Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 1 | Compatibility with previous versions |
| 2 | ==================================== |
| 3 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 4 | This document details the incompatibilities between this version of bash, |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 5 | bash-4.3, and the previous widely-available versions, bash-3.x (which is |
| 6 | still the `standard' version for Mac OS X), 4.0/4.1 (which are still |
| 7 | standard on a few Linux distributions), and bash-4.2, the current |
| 8 | widely-available version. These were discovered by users of bash-2.x |
| 9 | through 4.x, so this list is not comprehensive. Some of these |
| 10 | incompatibilities occur between the current version and versions 2.0 and |
| 11 | above. |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 12 | |
Jari Aalto | b80f644 | 2004-07-27 13:29:18 +0000 | [diff] [blame] | 13 | 1. Bash uses a new quoting syntax, $"...", to do locale-specific |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 14 | string translation. Users who have relied on the (undocumented) |
| 15 | behavior of bash-1.14 will have to change their scripts. For |
| 16 | instance, if you are doing something like this to get the value of |
| 17 | a variable whose name is the value of a second variable: |
| 18 | |
| 19 | eval var2=$"$var1" |
| 20 | |
| 21 | you will have to change to a different syntax. |
| 22 | |
| 23 | This capability is directly supported by bash-2.0: |
| 24 | |
| 25 | var2=${!var1} |
| 26 | |
| 27 | This alternate syntax will work portably between bash-1.14 and bash-2.0: |
| 28 | |
| 29 | eval var2=\$${var1} |
| 30 | |
| 31 | 2. One of the bugs fixed in the YACC grammar tightens up the rules |
| 32 | concerning group commands ( {...} ). The `list' that composes the |
| 33 | body of the group command must be terminated by a newline or |
| 34 | semicolon. That's because the braces are reserved words, and are |
| 35 | recognized as such only when a reserved word is legal. This means |
| 36 | that while bash-1.14 accepted shell function definitions like this: |
| 37 | |
| 38 | foo() { : } |
| 39 | |
| 40 | bash-2.0 requires this: |
| 41 | |
| 42 | foo() { :; } |
| 43 | |
| 44 | This is also an issue for commands like this: |
| 45 | |
| 46 | mkdir dir || { echo 'could not mkdir' ; exit 1; } |
| 47 | |
| 48 | The syntax required by bash-2.0 is also accepted by bash-1.14. |
| 49 | |
| 50 | 3. The options to `bind' have changed to make them more consistent with |
| 51 | the rest of the bash builtins. If you are using `bind -d' to list |
Jari Aalto | 7117c2d | 2002-07-17 14:10:11 +0000 | [diff] [blame] | 52 | the readline key bindings in a form that can be re-read, use `bind -p' |
| 53 | instead. If you were using `bind -v' to list the key bindings, use |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 54 | `bind -P' instead. |
| 55 | |
| 56 | 4. The `long' invocation options must now be prefixed by `--' instead |
| 57 | of `-'. (The old form is still accepted, for the time being.) |
| 58 | |
| 59 | 5. There was a bug in the version of readline distributed with bash-1.14 |
| 60 | that caused it to write badly-formatted key bindings when using |
| 61 | `bind -d'. The only key sequences that were affected are C-\ (which |
| 62 | should appear as \C-\\ in a key binding) and C-" (which should appear |
| 63 | as \C-\"). If these key sequences appear in your inputrc, as, for |
| 64 | example, |
| 65 | |
| 66 | "\C-\": self-insert |
| 67 | |
| 68 | they will need to be changed to something like the following: |
| 69 | |
| 70 | "\C-\\": self-insert |
| 71 | |
Jari Aalto | 7117c2d | 2002-07-17 14:10:11 +0000 | [diff] [blame] | 72 | 6. A number of people complained about having to use ESC to terminate an |
Jari Aalto | b72432f | 1999-02-19 17:11:39 +0000 | [diff] [blame] | 73 | incremental search, and asked for an alternate mechanism. Bash-2.03 |
| 74 | uses the value of the settable readline variable `isearch-terminators' |
| 75 | to decide which characters should terminate an incremental search. If |
| 76 | that variable has not been set, ESC and Control-J will terminate a |
| 77 | search. |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 78 | |
| 79 | 7. Some variables have been removed: MAIL_WARNING, notify, history_control, |
