthogonal to each other, to a large extend. | |
1148 However, for historical reasons, there also exist distinct tools | |
1149 that cover the same task. | |
1150 .PP | |
1151 The toolchest approach offers great flexibility to the user. | 1155 The toolchest approach offers great flexibility to the user. |
1152 He can use the complete power of the Unix shell with \s-1MH\s0. | 1156 It is possible to utilize the complete power of the Unix shell with \s-1MH\s0. |
1153 This makes \s-1MH\s0 a very powerful mail system. | 1157 This makes \s-1MH\s0 a very powerful mail system. |
1154 Extending and customizing \s-1MH\s0 is easy and encouraged, too. | 1158 Extending and customizing \s-1MH\s0 is easy and encouraged. |
1155 .PP | 1159 .PP |
1156 Apart from the user's perspective, \s-1MH\s0 is development-friendly. | 1160 Apart from the user's perspective, \s-1MH\s0 is development-friendly. |
1157 Its overall design follows clear rules. | 1161 Its overall design follows clear rules. |
1158 The single tools do only one job, thus they are easy to understand, | 1162 The single tools do only one job, thus they are easy to understand, |
1159 easy to write, and good to maintain. | 1163 easy to write, and good to maintain. |
1173 .sp .5v | 1177 .sp .5v |
1174 \*(SN Case study: uzbl | 1178 \*(SN Case study: uzbl |
1175 .XE | 1179 .XE |
1176 .LP | 1180 .LP |
1177 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0, | 1181 The last chapter took a look on the \s-1MUA\s0 \s-1MH\s0, |
1178 this chapter is about uzbl, a web browser that adheres to the Unix Philosophy. | 1182 which is an old and established software. |
1179 ``uzbl'' is the \fIlolcat\fP's word for the English adjective ``usable''. | 1183 This chapter covers uzbl, a fresh new project. |
1180 It is pronounced the identical. | 1184 Uzbl is a web browser that adheres to the Unix Philosophy. |
1185 Its name comes from the \fILolspeak\fP word for ``usable''; | |
1186 it is pronounced identical. | |
1181 | 1187 |
1182 .NH 2 | 1188 .NH 2 |
1183 Historical background | 1189 Historical background |
1184 .XS | 1190 .XS |
1185 \*(SN Historical background | 1191 \*(SN Historical background |
1201 Fortunately, he found the time. | 1207 Fortunately, he found the time. |
1202 One day later, the first prototype was out. | 1208 One day later, the first prototype was out. |
1203 One week later, uzbl had an own website. | 1209 One week later, uzbl had an own website. |
1204 One month after the first code showed up, | 1210 One month after the first code showed up, |
1205 a mailing list was installed to coordinate and discuss further development. | 1211 a mailing list was installed to coordinate and discuss further development. |
1206 A wiki was set up to store documentation and scripts that showed up on the | 1212 Then a wiki followed to store documentation and scripts that showed up on the |
1207 mailing list and elsewhere. | 1213 mailing list and elsewhere. |
1208 .PP | 1214 .PP |
1209 In the, now, one year of uzbl's existence, it was heavily developed in various branches. | 1215 In the, now, one year of uzbl's existence, it was heavily developed on various branches. |
1210 Plaetinck's task became more and more to only merge the best code from the | 1216 Plaetinck's task became more and more to only merge the best code from the |
1211 different branches into his main branch, and to apply patches. | 1217 different branches into his main branch, and to apply patches. |
1212 About once a month, Plaetinck released a new version. | 1218 About once a month, Plaetinck released a new version. |
1213 In September 2009, he presented several forks of uzbl. | 1219 In September 2009, he presented several forks of uzbl. |
1214 Uzbl, actually, opened the field for a whole family of web browsers with similar shape. | 1220 Uzbl, actually, opened the field for a whole family of web browsers with similar shape. |
1226 most web browsers are monolithic, but uzbl is a frontend to a toolchest. | 1232 most web browsers are monolithic, but uzbl is a frontend to a toolchest. |
1227 .PP | 1233 .PP |
1228 Today, uzbl is divided into uzbl-core and uzbl-browser. | 1234 Today, uzbl is divided into uzbl-core and uzbl-browser. |
1229 Uzbl-core is, how its name already indicates, the core of uzbl. | 1235 Uzbl-core is, how its name already indicates, the core of uzbl. |
