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74091dd4 CR |
1 | This is the Bash FAQ, version 4.15, for Bash version 5.1. |
2 | ||
3 | [This document is no longer maintained.] | |
ccc6cda3 JA |
4 | |
5 | This document contains a set of frequently-asked questions concerning | |
6 | Bash, the GNU Bourne-Again Shell. Bash is a freely-available command | |
7 | interpreter with advanced features for both interactive use and shell | |
8 | programming. | |
9 | ||
10 | Another good source of basic information about shells is the collection | |
11 | of FAQ articles periodically posted to comp.unix.shell. | |
12 | ||
13 | Questions and comments concerning this document should be sent to | |
0628567a | 14 | chet.ramey@case.edu. |
ccc6cda3 JA |
15 | |
16 | This document is available for anonymous FTP with the URL | |
17 | ||
cce855bc | 18 | ftp://ftp.cwru.edu/pub/bash/FAQ |
ccc6cda3 | 19 | |
bb70624e JA |
20 | The Bash home page is http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html |
21 | ||
ccc6cda3 JA |
22 | ---------- |
23 | Contents: | |
24 | ||
25 | Section A: The Basics | |
26 | ||
b72432fd JA |
27 | A1) What is it? |
28 | A2) What's the latest version? | |
29 | A3) Where can I get it? | |
30 | A4) On what machines will bash run? | |
31 | A5) Will bash run on operating systems other than Unix? | |
32 | A6) How can I build bash with gcc? | |
33 | A7) How can I make bash my login shell? | |
34 | A8) I just changed my login shell to bash, and now I can't FTP into my | |
35 | machine. Why not? | |
b80f6443 | 36 | A9) What's the `POSIX Shell and Utilities standard'? |
b72432fd | 37 | A10) What is the bash `posix mode'? |
ccc6cda3 JA |
38 | |
39 | Section B: The latest version | |
40 | ||
ac50fbac CR |
41 | B1) What's new in version 4.3? |
42 | B2) Are there any user-visible incompatibilities between bash-4.3 and | |
0001803f | 43 | previous bash versions? |
ccc6cda3 JA |
44 | |
45 | Section C: Differences from other Unix shells | |
46 | ||
b72432fd JA |
47 | C1) How does bash differ from sh, the Bourne shell? |
48 | C2) How does bash differ from the Korn shell, version ksh88? | |
49 | C3) Which new features in ksh-93 are not in bash, and which are? | |
ccc6cda3 JA |
50 | |
51 | Section D: Why does bash do some things differently than other Unix shells? | |
52 | ||
b72432fd | 53 | D1) Why does bash run a different version of `command' than |
ccc6cda3 | 54 | `which command' says it will? |
b72432fd JA |
55 | D2) Why doesn't bash treat brace expansions exactly like csh? |
56 | D3) Why doesn't bash have csh variable modifiers? | |
57 | D4) How can I make my csh aliases work when I convert to bash? | |
58 | D5) How can I pipe standard output and standard error from one command to | |
ccc6cda3 | 59 | another, like csh does with `|&'? |
b72432fd | 60 | D6) Now that I've converted from ksh to bash, are there equivalents to |
ccc6cda3 JA |
61 | ksh features like autoloaded functions and the `whence' command? |
62 | ||
bb70624e | 63 | Section E: Why does bash do certain things the way it does? |
ccc6cda3 | 64 | |
b72432fd JA |
65 | E1) Why is the bash builtin `test' slightly different from /bin/test? |
66 | E2) Why does bash sometimes say `Broken pipe'? | |
bb70624e | 67 | E3) When I have terminal escape sequences in my prompt, why does bash |
ccc6cda3 | 68 | wrap lines at the wrong column? |
bb70624e | 69 | E4) If I pipe the output of a command into `read variable', why doesn't |
ccc6cda3 | 70 | the output show up in $variable when the read command finishes? |
bb70624e | 71 | E5) I have a bunch of shell scripts that use backslash-escaped characters |
ccc6cda3 JA |
72 | in arguments to `echo'. Bash doesn't interpret these characters. Why |
73 | not, and how can I make it understand them? | |
bb70624e | 74 | E6) Why doesn't a while or for loop get suspended when I type ^Z? |
28ef6c31 JA |
75 | E7) What about empty for loops in Makefiles? |
76 | E8) Why does the arithmetic evaluation code complain about `08'? | |
77 | E9) Why does the pattern matching expression [A-Z]* match files beginning | |
78 | with every letter except `z'? | |
7117c2d2 | 79 | E10) Why does `cd //' leave $PWD as `//'? |
b80f6443 JA |
80 | E11) If I resize my xterm while another program is running, why doesn't bash |
81 | notice the change? | |
82 | E12) Why don't negative offsets in substring expansion work like I expect? | |
0628567a | 83 | E13) Why does filename completion misbehave if a colon appears in the filename? |
3185942a JA |
84 | E14) Why does quoting the pattern argument to the regular expression matching |
85 | conditional operator (=~) cause matching to stop working? | |
0001803f | 86 | E15) Tell me more about the shell compatibility level. |
ccc6cda3 JA |
87 | |
88 | Section F: Things to watch out for on certain Unix versions | |
89 | ||
b72432fd JA |
90 | F1) Why can't I use command line editing in my `cmdtool'? |
91 | F2) I built bash on Solaris 2. Why do globbing expansions and filename | |
ccc6cda3 | 92 | completion chop off the first few characters of each filename? |
b72432fd | 93 | F3) Why does bash dump core after I interrupt username completion or |
ccc6cda3 | 94 | `~user' tilde expansion on a machine running NIS? |
b72432fd JA |
95 | F4) I'm running SVR4.2. Why is the line erased every time I type `@'? |
96 | F5) Why does bash report syntax errors when my C News scripts use a | |
ccc6cda3 | 97 | redirection before a subshell command? |
bb70624e | 98 | F6) Why can't I use vi-mode editing on Red Hat Linux 6.1? |
7117c2d2 JA |
99 | F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on |
100 | HP/UX 11.x? | |
bb70624e JA |
101 | |
102 | Section G: How can I get bash to do certain common things? | |
103 | ||
104 | G1) How can I get bash to read and display eight-bit characters? | |
105 | G2) How do I write a function `x' to replace builtin command `x', but | |
106 | still invoke the command from within the function? | |
107 | G3) How can I find the value of a shell variable whose name is the value | |
108 | of another shell variable? | |
109 | G4) How can I make the bash `time' reserved word print timing output that | |
110 | looks like the output from my system's /usr/bin/time? | |
111 | G5) How do I get the current directory into my prompt? | |
112 | G6) How can I rename "*.foo" to "*.bar"? | |
113 | G7) How can I translate a filename from uppercase to lowercase? | |
114 | G8) How can I write a filename expansion (globbing) pattern that will match | |
115 | all files in the current directory except "." and ".."? | |
ccc6cda3 | 116 | |
bb70624e | 117 | Section H: Where do I go from here? |
ccc6cda3 | 118 | |
bb70624e | 119 | H1) How do I report bugs in bash, and where should I look for fixes and |
ccc6cda3 | 120 | advice? |
bb70624e JA |
121 | H2) What kind of bash documentation is there? |
122 | H3) What's coming in future versions? | |
123 | H4) What's on the bash `wish list'? | |
124 | H5) When will the next release appear? | |
ccc6cda3 JA |
125 | |
126 | ---------- | |
127 | Section A: The Basics | |
128 | ||
b72432fd | 129 | A1) What is it? |
ccc6cda3 JA |
130 | |
131 | Bash is a Unix command interpreter (shell). It is an implementation of | |
132 | the Posix 1003.2 shell standard, and resembles the Korn and System V | |
133 | shells. | |
134 | ||
135 | Bash contains a number of enhancements over those shells, both | |
136 | for interactive use and shell programming. Features geared | |
137 | toward interactive use include command line editing, command | |
138 | history, job control, aliases, and prompt expansion. Programming | |
139 | features include additional variable expansions, shell | |
140 | arithmetic, and a number of variables and options to control | |
141 | shell behavior. | |
142 | ||
143 | Bash was originally written by Brian Fox of the Free Software | |
144 | Foundation. The current developer and maintainer is Chet Ramey | |
145 | of Case Western Reserve University. | |
146 | ||
b72432fd | 147 | A2) What's the latest version? |
ccc6cda3 | 148 | |
a0c0a00f | 149 | The latest version is 4.3, first made available on 26 February, 2014. |
ccc6cda3 | 150 | |
b72432fd | 151 | A3) Where can I get it? |
ccc6cda3 JA |
152 | |
153 | Bash is the GNU project's shell, and so is available from the | |
b72432fd | 154 | master GNU archive site, ftp.gnu.org, and its mirrors. The |
cce855bc | 155 | latest version is also available for FTP from ftp.cwru.edu. |
ac50fbac | 156 | The following URLs tell how to get version 4.3: |
ccc6cda3 | 157 | |
ac50fbac CR |
158 | ftp://ftp.gnu.org/pub/gnu/bash/bash-4.3.tar.gz |
159 | ftp://ftp.cwru.edu/pub/bash/bash-4.3.tar.gz | |
ccc6cda3 JA |
160 | |
161 | Formatted versions of the documentation are available with the URLs: | |
162 | ||
ac50fbac CR |
163 | ftp://ftp.gnu.org/pub/gnu/bash/bash-doc-4.3.tar.gz |
164 | ftp://ftp.cwru.edu/pub/bash/bash-doc-4.3.tar.gz | |
95732b49 JA |
165 | |
166 | Any patches for the current version are available with the URL: | |
167 | ||
ac50fbac | 168 | ftp://ftp.cwru.edu/pub/bash/bash-4.3-patches/ |
ccc6cda3 | 169 | |
b72432fd | 170 | A4) On what machines will bash run? |
ccc6cda3 | 171 | |
b80f6443 | 172 | Bash has been ported to nearly every version of Unix. All you |
ccc6cda3 JA |
173 | should have to do to build it on a machine for which a port |
174 | exists is to type `configure' and then `make'. The build process | |
b80f6443 | 175 | will attempt to discover the version of Unix you have and tailor |
ccc6cda3 JA |
176 | itself accordingly, using a script created by GNU autoconf. |
177 | ||
178 | More information appears in the file `INSTALL' in the distribution. | |
179 | ||
f73dda09 JA |
180 | The Bash web page (http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html) |
181 | explains how to obtain binary versions of bash for most of the major | |
182 | commercial Unix systems. | |
183 | ||
b72432fd | 184 | A5) Will bash run on operating systems other than Unix? |
d166f048 JA |
185 | |
186 | Configuration specifics for Unix-like systems such as QNX and | |
f73dda09 JA |
187 | LynxOS are included in the distribution. Bash-2.05 and later |
188 | versions should compile and run on Minix 2.0 (patches were | |
189 | contributed), but I don't believe anyone has built bash-2.x on | |
190 | earlier Minix versions yet. | |
d166f048 JA |
191 | |
192 | Bash has been ported to versions of Windows implementing the Win32 | |
193 | programming interface. This includes Windows 95 and Windows NT. | |
95732b49 JA |
194 | The port was done by Cygnus Solutions (now part of Red Hat) as part |
195 | of their CYGWIN project. For more information about the project, see | |
196 | http://www.cygwin.com/. | |
d166f048 | 197 | |
b72432fd | 198 | Cygnus originally ported bash-1.14.7, and that port was part of their |
95732b49 | 199 | early GNU-Win32 (the original name) releases. Cygnus has also done |
0001803f | 200 | ports of bash-3.2 and bash-4.0 to the CYGWIN environment, and both |
17345e5a | 201 | are available as part of their current release. |
cce855bc | 202 | |
b80f6443 JA |
203 | Bash-2.05b and later versions should require no local Cygnus changes to |
204 | build and run under CYGWIN. | |
cce855bc | 205 | |
f73dda09 | 206 | DJ Delorie has a port of bash-2.x which runs under MS-DOS, as part |
28ef6c31 | 207 | of the DJGPP project. For more information on the project, see |
d166f048 JA |
208 | |
209 | http://www.delorie.com/djgpp/ | |
210 | ||
28ef6c31 JA |
211 | I have been told that the original DJGPP port was done by Daisuke Aoyama. |
212 | ||
f73dda09 JA |
213 | Mark Elbrecht <snowball3@bigfoot.com> has sent me notice that bash-2.04 |
214 | is available for DJGPP V2. The files are available as: | |
bb70624e | 215 | |
f73dda09 JA |
216 | ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204b.zip binary |
217 | ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204d.zip documentation | |
218 | ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204s.zip source | |
bb70624e | 219 | |
b80f6443 | 220 | Mark began to work with bash-2.05, but I don't know the current status. |
d166f048 | 221 | |
b80f6443 | 222 | Bash-3.0 compiles and runs with no modifications under Microsoft's Services |
95732b49 | 223 | for Unix (SFU), once known as Interix. I do not anticipate any problems |
ac50fbac CR |
224 | with building bash-4.2 and later, but will gladly accept any patches that |
225 | are needed. | |
bb70624e | 226 | |
b72432fd | 227 | A6) How can I build bash with gcc? |
ccc6cda3 JA |
228 | |
229 | Bash configures to use gcc by default if it is available. Read the | |
230 | file INSTALL in the distribution for more information. | |
231 | ||
b72432fd | 232 | A7) How can I make bash my login shell? |
ccc6cda3 JA |
233 | |
234 | Some machines let you use `chsh' to change your login shell. Other | |
cce855bc JA |
235 | systems use `passwd -s' or `passwd -e'. If one of these works for |
236 | you, that's all you need. Note that many systems require the full | |
237 | pathname to a shell to appear in /etc/shells before you can make it | |
238 | your login shell. For this, you may need the assistance of your | |
239 | friendly local system administrator. | |
ccc6cda3 JA |
240 | |
241 | If you cannot do this, you can still use bash as your login shell, but | |
242 | you need to perform some tricks. The basic idea is to add a command | |
243 | to your login shell's startup file to replace your login shell with | |
244 | bash. | |
245 | ||
246 | For example, if your login shell is csh or tcsh, and you have installed | |
247 | bash in /usr/gnu/bin/bash, add the following line to ~/.login: | |
248 | ||
249 | if ( -f /usr/gnu/bin/bash ) exec /usr/gnu/bin/bash --login | |
250 | ||
251 | (the `--login' tells bash that it is a login shell). | |
252 | ||
253 | It's not a good idea to put this command into ~/.cshrc, because every | |
254 | csh you run without the `-f' option, even ones started to run csh scripts, | |
255 | reads that file. If you must put the command in ~/.cshrc, use something | |
256 | like | |
257 | ||
258 | if ( $?prompt ) exec /usr/gnu/bin/bash --login | |
259 | ||
260 | to ensure that bash is exec'd only when the csh is interactive. | |
261 | ||
d166f048 | 262 | If your login shell is sh or ksh, you have to do two things. |
ccc6cda3 | 263 | |
d166f048 | 264 | First, create an empty file in your home directory named `.bash_profile'. |
ccc6cda3 JA |
265 | The existence of this file will prevent the exec'd bash from trying to |
266 | read ~/.profile, and re-execing itself over and over again. ~/.bash_profile | |
d166f048 JA |
267 | is the first file bash tries to read initialization commands from when |
268 | it is invoked as a login shell. | |
269 | ||
270 | Next, add a line similar to the above to ~/.profile: | |
271 | ||
b80f6443 JA |
272 | [ -f /usr/gnu/bin/bash ] && [ -x /usr/gnu/bin/bash ] && \ |
273 | exec /usr/gnu/bin/bash --login | |
ccc6cda3 | 274 | |
d166f048 JA |
275 | This will cause login shells to replace themselves with bash running as |
276 | a login shell. Once you have this working, you can copy your initialization | |
277 | code from ~/.profile to ~/.bash_profile. | |
278 | ||
bb70624e JA |
279 | I have received word that the recipe supplied above is insufficient for |
280 | machines running CDE. CDE has a maze of twisty little startup files, all | |
281 | slightly different. | |
282 | ||
283 | If you cannot change your login shell in the password file to bash, you | |
284 | will have to (apparently) live with CDE using the shell in the password | |
285 | file to run its startup scripts. If you have changed your shell to bash, | |
f73dda09 JA |
286 | there is code in the CDE startup files (on Solaris, at least) that attempts |
287 | to do the right thing. It is, however, often broken, and may require that | |
288 | you use the $BASH_ENV trick described below. | |
bb70624e JA |
289 | |