| 80 | command_oriented_history, glob_dot_filenames, allow_null_glob_expansion, |
| 81 | nolinks, hostname_completion_file, noclobber, no_exit_on_failed_exec, and |
| 82 | cdable_vars. Most of them are now implemented with the new `shopt' |
Jari Aalto | d166f04 | 1997-06-05 14:59:13 +0000 | [diff] [blame] | 83 | builtin; others were already implemented by `set'. Here is a list of |
| 84 | correspondences: |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 85 | |
Jari Aalto | d166f04 | 1997-06-05 14:59:13 +0000 | [diff] [blame] | 86 | MAIL_WARNING shopt mailwarn |
| 87 | notify set -o notify |
| 88 | history_control HISTCONTROL |
| 89 | command_oriented_history shopt cmdhist |
| 90 | glob_dot_filenames shopt dotglob |
| 91 | allow_null_glob_expansion shopt nullglob |
| 92 | nolinks set -o physical |
| 93 | hostname_completion_file HOSTFILE |
| 94 | noclobber set -o noclobber |
| 95 | no_exit_on_failed_exec shopt execfail |
| 96 | cdable_vars shopt cdable_vars |
| 97 | |
| 98 | 8. `ulimit' now sets both hard and soft limits and reports the soft limit |
| 99 | by default (when neither -H nor -S is specified). This is compatible |
| 100 | with versions of sh and ksh that implement `ulimit'. The bash-1.14 |
| 101 | behavior of, for example, |
| 102 | |
| 103 | ulimit -c 0 |
| 104 | |
| 105 | can be obtained with |
| 106 | |
| 107 | ulimit -S -c 0 |
| 108 | |
| 109 | It may be useful to define an alias: |
| 110 | |
| 111 | alias ulimit="ulimit -S" |
| 112 | |
Jari Aalto | cce855b | 1998-04-17 19:52:44 +0000 | [diff] [blame] | 113 | 9. Bash-2.01 uses a new quoting syntax, $'...' to do ANSI-C string |
| 114 | translation. Backslash-escaped characters in ... are expanded and |
| 115 | replaced as specified by the ANSI C standard. |
| 116 | |
| 117 | 10. The sourcing of startup files has changed somewhat. This is explained |
| 118 | more completely in the INVOCATION section of the manual page. |
| 119 | |
| 120 | A non-interactive shell not named `sh' and not in posix mode reads |
| 121 | and executes commands from the file named by $BASH_ENV. A |
| 122 | non-interactive shell started by `su' and not in posix mode will read |
| 123 | startup files. No other non-interactive shells read any startup files. |
| 124 | |
| 125 | An interactive shell started in posix mode reads and executes commands |
| 126 | from the file named by $ENV. |
Jari Aalto | b72432f | 1999-02-19 17:11:39 +0000 | [diff] [blame] | 127 | |
| 128 | 11. The <> redirection operator was changed to conform to the POSIX.2 spec. |
| 129 | In the absence of any file descriptor specification preceding the `<>', |
| 130 | file descriptor 0 is used. In bash-1.14, this was the behavior only |
| 131 | when in POSIX mode. The bash-1.14 behavior may be obtained with |
| 132 | |
| 133 | <>filename 1>&0 |
Jari Aalto | bb70624 | 2000-03-17 21:46:59 +0000 | [diff] [blame] | 134 | |
| 135 | 12. The `alias' builtin now checks for invalid options and takes a `-p' |
| 136 | option to display output in POSIX mode. If you have old aliases beginning |
| 137 | with `-' or `+', you will have to add the `--' to the alias command |
| 138 | that declares them: |
| 139 | |
| 140 | alias -x='chmod a-x' --> alias -- -x='chmod a-x' |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 141 | |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 142 | 13. The behavior of range specificiers within bracket matching expressions |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 143 | in the pattern matcher (e.g., [A-Z]) depends on the current locale, |
| 144 | specifically the value of the LC_COLLATE environment variable. Setting |
| 145 | this variable to C or POSIX will result in the traditional ASCII behavior |
| 146 | for range comparisons. If the locale is set to something else, e.g., |
| 147 | en_US (specified by the LANG or LC_ALL variables), collation order is |
| 148 | locale-dependent. For example, the en_US locale sorts the upper and |
| 149 | lower case letters like this: |
| 150 | |
| 151 | AaBb...Zz |
| 152 | |
| 153 | so a range specification like [A-Z] will match every letter except `z'. |
Jari Aalto | 7117c2d | 2002-07-17 14:10:11 +0000 | [diff] [blame] | 154 | Other locales collate like |
| 155 | |
| 156 | aAbBcC...zZ |
| 157 | |
| 158 | which means that [A-Z] matches every letter except `a'. |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 159 | |