1230 It handles commands and events to interface other programs, | 1236 It handles commands and events to interface other programs, |
1231 and also displays webpages by using webkit as render engine. | 1237 and also displays webpages by using \fIwebkit\fP as render engine. |
1232 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar, | 1238 Uzbl-browser combines uzbl-core with a bunch of handler scripts, a status bar, |
1233 an event manager, yanking, pasting, page searching, zooming, and more stuff, | 1239 an event manager, yanking, pasting, page searching, zooming, and more stuff, |
1234 to form a ``complete'' web browser. | 1240 to form a ``complete'' web browser. |
1235 In the following text, the term ``uzbl'' usually stands for uzbl-browser, | 1241 In the following text, the term ``uzbl'' usually stands for uzbl-browser, |
1236 so uzbl-core is included. | 1242 so uzbl-core is included. |
1237 .PP | 1243 .PP |
1238 Unlike most other web browsers, uzbl is mainly the mediator between the | 1244 Unlike most other web browsers, uzbl is mainly the mediator between the |
1239 various tools that cover single jobs of web browsing. | 1245 various tools that cover single jobs. |
1240 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket, | 1246 Therefore, uzbl listens for commands on a named pipe (fifo), a Unix socket, |
1241 and on stdin, and it writes events to a Unix socket and to stdout. | 1247 and on stdin, and it writes events to a Unix socket and to stdout. |
1242 The graphical rendering of the webpage is done by webkit, a web content engine. | |
1243 Uzbl-core is build around this library. | |
1244 Loading a webpage in a running uzbl instance requires only: | 1248 Loading a webpage in a running uzbl instance requires only: |
1245 .DS | 1249 .DS |
1246 .CW | 1250 .CW |
1247 echo 'uri http://example.org' >/path/to/uzbl-fifo | 1251 echo 'uri http://example.org' >/path/to/uzbl-fifo |
1248 .DE | 1252 .DE |
1249 .PP | 1253 The graphical rendering of the webpage is done by webkit, |
1250 Downloads, browsing history, bookmarks, and thelike are not provided | 1254 a web content engine. |
1251 by uzbl-core itself, as they are in other web browsers. | 1255 Uzbl-core is built around libwebkit. |
1256 .PP | |
1257 Downloads, browsing history, bookmarks, and the like are not provided | |
1258 by the core itself, like they are in other web browsers. | |
1252 Uzbl-browser also only provides, so called, handler scripts that wrap | 1259 Uzbl-browser also only provides, so called, handler scripts that wrap |
1253 external applications which provide the actual functionality. | 1260 external applications which provide the actual functionality. |
1254 For instance, \fIwget\fP is used to download files and uzbl-browser | 1261 For instance, \fIwget\fP is used to download files and uzbl-browser |
1255 includes a script that calls wget with appropriate options in | 1262 includes a script that calls wget with appropriate options in |
1256 a prepared environment. | 1263 a prepared environment. |
1257 .PP | 1264 .PP |
1258 Modern web browsers are proud to have addons, plugins, and modules, instead. | 1265 Modern web browsers are proud to have addons, plugins, and modules, instead. |
1259 This is their effort to achieve similar goals. | 1266 This is their effort to achieve similar goals. |
1260 But instead of using existing, external programs, modern web browsers | 1267 But instead of using existing, external programs, modern web browsers |
1261 include these functions, although they might be loaded at runtime. | 1268 include these functions. |
1262 | 1269 |
1263 .NH 2 | 1270 .NH 2 |
1264 Discussion of the design | 1271 Discussion of the design |
1265 .XS | 1272 .XS |
1266 \*(SN Discussion of the design | 1273 \*(SN Discussion of the design |
1273 .B "Make each program do one thing well" . | 1280 .B "Make each program do one thing well" . |
1274 Uzbl tries to be a web browser and nothing else. | 1281 Uzbl tries to be a web browser and nothing else. |
1275 The common definition of a web browser is, of course, highly influenced by | 1282 The common definition of a web browser is, of course, highly influenced by |
1276 existing implementations of web browsers, although they are degenerated. | 1283 existing implementations of web browsers, although they are degenerated. |