290 | `dtterm' claims to use $SHELL as the default program to start, so if you | |
291 | can change $SHELL in the CDE startup files, you should be able to use bash | |
292 | in your terminal windows. | |
293 | ||
294 | Setting DTSOURCEPROFILE in ~/.dtprofile will cause the `Xsession' program | |
295 | to read your login shell's startup files. You may be able to use bash for | |
296 | the rest of the CDE programs by setting SHELL to bash in ~/.dtprofile as | |
297 | well, but I have not tried this. | |
298 | ||
299 | You can use the above `exec' recipe to start bash when not logging in with | |
300 | CDE by testing the value of the DT variable: | |
301 | ||
302 | if [ -n "$DT" ]; then | |
303 | [ -f /usr/gnu/bin/bash ] && exec /usr/gnu/bin/bash --login | |
304 | fi | |
305 | ||
f73dda09 JA |
306 | If CDE starts its shells non-interactively during login, the login shell |
307 | startup files (~/.profile, ~/.bash_profile) will not be sourced at login. | |
308 | To get around this problem, append a line similar to the following to your | |
309 | ~/.dtprofile: | |
310 | ||
311 | BASH_ENV=${HOME}/.bash_profile ; export BASH_ENV | |
312 | ||
313 | and add the following line to the beginning of ~/.bash_profile: | |
314 | ||
315 | unset BASH_ENV | |
bb70624e | 316 | |
b72432fd | 317 | A8) I just changed my login shell to bash, and now I can't FTP into my |
ccc6cda3 JA |
318 | machine. Why not? |
319 | ||
320 | You must add the full pathname to bash to the file /etc/shells. As | |
321 | noted in the answer to the previous question, many systems require | |
322 | this before you can make bash your login shell. | |
323 | ||
324 | Most versions of ftpd use this file to prohibit `special' users | |
325 | such as `uucp' and `news' from using FTP. | |
326 | ||
b80f6443 | 327 | A9) What's the `POSIX Shell and Utilities standard'? |
ccc6cda3 JA |
328 | |
329 | POSIX is a name originally coined by Richard Stallman for a | |
330 | family of open system standards based on UNIX. There are a | |
331 | number of aspects of UNIX under consideration for | |
332 | standardization, from the basic system services at the system | |
333 | call and C library level to applications and tools to system | |
334 | administration and management. Each area of standardization is | |
335 | assigned to a working group in the 1003 series. | |
336 | ||
b80f6443 JA |
337 | The POSIX Shell and Utilities standard was originally developed by |
338 | IEEE Working Group 1003.2 (POSIX.2). Today it has been merged with | |
339 | the original 1003.1 Working Group and is maintained by the Austin | |
340 | Group (a joint working group of the IEEE, The Open Group and | |
341 | ISO/IEC SC22/WG15). Today the Shell and Utilities are a volume | |
342 | within the set of documents that make up IEEE Std 1003.1-2001, and | |
343 | thus now the former POSIX.2 (from 1992) is now part of the current | |
344 | POSIX.1 standard (POSIX 1003.1-2001). | |
345 | ||
346 | The Shell and Utilities volume concentrates on the command | |
ccc6cda3 | 347 | interpreter interface and utility programs commonly executed from |
b80f6443 JA |
348 | the command line or by other programs. The standard is freely |
349 | available on the web at http://www.UNIX-systems.org/version3/ . | |
350 | Work continues at the Austin Group on maintenance issues; see | |
351 | http://www.opengroup.org/austin/ to join the discussions. | |
ccc6cda3 | 352 | |
b80f6443 JA |
353 | Bash is concerned with the aspects of the shell's behavior defined |
354 | by the POSIX Shell and Utilities volume. The shell command | |
355 | language has of course been standardized, including the basic flow | |
356 | control and program execution constructs, I/O redirection and | |
357 | pipelining, argument handling, variable expansion, and quoting. | |
ccc6cda3 JA |
358 | |
359 | The `special' builtins, which must be implemented as part of the | |
360 | shell to provide the desired functionality, are specified as | |
361 | being part of the shell; examples of these are `eval' and | |
b80f6443 | 362 | `export'. Other utilities appear in the sections of POSIX not |
ccc6cda3 JA |
363 | devoted to the shell which are commonly (and in some cases must |
364 | be) implemented as builtin commands, such as `read' and `test'. | |
b80f6443 | 365 | POSIX also specifies aspects of the shell's interactive |
ccc6cda3 JA |
366 | behavior as part of the UPE, including job control and command |
367 | line editing. Only vi-style line editing commands have been | |
368 | standardized; emacs editing commands were left out due to | |
369 | objections. | |
370 | ||
b80f6443 JA |
371 | The latest version of the POSIX Shell and Utilities standard is |
372 | available (now updated to the 2004 Edition) as part of the Single | |
373 | UNIX Specification Version 3 at | |
7117c2d2 | 374 | |
b80f6443 | 375 | http://www.UNIX-systems.org/version3/ |
7117c2d2 | 376 | |
b72432fd | 377 | A10) What is the bash `posix mode'? |
ccc6cda3 | 378 | |
b80f6443 | 379 | Although bash is an implementation of the POSIX shell |
ccc6cda3 JA |
380 | specification, there are areas where the bash default behavior |
381 | differs from that spec. The bash `posix mode' changes the bash | |
382 | behavior in these areas so that it obeys the spec more closely. | |
383 | ||
7117c2d2 JA |
384 | Posix mode is entered by starting bash with the --posix or |
385 | '-o posix' option or executing `set -o posix' after bash is running. | |
ccc6cda3 JA |
386 | |
387 | The specific aspects of bash which change when posix mode is | |
7117c2d2 JA |
388 | active are listed in the file POSIX in the bash distribution. |
389 | They are also listed in a section in the Bash Reference Manual | |
390 | (from which that file is generated). | |
ccc6cda3 JA |
391 | |
392 | Section B: The latest version | |
393 | ||
ac50fbac | 394 | B1) What's new in version 4.3? |
95732b49 | 395 | |
ac50fbac | 396 | Bash-4.3 is the third revision to the fourth major release of bash. |
17345e5a | 397 | |
ac50fbac CR |
398 | Bash-4.3 contains the following new features (see the manual page for |
399 | complete descriptions and the CHANGES and NEWS files in the bash-4.3 | |
17345e5a JA |
400 | distribution): |
401 | ||
ac50fbac CR |
402 | o The `helptopic' completion action now maps to all the help topics, not just |
403 | the shell builtins. | |
404 | ||
405 | o The `help' builtin no longer does prefix substring matching first, so | |
406 | `help read' does not match `readonly', but will do it if exact string | |
407 | matching fails. | |
408 | ||
409 | o The shell can be compiled to not display a message about processes that | |
410 | terminate due to SIGTERM. | |
411 | ||
412 | o Non-interactive shells now react to the setting of checkwinsize and set | |
413 | LINES and COLUMNS after a foreground job exits. | |
414 | ||
415 | o There is a new shell option, `globasciiranges', which, when set to on, | |
416 | forces globbing range comparisons to use character ordering as if they | |
417 | were run in the C locale. | |
418 | ||
419 | o There is a new shell option, `direxpand', which makes filename completion | |
420 | expand variables in directory names in the way bash-4.1 did. | |
421 | ||
422 | o In Posix mode, the `command' builtin does not change whether or not a | |
423 | builtin it shadows is treated as an assignment builtin. | |
424 | ||
425 | o The `return' and `exit' builtins accept negative exit status arguments. | |
426 | ||
427 | o The word completion code checks whether or not a filename containing a | |
428 | shell variable expands to a directory name and appends `/' to the word | |
429 | as appropriate. The same code expands shell variables in command names | |
430 | when performing command completion. | |
431 | ||
432 | o In Posix mode, it is now an error to attempt to define a shell function | |
433 | with the same name as a Posix special builtin. | |
434 | ||
435 | o When compiled for strict Posix conformance, history expansion is disabled | |
436 | by default. | |
437 | ||
438 | o The history expansion character (!) does not cause history expansion when | |
439 | followed by the closing quote in a double-quoted string. | |
440 | ||
441 | o `complete' and its siblings compgen/compopt now takes a new `-o noquote' | |
442 | option to inhibit quoting of the completions. | |
443 | ||
444 | o Setting HISTSIZE to a value less than zero causes the history list to be | |
445 | unlimited (setting it 0 zero disables the history list). | |
446 | ||
447 | o Setting HISTFILESIZE to a value less than zero causes the history file size | |
448 | to be unlimited (setting it to 0 causes the history file to be truncated | |
449 | to zero size). | |
450 | ||
451 | o The `read' builtin now skips NUL bytes in the input. | |
452 | ||
453 | o There is a new `bind -X' option to print all key sequences bound to Unix | |
454 | commands. | |
455 | ||
456 | o When in Posix mode, `read' is interruptible by a trapped signal. After | |
457 | running the trap handler, read returns 128+signal and throws away any | |
458 | partially-read input. | |
459 | ||
460 | o The command completion code skips whitespace and assignment statements | |
461 | before looking for the command name word to be completed. | |
462 | ||
463 | o The build process has a new mechanism for constructing separate help files | |
464 | that better reflects the current set of compilation options. | |
465 | ||
466 | o The -nt and -ot options to test now work with files with nanosecond | |
467 | timestamp resolution. | |
468 | ||
469 | o The shell saves the command history in any shell for which history is | |
470 | enabled and HISTFILE is set, not just interactive shells. | |
471 | ||
472 | o The shell has `nameref' variables and new -n(/+n) options to declare and | |
473 | unset to use them, and a `test -R' option to test for them. | |
474 | ||
475 | o The shell now allows assigning, referencing, and unsetting elements of | |
476 | indexed arrays using negative subscripts (a[-1]=2, echo ${a[-1]}) which | |
477 | count back from the last element of the array. | |
478 | ||
479 | o The {x}<word redirection feature now allows words like {array[ind]} and | |
480 | can use variables with special meanings to the shell (e.g., BASH_XTRACEFD). | |
481 | ||
482 | o There is a new CHILD_MAX special shell variable; its value controls the | |
483 | number of exited child statues the shell remembers. | |
484 | ||
485 | o There is a new configuration option (--enable-direxpand-default) that | |
486 | causes the `direxpand' shell option to be enabled by default. | |
487 | ||
488 | o Bash does not do anything special to ensure that the file descriptor | |
489 | assigned to X in {x}<foo remains open after the block containing it | |
490 | completes. | |
491 | ||
492 | o The `wait' builtin has a new `-n' option to wait for the next child to | |
493 | change status. | |
494 | ||
495 | o The `printf' %(...)T format specifier now uses the current time if no | |
496 | argument is supplied. | |
497 | ||
498 | o There is a new variable, BASH_COMPAT, that controls the current shell | |
499 | compatibility level. | |
500 | ||
501 | o The `popd' builtin now treats additional arguments as errors. | |
502 | ||
503 | o The brace expansion code now treats a failed sequence expansion as a | |
504 | simple string and will continue to expand brace terms in the remainder | |
505 | of the word. | |
506 | ||
507 | o Shells started to run process substitutions now run any trap set on EXIT. | |
508 | ||
509 | o The fc builtin now interprets -0 as the current command line. | |
510 | ||
511 | o Completing directory names containing shell variables now adds a trailing | |
512 | slash if the expanded result is a directory. | |
513 | ||
514 | A short feature history dating back to Bash-2.0: | |
515 | ||
516 | Bash-4.2 contained the following new features: | |
517 | ||
495aee44 CR |
518 | o `exec -a foo' now sets $0 to `foo' in an executable shell script without a |
519 | leading #!. | |
520 | ||
521 | o Subshells begun to execute command substitutions or run shell functions or | |
522 | builtins in subshells do not reset trap strings until a new trap is | |
523 | specified. This allows $(trap) to display the caller's traps and the | |
524 | trap strings to persist until a new trap is set. | |
525 | ||
526 | o `trap -p' will now show signals ignored at shell startup, though their | |
527 | disposition still cannot be modified. | |
528 | ||
529 | o $'...', echo, and printf understand \uXXXX and \UXXXXXXXX escape sequences. | |
530 | ||
531 | o declare/typeset has a new `-g' option, which creates variables in the | |
532 | global scope even when run in a shell function. | |
533 | ||
534 | o test/[/[[ have a new -v variable unary operator, which returns success if | |
535 | `variable' has been set. | |
536 | ||
537 | o Posix parsing changes to allow `! time command' and multiple consecutive | |
538 | instances of `!' (which toggle) and `time' (which have no cumulative | |
539 | effect). | |
540 | ||
541 | o Posix change to allow `time' as a command by itself to print the elapsed | |
542 | user, system, and real times for the shell and its children. | |
543 | ||
544 | o $((...)) is always parsed as an arithmetic expansion first, instead of as | |
545 | a potential nested command substitution, as Posix requires. | |
546 | ||
547 | o A new FUNCNEST variable to allow the user to control the maximum shell | |
548 | function nesting (recursive execution) level. | |
549 | ||
550 | o The mapfile builtin now supplies a third argument to the callback command: | |
551 | the line about to be assigned to the supplied array index. | |
552 | ||
553 | o The printf builtin has as new %(fmt)T specifier, which allows time values | |
554 | to use strftime-like formatting. | |
555 | ||
556 | o There is a new `compat41' shell option. | |
557 | ||
558 | o The cd builtin has a new Posix-mandated `-e' option. | |
559 | ||
560 | o Negative subscripts to indexed arrays, previously errors, now are treated | |
561 | as offsets from the maximum assigned index + 1. | |
562 | ||
563 | o Negative length specifications in the ${var:offset:length} expansion, | |
564 | previously errors, are now treated as offsets from the end of the variable. | |
565 | ||
566 | o Parsing change to allow `time -p --'. | |
567 | ||
568 | o Posix-mode parsing change to not recognize `time' as a keyword if the | |
569 | following token begins with a `-'. This means no more Posix-mode | |
570 | `time -p'. Posix interpretation 267. | |
571 | ||
572 | o There is a new `lastpipe' shell option that runs the last command of a | |
573 | pipeline in the current shell context. The lastpipe option has no | |
574 | effect if job control is enabled. | |
575 | ||
576 | o History expansion no longer expands the `$!' variable expansion. | |
577 | ||
578 | o Posix mode shells no longer exit if a variable assignment error occurs | |
579 | with an assignment preceding a command that is not a special builtin. | |
580 | ||
581 | o Non-interactive mode shells exit if -u is enabled an an attempt is made | |
582 | to use an unset variable with the % or # expansions, the `//', `^', or | |
583 | `,' expansions, or the parameter length expansion. | |
584 | ||
585 | o Posix-mode shells use the argument passed to `.' as-is if a $PATH search | |
586 | fails, effectively searching the current directory. Posix-2008 change. | |
587 | ||
588 | A short feature history dating back to Bash-2.0: | |
589 | ||
590 | Bash-4.1 contained the following new features: | |
591 | ||
0001803f CR |
592 | o Here-documents within $(...) command substitutions may once more be |
593 | delimited by the closing right paren, instead of requiring a newline. | |
594 | ||
595 | o Bash's file status checks (executable, readable, etc.) now take file | |
596 | system ACLs into account on file systems that support them. | |