| 160 | The portable way to specify upper case letters is [:upper:] instead of |
| 161 | A-Z; lower case may be specified as [:lower:] instead of a-z. |
| 162 | |
| 163 | Look at the manual pages for setlocale(3), strcoll(3), and, if it is |
| 164 | present, locale(1). |
| 165 | |
| 166 | You can find your current locale information by running locale(1): |
| 167 | |
| 168 | caleb.ins.cwru.edu(2)$ locale |
| 169 | LANG=en_US |
| 170 | LC_CTYPE="en_US" |
| 171 | LC_NUMERIC="en_US" |
| 172 | LC_TIME="en_US" |
| 173 | LC_COLLATE="en_US" |
| 174 | LC_MONETARY="en_US" |
| 175 | LC_MESSAGES="en_US" |
| 176 | LC_ALL=en_US |
| 177 | |
| 178 | My advice is to put |
| 179 | |
| 180 | export LC_COLLATE=C |
| 181 | |
| 182 | into /etc/profile and inspect any shell scripts run from cron for |
| 183 | constructs like [A-Z]. This will prevent things like |
| 184 | |
| 185 | rm [A-Z]* |
| 186 | |
| 187 | from removing every file in the current directory except those beginning |
| 188 | with `z' and still allow individual users to change the collation order. |
| 189 | Users may put the above command into their own profiles as well, of course. |
| 190 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 191 | 14. Bash versions up to 1.14.7 included an undocumented `-l' operator to |
| 192 | the `test/[' builtin. It was a unary operator that expanded to the |
| 193 | length of its string argument. This let you do things like |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 194 | |
| 195 | test -l $variable -lt 20 |
| 196 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 197 | for example. |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 198 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 199 | This was included for backwards compatibility with old versions of the |
| 200 | Bourne shell, which did not provide an easy way to obtain the length of |
| 201 | the value of a shell variable. |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 202 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 203 | This operator is not part of the POSIX standard, because one can (and |
| 204 | should) use ${#variable} to get the length of a variable's value. |
| 205 | Bash-2.x does not support it. |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 206 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 207 | 15. Bash no longer auto-exports the HOME, PATH, SHELL, TERM, HOSTNAME, |
| 208 | HOSTTYPE, MACHTYPE, or OSTYPE variables. If they appear in the initial |
| 209 | environment, the export attribute will be set, but if bash provides a |
| 210 | default value, they will remain local to the current shell. |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 211 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 212 | 16. Bash no longer initializes the FUNCNAME, GROUPS, or DIRSTACK variables |
| 213 | to have special behavior if they appear in the initial environment. |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 214 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 215 | 17. Bash no longer removes the export attribute from the SSH_CLIENT or |
| 216 | SSH2_CLIENT variables, and no longer attempts to discover whether or |
| 217 | not it has been invoked by sshd in order to run the startup files. |
Jari Aalto | b80f644 | 2004-07-27 13:29:18 +0000 | [diff] [blame] | 218 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 219 | 18. Bash no longer requires that the body of a function be a group command; |
| 220 | any compound command is accepted. |
Jari Aalto | 95732b4 | 2005-12-07 14:08:12 +0000 | [diff] [blame] | 221 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 222 | 19. As of bash-3.0, the pattern substitution operators no longer perform |
| 223 | quote removal on the pattern before attempting the match. This is the |
| 224 | way the pattern removal functions behave, and is more consistent. |
Jari Aalto | 95732b4 | 2005-12-07 14:08:12 +0000 | [diff] [blame] | 225 | |
Jari Aalto | 0628567 | 2006-10-10 14:15:34 +0000 | [diff] [blame] | 226 | 20. After bash-3.0 was released, I reimplemented tilde expansion, incorporating |
| 227 | it into the mainline word expansion code. This fixes the bug that caused |
| 228 | the results of tilde expansion to be re-expanded. There is one |
| 229 | incompatibility: a ${paramOPword} expansion within double quotes will not |