1277 Web browsers should be programs to browse the web, and nothing more. | 1284 Web browsers should be programs to browse the web, and nothing more. |
1278 This is the one thing they should do, as demanded by the Unix Philosophy. | 1285 This is the one thing they should do. |
1279 .PP | 1286 .PP |
1280 Web browsers should, for instance, not manage downloads. | 1287 Web browsers should not, for instance, manage downloads. |
1281 This is the job download managers exist for. | 1288 This is the job download managers exist for. |
1282 Download managers do primary care about being good in downloading files. | 1289 Download managers do primary care about being good in downloading files. |
1283 Modern web browsers provide download management only as a secondary feature. | 1290 Modern web browsers provide download management only as a secondary feature. |
1284 How could they perform this job better, than programs that exist only for | 1291 How could they do this job better, than programs that exist only for |
1285 this very job? | 1292 this very job? |
1286 And how could anyone want less than the best download manager available? | 1293 And how could anyone want less than the best download manager available? |
1287 .PP | 1294 .PP |
1288 A web browser's job is to let the user browse the web. | 1295 A web browser's job is to let the user browse the web. |
1289 This means, navigating through websites by following links. | 1296 This means, navigating through websites by following links. |
1304 The lesser tenet | 1311 The lesser tenet |
1305 .B "allow the user to tailor the environment | 1312 .B "allow the user to tailor the environment |
1306 matches good here. | 1313 matches good here. |
1307 There was the question, how anyone could want anything less than the | 1314 There was the question, how anyone could want anything less than the |
1308 best program for the job. | 1315 best program for the job. |
1309 But as personal preferences matter much, | 1316 But as personal preferences matter, it is probably more important to ask: |
1310 it is probably more important to ask: | |
1311 How could anyone want something else than his preferred program for the job? | 1317 How could anyone want something else than his preferred program for the job? |
1312 .PP | 1318 .PP |
1313 Usually users want one program for one job. | 1319 Usually users want one program for a specific job. |
1314 Hence, whenever the task is, for instance, downloading, | 1320 Hence, whenever the task is, for instance, downloading, |
1315 exactly one download manager should be used. | 1321 the same download manager should be used. |
1316 More advanced users might want to have this download manager in this | 1322 More advanced users might want to have this download manager in this |
1317 situation and that one in that situation. | 1323 situation and that one in that situation. |
1318 They should be able to configure it this way. | 1324 They should be able to configure it this way. |
1319 With uzbl, one can use any download manager the user wants. | 1325 With uzbl, one can use any download manager the user wants. |
1320 To switch to a different one, only one line in a small handler script | 1326 To switch to a different one, only one line in a small handler script |
1321 needs to be changed. | 1327 needs to be changed. |
1322 Alternatively it would be possible to query an entry in a global file | 1328 Alternatively it would be possible to query the program to use by |
1323 or an environment variable, which specifies the download manager to use, | 1329 reading a global file or an environment variable, in the handler script. |
1324 in the handler script. | 1330 .PP |
1325 .PP | 1331 Uzbl does neither have its own download manager nor depends on a |
1326 As uzbl does neither have its own download manager nor depends on a | 1332 specific one, hence uzbl's browsing abilities will not be lowered by having |
1327 specific one, thus uzbl's browsing abilities will not be lowered by having | |
1328 a bad download manager. | 1333 a bad download manager. |
1329 Uzbl's download capabilities will just as good as the ones of the best | 1334 Uzbl's download capabilities will be just as good as the ones of the best |
1330 download manager available on the system. | 1335 download manager available on the system. |
1331 Of course, this applies to all of the other supplementary tools, too. | 1336 Of course, this applies to all of the other supplementary tools, too. |