597 | ||
598 | o Bash now passes environment variables with names that are not valid | |
599 | shell variable names through into the environment passed to child | |
600 | processes. | |
601 | ||
602 | o The `execute-unix-command' readline function now attempts to clear and | |
603 | reuse the current line rather than move to a new one after the command | |
604 | executes. | |
605 | ||
606 | o `printf -v' can now assign values to array indices. | |
607 | ||
608 | o New `complete -E' and `compopt -E' options that work on the "empty" | |
609 | completion: completion attempted on an empty command line. | |
610 | ||
611 | o New complete/compgen/compopt -D option to define a `default' completion: | |
612 | a completion to be invoked on command for which no completion has been | |
613 | defined. If this function returns 124, programmable completion is | |
614 | attempted again, allowing a user to dynamically build a set of completions | |
615 | as completion is attempted by having the default completion function | |
616 | install individual completion functions each time it is invoked. | |
617 | ||
618 | o When displaying associative arrays, subscripts are now quoted. | |
619 | ||
620 | o Changes to dabbrev-expand to make it more `emacs-like': no space appended | |
621 | after matches, completions are not sorted, and most recent history entries | |
622 | are presented first. | |
623 | ||
624 | o The [[ and (( commands are now subject to the setting of `set -e' and the | |
625 | ERR trap. | |
626 | ||
627 | o The source/. builtin now removes NUL bytes from the file before attempting | |
628 | to parse commands. | |
629 | ||
630 | o There is a new configuration option (in config-top.h) that forces bash to | |
631 | forward all history entries to syslog. | |
632 | ||
633 | o A new variable $BASHOPTS to export shell options settable using `shopt' to | |
634 | child processes. | |
635 | ||
74091dd4 | 636 | o There is a new configure option that forces the extglob option to be |
0001803f CR |
637 | enabled by default. |
638 | ||
639 | o New variable $BASH_XTRACEFD; when set to an integer bash will write xtrace | |
640 | output to that file descriptor. | |
641 | ||
642 | o If the optional left-hand-side of a redirection is of the form {var}, the | |
643 | shell assigns the file descriptor used to $var or uses $var as the file | |
644 | descriptor to move or close, depending on the redirection operator. | |
645 | ||
646 | o The < and > operators to the [[ conditional command now do string | |
647 | comparison according to the current locale. | |
648 | ||
649 | o Programmable completion now uses the completion for `b' instead of `a' | |
650 | when completion is attempted on a line like: a $(b c. | |
651 | ||
652 | o Force extglob on temporarily when parsing the pattern argument to | |
653 | the == and != operators to the [[ command, for compatibility. | |
654 | ||
655 | o Changed the behavior of interrupting the wait builtin when a SIGCHLD is | |
656 | received and a trap on SIGCHLD is set to be Posix-mode only. | |
657 | ||
658 | o The read builtin has a new `-N nchars' option, which reads exactly NCHARS | |
659 | characters, ignoring delimiters like newline. | |
660 | ||
661 | o The mapfile/readarray builtin no longer stores the commands it invokes via | |
662 | callbacks in the history list. | |
663 | ||
664 | o There is a new `compat40' shopt option. | |
665 | ||
666 | o The < and > operators to [[ do string comparisons using the current locale | |
667 | only if the compatibility level is greater than 40 (set to 41 by default). | |
668 | ||
669 | o New bindable readline function: menu-complete-backward. | |
670 | ||
671 | o In the readline vi-mode insertion keymap, C-n is now bound to menu-complete | |
672 | by default, and C-p to menu-complete-backward. | |
673 | ||
674 | o When in readline vi command mode, repeatedly hitting ESC now does nothing, | |
675 | even when ESC introduces a bound key sequence. This is closer to how | |
676 | historical vi behaves. | |
677 | ||
678 | o New bindable readline function: skip-csi-sequence. Can be used as a | |
679 | default to consume key sequences generated by keys like Home and End | |
680 | without having to bind all keys. | |
681 | ||
682 | o New bindable readline variable: skip-completed-text, active when | |
683 | completing in the middle of a word. If enabled, it means that characters | |
684 | in the completion that match characters in the remainder of the word are | |
685 | "skipped" rather than inserted into the line. | |
686 | ||
687 | o The pre-readline-6.0 version of menu completion is available as | |
688 | "old-menu-complete" for users who do not like the readline-6.0 version. | |
689 | ||
690 | o New bindable readline variable: echo-control-characters. If enabled, and | |
691 | the tty ECHOCTL bit is set, controls the echoing of characters | |
692 | corresponding to keyboard-generated signals. | |
693 | ||
694 | o New bindable readline variable: enable-meta-key. Controls whether or not | |
695 | readline sends the smm/rmm sequences if the terminal indicates it has a | |
696 | meta key that enables eight-bit characters. | |
697 | ||
0001803f CR |
698 | Bash-4.0 contained the following new features: |
699 | ||
17345e5a JA |
700 | o When using substring expansion on the positional parameters, a starting |
701 | index of 0 now causes $0 to be prefixed to the list. | |
702 | ||
703 | o There is a new variable, $BASHPID, which always returns the process id of | |
704 | the current shell. | |
705 | ||
706 | o There is a new `autocd' option that, when enabled, causes bash to attempt | |
707 | to `cd' to a directory name that is supplied as the first word of a | |
708 | simple command. | |
709 | ||
710 | o There is a new `checkjobs' option that causes the shell to check for and | |
711 | report any running or stopped jobs at exit. | |
712 | ||
713 | o The programmable completion code exports a new COMP_TYPE variable, set to | |
714 | a character describing the type of completion being attempted. | |
715 | ||
716 | o The programmable completion code exports a new COMP_KEY variable, set to | |
717 | the character that caused the completion to be invoked (e.g., TAB). | |
718 | ||
719 | o The programmable completion code now uses the same set of characters as | |
720 | readline when breaking the command line into a list of words. | |
721 | ||
722 | o The block multiplier for the ulimit -c and -f options is now 512 when in | |
723 | Posix mode, as Posix specifies. | |
724 | ||
725 | o Changed the behavior of the read builtin to save any partial input received | |
726 | in the specified variable when the read builtin times out. This also | |
727 | results in variables specified as arguments to read to be set to the empty | |
728 | string when there is no input available. When the read builtin times out, | |
729 | it returns an exit status greater than 128. | |
730 | ||
731 | o The shell now has the notion of a `compatibility level', controlled by | |
732 | new variables settable by `shopt'. Setting this variable currently | |
733 | restores the bash-3.1 behavior when processing quoted strings on the rhs | |
734 | of the `=~' operator to the `[[' command. | |
735 | ||
736 | o The `ulimit' builtin now has new -b (socket buffer size) and -T (number | |
737 | of threads) options. | |
738 | ||
739 | o There is a new `compopt' builtin that allows completion functions to modify | |
740 | completion options for existing completions or the completion currently | |
741 | being executed. | |
742 | ||
743 | o The `read' builtin has a new -i option which inserts text into the reply | |
744 | buffer when using readline. | |
745 | ||
746 | o A new `-E' option to the complete builtin allows control of the default | |
747 | behavior for completion on an empty line. | |
748 | ||
749 | o There is now limited support for completing command name words containing | |
750 | globbing characters. | |
751 | ||
752 | o The `help' builtin now has a new -d option, to display a short description, | |
753 | and a -m option, to print help information in a man page-like format. | |
754 | ||
755 | o There is a new `mapfile' builtin to populate an array with lines from a | |
756 | given file. | |
757 | ||
758 | o If a command is not found, the shell attempts to execute a shell function | |
759 | named `command_not_found_handle', supplying the command words as the | |
760 | function arguments. | |
761 | ||
762 | o There is a new shell option: `globstar'. When enabled, the globbing code | |
763 | treats `**' specially -- it matches all directories (and files within | |
764 | them, when appropriate) recursively. | |
765 | ||
766 | o There is a new shell option: `dirspell'. When enabled, the filename | |
767 | completion code performs spelling correction on directory names during | |
768 | completion. | |
769 | ||
770 | o The `-t' option to the `read' builtin now supports fractional timeout | |
771 | values. | |
772 | ||
773 | o Brace expansion now allows zero-padding of expanded numeric values and | |
774 | will add the proper number of zeroes to make sure all values contain the | |
775 | same number of digits. | |
776 | ||
777 | o There is a new bash-specific bindable readline function: `dabbrev-expand'. | |
778 | It uses menu completion on a set of words taken from the history list. | |
779 | ||
780 | o The command assigned to a key sequence with `bind -x' now sets two new | |
781 | variables in the environment of the executed command: READLINE_LINE_BUFFER | |
782 | and READLINE_POINT. The command can change the current readline line | |
783 | and cursor position by modifying READLINE_LINE_BUFFER and READLINE_POINT, | |
784 | respectively. | |
785 | ||
786 | o There is a new >>& redirection operator, which appends the standard output | |
787 | and standard error to the named file. | |
788 | ||
789 | o The parser now understands `|&' as a synonym for `2>&1 |', which redirects | |
790 | the standard error for a command through a pipe. | |
791 | ||
792 | o The new `;&' case statement action list terminator causes execution to | |
793 | continue with the action associated with the next pattern in the | |
794 | statement rather than terminating the command. | |
795 | ||
796 | o The new `;;&' case statement action list terminator causes the shell to | |
797 | test the next set of patterns after completing execution of the current | |
798 | action, rather than terminating the command. | |
799 | ||
800 | o The shell understands a new variable: PROMPT_DIRTRIM. When set to an | |
801 | integer value greater than zero, prompt expansion of \w and \W will | |
802 | retain only that number of trailing pathname components and replace | |
803 | the intervening characters with `...'. | |
804 | ||
805 | o There are new case-modifying word expansions: uppercase (^[^]) and | |
806 | lowercase (,[,]). They can work on either the first character or | |
807 | array element, or globally. They accept an optional shell pattern | |
808 | that determines which characters to modify. There is an optionally- | |
809 | configured feature to include capitalization operators. | |
810 | ||
811 | o The shell provides associative array variables, with the appropriate | |
812 | support to create, delete, assign values to, and expand them. | |
813 | ||
814 | o The `declare' builtin now has new -l (convert value to lowercase upon | |
815 | assignment) and -u (convert value to uppercase upon assignment) options. | |
816 | There is an optionally-configurable -c option to capitalize a value at | |
817 | assignment. | |
818 | ||
819 | o There is a new `coproc' reserved word that specifies a coprocess: an | |
820 | asynchronous command run with two pipes connected to the creating shell. | |
821 | Coprocs can be named. The input and output file descriptors and the | |
822 | PID of the coprocess are available to the calling shell in variables | |
823 | with coproc-specific names. | |
824 | ||
825 | o A value of 0 for the -t option to `read' now returns success if there is | |
826 | input available to be read from the specified file descriptor. | |
827 | ||
828 | o CDPATH and GLOBIGNORE are ignored when the shell is running in privileged | |
829 | mode. | |
830 | ||
831 | o New bindable readline functions shell-forward-word and shell-backward-word, | |
832 | which move forward and backward words delimited by shell metacharacters | |
833 | and honor shell quoting. | |
834 | ||
835 | o New bindable readline functions shell-backward-kill-word and shell-kill-word | |
836 | which kill words backward and forward, but use the same word boundaries | |
837 | as shell-forward-word and shell-backward-word. | |
838 | ||
17345e5a | 839 | Bash-3.2 contained the following new features: |
0628567a JA |
840 | |
841 | o Bash-3.2 now checks shell scripts for NUL characters rather than non-printing | |
842 | characters when deciding whether or not a script is a binary file. | |
843 | ||
844 | o Quoting the string argument to the [[ command's =~ (regexp) operator now | |
845 | forces string matching, as with the other pattern-matching operators. | |
846 | ||
0628567a | 847 | Bash-3.1 contained the following new features: |
95732b49 JA |
848 | |
849 | o Bash-3.1 may now be configured and built in a mode that enforces strict | |
850 | POSIX compliance. | |
f73dda09 | 851 | |
95732b49 JA |
852 | o The `+=' assignment operator, which appends to the value of a string or |
853 | array variable, has been implemented. | |
bb70624e | 854 | |
95732b49 JA |
855 | o It is now possible to ignore case when matching in contexts other than |
856 | filename generation using the new `nocasematch' shell option. | |
857 | ||
95732b49 | 858 | Bash-3.0 contained the following new features: |
bb70624e | 859 | |
b80f6443 JA |
860 | o Features to support the bash debugger have been implemented, and there |
861 | is a new `extdebug' option to turn the non-default options on | |
862 | ||
863 | o HISTCONTROL is now a colon-separated list of options and has been | |
864 | extended with a new `erasedups' option that will result in only one | |
865 | copy of a command being kept in the history list | |
866 | ||
867 | o Brace expansion has been extended with a new {x..y} form, producing | |
868 | sequences of digits or characters | |
869 | ||
870 | o Timestamps are now kept with history entries, with an option to save | |
871 | and restore them from the history file; there is a new HISTTIMEFORMAT | |
872 | variable describing how to display the timestamps when listing history | |
873 | entries | |
874 | ||
875 | o The `[[' command can now perform extended regular expression (egrep-like) | |
876 | matching, with matched subexpressions placed in the BASH_REMATCH array | |
877 | variable | |
878 | ||
879 | o A new `pipefail' option causes a pipeline to return a failure status if | |
880 | any command in it fails | |
881 | ||
882 | o The `jobs', `kill', and `wait' builtins now accept job control notation | |
883 | in their arguments even if job control is not enabled | |
884 | ||
885 | o The `gettext' package and libintl have been integrated, and the shell | |
886 | messages may be translated into other languages | |
887 | ||
b80f6443 JA |
888 | Bash-2.05b introduced the following new features: |
889 | ||
7117c2d2 JA |
890 | o support for multibyte characters has been added to both bash and readline |
891 | ||
892 | o the DEBUG trap is now run *before* simple commands, ((...)) commands, | |
893 | [[...]] conditional commands, and for ((...)) loops | |
894 | ||
895 | o the shell now performs arithmetic in the largest integer size the machine | |
896 | supports (intmax_t) | |
897 | ||
898 | o there is a new \D{...} prompt expansion; passes the `...' to strftime(3) | |
899 | and inserts the result into the expanded prompt | |
900 | ||