| 230 | perform tilde expansion on WORD. This is consistent with the other |
| 231 | expansions, and what POSIX specifies. |
| 232 | |
| 233 | 21. A number of variables have the integer attribute by default, so the += |
| 234 | assignment operator returns expected results: RANDOM, LINENO, MAILCHECK, |
| 235 | HISTCMD, OPTIND. |
| 236 | |
| 237 | 22. Bash-3.x is much stricter about $LINENO correctly reflecting the line |
| 238 | number in a script; assignments to LINENO have little effect. |
| 239 | |
| 240 | 23. By default, readline binds the terminal special characters to their |
| 241 | readline equivalents. As of bash-3.1/readline-5.1, this is optional and |
| 242 | controlled by the bind-tty-special-chars readline variable. |
| 243 | |
| 244 | 24. The \W prompt string expansion abbreviates $HOME as `~'. The previous |
| 245 | behavior is available with ${PWD##/*/}. |
| 246 | |
| 247 | 25. The arithmetic exponentiation operator is right-associative as of bash-3.1. |
| 248 | |
| 249 | 26. The rules concerning valid alias names are stricter, as per POSIX.2. |
| 250 | |
| 251 | 27. The Readline key binding functions now obey the convert-meta setting active |
| 252 | when the binding takes place, as the dispatch code does when characters |
| 253 | are read and processed. |
| 254 | |
| 255 | 28. The historical behavior of `trap' reverting signal disposition to the |
| 256 | original handling in the absence of a valid first argument is implemented |
| 257 | only if the first argument is a valid signal number. |
| 258 | |
| 259 | 29. In versions of bash after 3.1, the ${parameter//pattern/replacement} |
| 260 | expansion does not interpret `%' or `#' specially. Those anchors don't |
| 261 | have any real meaning when replacing every match. |
| 262 | |
| 263 | 30. Beginning with bash-3.1, the combination of posix mode and enabling the |
| 264 | `xpg_echo' option causes echo to ignore all options, not looking for `-n' |
| 265 | |
| 266 | 31. Beginning with bash-3.2, bash follows the Bourne-shell-style (and POSIX- |
| 267 | style) rules for parsing the contents of old-style backquoted command |
| 268 | substitutions. Previous versions of bash attempted to recursively parse |
| 269 | embedded quoted strings and shell constructs; bash-3.2 uses strict POSIX |
| 270 | rules to find the closing backquote and simply passes the contents of the |
| 271 | command substitution to a subshell for parsing and execution. |
| 272 | |
| 273 | 32. Beginning with bash-3.2, bash uses access(2) when executing primaries for |
| 274 | the test builtin and the [[ compound command, rather than looking at the |
| 275 | file permission bits obtained with stat(2). This obeys restrictions of |
| 276 | the file system (e.g., read-only or noexec mounts) not available via stat. |
| 277 | |
Jari Aalto | 3185942 | 2009-01-12 13:36:28 +0000 | [diff] [blame] | 278 | 33. Bash-3.2 adopts the convention used by other string and pattern matching |
| 279 | operators for the `[[' compound command, and matches any quoted portion |
| 280 | of the right-hand-side argument to the =~ operator as a string rather |
| 281 | than a regular expression. |
| 282 | |
| 283 | 34. Bash-4.0 allows the behavior in the previous item to be modified using |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 284 | the notion of a shell `compatibility level'. If the compat31 shopt |
| 285 | option is set, quoting the pattern has no special effect. |
Jari Aalto | 3185942 | 2009-01-12 13:36:28 +0000 | [diff] [blame] | 286 | |
| 287 | 35. Bash-3.2 (patched) and Bash-4.0 fix a bug that leaves the shell in an |
| 288 | inconsistent internal state following an assignment error. One of the |
| 289 | changes means that compound commands or { ... } grouping commands are |
| 290 | aborted under some circumstances in which they previously were not. |
| 291 | This is what Posix specifies. |
| 292 | |
| 293 | 36. Bash-4.0 now allows process substitution constructs to pass unchanged |
| 294 | through brace expansion, so any expansion of the contents will have to be |
| 295 | separately specified, and each process subsitution will have to be |
| 296 | separately entered. |
| 297 | |
| 298 | 37. Bash-4.0 now allows SIGCHLD to interrupt the wait builtin, as Posix |
| 299 | specifies, so the SIGCHLD trap is no longer always invoked once per |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 300 | exiting child if you are using `wait' to wait for all children. As |