1332 | 1337 |
1333 .PP | 1338 .PP |
1334 .B "Use software leverage to your advantage" . | 1339 .B "Use software leverage to your advantage" . |
1335 Shell scripts are a good choice to extend uzbl. | |
1336 Uzbl is designed to be extended by external tools. | 1340 Uzbl is designed to be extended by external tools. |
1337 These external tools are usually wrapped by small handler shell scripts. | 1341 These external tools are usually wrapped by small handler shell scripts. |
1338 Shell scripts are the glue in this approach. | 1342 Shell scripts are the glue in this approach. |
1339 They make the various parts fit together. | 1343 They make the various parts fit together. |
1340 .PP | 1344 .PP |
1341 As an example, the history mechanism of uzbl shall be presented. | 1345 The history mechanism of uzbl shall be presented as an example. |
1342 Uzbl is configured to spawn a script to append an entry to the history | 1346 Uzbl is configured to spawn a script to append an entry to the history |
1343 whenever the event of a fully loaded page occurs. | 1347 whenever the event of a fully loaded page occurs. |
1344 The script to append the entry to the history not much more than: | 1348 The script to append the entry to the history is not much more than: |
1345 .DS | 1349 .DS |
1346 .CW | 1350 .CW |
1347 #!/bin/sh | 1351 #!/bin/sh |
1348 file=/path/to/uzbl-history | 1352 file=/path/to/uzbl-history |
1349 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file | 1353 echo `date +'%Y-%m-%d %H:%M:%S'`" $6 $7" >> $file |
1350 .DE | 1354 .DE |
1351 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title. | 1355 \f(CW$6\fP and \f(CW$7\fP expand to the \s-1URL\s0 and the page title. |
1352 For loading an entry, a key is bound to spawn a load from history script. | 1356 .PP |
1357 For loading an entry, a key is bound to spawn a load-from-history script. | |
1353 The script reverses the history to have newer entries first, | 1358 The script reverses the history to have newer entries first, |
1354 then displays \fIdmenu\fP to select an item, | 1359 then displays \fIdmenu\fP to let the user select an item, |
1355 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe. | 1360 and afterwards writes the selected \s-1URL\s0 into uzbl's command input pipe. |
1356 With error checking and corner cases removed, the script looks like this: | 1361 With error checking and corner case handling removed, |
1362 the script looks like this: | |
1357 .DS | 1363 .DS |
1358 .CW | 1364 .CW |
1359 #!/bin/sh | 1365 #!/bin/sh |
1360 file=/path/to/uzbl-history | 1366 file=/path/to/uzbl-history |
1361 goto=`tac $file | dmenu | cut -d' ' -f 3` | 1367 goto=`tac $file | dmenu | cut -d' ' -f 3` |
1367 .PP | 1373 .PP |
1368 .B "Avoid captive user interfaces" . | 1374 .B "Avoid captive user interfaces" . |
1369 One could say, that uzbl, to a large extend, actually \fIis\fP | 1375 One could say, that uzbl, to a large extend, actually \fIis\fP |
1370 a captive user interface. | 1376 a captive user interface. |
1371 But the difference to most other web browsers is, that uzbl is only | 1377 But the difference to most other web browsers is, that uzbl is only |
1372 the captive user interface frontend and the core of the backend. | 1378 the captive user interface frontend (and the core of the backend). |
1373 Many parts of the backend are independent of uzbl. | 1379 Many parts of the backend are independent of uzbl. |
1374 Some are distributed with uzbl, for some external programs, handler scripts | 1380 Some are distributed with uzbl, for some external programs, |
1375 are distributed, arbitrary additional functionality can be added if desired. | 1381 handler scripts are distributed, |
1382 but arbitrary additional functionality can be added if desired. | |
1376 .PP | 1383 .PP |
1377 The frontend is captive \(en that is true. | 1384 The frontend is captive \(en that is true. |
1378 This is okay for the task of browsing the web, as this task is only relevant | 1385 This is okay for the task of browsing the web, as this task is only relevant |
1379 for humans. | 1386 for humans. |
1380 Automated programs would \fIcrawl\fP the web. | 1387 Automated programs would \fIcrawl\fP the web. |
1385 | 1392 |
1386 .PP | 1393 .PP |
1387 .B "Make every program a filter" . | 1394 .B "Make every program a filter" . |