901 | o there is a new `here-string' redirection operator: <<< word | |
902 | ||
903 | o when displaying variables, function attributes and definitions are shown | |
904 | separately, allowing them to be re-used as input (attempting to re-use | |
905 | the old output would result in syntax errors). | |
906 | ||
907 | o `read' has a new `-u fd' option to read from a specified file descriptor | |
908 | ||
909 | o the bash debugger in examples/bashdb has been modified to work with the | |
910 | new DEBUG trap semantics, the command set has been made more gdb-like, | |
911 | and the changes to $LINENO make debugging functions work better | |
912 | ||
913 | o the expansion of $LINENO inside a shell function is only relative to the | |
914 | function start if the shell is interactive -- if the shell is running a | |
915 | script, $LINENO expands to the line number in the script. This is as | |
916 | POSIX-2001 requires | |
917 | ||
7117c2d2 JA |
918 | Bash-2.05a introduced the following new features: |
919 | ||
f73dda09 JA |
920 | o The `printf' builtin has undergone major work |
921 | ||
922 | o There is a new read-only `shopt' option: login_shell, which is set by | |
923 | login shells and unset otherwise | |
924 | ||
925 | o New `\A' prompt string escape sequence; expanding to time in 24-hour | |
926 | HH:MM format | |
927 | ||
928 | o New `-A group/-g' option to complete and compgen; goes group name | |
929 | completion | |
930 | ||
931 | o New [+-]O invocation option to set and unset `shopt' options at startup | |
932 | ||
933 | o ksh-like `ERR' trap | |
934 | ||
935 | o `for' loops now allow empty word lists after the `in' reserved word | |
936 | ||
937 | o new `hard' and `soft' arguments for the `ulimit' builtin | |
938 | ||
939 | o Readline can be configured to place the user at the same point on the line | |
940 | when retrieving commands from the history list | |
941 | ||
942 | o Readline can be configured to skip `hidden' files (filenames with a leading | |
943 | `.' on Unix) when performing completion | |
944 | ||
f73dda09 JA |
945 | Bash-2.05 introduced the following new features: |
946 | ||
28ef6c31 JA |
947 | o This version has once again reverted to using locales and strcoll(3) when |
948 | processing pattern matching bracket expressions, as POSIX requires. | |
949 | o Added a new `--init-file' invocation argument as a synonym for `--rcfile', | |
950 | per the new GNU coding standards. | |
951 | o The /dev/tcp and /dev/udp redirections now accept service names as well as | |
952 | port numbers. | |
953 | o `complete' and `compgen' now take a `-o value' option, which controls some | |
954 | of the aspects of that compspec. Valid values are: | |
955 | ||
956 | default - perform bash default completion if programmable | |
957 | completion produces no matches | |
958 | dirnames - perform directory name completion if programmable | |
959 | completion produces no matches | |
960 | filenames - tell readline that the compspec produces filenames, | |
961 | so it can do things like append slashes to | |
962 | directory names and suppress trailing spaces | |
963 | o A new loadable builtin, realpath, which canonicalizes and expands symlinks | |
964 | in pathname arguments. | |
d233b485 | 965 | o When `set' is called without options, it prints function definitions in a |
28ef6c31 JA |
966 | way that allows them to be reused as input. This affects `declare' and |
967 | `declare -p' as well. This only happens when the shell is not in POSIX | |
968 | mode, since POSIX.2 forbids this behavior. | |
969 | ||
28ef6c31 JA |
970 | Bash-2.04 introduced the following new features: |
971 | ||
bb70624e JA |
972 | o Programmable word completion with the new `complete' and `compgen' builtins; |
973 | examples are provided in examples/complete/complete-examples | |
974 | o `history' has a new `-d' option to delete a history entry | |
975 | o `bind' has a new `-x' option to bind key sequences to shell commands | |
976 | o The prompt expansion code has new `\j' and `\l' escape sequences | |
28ef6c31 | 977 | o The `no_empty_cmd_completion' shell option, if enabled, inhibits |
bb70624e JA |
978 | command completion when TAB is typed on an empty line |
979 | o `help' has a new `-s' option to print a usage synopsis | |
980 | o New arithmetic operators: var++, var--, ++var, --var, expr1,expr2 (comma) | |
981 | o New ksh93-style arithmetic for command: | |
982 | for ((expr1 ; expr2; expr3 )); do list; done | |
983 | o `read' has new options: `-t', `-n', `-d', `-s' | |
984 | o The redirection code handles several filenames specially: /dev/fd/N, | |
985 | /dev/stdin, /dev/stdout, /dev/stderr | |
986 | o The redirection code now recognizes /dev/tcp/HOST/PORT and | |
987 | /dev/udp/HOST/PORT and tries to open a TCP or UDP socket, respectively, | |
988 | to the specified port on the specified host | |
989 | o The ${!prefix*} expansion has been implemented | |
990 | o A new FUNCNAME variable, which expands to the name of a currently-executing | |
991 | function | |
992 | o The GROUPS variable is no longer readonly | |
993 | o A new shopt `xpg_echo' variable, to control the behavior of echo with | |
994 | respect to backslash-escape sequences at runtime | |
995 | o The NON_INTERACTIVE_LOGIN_SHELLS #define has returned | |
996 | ||
28ef6c31 | 997 | The version of Readline released with Bash-2.04, Readline-4.1, had several |
bb70624e JA |
998 | new features as well: |
999 | ||
1000 | o Parentheses matching is always compiled into readline, and controllable | |
1001 | with the new `blink-matching-paren' variable | |
1002 | o The history-search-forward and history-search-backward functions now leave | |
1003 | point at the end of the line when the search string is empty, like | |
1004 | reverse-search-history, and forward-search-history | |
1005 | o A new function for applications: rl_on_new_line_with_prompt() | |
1006 | o New variables for applications: rl_already_prompted, and rl_gnu_readline_p | |
1007 | ||
1008 | ||
bb70624e | 1009 | Bash-2.03 had very few new features, in keeping with the convention |
b72432fd JA |
1010 | that odd-numbered releases provide mainly bug fixes. A number of new |
1011 | features were added to Readline, mostly at the request of the Cygnus | |
1012 | folks. | |
cce855bc | 1013 | |
bb70624e | 1014 | A new shopt option, `restricted_shell', so that startup files can test |
b72432fd | 1015 | whether or not the shell was started in restricted mode |
bb70624e | 1016 | Filename generation is now performed on the words between ( and ) in |
b72432fd JA |
1017 | compound array assignments (this is really a bug fix) |
1018 | OLDPWD is now auto-exported, as POSIX.2 requires | |
1019 | ENV and BASH_ENV are read-only variables in a restricted shell | |
1020 | Bash may now be linked against an already-installed Readline library, | |
1021 | as long as the Readline library is version 4 or newer | |
1022 | All shells begun with the `--login' option will source the login shell | |
1023 | startup files, even if the shell is not interactive | |
1024 | ||
bb70624e | 1025 | There were lots of changes to the version of the Readline library released |
b72432fd JA |
1026 | along with Bash-2.03. For a complete list of the changes, read the file |
1027 | CHANGES in the Bash-2.03 distribution. | |
1028 | ||
1029 | Bash-2.02 contained the following new features: | |
d166f048 | 1030 | |
cce855bc JA |
1031 | a new version of malloc (based on the old GNU malloc code in previous |
1032 | bash versions) that is more page-oriented, more conservative | |
1033 | with memory usage, does not `orphan' large blocks when they | |
1034 | are freed, is usable on 64-bit machines, and has allocation | |
1035 | checking turned on unconditionally | |
1036 | POSIX.2-style globbing character classes ([:alpha:], [:alnum:], etc.) | |
1037 | POSIX.2-style globbing equivalence classes | |
1038 | POSIX.2-style globbing collating symbols | |
1039 | the ksh [[...]] extended conditional command | |
1040 | the ksh egrep-style extended pattern matching operators | |
1041 | a new `printf' builtin | |
1042 | the ksh-like $(<filename) command substitution, which is equivalent to | |
1043 | $(cat filename) | |
1044 | new tilde prefixes that expand to directories from the directory stack | |
1045 | new `**' arithmetic operator to do exponentiation | |
1046 | case-insensitive globbing (filename expansion) | |
1047 | menu completion a la tcsh | |
1048 | `magic-space' history expansion function like tcsh | |
1049 | the readline inputrc `language' has a new file inclusion directive ($include) | |
1050 | ||
1051 | Bash-2.01 contained only a few new features: | |
d166f048 JA |
1052 | |
1053 | new `GROUPS' builtin array variable containing the user's group list | |
1054 | new bindable readline commands: history-and-alias-expand-line and | |
1055 | alias-expand-line | |
ccc6cda3 | 1056 | |
cce855bc | 1057 | Bash-2.0 contained extensive changes and new features from bash-1.14.7. |
d166f048 | 1058 | Here's a short list: |
ccc6cda3 JA |
1059 | |
1060 | new `time' reserved word to time pipelines, shell builtins, and | |
1061 | shell functions | |
1062 | one-dimensional arrays with a new compound assignment statement, | |
1063 | appropriate expansion constructs and modifications to some | |
1064 | of the builtins (read, declare, etc.) to use them | |
1065 | new quoting syntaxes for ANSI-C string expansion and locale-specific | |
1066 | string translation | |
1067 | new expansions to do substring extraction, pattern replacement, and | |
1068 | indirect variable expansion | |
1069 | new builtins: `disown' and `shopt' | |
1070 | new variables: HISTIGNORE, SHELLOPTS, PIPESTATUS, DIRSTACK, GLOBIGNORE, | |
1071 | MACHTYPE, BASH_VERSINFO | |
1072 | special handling of many unused or redundant variables removed | |
1073 | (e.g., $notify, $glob_dot_filenames, $no_exit_on_failed_exec) | |
1074 | dynamic loading of new builtin commands; many loadable examples provided | |
1075 | new prompt expansions: \a, \e, \n, \H, \T, \@, \v, \V | |
1076 | history and aliases available in shell scripts | |
1077 | new readline variables: enable-keypad, mark-directories, input-meta, | |
1078 | visible-stats, disable-completion, comment-begin | |
1079 | new readline commands to manipulate the mark and operate on the region | |
1080 | new readline emacs mode commands and bindings for ksh-88 compatibility | |
1081 | updated and extended builtins | |
1082 | new DEBUG trap | |
1083 | expanded (and now documented) restricted shell mode | |
1084 | ||
1085 | implementation stuff: | |
1086 | autoconf-based configuration | |
1087 | nearly all of the bugs reported since version 1.14 have been fixed | |
1088 | most builtins converted to use builtin `getopt' for consistency | |
1089 | most builtins use -p option to display output in a reusable form | |
1090 | (for consistency) | |
1091 | grammar tighter and smaller (66 reduce-reduce conflicts gone) | |
1092 | lots of code now smaller and faster | |
1093 | test suite greatly expanded | |
1094 | ||
ac50fbac | 1095 | B2) Are there any user-visible incompatibilities between bash-4.3 and |
0001803f | 1096 | previous bash versions? |
ccc6cda3 | 1097 | |
ac50fbac | 1098 | There are a few incompatibilities between version 4.3 and previous |
0001803f CR |
1099 | versions. They are detailed in the file COMPAT in the bash distribution. |
1100 | That file is not meant to be all-encompassing; send mail to | |
1101 | bash-maintainers@gnu.org (or bug-bash@gnu.org if you would like | |
495aee44 | 1102 | community discussion) if you find something that's not mentioned there. |
ccc6cda3 JA |
1103 | |
1104 | Section C: Differences from other Unix shells | |
1105 | ||
b72432fd | 1106 | C1) How does bash differ from sh, the Bourne shell? |
ccc6cda3 JA |
1107 | |
1108 | This is a non-comprehensive list of features that differentiate bash | |
1109 | from the SVR4.2 shell. The bash manual page explains these more | |
1110 | completely. | |
1111 | ||
1112 | Things bash has that sh does not: | |
1113 | long invocation options | |
f73dda09 | 1114 | [+-]O invocation option |
7117c2d2 | 1115 | -l invocation option |
ccc6cda3 JA |
1116 | `!' reserved word to invert pipeline return value |
1117 | `time' reserved word to time pipelines and shell builtins | |
1118 | the `function' reserved word | |
bb70624e JA |
1119 | the `select' compound command and reserved word |
1120 | arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done | |
ccc6cda3 JA |
1121 | new $'...' and $"..." quoting |
1122 | the $(...) form of command substitution | |
bc4cd23c JA |
1123 | the $(<filename) form of command substitution, equivalent to |
1124 | $(cat filename) | |
ccc6cda3 JA |
1125 | the ${#param} parameter value length operator |
1126 | the ${!param} indirect parameter expansion operator | |
bb70624e | 1127 | the ${!param*} prefix expansion operator |
7117c2d2 | 1128 | the ${param:offset[:length]} parameter substring operator |
ccc6cda3 JA |
1129 | the ${param/pat[/string]} parameter pattern substitution operator |
1130 | expansions to perform substring removal (${p%[%]w}, ${p#[#]w}) | |
1131 | expansion of positional parameters beyond $9 with ${num} | |
17345e5a | 1132 | variables: BASH, BASHPID, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY, |
ccc6cda3 JA |
1133 | TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS, |
1134 | LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME, | |
1135 | ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE, | |
bc4cd23c | 1136 | HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS, |
ccc6cda3 | 1137 | PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC, |
bb70624e | 1138 | SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars, |
0001803f | 1139 | auto_resume, PROMPT_DIRTRIM, BASHOPTS, BASH_XTRACEFD |
ccc6cda3 | 1140 | DEBUG trap |
f73dda09 | 1141 | ERR trap |
ccc6cda3 | 1142 | variable arrays with new compound assignment syntax |
17345e5a | 1143 | redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-, >>& |
ccc6cda3 | 1144 | prompt string special char translation and variable expansion |
bb70624e | 1145 | auto-export of variables in initial environment |
ccc6cda3 JA |
1146 | command search finds functions before builtins |
1147 | bash return builtin will exit a file sourced with `.' | |
ac50fbac | 1148 | builtins: cd -/-L/-P/-@, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t. |
bb70624e | 1149 | export -n/-f/-p/name=value, pwd -L/-P, |
0001803f | 1150 | read -e/-p/-a/-t/-n/-d/-s/-u/-i/-N, |
ccc6cda3 JA |
1151 | readonly -a/-f/name=value, trap -l, set +o, |
1152 | set -b/-m/-o option/-h/-p/-B/-C/-H/-P, | |
ac50fbac | 1153 | unset -f/-n/-v, ulimit -i/-m/-p/-q/-u/-x, |
7117c2d2 | 1154 | type -a/-p/-t/-f/-P, suspend -f, kill -n, |
ac50fbac | 1155 | test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S/-R |
ccc6cda3 JA |
1156 | bash reads ~/.bashrc for interactive shells, $ENV for non-interactive |
1157 | bash restricted shell mode is more extensive | |
1158 | bash allows functions and variables with the same name | |
1159 | brace expansion | |
1160 | tilde expansion | |
1161 | arithmetic expansion with $((...)) and `let' builtin | |
bc4cd23c | 1162 | the `[[...]]' extended conditional command |
ccc6cda3 JA |
1163 | process substitution |
1164 | aliases and alias/unalias builtins | |
1165 | local variables in functions and `local' builtin | |
bb70624e | 1166 | readline and command-line editing with programmable completion |
ccc6cda3 JA |
1167 | command history and history/fc builtins |
1168 | csh-like history expansion | |
bb70624e JA |
1169 | other new bash builtins: bind, command, compgen, complete, builtin, |
1170 | declare/typeset, dirs, enable, fc, help, | |
1171 | history, logout, popd, pushd, disown, shopt, | |
17345e5a | 1172 | printf, compopt, mapfile |
ccc6cda3 JA |
1173 | exported functions |