| 301 | of bash-4.2, this is the status quo only when in posix mode. |
Jari Aalto | 3185942 | 2009-01-12 13:36:28 +0000 | [diff] [blame] | 302 | |
| 303 | 38. Since bash-4.0 now follows Posix rules for finding the closing delimiter |
| 304 | of a $() command substitution, it will not behave as previous versions |
| 305 | did, but will catch more syntax and parsing errors before spawning a |
| 306 | subshell to evaluate the command substitution. |
| 307 | |
| 308 | 39. The programmable completion code uses the same set of delimiting characters |
| 309 | as readline when breaking the command line into words, rather than the |
| 310 | set of shell metacharacters, so programmable completion and readline |
| 311 | should be more consistent. |
| 312 | |
| 313 | 40. When the read builtin times out, it attempts to assign any input read to |
| 314 | specified variables, which also causes variables to be set to the empty |
| 315 | string if there is not enough input. Previous versions discarded the |
| 316 | characters read. |
| 317 | |
| 318 | 41. Beginning with bash-4.0, when one of the commands in a pipeline is killed |
| 319 | by a SIGINT while executing a command list, the shell acts as if it |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 320 | received the interrupt. This can be disabled by setting the compat31 or |
| 321 | compat32 shell options. |
Jari Aalto | 17345e5 | 2009-02-19 22:21:29 +0000 | [diff] [blame] | 322 | |
| 323 | 42. Bash-4.0 changes the handling of the set -e option so that the shell exits |
| 324 | if a pipeline fails (and not just if the last command in the failing |
| 325 | pipeline is a simple command). This is not as Posix specifies. There is |
| 326 | work underway to update this portion of the standard; the bash-4.0 |
| 327 | behavior attempts to capture the consensus at the time of release. |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 328 | |
| 329 | 43. Bash-4.0 fixes a Posix mode bug that caused the . (source) builtin to |
| 330 | search the current directory for its filename argument, even if "." is |
| 331 | not in $PATH. Posix says that the shell shouldn't look in $PWD in this |
| 332 | case. |
| 333 | |
| 334 | 44. Bash-4.1 uses the current locale when comparing strings using the < and |
| 335 | > operators to the `[[' command. This can be reverted to the previous |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 336 | behavior (ASCII collating and strcmp(3)) by setting one of the |
| 337 | `compatNN' shopt options, where NN is less than 41. |
| 338 | |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 339 | 45. Bash-4.1 conforms to the current Posix specification for `set -u': |
| 340 | expansions of $@ and $* when there are no positional parameters do not |
| 341 | cause the shell to exit. |
| 342 | |
| 343 | 46. Bash-4.1 implements the current Posix specification for `set -e' and |
| 344 | exits when any command fails, not just a simple command or pipeline. |
| 345 | |
| 346 | 47. Command substitutions now remove the caller's trap strings when trap is |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 347 | run to set a new trap in the subshell. Previous to bash-4.2, the old |
| 348 | trap strings persisted even though the actual signal handlers were reset. |
| 349 | |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 350 | 48. When in Posix mode, a single quote is not treated specially in a |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 351 | double-quoted ${...} expansion, unless the expansion operator is |
| 352 | # or % or the new `//', `^', or `,' expansions. In particular, it |
| 353 | does not define a new quoting context. This is from Posix interpretation |
| 354 | 221. |
| 355 | |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 356 | 49. Posix mode shells no longer exit if a variable assignment error occurs |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 357 | with an assignment preceding a command that is not a special builtin. |
| 358 | |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 359 | 50. Bash-4.2 attempts to preserve what the user typed when performing word |
| 360 | completion, instead of, for instance, expanding shell variable |
| 361 | references to their value. |
| 362 | |