1388 Graphical web browsers are almost dead ends in the chain of information flow. | 1395 Graphical web browsers are almost dead ends in the chain of information flow. |
1389 Thus it is difficult to see what graphical web browsers should filter. | 1396 Thus it is difficult to see what graphical web browsers should filter. |
1390 Graphical web browsers exist almost only for interactive use by humans. | 1397 Graphical web browsers exist almost only to be interactively used by humans. |
1391 The only case when one might want to automate the rendering function is | 1398 The only case when one might want to automate the rendering function is |
1392 to generate images of rendered webpages. | 1399 to generate images of rendered webpages. |
1393 | 1400 |
1394 .PP | 1401 .PP |
1395 .B "Small is beautiful" | 1402 .B "Small is beautiful" |
1396 is not easy to apply to a web browser, primary because modern web technology | 1403 is not easy to apply to a web browser, because modern web technology |
1397 is very complex; hence the rendering task is very complex. | 1404 is very complex, hence the rendering task is very complex. |
1398 Modern web browsers will always consist of many thousand lines of code, | 1405 Modern web browsers have to consist of many thousand lines of code, |
1399 unfortunately. | 1406 unfortunately. |
1400 Using the toolchest approach and wrappers can split the browser into | 1407 Using the toolchest approach and wrappers can split the browser into |
1401 several small parts, tough. | 1408 several small parts, tough. |
1402 .PP | 1409 .PP |
1403 Uzbl-core consists of about 3\,500 lines of C code. | 1410 As of March 2010, uzbl-core consists of about 3\,500 lines of C code. |
1404 The distribution includes another 3\,500 lines of Shell and Python code, | 1411 The distribution includes another 3\,500 lines of Shell and Python code, |
1405 which are the handler scripts and plugins like a modal interface. | 1412 which are the handler scripts and plugins like a modal interface. |
1406 Further more, uzbl uses functionality of external tools like | 1413 Further more, uzbl uses functionality of external tools like |
1407 \fIwget\fP and \fInetcat\fP. | 1414 \fIwget\fP and \fInetcat\fP. |
1408 Up to this point, uzbl looks pretty neat and small. | 1415 Up to this point, uzbl looks pretty neat and small. |
1409 The ugly part of uzbl is the web content renderer, webkit. | 1416 The ugly part of uzbl is the web content renderer, webkit. |
1410 Webkit consists of roughly 400\,000 (!) lines of code. | 1417 Webkit consists of roughly 400\,000 (!) lines of code. |
1411 Unfortunately, small web render engines are not possible anymore | 1418 Unfortunately, small web render engines are not possible anymore |
1412 because of the modern web. | 1419 because of the modern web. |
1413 The problems section will explain this in more detail. | |
1414 | 1420 |
1415 .PP | 1421 .PP |
1416 .B "Build a prototype as soon as possible" . | 1422 .B "Build a prototype as soon as possible" . |
1417 Plaetinck made his code public, right from the beginning. | 1423 Plaetinck made his code public, right from the beginning. |
1418 Discussion and development was, and still is, open to everyone interested. | 1424 Discussion and development was, and still is, open to everyone interested. |
1419 Development versions of uzbl can be obtained very simply from the code | 1425 Development versions of uzbl can be obtained very simply from the code |
1420 repository. | 1426 repository. |
1421 Within the first year of uzbl's existence, a new version was released | 1427 Within the first year of uzbl's existence, a new version was released |
1422 more often than once a month. | 1428 more often than once a month. |
1423 Different forks and branches arose. | 1429 Different forks and branches arose. |
1424 They introduced new features, which were tested for suitability. | 1430 They introduced new features, which were tested for suitability |
1431 for the main branch. | |
1425 The experiences of using prototypes influenced further development. | 1432 The experiences of using prototypes influenced further development. |
1426 Actually, all development was community driven. | 1433 Actually, all development was community driven. |
1427 Plaetinck says, three months after uzbl's birth: | 1434 Plaetinck says, three months after uzbl's birth: |
