Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 1 | This document details the incompatibilites between this version of bash, |
Jari Aalto | 95732b4 | 2005-12-07 14:08:12 +0000 | [diff] [blame^] | 2 | bash-3.1, and a previous widely-available version, bash-1.14 (which |
Jari Aalto | b80f644 | 2004-07-27 13:29:18 +0000 | [diff] [blame] | 3 | is still the `standard' version for a few Linux distributions). These |
| 4 | were discovered by users of bash-2.x and 3.x, so this list is not |
| 5 | comprehensive. Some of these incompatibilities occur between the current |
| 6 | version and versions 2.0 and above. (The differences between bash-1.14 |
| 7 | and bash-2.0 were significant.) |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 8 | |
Jari Aalto | b80f644 | 2004-07-27 13:29:18 +0000 | [diff] [blame] | 9 | 1. Bash uses a new quoting syntax, $"...", to do locale-specific |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 10 | string translation. Users who have relied on the (undocumented) |
| 11 | behavior of bash-1.14 will have to change their scripts. For |
| 12 | instance, if you are doing something like this to get the value of |
| 13 | a variable whose name is the value of a second variable: |
| 14 | |
| 15 | eval var2=$"$var1" |
| 16 | |
| 17 | you will have to change to a different syntax. |
| 18 | |
| 19 | This capability is directly supported by bash-2.0: |
| 20 | |
| 21 | var2=${!var1} |
| 22 | |
| 23 | This alternate syntax will work portably between bash-1.14 and bash-2.0: |
| 24 | |
| 25 | eval var2=\$${var1} |
| 26 | |
| 27 | 2. One of the bugs fixed in the YACC grammar tightens up the rules |
| 28 | concerning group commands ( {...} ). The `list' that composes the |
| 29 | body of the group command must be terminated by a newline or |
| 30 | semicolon. That's because the braces are reserved words, and are |
| 31 | recognized as such only when a reserved word is legal. This means |
| 32 | that while bash-1.14 accepted shell function definitions like this: |
| 33 | |
| 34 | foo() { : } |
| 35 | |
| 36 | bash-2.0 requires this: |
| 37 | |
| 38 | foo() { :; } |
| 39 | |
| 40 | This is also an issue for commands like this: |
| 41 | |
| 42 | mkdir dir || { echo 'could not mkdir' ; exit 1; } |
| 43 | |
| 44 | The syntax required by bash-2.0 is also accepted by bash-1.14. |
| 45 | |
| 46 | 3. The options to `bind' have changed to make them more consistent with |
| 47 | 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] | 48 | the readline key bindings in a form that can be re-read, use `bind -p' |
| 49 | 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] | 50 | `bind -P' instead. |
| 51 | |
| 52 | 4. The `long' invocation options must now be prefixed by `--' instead |
| 53 | of `-'. (The old form is still accepted, for the time being.) |
| 54 | |
| 55 | 5. There was a bug in the version of readline distributed with bash-1.14 |
| 56 | that caused it to write badly-formatted key bindings when using |
| 57 | `bind -d'. The only key sequences that were affected are C-\ (which |
| 58 | should appear as \C-\\ in a key binding) and C-" (which should appear |
| 59 | as \C-\"). If these key sequences appear in your inputrc, as, for |
| 60 | example, |
| 61 | |
| 62 | "\C-\": self-insert |
| 63 | |
| 64 | they will need to be changed to something like the following: |
| 65 | |
| 66 | "\C-\\": self-insert |
| 67 | |
Jari Aalto | 7117c2d | 2002-07-17 14:10:11 +0000 | [diff] [blame] | 68 | 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] | 69 | incremental search, and asked for an alternate mechanism. Bash-2.03 |
| 70 | uses the value of the settable readline variable `isearch-terminators' |
| 71 | to decide which characters should terminate an incremental search. If |
| 72 | that variable has not been set, ESC and Control-J will terminate a |
| 73 | search. |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 74 | |