1174 | filename generation when using output redirection (command >a*) | |
bc4cd23c JA |
1175 | POSIX.2-style globbing character classes |
1176 | POSIX.2-style globbing equivalence classes | |
1177 | POSIX.2-style globbing collating symbols | |
1178 | egrep-like extended pattern matching operators | |
1179 | case-insensitive pattern matching and globbing | |
ccc6cda3 JA |
1180 | variable assignments preceding commands affect only that command, |
1181 | even for builtins and functions | |
95732b49 | 1182 | posix mode and strict posix conformance |
bb70624e JA |
1183 | redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr, |
1184 | /dev/tcp/host/port, /dev/udp/host/port | |
b80f6443 JA |
1185 | debugger support, including `caller' builtin and new variables |
1186 | RETURN trap | |
95732b49 | 1187 | the `+=' assignment operator |
17345e5a JA |
1188 | autocd shell option and behavior |
1189 | command-not-found hook with command_not_found_handle shell function | |
1190 | globstar shell option and `**' globbing behavior | |
1191 | |& synonym for `2>&1 |' | |
1192 | ;& and ;;& case action list terminators | |
1193 | case-modifying word expansions and variable attributes | |
1194 | associative arrays | |
1195 | coprocesses using the `coproc' reserved word and variables | |
0001803f | 1196 | shell assignment of a file descriptor used in a redirection to a variable |
ccc6cda3 JA |
1197 | |
1198 | Things sh has that bash does not: | |
1199 | uses variable SHACCT to do shell accounting | |
1200 | includes `stop' builtin (bash can use alias stop='kill -s STOP') | |
1201 | `newgrp' builtin | |
1202 | turns on job control if called as `jsh' | |
ccc6cda3 JA |
1203 | $TIMEOUT (like bash $TMOUT) |
1204 | `^' is a synonym for `|' | |
1205 | new SVR4.2 sh builtins: mldmode, priv | |
1206 | ||
1207 | Implementation differences: | |
1208 | redirection to/from compound commands causes sh to create a subshell | |
1209 | bash does not allow unbalanced quotes; sh silently inserts them at EOF | |
1210 | bash does not mess with signal 11 | |
1211 | sh sets (euid, egid) to (uid, gid) if -p not supplied and uid < 100 | |
1212 | bash splits only the results of expansions on IFS, using POSIX.2 | |
1213 | field splitting rules; sh splits all words on IFS | |
1214 | sh does not allow MAILCHECK to be unset (?) | |
1215 | sh does not allow traps on SIGALRM or SIGCHLD | |
1216 | bash allows multiple option arguments when invoked (e.g. -x -v); | |
1217 | sh allows only a single option argument (`sh -x -v' attempts | |
d166f048 | 1218 | to open a file named `-v', and, on SunOS 4.1.4, dumps core. |
b72432fd JA |
1219 | On Solaris 2.4 and earlier versions, sh goes into an infinite |
1220 | loop.) | |
ccc6cda3 JA |
1221 | sh exits a script if any builtin fails; bash exits only if one of |
1222 | the POSIX.2 `special' builtins fails | |
1223 | ||
b72432fd | 1224 | C2) How does bash differ from the Korn shell, version ksh88? |
ccc6cda3 JA |
1225 | |
1226 | Things bash has or uses that ksh88 does not: | |
1227 | long invocation options | |
f73dda09 | 1228 | [-+]O invocation option |
7117c2d2 | 1229 | -l invocation option |
ccc6cda3 | 1230 | `!' reserved word |
bb70624e | 1231 | arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done |
7117c2d2 | 1232 | arithmetic in largest machine-supported size (intmax_t) |
ccc6cda3 JA |
1233 | posix mode and posix conformance |
1234 | command hashing | |
1235 | tilde expansion for assignment statements that look like $PATH | |
1236 | process substitution with named pipes if /dev/fd is not available | |
1237 | the ${!param} indirect parameter expansion operator | |
bb70624e | 1238 | the ${!param*} prefix expansion operator |
7117c2d2 | 1239 | the ${param:offset[:length]} parameter substring operator |
ccc6cda3 | 1240 | the ${param/pat[/string]} parameter pattern substitution operator |
17345e5a | 1241 | variables: BASH, BASH_VERSION, BASH_VERSINFO, BASHPID, UID, EUID, SHLVL, |
ccc6cda3 JA |
1242 | TIMEFORMAT, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, |
1243 | HISTFILESIZE, HISTIGNORE, HISTCONTROL, PROMPT_COMMAND, | |
1244 | IGNOREEOF, FIGNORE, INPUTRC, HOSTFILE, DIRSTACK, | |
1245 | PIPESTATUS, HOSTNAME, OPTERR, SHELLOPTS, GLOBIGNORE, | |
17345e5a | 1246 | GROUPS, FUNCNAME, histchars, auto_resume, PROMPT_DIRTRIM |
ccc6cda3 | 1247 | prompt expansion with backslash escapes and command substitution |
17345e5a | 1248 | redirection: &> (stdout and stderr), <<<, [n]<&word-, [n]>&word-, >>& |
bb70624e | 1249 | more extensive and extensible editing and programmable completion |
ccc6cda3 JA |
1250 | builtins: bind, builtin, command, declare, dirs, echo -e/-E, enable, |
1251 | exec -l/-c/-a, fc -s, export -n/-f/-p, hash, help, history, | |
1252 | jobs -x/-r/-s, kill -s/-n/-l, local, logout, popd, pushd, | |
0001803f | 1253 | read -e/-p/-a/-t/-n/-d/-s/-N, readonly -a/-n/-f/-p, |
bb70624e JA |
1254 | set -o braceexpand/-o histexpand/-o interactive-comments/ |
1255 | -o notify/-o physical/-o posix/-o hashall/-o onecmd/ | |
1256 | -h/-B/-C/-b/-H/-P, set +o, suspend, trap -l, type, | |
0628567a | 1257 | typeset -a/-F/-p, ulimit -i/-q/-u/-x, umask -S, alias -p, |
17345e5a | 1258 | shopt, disown, printf, complete, compgen, compopt, mapfile |
ccc6cda3 | 1259 | `!' csh-style history expansion |
bc4cd23c JA |
1260 | POSIX.2-style globbing character classes |
1261 | POSIX.2-style globbing equivalence classes | |
1262 | POSIX.2-style globbing collating symbols | |
1263 | egrep-like extended pattern matching operators | |
1264 | case-insensitive pattern matching and globbing | |
1265 | `**' arithmetic operator to do exponentiation | |
bb70624e | 1266 | redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr |
f73dda09 | 1267 | arrays of unlimited size |
7117c2d2 | 1268 | TMOUT is default timeout for `read' and `select' |
b80f6443 JA |
1269 | debugger support, including the `caller' builtin |
1270 | RETURN trap | |
1271 | Timestamps in history entries | |
1272 | {x..y} brace expansion | |
95732b49 | 1273 | The `+=' assignment operator |
17345e5a JA |
1274 | autocd shell option and behavior |
1275 | command-not-found hook with command_not_found_handle shell function | |
1276 | globstar shell option and `**' globbing behavior | |
1277 | |& synonym for `2>&1 |' | |
1278 | ;& and ;;& case action list terminators | |
1279 | case-modifying word expansions and variable attributes | |
1280 | associative arrays | |
1281 | coprocesses using the `coproc' reserved word and variables | |
0001803f | 1282 | shell assignment of a file descriptor used in a redirection to a variable |
ccc6cda3 JA |
1283 | |
1284 | Things ksh88 has or uses that bash does not: | |
f73dda09 | 1285 | tracked aliases (alias -t) |
bb70624e | 1286 | variables: ERRNO, FPATH, EDITOR, VISUAL |
17345e5a | 1287 | co-processes (bash uses different syntax) |
ccc6cda3 JA |
1288 | weirdly-scoped functions |
1289 | typeset +f to list all function names without definitions | |
1290 | text of command history kept in a file, not memory | |
b80f6443 | 1291 | builtins: alias -x, cd old new, newgrp, print, |
7117c2d2 | 1292 | read -p/-s/var?prompt, set -A/-o gmacs/ |
b80f6443 | 1293 | -o bgnice/-o markdirs/-o trackall/-o viraw/-s, |
17345e5a | 1294 | typeset -H/-L/-R/-Z/-A/-ft/-fu/-fx/-t, whence |
f73dda09 JA |
1295 | using environment to pass attributes of exported variables |
1296 | arithmetic evaluation done on arguments to some builtins | |
1297 | reads .profile from $PWD when invoked as login shell | |
ccc6cda3 JA |
1298 | |
1299 | Implementation differences: | |
1300 | ksh runs last command of a pipeline in parent shell context | |
ccc6cda3 JA |
1301 | bash has brace expansion by default (ksh88 compile-time option) |
1302 | bash has fixed startup file for all interactive shells; ksh reads $ENV | |
1303 | bash has exported functions | |
1304 | bash command search finds functions before builtins | |
f73dda09 JA |
1305 | bash waits for all commands in pipeline to exit before returning status |
1306 | emacs-mode editing has some slightly different key bindings | |
ccc6cda3 | 1307 | |
b72432fd | 1308 | C3) Which new features in ksh-93 are not in bash, and which are? |
ccc6cda3 | 1309 | |
ac50fbac | 1310 | This list is current through ksh93v (10/08/2013) |
17345e5a | 1311 | |
ac50fbac CR |
1312 | New things in ksh-93 not in bash-4.3: |
1313 | floating point arithmetic, variables, and constants | |
1314 | math library functions, including user-defined math functions | |
ccc6cda3 | 1315 | ${!name[sub]} name of subscript for associative array |
ccc6cda3 JA |
1316 | `.' is allowed in variable names to create a hierarchical namespace |
1317 | more extensive compound assignment syntax | |
1318 | discipline functions | |
ccc6cda3 | 1319 | KEYBD trap |
bb70624e | 1320 | variables: .sh.edchar, .sh.edmode, .sh.edcol, .sh.edtext, .sh.version, |
ac50fbac CR |
1321 | .sh.name, .sh.subscript, .sh.value, .sh.match, HISTEDIT, |
1322 | .sh.sig, .sh.stats, .sh.siginfo, .sh.pwdfd, .sh.op_astbin, | |
1323 | .sh.pool | |
f73dda09 | 1324 | backreferences in pattern matching (\N) |
17345e5a | 1325 | `&' operator in pattern lists for matching (match all instead of any) |
f73dda09 | 1326 | exit statuses between 0 and 255 |
f73dda09 | 1327 | FPATH and PATH mixing |
b80f6443 JA |
1328 | lexical scoping for local variables in `ksh' functions |
1329 | no scoping for local variables in `POSIX' functions | |
17345e5a JA |
1330 | $'' \C[.collating-element.] escape sequence |
1331 | -C/-I invocation options | |
ac50fbac CR |
1332 | print -f (bash uses printf) and rest of print builtin options |
1333 | printf %(type)q, %#q | |
17345e5a JA |
1334 | `fc' has been renamed to `hist' |
1335 | `.' can execute shell functions | |
1336 | getopts -a | |
495aee44 | 1337 | printf %B, %H, %P, %R, %Z modifiers, output base for %d, `=' flag |
ac50fbac | 1338 | read -n/-N differ/-v/-S |
17345e5a | 1339 | set -o showme/-o multiline (bash default) |
ac50fbac CR |
1340 | set -K |
1341 | kill -Q/-q/-L | |
1342 | trap -a | |
17345e5a | 1343 | `sleep' and `getconf' builtins (bash has loadable versions) |
0001803f | 1344 | [[ -R name ]] (checks whether or not name is a nameref) |
ac50fbac | 1345 | typeset -C/-S/-T/-X/-h/-s/-c/-M |
17345e5a | 1346 | experimental `type' definitions (a la typedef) using typeset |
17345e5a JA |
1347 | array expansions ${array[sub1..sub2]} and ${!array[sub1..sub2]} |
1348 | associative array assignments using `;' as element separator | |
1349 | command substitution $(n<#) expands to current byte offset for fd N | |
1350 | new '${ ' form of command substitution, executed in current shell | |
0001803f | 1351 | new >;/<>;/<#pat/<##pat/<#/># redirections |
17345e5a | 1352 | brace expansion printf-like formats |
ac50fbac CR |
1353 | CHLD trap triggered by SIGSTOP and SIGCONT |
1354 | ~{fd} expansion, which replaces fd with the corresponding path name | |
1355 | $"string" expanded when referenced rather than when first parsed | |
1356 | job "pools", which allow a collection of jobs to be managed as a unit | |
17345e5a | 1357 | |
ac50fbac | 1358 | New things in ksh-93 present in bash-4.3: |
17345e5a | 1359 | associative arrays |
7117c2d2 | 1360 | [n]<&word- and [n]>&word- redirections (combination dup and close) |
bb70624e JA |
1361 | for (( expr1; expr2; expr3 )) ; do list; done - arithmetic for command |
1362 | ?:, ++, --, `expr1 , expr2' arithmetic operators | |
1363 | expansions: ${!param}, ${param:offset[:len]}, ${param/pat[/str]}, | |
1364 | ${!param*} | |
ccc6cda3 | 1365 | compound array assignment |
495aee44 | 1366 | negative subscripts for indexed array variables |
ccc6cda3 JA |
1367 | the `!' reserved word |
1368 | loadable builtins -- but ksh uses `builtin' while bash uses `enable' | |
ccc6cda3 JA |
1369 | new $'...' and $"..." quoting |
1370 | FIGNORE (but bash uses GLOBIGNORE), HISTCMD | |
17345e5a | 1371 | brace expansion and set -B |
ccc6cda3 | 1372 | changes to kill builtin |
17345e5a JA |
1373 | `command', `builtin', `disown' builtins |
1374 | echo -e | |
1375 | exec -c/-a | |
495aee44 | 1376 | printf %T modifier |
ccc6cda3 | 1377 | read -A (bash uses read -a) |
bb70624e | 1378 | read -t/-d |
ccc6cda3 | 1379 | trap -p |
ccc6cda3 | 1380 | `.' restores the positional parameters when it completes |
17345e5a JA |
1381 | set -o notify/-C |
1382 | set -o pipefail | |
1383 | set -G (-o globstar) and ** | |
ccc6cda3 JA |
1384 | POSIX.2 `test' |
1385 | umask -S | |
1386 | unalias -a | |
1387 | command and arithmetic substitution performed on PS1, PS4, and ENV | |
17345e5a | 1388 | command name completion, TAB displaying possible completions |
d166f048 | 1389 | ENV processed only for interactive shells |
95732b49 | 1390 | The `+=' assignment operator |
17345e5a JA |
1391 | the `;&' case statement "fallthrough" pattern list terminator |
1392 | csh-style history expansion and set -H | |
1393 | negative offsets in ${param:offset:length} | |
0001803f CR |
1394 | redirection operators preceded with {varname} to store fd number in varname |
1395 | DEBUG can force skipping following command | |
495aee44 | 1396 | [[ -v var ]] operator (checks whether or not var is set) |
ac50fbac CR |
1397 | typeset -n and `nameref' variables |
1398 | process substitutions work without /dev/fd | |
ccc6cda3 JA |
1399 | |
1400 | Section D: Why does bash do some things differently than other Unix shells? | |
1401 | ||
b72432fd | 1402 | D1) Why does bash run a different version of `command' than |
ccc6cda3 JA |
1403 | `which command' says it will? |
1404 | ||
b72432fd JA |
1405 | On many systems, `which' is actually a csh script that assumes |
1406 | you're running csh. In tcsh, `which' and its cousin `where' | |
1407 | are builtins. On other Unix systems, `which' is a perl script | |
3185942a JA |
1408 | that uses the PATH environment variable. Many Linux distributions |
1409 | use GNU `which', which is a C program that can understand shell | |
1410 | aliases. | |
b72432fd JA |
1411 | |
1412 | The csh script version reads the csh startup files from your | |
1413 | home directory and uses those to determine which `command' will | |
1414 | be invoked. Since bash doesn't use any of those startup files, | |
1415 | there's a good chance that your bash environment differs from | |
1416 | your csh environment. The bash `type' builtin does everything | |
1417 | `which' does, and will report correct results for the running | |
1418 | shell. If you're really wedded to the name `which', try adding | |
1419 | the following function definition to your .bashrc: | |
1420 | ||
1421 | which() | |
1422 | { | |
bb70624e | 1423 | builtin type "$@" |
b72432fd JA |
1424 | } |
1425 | ||
1426 | If you're moving from tcsh and would like to bring `where' along | |
1427 | as well, use this function: | |
1428 | ||
1429 | where() | |
1430 | { | |
1431 | builtin type -a "$@" | |
1432 | } | |
ccc6cda3 | 1433 | |
b72432fd | 1434 | D2) Why doesn't bash treat brace expansions exactly like csh? |
ccc6cda3 JA |
1435 | |
1436 | The only difference between bash and csh brace expansion is that | |
1437 | bash requires a brace expression to contain at least one unquoted | |
1438 | comma if it is to be expanded. Any brace-surrounded word not | |
1439 | containing an unquoted comma is left unchanged by the brace | |
1440 | expansion code. This affords the greatest degree of sh | |
1441 | compatibility. | |
1442 | ||
1443 | Bash, ksh, zsh, and pd-ksh all implement brace expansion this way. | |
1444 | ||
b72432fd | 1445 | D3) Why doesn't bash have csh variable modifiers? |
ccc6cda3 JA |
1446 | |
1447 | Posix has specified a more powerful, albeit somewhat more cryptic, | |
1448 | mechanism cribbed from ksh, and bash implements it. | |
1449 | ||
1450 | ${parameter%word} | |
1451 | Remove smallest suffix pattern. The WORD is expanded to produce | |
1452 | a pattern. It then expands to the value of PARAMETER, with the | |