| 363 | 51. When in Posix mode, bash-4.2 exits if the filename supplied as an argument |
| 364 | to `.' is not found and the shell is not interactive. |
| 365 | |
| 366 | 52. When compiled for strict Posix compatibility, bash-4.3 does not enable |
| 367 | history expansion by default in interactive shells, since it results in |
| 368 | a non-conforming environment. |
| 369 | |
| 370 | 53. Bash-4.3 runs the replacement string in the pattern substitution word |
| 371 | expansion through quote removal. The code already treats quote |
| 372 | characters in the replacement string as special; if it treats them as |
| 373 | special, then quote removal should remove them. |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 374 | |
| 375 | Shell Compatibility Level |
| 376 | ========================= |
| 377 | |
| 378 | Bash-4.0 introduced the concept of a `shell compatibility level', specified |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 379 | as a set of options to the shopt builtin (compat31, compat32, compat40, |
| 380 | compat41, and compat42 at this writing). There is only one current |
| 381 | compatibility level -- each option is mutually exclusive. This list does not |
| 382 | mention behavior that is standard for a particular version (e.g., setting |
| 383 | compat32 means that quoting the rhs of the regexp matching operator quotes |
| 384 | special regexp characters in the word, which is default behavior in bash-3.2 |
| 385 | and above). |
| 386 | |
| 387 | Bash-4.3 introduces a new shell variable: BASH_COMPAT. The value assigned |
| 388 | to this variable (a decimal version number like 4.2, or an integer |
| 389 | corresponding to the compatNN option, like 42) determines the compatibility |
| 390 | level. |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 391 | |
| 392 | compat31 set |
| 393 | - the < and > operators to the [[ command do not consider the current |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 394 | locale when comparing strings; they use ASCII ordering |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 395 | - quoting the rhs of the regexp matching operator (=~) has no |
| 396 | special effect |
| 397 | |
| 398 | compat32 set |
| 399 | - the < and > operators to the [[ command do not consider the current |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 400 | locale when comparing strings; they use ASCII ordering |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 401 | |
| 402 | compat40 set |
| 403 | - the < and > operators to the [[ command do not consider the current |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 404 | locale when comparing strings; they use ASCII ordering |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 405 | - interrupting a command list such as "a ; b ; c" causes the execution |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 406 | of the entire list to be aborted (in versions before bash-4.0, |
| 407 | interrupting one command in a list caused the next to be executed) |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 408 | |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 409 | compat41 set |
| 410 | - interrupting a command list such as "a ; b ; c" causes the execution |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 411 | of the entire list to be aborted (in versions before bash-4.1, |
Chet Ramey | 495aee4 | 2011-11-22 19:11:26 -0500 | [diff] [blame] | 412 | interrupting one command in a list caused the next to be executed) |
| 413 | - when in posix mode, single quotes in the `word' portion of a |
| 414 | double-quoted parameter expansion define a new quoting context and |
| 415 | are treated specially |
Chet Ramey | ac50fba | 2014-02-26 09:36:43 -0500 | [diff] [blame] | 416 | |
| 417 | compat42 set |
| 418 | - the replacement string in double-quoted pattern substitution is not |
| 419 | run through quote removal, as in previous versions |
Chet Ramey | 0001803 | 2011-11-21 20:51:19 -0500 | [diff] [blame] | 420 | ------------------------------------------------------------------------------- |
| 421 | |
| 422 | Copying and distribution of this file, with or without modification, |
| 423 | are permitted in any medium without royalty provided the copyright |
| 424 | notice and this notice are preserved. This file is offered as-is, |
| 425 | without any warranty. |