1428 ``Right now I hardly code anything myself for Uzbl. | 1435 ``Right now I hardly code anything myself for Uzbl. |
1429 I just merge in other people's code, ponder a lot, and lead the discussions.'' | 1436 I just merge in other people's code, ponder a lot, and lead the discussions.'' |
1445 same as the one of the well known web browsers, | 1452 same as the one of the well known web browsers, |
1446 hiding the internal differences. | 1453 hiding the internal differences. |
1447 But uzbl has to provide this similar look and feel to be accepted | 1454 But uzbl has to provide this similar look and feel to be accepted |
1448 as a ``normal'' browser by ``normal'' users. | 1455 as a ``normal'' browser by ``normal'' users. |
1449 .PP | 1456 .PP |
1450 The more important problem is the modern web. | 1457 Though, the more important problem is the modern web. |
1451 The modern web is simply broken. | 1458 The modern web is simply broken. |
1452 It has state in a state-less protocol, | 1459 It has state in a state-less protocol, |
1453 it misuses technologies, | 1460 it misuses technologies, |
1454 and it is helplessly overloaded. | 1461 and it is helplessly overloaded. |
1455 The result are web content render engines that must consist | 1462 The result are web content render engines that must consist |
1456 of hundreds of thousands lines of code. | 1463 of hundreds of thousands lines of code. |
1457 They also must combine and integrate many different technologies, | 1464 They also must combine and integrate many different technologies, |
1458 only to make our modern web usable. | 1465 only to make our modern web accessible. |
1459 Website to image converter are hardly possible to run without | 1466 Website to image converter are hardly possible to run without |
1460 human interaction because of state in sessions, impossible | 1467 human interaction because of state in sessions, impossible |
1461 deep-linking, and unautomatable technologies. | 1468 deep-linking, and unautomatable technologies. |
1462 .PP | 1469 .PP |
1463 The web was misused to provide all kinds of imaginable wishes. | 1470 The web was misused to provide all kinds of imaginable wishes. |
1472 .LP | 1479 .LP |
1473 ``Uzbl is a browser that adheres to the Unix Philosophy'', | 1480 ``Uzbl is a browser that adheres to the Unix Philosophy'', |
1474 that is how uzbl is seen by its authors. | 1481 that is how uzbl is seen by its authors. |
1475 Indeed, uzbl follows the Unix Philosophy in many ways. | 1482 Indeed, uzbl follows the Unix Philosophy in many ways. |
1476 It consists of independent parts that work together, | 1483 It consists of independent parts that work together, |
1477 its core is mainly a mediator which glues the parts together. | 1484 while its core is mainly a mediator which glues the parts together. |
1478 .PP | 1485 .PP |
1479 Software leverage can excellently be seen in uzbl. | 1486 Software leverage can excellently be seen in uzbl. |
1480 It makes use of external tools, separates independent tasks | 1487 External tools are used, independent tasks are separated |
1481 in independent parts, and glues them together with small | 1488 in independent parts and glued together with small handler scripts. |
1482 handler scripts, around uzbl-core. | |
1483 .PP | 1489 .PP |
1484 As uzbl, more or less, consists of a set of tools and a bit | 1490 As uzbl, more or less, consists of a set of tools and a bit |
1485 of glue, anyone can put the parts together and expand it | 1491 of glue, anyone can put the parts together and expand it |
1486 in any desired way. | 1492 in any desired way. |
1487 Uzbl is very flexible and customizable. | 1493 Uzbl is very flexible and customizable. |
1488 These properties make it valuable for advanced users, | 1494 These properties make it valuable for advanced users, |
1489 but may keep novice users from using it. | 1495 but may keep novice users from using it. |
1490 .PP | 1496 .PP |
1491 Uzbl's main problem is the modern web, that makes it hard | 1497 But uzbl's main problem is the modern web, that makes it hard |
1492 to design a sane web browser. | 1498 to design a sane web browser. |
1493 Despite this bad situation, uzbl does a fairly good job. | 1499 Despite this bad situation, uzbl does a fairly good job. |
1494 | 1500 |
1495 | 1501 |
1496 .NH 1 | 1502 .NH 1 |