1453 | smallest portion of the suffix matched by the pattern deleted. | |
1454 | ||
1455 | x=file.c | |
1456 | echo ${x%.c}.o | |
1457 | -->file.o | |
1458 | ||
1459 | ${parameter%%word} | |
1460 | ||
1461 | Remove largest suffix pattern. The WORD is expanded to produce | |
1462 | a pattern. It then expands to the value of PARAMETER, with the | |
1463 | largest portion of the suffix matched by the pattern deleted. | |
1464 | ||
1465 | x=posix/src/std | |
1466 | echo ${x%%/*} | |
1467 | -->posix | |
1468 | ||
1469 | ${parameter#word} | |
1470 | Remove smallest prefix pattern. The WORD is expanded to produce | |
1471 | a pattern. It then expands to the value of PARAMETER, with the | |
1472 | smallest portion of the prefix matched by the pattern deleted. | |
1473 | ||
1474 | x=$HOME/src/cmd | |
1475 | echo ${x#$HOME} | |
1476 | -->/src/cmd | |
1477 | ||
1478 | ${parameter##word} | |
1479 | Remove largest prefix pattern. The WORD is expanded to produce | |
1480 | a pattern. It then expands to the value of PARAMETER, with the | |
1481 | largest portion of the prefix matched by the pattern deleted. | |
1482 | ||
1483 | x=/one/two/three | |
1484 | echo ${x##*/} | |
1485 | -->three | |
1486 | ||
1487 | ||
1488 | Given | |
1489 | a=/a/b/c/d | |
1490 | b=b.xxx | |
1491 | ||
1492 | csh bash result | |
1493 | --- ---- ------ | |
1494 | $a:h ${a%/*} /a/b/c | |
1495 | $a:t ${a##*/} d | |
1496 | $b:r ${b%.*} b | |
1497 | $b:e ${b##*.} xxx | |
1498 | ||
1499 | ||
b72432fd | 1500 | D4) How can I make my csh aliases work when I convert to bash? |
ccc6cda3 JA |
1501 | |
1502 | Bash uses a different syntax to support aliases than csh does. | |
1503 | The details can be found in the documentation. We have provided | |
1504 | a shell script which does most of the work of conversion for you; | |
28ef6c31 | 1505 | this script can be found in ./examples/misc/aliasconv.sh. Here is |
ccc6cda3 JA |
1506 | how you use it: |
1507 | ||
1508 | Start csh in the normal way for you. (e.g., `csh') | |
1509 | ||
28ef6c31 | 1510 | Pipe the output of `alias' through `aliasconv.sh', saving the |
ccc6cda3 JA |
1511 | results into `bash_aliases': |
1512 | ||
28ef6c31 | 1513 | alias | bash aliasconv.sh >bash_aliases |
ccc6cda3 JA |
1514 | |
1515 | Edit `bash_aliases', carefully reading through any created | |
1516 | functions. You will need to change the names of some csh specific | |
1517 | variables to the bash equivalents. The script converts $cwd to | |
1518 | $PWD, $term to $TERM, $home to $HOME, $user to $USER, and $prompt | |
1519 | to $PS1. You may also have to add quotes to avoid unwanted | |
1520 | expansion. | |
1521 | ||
1522 | For example, the csh alias: | |
1523 | ||
1524 | alias cd 'cd \!*; echo $cwd' | |
1525 | ||
1526 | is converted to the bash function: | |
1527 | ||
1528 | cd () { command cd "$@"; echo $PWD ; } | |
1529 | ||
1530 | The only thing that needs to be done is to quote $PWD: | |
1531 | ||
1532 | cd () { command cd "$@"; echo "$PWD" ; } | |
1533 | ||
1534 | Merge the edited file into your ~/.bashrc. | |
1535 | ||
1536 | There is an additional, more ambitious, script in | |
1537 | examples/misc/cshtobash that attempts to convert your entire csh | |
1538 | environment to its bash equivalent. This script can be run as | |
1539 | simply `cshtobash' to convert your normal interactive | |
1540 | environment, or as `cshtobash ~/.login' to convert your login | |
1541 | environment. | |
1542 | ||
b72432fd | 1543 | D5) How can I pipe standard output and standard error from one command to |
ccc6cda3 JA |
1544 | another, like csh does with `|&'? |
1545 | ||
1546 | Use | |
1547 | command 2>&1 | command2 | |
1548 | ||
1549 | The key is to remember that piping is performed before redirection, so | |
1550 | file descriptor 1 points to the pipe when it is duplicated onto file | |
1551 | descriptor 2. | |
1552 | ||
b72432fd | 1553 | D6) Now that I've converted from ksh to bash, are there equivalents to |
ccc6cda3 JA |
1554 | ksh features like autoloaded functions and the `whence' command? |
1555 | ||
bb70624e JA |
1556 | There are features in ksh-88 and ksh-93 that do not have direct bash |
1557 | equivalents. Most, however, can be emulated with very little trouble. | |
ccc6cda3 JA |
1558 | |
1559 | ksh-88 feature Bash equivalent | |
1560 | -------------- --------------- | |
ccc6cda3 JA |
1561 | compiled-in aliases set up aliases in .bashrc; some ksh aliases are |
1562 | bash builtins (hash, history, type) | |
ccc6cda3 JA |
1563 | coprocesses named pipe pairs (one for read, one for write) |
1564 | typeset +f declare -F | |
1565 | cd, print, whence function substitutes in examples/functions/kshenv | |
1566 | autoloaded functions examples/functions/autoload is the same as typeset -fu | |
1567 | read var?prompt read -p prompt var | |
1568 | ||
bb70624e JA |
1569 | ksh-93 feature Bash equivalent |
1570 | -------------- --------------- | |
1571 | sleep, getconf Bash has loadable versions in examples/loadables | |
1572 | ${.sh.version} $BASH_VERSION | |
1573 | print -f printf | |
7117c2d2 | 1574 | hist alias hist=fc |
bb70624e JA |
1575 | $HISTEDIT $FCEDIT |
1576 | ||
ccc6cda3 JA |
1577 | Section E: How can I get bash to do certain things, and why does bash do |
1578 | things the way it does? | |
1579 | ||
b72432fd | 1580 | E1) Why is the bash builtin `test' slightly different from /bin/test? |
ccc6cda3 JA |
1581 | |
1582 | The specific example used here is [ ! x -o x ], which is false. | |
1583 | ||
1584 | Bash's builtin `test' implements the Posix.2 spec, which can be | |
1585 | summarized as follows (the wording is due to David Korn): | |
1586 | ||
1587 | Here is the set of rules for processing test arguments. | |
1588 | ||
1589 | 0 Args: False | |
1590 | 1 Arg: True iff argument is not null. | |
1591 | 2 Args: If first arg is !, True iff second argument is null. | |
1592 | If first argument is unary, then true if unary test is true | |
1593 | Otherwise error. | |
1594 | 3 Args: If second argument is a binary operator, do binary test of $1 $3 | |
1595 | If first argument is !, negate two argument test of $2 $3 | |
1596 | If first argument is `(' and third argument is `)', do the | |
1597 | one-argument test of the second argument. | |
1598 | Otherwise error. | |
1599 | 4 Args: If first argument is !, negate three argument test of $2 $3 $4. | |
1600 | Otherwise unspecified | |
1601 | 5 or more Args: unspecified. (Historical shells would use their | |
1602 | current algorithm). | |
1603 | ||
1604 | The operators -a and -o are considered binary operators for the purpose | |
1605 | of the 3 Arg case. | |
1606 | ||
1607 | As you can see, the test becomes (not (x or x)), which is false. | |
1608 | ||
b72432fd | 1609 | E2) Why does bash sometimes say `Broken pipe'? |
ccc6cda3 JA |
1610 | |
1611 | If a sequence of commands appears in a pipeline, and one of the | |
1612 | reading commands finishes before the writer has finished, the | |
1613 | writer receives a SIGPIPE signal. Many other shells special-case | |
1614 | SIGPIPE as an exit status in the pipeline and do not report it. | |
1615 | For example, in: | |
1616 | ||
1617 | ps -aux | head | |
1618 | ||
1619 | `head' can finish before `ps' writes all of its output, and ps | |
1620 | will try to write on a pipe without a reader. In that case, bash | |
1621 | will print `Broken pipe' to stderr when ps is killed by a | |
1622 | SIGPIPE. | |
1623 | ||
0628567a | 1624 | As of bash-3.1, bash does not report SIGPIPE errors by default. You |
95732b49 | 1625 | can build a version of bash that will report such errors. |
b72432fd | 1626 | |
bb70624e | 1627 | E3) When I have terminal escape sequences in my prompt, why does bash |
ccc6cda3 JA |
1628 | wrap lines at the wrong column? |
1629 | ||
1630 | Readline, the line editing library that bash uses, does not know | |
1631 | that the terminal escape sequences do not take up space on the | |
1632 | screen. The redisplay code assumes, unless told otherwise, that | |
1633 | each character in the prompt is a `printable' character that | |
1634 | takes up one character position on the screen. | |
1635 | ||
1636 | You can use the bash prompt expansion facility (see the PROMPTING | |
1637 | section in the manual page) to tell readline that sequences of | |
1638 | characters in the prompt strings take up no screen space. | |
1639 | ||
1640 | Use the \[ escape to begin a sequence of non-printing characters, | |
1641 | and the \] escape to signal the end of such a sequence. | |
1642 | ||
bb70624e | 1643 | E4) If I pipe the output of a command into `read variable', why doesn't |
ccc6cda3 JA |
1644 | the output show up in $variable when the read command finishes? |
1645 | ||
1646 | This has to do with the parent-child relationship between Unix | |
28ef6c31 JA |
1647 | processes. It affects all commands run in pipelines, not just |
1648 | simple calls to `read'. For example, piping a command's output | |
1649 | into a `while' loop that repeatedly calls `read' will result in | |
1650 | the same behavior. | |
ccc6cda3 | 1651 | |
95732b49 JA |
1652 | Each element of a pipeline, even a builtin or shell function, |
1653 | runs in a separate process, a child of the shell running the | |
1654 | pipeline. A subprocess cannot affect its parent's environment. | |
1655 | When the `read' command sets the variable to the input, that | |
1656 | variable is set only in the subshell, not the parent shell. When | |
1657 | the subshell exits, the value of the variable is lost. | |
ccc6cda3 JA |
1658 | |
1659 | Many pipelines that end with `read variable' can be converted | |
1660 | into command substitutions, which will capture the output of | |
1661 | a specified command. The output can then be assigned to a | |
1662 | variable: | |
1663 | ||
1664 | grep ^gnu /usr/lib/news/active | wc -l | read ngroup | |
1665 | ||
1666 | can be converted into | |
1667 | ||
1668 | ngroup=$(grep ^gnu /usr/lib/news/active | wc -l) | |
1669 | ||
1670 | This does not, unfortunately, work to split the text among | |
1671 | multiple variables, as read does when given multiple variable | |
1672 | arguments. If you need to do this, you can either use the | |
1673 | command substitution above to read the output into a variable | |
1674 | and chop up the variable using the bash pattern removal | |
1675 | expansion operators or use some variant of the following | |
1676 | approach. | |
1677 | ||
1678 | Say /usr/local/bin/ipaddr is the following shell script: | |
1679 | ||
1680 | #! /bin/sh | |
1681 | host `hostname` | awk '/address/ {print $NF}' | |
1682 | ||
1683 | Instead of using | |
1684 | ||
1685 | /usr/local/bin/ipaddr | read A B C D | |
1686 | ||
1687 | to break the local machine's IP address into separate octets, use | |
1688 | ||
1689 | OIFS="$IFS" | |
1690 | IFS=. | |
1691 | set -- $(/usr/local/bin/ipaddr) | |
1692 | IFS="$OIFS" | |
1693 | A="$1" B="$2" C="$3" D="$4" | |
1694 | ||
1695 | Beware, however, that this will change the shell's positional | |
1696 | parameters. If you need them, you should save them before doing | |
1697 | this. | |
1698 | ||
1699 | This is the general approach -- in most cases you will not need to | |
1700 | set $IFS to a different value. | |
1701 | ||
f73dda09 JA |
1702 | Some other user-supplied alternatives include: |
1703 | ||
1704 | read A B C D << HERE | |
1705 | $(IFS=.; echo $(/usr/local/bin/ipaddr)) | |
1706 | HERE | |
1707 | ||
1708 | and, where process substitution is available, | |
1709 | ||
1710 | read A B C D < <(IFS=.; echo $(/usr/local/bin/ipaddr)) | |
1711 | ||
bb70624e | 1712 | E5) I have a bunch of shell scripts that use backslash-escaped characters |
ccc6cda3 JA |
1713 | in arguments to `echo'. Bash doesn't interpret these characters. Why |
1714 | not, and how can I make it understand them? | |
1715 | ||
1716 | This is the behavior of echo on most Unix System V machines. | |
1717 | ||
bb70624e | 1718 | The bash builtin `echo' is modeled after the 9th Edition |
ccc6cda3 JA |
1719 | Research Unix version of `echo'. It does not interpret |
1720 | backslash-escaped characters in its argument strings by default; | |
1721 | it requires the use of the -e option to enable the | |
1722 | interpretation. The System V echo provides no way to disable the | |
1723 | special characters; the bash echo has a -E option to disable | |
1724 | them. | |
1725 | ||
1726 | There is a configuration option that will make bash behave like | |
1727 | the System V echo and interpret things like `\t' by default. Run | |
f73dda09 | 1728 | configure with the --enable-xpg-echo-default option to turn this |
ccc6cda3 JA |
1729 | on. Be aware that this will cause some of the tests run when you |
1730 | type `make tests' to fail. | |
1731 | ||
7117c2d2 | 1732 | There is a shell option, `xpg_echo', settable with `shopt', that will |
bb70624e JA |
1733 | change the behavior of echo at runtime. Enabling this option turns |
1734 | on expansion of backslash-escape sequences. | |
1735 | ||
1736 | E6) Why doesn't a while or for loop get suspended when I type ^Z? | |
ccc6cda3 JA |
1737 | |
1738 | This is a consequence of how job control works on Unix. The only | |
1739 | thing that can be suspended is the process group. This is a single | |
1740 | command or pipeline of commands that the shell forks and executes. | |
1741 | ||
1742 | When you run a while or for loop, the only thing that the shell forks | |
1743 | and executes are any commands in the while loop test and commands in | |
1744 | the loop bodies. These, therefore, are the only things that can be | |
1745 | suspended when you type ^Z. | |
1746 | ||
1747 | If you want to be able to stop the entire loop, you need to put it | |
1748 | within parentheses, which will force the loop into a subshell that | |
1749 | may be stopped (and subsequently restarted) as a single unit. | |
1750 | ||
28ef6c31 JA |
1751 | E7) What about empty for loops in Makefiles? |
1752 | ||
1753 | It's fairly common to see constructs like this in automatically-generated | |
1754 | Makefiles: | |
1755 | ||
1756 | SUBDIRS = @SUBDIRS@ | |
1757 | ||
1758 | ... | |
1759 | ||
1760 | subdirs-clean: | |
1761 | for d in ${SUBDIRS}; do \ | |
1762 | ( cd $$d && ${MAKE} ${MFLAGS} clean ) \ | |
1763 | done | |
1764 | ||
1765 | When SUBDIRS is empty, this results in a command like this being passed to | |
1766 | bash: | |
1767 | ||
1768 | for d in ; do | |
1769 | ( cd $d && ${MAKE} ${MFLAGS} clean ) | |
1770 | done | |
1771 | ||
f73dda09 JA |
1772 | In versions of bash before bash-2.05a, this was a syntax error. If the |
1773 | reserved word `in' was present, a word must follow it before the semicolon | |
1774 | or newline. The language in the manual page referring to the list of words | |
1775 | being empty referred to the list after it is expanded. These versions of | |
1776 | bash required that there be at least one word following the `in' when the | |
1777 | construct was parsed. | |
28ef6c31 JA |
1778 | |
1779 | The idiomatic Makefile solution is something like: | |
1780 | ||
1781 | SUBDIRS = @SUBDIRS@ | |
1782 | ||
1783 | subdirs-clean: | |
1784 | subdirs=$SUBDIRS ; for d in $$subdirs; do \ | |
1785 | ( cd $$d && ${MAKE} ${MFLAGS} clean ) \ | |
1786 | done | |
1787 | ||
b80f6443 JA |
1788 | The latest updated POSIX standard has changed this: the word list |
1789 | is no longer required. Bash versions 2.05a and later accept the | |
1790 | new syntax. | |
28ef6c31 JA |
1791 | |
1792 | E8) Why does the arithmetic evaluation code complain about `08'? | |
1793 | ||
1794 | The bash arithmetic evaluation code (used for `let', $(()), (()), and in | |
1795 | other places), interprets a leading `0' in numeric constants as denoting | |
1796 | an octal number, and a leading `0x' as denoting hexadecimal. This is | |
1797 | in accordance with the POSIX.2 spec, section 2.9.2.1, which states that | |
1798 | arithmetic constants should be handled as signed long integers as defined | |