| 75 | 7. Some variables have been removed: MAIL_WARNING, notify, history_control, |
| 76 | command_oriented_history, glob_dot_filenames, allow_null_glob_expansion, |
| 77 | nolinks, hostname_completion_file, noclobber, no_exit_on_failed_exec, and |
| 78 | cdable_vars. Most of them are now implemented with the new `shopt' |
Jari Aalto | d166f04 | 1997-06-05 14:59:13 +0000 | [diff] [blame] | 79 | builtin; others were already implemented by `set'. Here is a list of |
| 80 | correspondences: |
Jari Aalto | ccc6cda | 1996-12-23 17:02:34 +0000 | [diff] [blame] | 81 | |
Jari Aalto | d166f04 | 1997-06-05 14:59:13 +0000 | [diff] [blame] | 82 | MAIL_WARNING shopt mailwarn |
| 83 | notify set -o notify |
| 84 | history_control HISTCONTROL |
| 85 | command_oriented_history shopt cmdhist |
| 86 | glob_dot_filenames shopt dotglob |
| 87 | allow_null_glob_expansion shopt nullglob |
| 88 | nolinks set -o physical |
| 89 | hostname_completion_file HOSTFILE |
| 90 | noclobber set -o noclobber |
| 91 | no_exit_on_failed_exec shopt execfail |
| 92 | cdable_vars shopt cdable_vars |
| 93 | |
| 94 | 8. `ulimit' now sets both hard and soft limits and reports the soft limit |
| 95 | by default (when neither -H nor -S is specified). This is compatible |
| 96 | with versions of sh and ksh that implement `ulimit'. The bash-1.14 |
| 97 | behavior of, for example, |
| 98 | |
| 99 | ulimit -c 0 |
| 100 | |
| 101 | can be obtained with |
| 102 | |
| 103 | ulimit -S -c 0 |
| 104 | |
| 105 | It may be useful to define an alias: |
| 106 | |
| 107 | alias ulimit="ulimit -S" |
| 108 | |
Jari Aalto | cce855b | 1998-04-17 19:52:44 +0000 | [diff] [blame] | 109 | 9. Bash-2.01 uses a new quoting syntax, $'...' to do ANSI-C string |
| 110 | translation. Backslash-escaped characters in ... are expanded and |
| 111 | replaced as specified by the ANSI C standard. |
| 112 | |
| 113 | 10. The sourcing of startup files has changed somewhat. This is explained |
| 114 | more completely in the INVOCATION section of the manual page. |
| 115 | |
| 116 | A non-interactive shell not named `sh' and not in posix mode reads |
| 117 | and executes commands from the file named by $BASH_ENV. A |
| 118 | non-interactive shell started by `su' and not in posix mode will read |
| 119 | startup files. No other non-interactive shells read any startup files. |
| 120 | |
| 121 | An interactive shell started in posix mode reads and executes commands |
| 122 | from the file named by $ENV. |
Jari Aalto | b72432f | 1999-02-19 17:11:39 +0000 | [diff] [blame] | 123 | |
| 124 | 11. The <> redirection operator was changed to conform to the POSIX.2 spec. |
| 125 | In the absence of any file descriptor specification preceding the `<>', |
| 126 | file descriptor 0 is used. In bash-1.14, this was the behavior only |
| 127 | when in POSIX mode. The bash-1.14 behavior may be obtained with |
| 128 | |
| 129 | <>filename 1>&0 |
Jari Aalto | bb70624 | 2000-03-17 21:46:59 +0000 | [diff] [blame] | 130 | |
| 131 | 12. The `alias' builtin now checks for invalid options and takes a `-p' |
| 132 | option to display output in POSIX mode. If you have old aliases beginning |
| 133 | with `-' or `+', you will have to add the `--' to the alias command |
| 134 | that declares them: |
| 135 | |
| 136 | alias -x='chmod a-x' --> alias -- -x='chmod a-x' |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 137 | |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 138 | 13. The behavior of range specificiers within bracket matching expressions |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 139 | in the pattern matcher (e.g., [A-Z]) depends on the current locale, |
| 140 | specifically the value of the LC_COLLATE environment variable. Setting |
| 141 | this variable to C or POSIX will result in the traditional ASCII behavior |
| 142 | for range comparisons. If the locale is set to something else, e.g., |
| 143 | en_US (specified by the LANG or LC_ALL variables), collation order is |
| 144 | locale-dependent. For example, the en_US locale sorts the upper and |
| 145 | lower case letters like this: |
| 146 | |
| 147 | AaBb...Zz |
| 148 | |
| 149 | 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] | 150 | Other locales collate like |
| 151 | |
| 152 | aAbBcC...zZ |
| 153 | |
| 154 | which means that [A-Z] matches every letter except `a'. |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 155 | |
| 156 | The portable way to specify upper case letters is [:upper:] instead of |
| 157 | A-Z; lower case may be specified as [:lower:] instead of a-z. |
| 158 | |
| 159 | Look at the manual pages for setlocale(3), strcoll(3), and, if it is |
| 160 | present, locale(1). |
| 161 | |
| 162 | You can find your current locale information by running locale(1): |
| 163 | |
| 164 | caleb.ins.cwru.edu(2)$ locale |
| 165 | LANG=en_US |
| 166 | LC_CTYPE="en_US" |
| 167 | LC_NUMERIC="en_US" |
| 168 | LC_TIME="en_US" |
| 169 | LC_COLLATE="en_US" |
| 170 | LC_MONETARY="en_US" |
| 171 | LC_MESSAGES="en_US" |
| 172 | LC_ALL=en_US |
| 173 | |
| 174 | My advice is to put |
| 175 | |
| 176 | export LC_COLLATE=C |
| 177 | |
| 178 | into /etc/profile and inspect any shell scripts run from cron for |
| 179 | constructs like [A-Z]. This will prevent things like |
| 180 | |
| 181 | rm [A-Z]* |
| 182 | |
| 183 | from removing every file in the current directory except those beginning |
| 184 | with `z' and still allow individual users to change the collation order. |
| 185 | Users may put the above command into their own profiles as well, of course. |
| 186 | |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 187 | 14. Bash versions up to 1.14.7 included an undocumented `-l' operator to |
Jari Aalto | 28ef6c3 | 2001-04-06 19:14:31 +0000 | [diff] [blame] | 188 | the `test/[' builtin. It was a unary operator that expanded to the |
| 189 | length of its string argument. This let you do things like |
| 190 | |
| 191 | test -l $variable -lt 20 |
| 192 | |
| 193 | for example. |
| 194 | |
| 195 | This was included for backwards compatibility with old versions of the |
| 196 | Bourne shell, which did not provide an easy way to obtain the length of |
| 197 | the value of a shell variable. |
| 198 | |
| 199 | This operator is not part of the POSIX standard, because one can (and |
| 200 | should) use ${#variable} to get the length of a variable's value. |
| 201 | Bash-2.x does not support it. |
Jari Aalto | f73dda0 | 2001-11-13 17:56:06 +0000 | [diff] [blame] | 202 | |
| 203 | 15. Bash no longer auto-exports the HOME, PATH, SHELL, TERM, HOSTNAME, |
| 204 | HOSTTYPE, MACHTYPE, or OSTYPE variables. |
| 205 | |
| 206 | 16. Bash no longer initializes the FUNCNAME, GROUPS, or DIRSTACK variables |
| 207 | to have special behavior if they appear in the initial environment. |
| 208 | |
| 209 | 17. Bash no longer removes the export attribute from the SSH_CLIENT or |
| 210 | SSH2_CLIENT variables, and no longer attempts to discover whether or |
| 211 | 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] | 212 | |
| 213 | 18. Bash no longer requires that the body of a function be a group command; |
| 214 | any compound command is accepted. |
Jari Aalto | 95732b4 | 2005-12-07 14:08:12 +0000 | [diff] [blame^] | 215 | |
| 216 | 19. As of bash-3.0, the pattern substitution operators no longer perform |
| 217 | quote removal on the pattern before attempting the match. This is the |
| 218 | way the pattern removal functions behave, and is more consistent. |
| 219 | |
| 220 | 20. After bash-3.0 was released, I reimplemented tilde expansion, incorporating |
| 221 | it into the mainline word expansion code. This fixes the bug that caused |
| 222 | the results of tilde expansion to be re-expanded. There is one |
| 223 | incompatibility: a ${paramOPword} expansion within double quotes will not |
| 224 | perform tilde expansion on WORD. This is consistent with the other |
| 225 | expansions, and what POSIX specifies. |