1799 | by the ANSI/ISO C standard. | |
1800 | ||
1801 | The POSIX.2 interpretation committee has confirmed this: | |
1802 | ||
1803 | http://www.pasc.org/interps/unofficial/db/p1003.2/pasc-1003.2-173.html | |
1804 | ||
1805 | E9) Why does the pattern matching expression [A-Z]* match files beginning | |
1806 | with every letter except `z'? | |
1807 | ||
7117c2d2 JA |
1808 | Bash-2.03, Bash-2.05 and later versions honor the current locale setting |
1809 | when processing ranges within pattern matching bracket expressions ([A-Z]). | |
1810 | This is what POSIX.2 and SUSv3/XPG6 specify. | |
28ef6c31 | 1811 | |
f73dda09 JA |
1812 | The behavior of the matcher in bash-2.05 and later versions depends on the |
1813 | current LC_COLLATE setting. Setting this variable to `C' or `POSIX' will | |
1814 | result in the traditional behavior ([A-Z] matches all uppercase ASCII | |
1815 | characters). Many other locales, including the en_US locale (the default | |
1816 | on many US versions of Linux) collate the upper and lower case letters like | |
1817 | this: | |
28ef6c31 JA |
1818 | |
1819 | AaBb...Zz | |
1820 | ||
7117c2d2 JA |
1821 | which means that [A-Z] matches every letter except `z'. Others collate like |
1822 | ||
1823 | aAbBcC...zZ | |
1824 | ||
1825 | which means that [A-Z] matches every letter except `a'. | |
28ef6c31 JA |
1826 | |
1827 | The portable way to specify upper case letters is [:upper:] instead of | |
1828 | A-Z; lower case may be specified as [:lower:] instead of a-z. | |
1829 | ||
1830 | Look at the manual pages for setlocale(3), strcoll(3), and, if it is | |
1831 | present, locale(1). If you have locale(1), you can use it to find | |
1832 | your current locale information even if you do not have any of the | |
1833 | LC_ variables set. | |
1834 | ||
1835 | My advice is to put | |
1836 | ||
1837 | export LC_COLLATE=C | |
1838 | ||
1839 | into /etc/profile and inspect any shell scripts run from cron for | |
1840 | constructs like [A-Z]. This will prevent things like | |
1841 | ||
1842 | rm [A-Z]* | |
1843 | ||
1844 | from removing every file in the current directory except those beginning | |
1845 | with `z' and still allow individual users to change the collation order. | |
1846 | Users may put the above command into their own profiles as well, of course. | |
1847 | ||
7117c2d2 JA |
1848 | E10) Why does `cd //' leave $PWD as `//'? |
1849 | ||
1850 | POSIX.2, in its description of `cd', says that *three* or more leading | |
1851 | slashes may be replaced with a single slash when canonicalizing the | |
1852 | current working directory. | |
1853 | ||
1854 | This is, I presume, for historical compatibility. Certain versions of | |
1855 | Unix, and early network file systems, used paths of the form | |
1856 | //hostname/path to access `path' on server `hostname'. | |
1857 | ||
b80f6443 JA |
1858 | E11) If I resize my xterm while another program is running, why doesn't bash |
1859 | notice the change? | |
1860 | ||
1861 | This is another issue that deals with job control. | |
1862 | ||
1863 | The kernel maintains a notion of a current terminal process group. Members | |
1864 | of this process group (processes whose process group ID is equal to the | |
1865 | current terminal process group ID) receive terminal-generated signals like | |
1866 | SIGWINCH. (For more details, see the JOB CONTROL section of the bash | |
1867 | man page.) | |
1868 | ||
1869 | If a terminal is resized, the kernel sends SIGWINCH to each member of | |
1870 | the terminal's current process group (the `foreground' process group). | |
1871 | ||
1872 | When bash is running with job control enabled, each pipeline (which may be | |
1873 | a single command) is run in its own process group, different from bash's | |
1874 | process group. This foreground process group receives the SIGWINCH; bash | |
1875 | does not. Bash has no way of knowing that the terminal has been resized. | |
1876 | ||
1877 | There is a `checkwinsize' option, settable with the `shopt' builtin, that | |
1878 | will cause bash to check the window size and adjust its idea of the | |
1879 | terminal's dimensions each time a process stops or exits and returns control | |
1880 | of the terminal to bash. Enable it with `shopt -s checkwinsize'. | |
1881 | ||
1882 | E12) Why don't negative offsets in substring expansion work like I expect? | |
1883 | ||
1884 | When substring expansion of the form ${param:offset[:length} is used, | |
1885 | an `offset' that evaluates to a number less than zero counts back from | |
1886 | the end of the expanded value of $param. | |
1887 | ||
1888 | When a negative `offset' begins with a minus sign, however, unexpected things | |
1889 | can happen. Consider | |
1890 | ||
1891 | a=12345678 | |
1892 | echo ${a:-4} | |
1893 | ||
1894 | intending to print the last four characters of $a. The problem is that | |
1895 | ${param:-word} already has a well-defined meaning: expand to word if the | |
1896 | expanded value of param is unset or null, and $param otherwise. | |
1897 | ||
1898 | To use negative offsets that begin with a minus sign, separate the | |
1899 | minus sign and the colon with a space. | |
1900 | ||
0628567a JA |
1901 | E13) Why does filename completion misbehave if a colon appears in the filename? |
1902 | ||
1903 | Filename completion (and word completion in general) may appear to behave | |
1904 | improperly if there is a colon in the word to be completed. | |
1905 | ||
1906 | The colon is special to readline's word completion code: it is one of the | |
1907 | characters that breaks words for the completer. Readline uses these characters | |
1908 | in sort of the same way that bash uses $IFS: they break or separate the words | |
1909 | the completion code hands to the application-specific or default word | |
1910 | completion functions. The original intent was to make it easy to edit | |
1911 | colon-separated lists (such as $PATH in bash) in various applications using | |
1912 | readline for input. | |
1913 | ||
1914 | This is complicated by the fact that some versions of the popular | |
1915 | `bash-completion' programmable completion package have problems with the | |
1916 | default completion behavior in the presence of colons. | |
1917 | ||
1918 | The current set of completion word break characters is available in bash as | |
1919 | the value of the COMP_WORDBREAKS variable. Removing `:' from that value is | |
1920 | enough to make the colon not special to completion: | |
1921 | ||
1922 | COMP_WORDBREAKS=${COMP_WORDBREAKS//:} | |
1923 | ||
1924 | You can also quote the colon with a backslash to achieve the same result | |
1925 | temporarily. | |
1926 | ||
3185942a JA |
1927 | E14) Why does quoting the pattern argument to the regular expression matching |
1928 | conditional operator (=~) cause regexp matching to stop working? | |
1929 | ||
1930 | In versions of bash prior to bash-3.2, the effect of quoting the regular | |
1931 | expression argument to the [[ command's =~ operator was not specified. | |
1932 | The practical effect was that double-quoting the pattern argument required | |
1933 | backslashes to quote special pattern characters, which interfered with the | |
1934 | backslash processing performed by double-quoted word expansion and was | |
1935 | inconsistent with how the == shell pattern matching operator treated | |
1936 | quoted characters. | |
1937 | ||
1938 | In bash-3.2, the shell was changed to internally quote characters in single- | |
1939 | and double-quoted string arguments to the =~ operator, which suppresses the | |
1940 | special meaning of the characters special to regular expression processing | |
1941 | (`.', `[', `\', `(', `), `*', `+', `?', `{', `|', `^', and `$') and forces | |
1942 | them to be matched literally. This is consistent with how the `==' pattern | |
1943 | matching operator treats quoted portions of its pattern argument. | |
1944 | ||
1945 | Since the treatment of quoted string arguments was changed, several issues | |
1946 | have arisen, chief among them the problem of white space in pattern arguments | |
1947 | and the differing treatment of quoted strings between bash-3.1 and bash-3.2. | |
1948 | Both problems may be solved by using a shell variable to hold the pattern. | |
1949 | Since word splitting is not performed when expanding shell variables in all | |
1950 | operands of the [[ command, this allows users to quote patterns as they wish | |
1951 | when assigning the variable, then expand the values to a single string that | |
1952 | may contain whitespace. The first problem may be solved by using backslashes | |
1953 | or any other quoting mechanism to escape the white space in the patterns. | |
1954 | ||
17345e5a JA |
1955 | Bash-4.0 introduces the concept of a `compatibility level', controlled by |
1956 | several options to the `shopt' builtin. If the `compat31' option is enabled, | |
1957 | bash reverts to the bash-3.1 behavior with respect to quoting the rhs of | |
1958 | the =~ operator. | |
1959 | ||
0001803f CR |
1960 | E15) Tell me more about the shell compatibility level. |
1961 | ||
1962 | Bash-4.0 introduced the concept of a `shell compatibility level', specified | |
1963 | as a set of options to the shopt builtin (compat31, compat32, compat40 at | |
1964 | this writing). There is only one current compatibility level -- each | |
1965 | option is mutually exclusive. This list does not mention behavior that is | |
1966 | standard for a particular version (e.g., setting compat32 means that quoting | |
1967 | the rhs of the regexp matching operator quotes special regexp characters in | |
1968 | the word, which is default behavior in bash-3.2 and above). | |
1969 | ||
1970 | compat31 set | |
1971 | - the < and > operators to the [[ command do not consider the current | |
1972 | locale when comparing strings | |
1973 | - quoting the rhs of the regexp matching operator (=~) has no | |
1974 | special effect | |
1975 | ||
1976 | compat32 set | |
1977 | - the < and > operators to the [[ command do not consider the current | |
1978 | locale when comparing strings | |
1979 | ||
1980 | compat40 set | |
1981 | - the < and > operators to the [[ command do not consider the current | |
1982 | locale when comparing strings | |
1983 | - interrupting a command list such as "a ; b ; c" causes the execution | |
495aee44 CR |
1984 | of the entire list to be aborted (in versions before bash-4.0, |
1985 | interrupting one command in a list caused the next to be executed) | |
0001803f | 1986 | |
ac50fbac CR |
1987 | compat41 set |
1988 | - interrupting a command list such as "a ; b ; c" causes the execution | |
1989 | of the entire list to be aborted (in versions before bash-4.1, | |
1990 | interrupting one command in a list caused the next to be executed) | |
1991 | - when in posix mode, single quotes in the `word' portion of a | |
1992 | double-quoted parameter expansion define a new quoting context and | |
1993 | are treated specially | |
1994 | ||
1995 | compat42 set | |
1996 | - the replacement string in double-quoted pattern substitution is not | |
1997 | run through quote removal, as in previous versions | |
1998 | ||
ccc6cda3 JA |
1999 | Section F: Things to watch out for on certain Unix versions |
2000 | ||
b72432fd | 2001 | F1) Why can't I use command line editing in my `cmdtool'? |
ccc6cda3 JA |
2002 | |
2003 | The problem is `cmdtool' and bash fighting over the input. When | |
2004 | scrolling is enabled in a cmdtool window, cmdtool puts the tty in | |
2005 | `raw mode' to permit command-line editing using the mouse for | |
2006 | applications that cannot do it themselves. As a result, bash and | |
2007 | cmdtool each try to read keyboard input immediately, with neither | |
2008 | getting enough of it to be useful. | |
2009 | ||
2010 | This mode also causes cmdtool to not implement many of the | |
2011 | terminal functions and control sequences appearing in the | |
2012 | `sun-cmd' termcap entry. For a more complete explanation, see | |
2013 | that file examples/suncmd.termcap in the bash distribution. | |
2014 | ||
2015 | `xterm' is a better choice, and gets along with bash much more | |
2016 | smoothly. | |
2017 | ||
2018 | If you must use cmdtool, you can use the termcap description in | |
2019 | examples/suncmd.termcap. Set the TERMCAP variable to the terminal | |
2020 | description contained in that file, i.e. | |
2021 | ||
2022 | TERMCAP='Mu|sun-cmd:am:bs:km:pt:li#34:co#80:cl=^L:ce=\E[K:cd=\E[J:rs=\E[s:' | |
2023 | ||
2024 | Then export TERMCAP and start a new cmdtool window from that shell. | |
2025 | The bash command-line editing should behave better in the new | |
2026 | cmdtool. If this works, you can put the assignment to TERMCAP | |
2027 | in your bashrc file. | |
2028 | ||
b72432fd | 2029 | F2) I built bash on Solaris 2. Why do globbing expansions and filename |
ccc6cda3 JA |
2030 | completion chop off the first few characters of each filename? |
2031 | ||
2032 | This is the consequence of building bash on SunOS 5 and linking | |
2033 | with the libraries in /usr/ucblib, but using the definitions | |
2034 | and structures from files in /usr/include. | |
2035 | ||
2036 | The actual conflict is between the dirent structure in | |
2037 | /usr/include/dirent.h and the struct returned by the version of | |
2038 | `readdir' in libucb.a (a 4.3-BSD style `struct direct'). | |
2039 | ||
2040 | Make sure you've got /usr/ccs/bin ahead of /usr/ucb in your $PATH | |
2041 | when configuring and building bash. This will ensure that you | |
2042 | use /usr/ccs/bin/cc or acc instead of /usr/ucb/cc and that you | |
2043 | link with libc before libucb. | |
2044 | ||
2045 | If you have installed the Sun C compiler, you may also need to | |
2046 | put /usr/ccs/bin and /opt/SUNWspro/bin into your $PATH before | |
2047 | /usr/ucb. | |
2048 | ||
b72432fd | 2049 | F3) Why does bash dump core after I interrupt username completion or |
ccc6cda3 JA |
2050 | `~user' tilde expansion on a machine running NIS? |
2051 | ||
2052 | This is a famous and long-standing bug in the SunOS YP (sorry, NIS) | |
2053 | client library, which is part of libc. | |
2054 | ||
2055 | The YP library code keeps static state -- a pointer into the data | |
2056 | returned from the server. When YP initializes itself (setpwent), | |
2057 | it looks at this pointer and calls free on it if it's non-null. | |
2058 | So far, so good. | |
2059 | ||
2060 | If one of the YP functions is interrupted during getpwent (the | |
2061 | exact function is interpretwithsave()), and returns NULL, the | |
2062 | pointer is freed without being reset to NULL, and the function | |
2063 | returns. The next time getpwent is called, it sees that this | |
2064 | pointer is non-null, calls free, and the bash free() blows up | |
2065 | because it's being asked to free freed memory. | |
2066 | ||
2067 | The traditional Unix mallocs allow memory to be freed multiple | |
2068 | times; that's probably why this has never been fixed. You can | |
2069 | run configure with the `--without-gnu-malloc' option to use | |
2070 | the C library malloc and avoid the problem. | |
2071 | ||
b72432fd | 2072 | F4) I'm running SVR4.2. Why is the line erased every time I type `@'? |
ccc6cda3 JA |
2073 | |
2074 | The `@' character is the default `line kill' character in most | |
2075 | versions of System V, including SVR4.2. You can change this | |
2076 | character to whatever you want using `stty'. For example, to | |
2077 | change the line kill character to control-u, type | |
2078 | ||
2079 | stty kill ^U | |
2080 | ||
2081 | where the `^' and `U' can be two separate characters. | |
2082 | ||
b72432fd | 2083 | F5) Why does bash report syntax errors when my C News scripts use a |
ccc6cda3 JA |
2084 | redirection before a subshell command? |
2085 | ||
2086 | The actual command in question is something like | |
2087 | ||
2088 | < file ( command ) | |
2089 | ||
2090 | According to the grammar given in the POSIX.2 standard, this construct | |
2091 | is, in fact, a syntax error. Redirections may only precede `simple | |
2092 | commands'. A subshell construct such as the above is one of the shell's | |
2093 | `compound commands'. A redirection may only follow a compound command. | |
2094 | ||
bb70624e JA |
2095 | This affects the mechanical transformation of commands that use `cat' |
2096 | to pipe a file into a command (a favorite Useless-Use-Of-Cat topic on | |
2097 | comp.unix.shell). While most commands of the form | |
2098 | ||
2099 | cat file | command | |
2100 | ||
2101 | can be converted to `< file command', shell control structures such as | |
2102 | loops and subshells require `command < file'. | |
2103 | ||
b80f6443 | 2104 | The file CWRU/sh-redir-hack in the bash distribution is an |
ccc6cda3 JA |
2105 | (unofficial) patch to parse.y that will modify the grammar to |
2106 | support this construct. It will not apply with `patch'; you must | |
2107 | modify parse.y by hand. Note that if you apply this, you must | |
2108 | recompile with -DREDIRECTION_HACK. This introduces a large | |
2109 | number of reduce/reduce conflicts into the shell grammar. | |
2110 | ||
bb70624e JA |
2111 | F6) Why can't I use vi-mode editing on Red Hat Linux 6.1? |
2112 | ||
2113 | The short answer is that Red Hat screwed up. | |
2114 | ||
2115 | The long answer is that they shipped an /etc/inputrc that only works | |
2116 | for emacs mode editing, and then screwed all the vi users by setting | |
2117 | INPUTRC to /etc/inputrc in /etc/profile. | |
2118 | ||
2119 | The short fix is to do one of the following: remove or rename | |
2120 | /etc/inputrc, set INPUTRC=~/.inputrc in ~/.bashrc (or .bash_profile, | |
2121 | but make sure you export it if you do), remove the assignment to | |
2122 | INPUTRC from /etc/profile, add | |
2123 | ||
2124 | set keymap emacs | |
2125 | ||
2126 | to the beginning of /etc/inputrc, or bracket the key bindings in | |
2127 | /etc/inputrc with these lines | |
2128 | ||
2129 | $if mode=emacs | |
2130 | [...] | |
2131 | $endif | |
2132 | ||
7117c2d2 JA |
2133 | F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on |
2134 | HP/UX 11.x? | |
2135 | ||
2136 | HP/UX's support for long double is imperfect at best. | |
2137 | ||
2138 | GCC will support it without problems, but the HP C library functions | |
2139 | like strtold(3) and printf(3) don't actually work with long doubles. | |
2140 | HP implemented a `long_double' type as a 4-element array of 32-bit | |
2141 | ints, and that is what the library functions use. The ANSI C | |
2142 | `long double' type is a 128-bit floating point scalar. | |
2143 | ||
2144 | The easiest fix, until HP fixes things up, is to edit the generated | |
2145 | config.h and #undef the HAVE_LONG_DOUBLE line. After doing that, | |
2146 | the compilation should complete successfully. | |
2147 | ||
bb70624e JA |
2148 | Section G: How can I get bash to do certain common things? |
2149 | ||
2150 | G1) How can I get bash to read and display eight-bit characters? | |
2151 | ||
2152 | This is a process requiring several steps. | |
2153 | ||
2154 | First, you must ensure that the `physical' data path is a full eight | |
2155 | bits. For xterms, for example, the `vt100' resources `eightBitInput' | |
2156 | and `eightBitOutput' should be set to `true'. | |
2157 | ||
2158 | Once you have set up an eight-bit path, you must tell the kernel and | |
2159 | tty driver to leave the eighth bit of characters alone when processing | |
2160 | keyboard input. Use `stty' to do this: | |
2161 | ||
2162 | stty cs8 -istrip -parenb | |
2163 | ||
2164 | For old BSD-style systems, you can use | |
2165 | ||
2166 | stty pass8 | |
2167 | ||
2168 | You may also need | |
2169 | ||
2170 | stty even odd | |
2171 | ||
2172 | Finally, you need to tell readline that you will be inputting and | |
2173 | displaying eight-bit characters. You use readline variables to do | |
d233b485 | 2174 | this. These variables can be set in your .inputrc or using the bash |
bb70624e JA |
2175 | `bind' builtin. Here's an example using `bind': |
2176 | ||
2177 | bash$ bind 'set convert-meta off' | |
d233b485 | 2178 | bash$ bind 'set meta-flag on' |
bb70624e JA |
2179 | bash$ bind 'set output-meta on' |
2180 | ||
2181 | The `set' commands between the single quotes may also be placed | |
2182 | in ~/.inputrc. | |
2183 | ||
0628567a JA |
2184 | The script examples/scripts.noah/meta.bash encapsulates the bind |
2185 | commands in a shell function. | |
2186 | ||
bb70624e JA |
2187 | G2) How do I write a function `x' to replace builtin command `x', but |
2188 | still invoke the command from within the function? | |
2189 | ||
2190 | This is why the `command' and `builtin' builtins exist. The | |
2191 | `command' builtin executes the command supplied as its first | |
2192 | argument, skipping over any function defined with that name. The | |
2193 | `builtin' builtin executes the builtin command given as its first | |
2194 | argument directly. | |
2195 | ||
2196 | For example, to write a function to replace `cd' that writes the | |
2197 | hostname and current directory to an xterm title bar, use | |
2198 | something like the following: | |
2199 | ||
2200 | cd() | |
2201 | { | |
2202 | builtin cd "$@" && xtitle "$HOST: $PWD" | |
2203 | } | |
2204 | ||
2205 | This could also be written using `command' instead of `builtin'; | |
2206 | the version above is marginally more efficient. | |
2207 | ||
2208 | G3) How can I find the value of a shell variable whose name is the value | |
2209 | of another shell variable? | |
2210 | ||
2211 | Versions of Bash newer than Bash-2.0 support this directly. You can use | |
2212 | ||
2213 | ${!var} | |
2214 | ||
2215 | For example, the following sequence of commands will echo `z': | |
2216 | ||
2217 | var1=var2 | |
2218 | var2=z | |
2219 | echo ${!var1} | |
2220 | ||
2221 | For sh compatibility, use the `eval' builtin. The important | |
2222 | thing to remember is that `eval' expands the arguments you give | |
2223 | it again, so you need to quote the parts of the arguments that | |
2224 | you want `eval' to act on. | |
2225 | ||
2226 | For example, this expression prints the value of the last positional | |
2227 | parameter: | |
2228 | ||
2229 | eval echo \"\$\{$#\}\" | |
2230 | ||
2231 | The expansion of the quoted portions of this expression will be | |
2232 | deferred until `eval' runs, while the `$#' will be expanded | |
2233 | before `eval' is executed. In versions of bash later than bash-2.0, | |
2234 | ||
2235 | echo ${!#} | |
2236 | ||
2237 | does the same thing. | |
2238 | ||
f73dda09 | 2239 | This is not the same thing as ksh93 `nameref' variables, though the syntax |
ac50fbac | 2240 | is similar. Namerefs are available bash version 4.3, and work as in ksh93. |
f73dda09 | 2241 | |
bb70624e JA |
2242 | G4) How can I make the bash `time' reserved word print timing output that |
2243 | looks like the output from my system's /usr/bin/time? | |
2244 | ||
2245 | The bash command timing code looks for a variable `TIMEFORMAT' and | |
2246 | uses its value as a format string to decide how to display the | |
2247 | timing statistics. | |
2248 | ||
2249 | The value of TIMEFORMAT is a string with `%' escapes expanded in a | |
2250 | fashion similar in spirit to printf(3). The manual page explains | |
2251 | the meanings of the escape sequences in the format string. | |
2252 | ||
2253 | If TIMEFORMAT is not set, bash acts as if the following assignment had | |
2254 | been performed: | |
2255 | ||
2256 | TIMEFORMAT=$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS' | |
2257 | ||
2258 | The POSIX.2 default time format (used by `time -p command') is | |
2259 | ||
2260 | TIMEFORMAT=$'real %2R\nuser %2U\nsys %2S' | |
2261 | ||
2262 | The BSD /usr/bin/time format can be emulated with: | |
2263 | ||
2264 | TIMEFORMAT=$'\t%1R real\t%1U user\t%1S sys' | |
2265 | ||
2266 | The System V /usr/bin/time format can be emulated with: | |
2267 | ||
2268 | TIMEFORMAT=$'\nreal\t%1R\nuser\t%1U\nsys\t%1S' | |
2269 | ||
2270 | The ksh format can be emulated with: | |
2271 | ||
2272 | TIMEFORMAT=$'\nreal\t%2lR\nuser\t%2lU\nsys\t%2lS' | |
2273 | ||
2274 | G5) How do I get the current directory into my prompt? | |
2275 | ||
2276 | Bash provides a number of backslash-escape sequences which are expanded | |
2277 | when the prompt string (PS1 or PS2) is displayed. The full list is in | |
2278 | the manual page. | |
2279 | ||
2280 | The \w expansion gives the full pathname of the current directory, with | |
2281 | a tilde (`~') substituted for the current value of $HOME. The \W | |
2282 | expansion gives the basename of the current directory. To put the full | |
2283 | pathname of the current directory into the path without any tilde | |
d233b485 | 2284 | substitution, use $PWD. Here are some examples: |
bb70624e JA |
2285 | |
2286 | PS1='\w$ ' # current directory with tilde | |
2287 | PS1='\W$ ' # basename of current directory | |
2288 | PS1='$PWD$ ' # full pathname of current directory | |
2289 | ||
2290 | The single quotes are important in the final example to prevent $PWD from | |
2291 | being expanded when the assignment to PS1 is performed. | |
2292 | ||
2293 | G6) How can I rename "*.foo" to "*.bar"? | |
2294 | ||
2295 | Use the pattern removal functionality described in D3. The following `for' | |
2296 | loop will do the trick: | |
2297 | ||
2298 | for f in *.foo; do | |
2299 | mv $f ${f%foo}bar | |
2300 | done | |
2301 | ||
2302 | G7) How can I translate a filename from uppercase to lowercase? | |
2303 | ||
2304 | The script examples/functions/lowercase, originally written by John DuBois, | |
2305 | will do the trick. The converse is left as an exercise. | |
2306 | ||
2307 | G8) How can I write a filename expansion (globbing) pattern that will match | |
2308 | all files in the current directory except "." and ".."? | |
2309 | ||
2310 | You must have set the `extglob' shell option using `shopt -s extglob' to use | |
2311 | this: | |
2312 | ||
2313 | echo .!(.|) * | |
2314 | ||
2315 | A solution that works without extended globbing is given in the Unix Shell | |
3185942a JA |
2316 | FAQ, posted periodically to comp.unix.shell. It's a variant of |
2317 | ||
2318 | echo .[!.]* ..?* * | |
2319 | ||
2320 | (The ..?* catches files with names of three or more characters beginning | |
2321 | with `..') | |
bb70624e JA |
2322 | |
2323 | Section H: Where do I go from here? | |
ccc6cda3 | 2324 | |
bb70624e | 2325 | H1) How do I report bugs in bash, and where should I look for fixes and |
ccc6cda3 JA |
2326 | advice? |
2327 | ||
2328 | Use the `bashbug' script to report bugs. It is built and | |
2329 | installed at the same time as bash. It provides a standard | |
2330 | template for reporting a problem and automatically includes | |
2331 | information about your configuration and build environment. | |
2332 | ||
b72432fd | 2333 | `bashbug' sends its reports to bug-bash@gnu.org, which |
ccc6cda3 JA |
2334 | is a large mailing list gatewayed to the usenet newsgroup gnu.bash.bug. |
2335 | ||
2336 | Bug fixes, answers to questions, and announcements of new releases | |
2337 | are all posted to gnu.bash.bug. Discussions concerning bash features | |
2338 | and problems also take place there. | |
2339 | ||
2340 | To reach the bash maintainers directly, send mail to | |
b72432fd | 2341 | bash-maintainers@gnu.org. |
ccc6cda3 | 2342 | |
bb70624e | 2343 | H2) What kind of bash documentation is there? |
ccc6cda3 JA |
2344 | |
2345 | First, look in the doc directory in the bash distribution. It should | |
2346 | contain at least the following files: | |
2347 | ||
2348 | bash.1 an extensive, thorough Unix-style manual page | |
2349 | builtins.1 a manual page covering just bash builtin commands | |
b72432fd JA |
2350 | bashref.texi a reference manual in GNU tex`info format |
2351 | bashref.info an info version of the reference manual | |
ccc6cda3 JA |
2352 | FAQ this file |
2353 | article.ms text of an article written for The Linux Journal | |
2354 | readline.3 a man page describing readline | |
2355 | ||
b72432fd JA |
2356 | Postscript, HTML, and ASCII files created from the above source are |
2357 | available in the documentation distribution. | |
ccc6cda3 JA |
2358 | |
2359 | There is additional documentation available for anonymous FTP from host | |
cce855bc | 2360 | ftp.cwru.edu in the `pub/bash' directory. |
ccc6cda3 JA |
2361 | |
2362 | Cameron Newham and Bill Rosenblatt have written a book on bash, published | |
2363 | by O'Reilly and Associates. The book is based on Bill Rosenblatt's Korn | |
d166f048 | 2364 | Shell book. The title is ``Learning the Bash Shell'', and the ISBN number |
0628567a JA |
2365 | of the third edition, published in March, 2005, is 0-596-00965-8. Look for |
2366 | it in fine bookstores near you. This edition of the book has been updated | |
2367 | to cover bash-3.0. | |
ccc6cda3 | 2368 | |
b80f6443 | 2369 | The GNU Bash Reference Manual has been published as a printed book by |
3185942a JA |
2370 | Network Theory Ltd (Paperback, ISBN: 0-9541617-7-7, Nov. 2006). It covers |
2371 | bash-3.2 and is available from most online bookstores (see | |
b80f6443 JA |
2372 | http://www.network-theory.co.uk/bash/manual/ for details). The publisher |
2373 | will donate $1 to the Free Software Foundation for each copy sold. | |
2374 | ||
0628567a JA |
2375 | Arnold Robbins and Nelson Beebe have written ``Classic Shell Scripting'', |
2376 | published by O'Reilly. The first edition, with ISBN number 0-596-00595-4, | |
2377 | was published in May, 2005. | |
2378 | ||
2379 | Chris F. A. Johnson, a frequent contributor to comp.unix.shell and | |
2380 | gnu.bash.bug, has written ``Shell Scripting Recipes: A Problem-Solution | |
2381 | Approach,'' a new book on shell scripting, concentrating on features of | |
2382 | the POSIX standard helpful to shell script writers. The first edition from | |
2383 | Apress, with ISBN number 1-59059-471-1, was published in May, 2005. | |
2384 | ||
bb70624e | 2385 | H3) What's coming in future versions? |
ccc6cda3 | 2386 | |
f73dda09 | 2387 | These are features I hope to include in a future version of bash. |
ccc6cda3 | 2388 | |
17345e5a | 2389 | Rocky Bernstein's bash debugger (support is included with bash-4.0) |
ccc6cda3 | 2390 | |
bb70624e | 2391 | H4) What's on the bash `wish list' for future versions? |
ccc6cda3 JA |
2392 | |
2393 | These are features that may or may not appear in a future version of bash. | |
2394 | ||
ccc6cda3 | 2395 | breaking some of the shell functionality into embeddable libraries |
bb70624e | 2396 | a module system like zsh's, using dynamic loading like builtins |
bb70624e JA |
2397 | a bash programmer's guide with a chapter on creating loadable builtins |
2398 | a better loadable interface to perl with access to the shell builtins and | |
2399 | variables (contributions gratefully accepted) | |
f73dda09 | 2400 | ksh93-like `xx.yy' variables (including some of the .sh.* variables) and |
d233b485 | 2401 | associated discipline functions |
f73dda09 | 2402 | Some of the new ksh93 pattern matching operators, like backreferencing |
ccc6cda3 | 2403 | |
bb70624e | 2404 | H5) When will the next release appear? |
ccc6cda3 | 2405 | |
ac50fbac | 2406 | The next version will appear sometime in 2015. Never make predictions. |
ccc6cda3 | 2407 | |
ac50fbac | 2408 | This document is Copyright 1995-2014 by Chester Ramey. |
ccc6cda3 JA |
2409 | |
2410 | Permission is hereby granted, without written agreement and | |
2411 | without license or royalty fees, to use, copy, and distribute | |
2412 | this document for any purpose, provided that the above copyright | |
2413 | notice appears in all copies of this document and that the | |
2414 | contents of this document remain unaltered. |