diff options
Diffstat (limited to 'COMPAT')
| -rw-r--r-- | COMPAT | 225 |
1 files changed, 225 insertions, 0 deletions
@@ -0,0 +1,225 @@ +This document details the incompatibilites between this version of bash, +bash-3.1, and a previous widely-available version, bash-1.14 (which +is still the `standard' version for a few Linux distributions). These +were discovered by users of bash-2.x and 3.x, so this list is not +comprehensive. Some of these incompatibilities occur between the current +version and versions 2.0 and above. (The differences between bash-1.14 +and bash-2.0 were significant.) + +1. Bash uses a new quoting syntax, $"...", to do locale-specific + string translation. Users who have relied on the (undocumented) + behavior of bash-1.14 will have to change their scripts. For + instance, if you are doing something like this to get the value of + a variable whose name is the value of a second variable: + + eval var2=$"$var1" + + you will have to change to a different syntax. + + This capability is directly supported by bash-2.0: + + var2=${!var1} + + This alternate syntax will work portably between bash-1.14 and bash-2.0: + + eval var2=\$${var1} + +2. One of the bugs fixed in the YACC grammar tightens up the rules + concerning group commands ( {...} ). The `list' that composes the + body of the group command must be terminated by a newline or + semicolon. That's because the braces are reserved words, and are + recognized as such only when a reserved word is legal. This means + that while bash-1.14 accepted shell function definitions like this: + + foo() { : } + + bash-2.0 requires this: + + foo() { :; } + + This is also an issue for commands like this: + + mkdir dir || { echo 'could not mkdir' ; exit 1; } + + The syntax required by bash-2.0 is also accepted by bash-1.14. + +3. The options to `bind' have changed to make them more consistent with + the rest of the bash builtins. If you are using `bind -d' to list + the readline key bindings in a form that can be re-read, use `bind -p' + instead. If you were using `bind -v' to list the key bindings, use + `bind -P' instead. + +4. The `long' invocation options must now be prefixed by `--' instead + of `-'. (The old form is still accepted, for the time being.) + +5. There was a bug in the version of readline distributed with bash-1.14 + that caused it to write badly-formatted key bindings when using + `bind -d'. The only key sequences that were affected are C-\ (which + should appear as \C-\\ in a key binding) and C-" (which should appear + as \C-\"). If these key sequences appear in your inputrc, as, for + example, + + "\C-\": self-insert + + they will need to be changed to something like the following: + + "\C-\\": self-insert + +6. A number of people complained about having to use ESC to terminate an + incremental search, and asked for an alternate mechanism. Bash-2.03 + uses the value of the settable readline variable `isearch-terminators' + to decide which characters should terminate an incremental search. If + that variable has not been set, ESC and Control-J will terminate a + search. + +7. Some variables have been removed: MAIL_WARNING, notify, history_control, + command_oriented_history, glob_dot_filenames, allow_null_glob_expansion, + nolinks, hostname_completion_file, noclobber, no_exit_on_failed_exec, and + cdable_vars. Most of them are now implemented with the new `shopt' + builtin; others were already implemented by `set'. Here is a list of + correspondences: + + MAIL_WARNING shopt mailwarn + notify set -o notify + history_control HISTCONTROL + command_oriented_history shopt cmdhist + glob_dot_filenames shopt dotglob + allow_null_glob_expansion shopt nullglob + nolinks set -o physical + hostname_completion_file HOSTFILE + noclobber set -o noclobber + no_exit_on_failed_exec shopt execfail + cdable_vars shopt cdable_vars + +8. `ulimit' now sets both hard and soft limits and reports the soft limit + by default (when neither -H nor -S is specified). This is compatible + with versions of sh and ksh that implement `ulimit'. The bash-1.14 + behavior of, for example, + + ulimit -c 0 + + can be obtained with + + ulimit -S -c 0 + + It may be useful to define an alias: + + alias ulimit="ulimit -S" + +9. Bash-2.01 uses a new quoting syntax, $'...' to do ANSI-C string + translation. Backslash-escaped characters in ... are expanded and + replaced as specified by the ANSI C standard. + +10. The sourcing of startup files has changed somewhat. This is explained + more completely in the INVOCATION section of the manual page. + + A non-interactive shell not named `sh' and not in posix mode reads + and executes commands from the file named by $BASH_ENV. A + non-interactive shell started by `su' and not in posix mode will read + startup files. No other non-interactive shells read any startup files. + + An interactive shell started in posix mode reads and executes commands + from the file named by $ENV. + +11. The <> redirection operator was changed to conform to the POSIX.2 spec. + In the absence of any file descriptor specification preceding the `<>', + file descriptor 0 is used. In bash-1.14, this was the behavior only + when in POSIX mode. The bash-1.14 behavior may be obtained with + + <>filename 1>&0 + +12. The `alias' builtin now checks for invalid options and takes a `-p' + option to display output in POSIX mode. If you have old aliases beginning + with `-' or `+', you will have to add the `--' to the alias command + that declares them: + + alias -x='chmod a-x' --> alias -- -x='chmod a-x' + +13. The behavior of range specificiers within bracket matching expressions + in the pattern matcher (e.g., [A-Z]) depends on the current locale, + specifically the value of the LC_COLLATE environment variable. Setting + this variable to C or POSIX will result in the traditional ASCII behavior + for range comparisons. If the locale is set to something else, e.g., + en_US (specified by the LANG or LC_ALL variables), collation order is + locale-dependent. For example, the en_US locale sorts the upper and + lower case letters like this: + + AaBb...Zz + + so a range specification like [A-Z] will match every letter except `z'. + Other locales collate like + + aAbBcC...zZ + + which means that [A-Z] matches every letter except `a'. + + The portable way to specify upper case letters is [:upper:] instead of + A-Z; lower case may be specified as [:lower:] instead of a-z. + + Look at the manual pages for setlocale(3), strcoll(3), and, if it is + present, locale(1). + + You can find your current locale information by running locale(1): + + caleb.ins.cwru.edu(2)$ locale + LANG=en_US + LC_CTYPE="en_US" + LC_NUMERIC="en_US" + LC_TIME="en_US" + LC_COLLATE="en_US" + LC_MONETARY="en_US" + LC_MESSAGES="en_US" + LC_ALL=en_US + + My advice is to put + + export LC_COLLATE=C + + into /etc/profile and inspect any shell scripts run from cron for + constructs like [A-Z]. This will prevent things like + + rm [A-Z]* + + from removing every file in the current directory except those beginning + with `z' and still allow individual users to change the collation order. + Users may put the above command into their own profiles as well, of course. + +14. Bash versions up to 1.14.7 included an undocumented `-l' operator to + the `test/[' builtin. It was a unary operator that expanded to the + length of its string argument. This let you do things like + + test -l $variable -lt 20 + + for example. + + This was included for backwards compatibility with old versions of the + Bourne shell, which did not provide an easy way to obtain the length of + the value of a shell variable. + + This operator is not part of the POSIX standard, because one can (and + should) use ${#variable} to get the length of a variable's value. + Bash-2.x does not support it. + +15. Bash no longer auto-exports the HOME, PATH, SHELL, TERM, HOSTNAME, + HOSTTYPE, MACHTYPE, or OSTYPE variables. + +16. Bash no longer initializes the FUNCNAME, GROUPS, or DIRSTACK variables + to have special behavior if they appear in the initial environment. + +17. Bash no longer removes the export attribute from the SSH_CLIENT or + SSH2_CLIENT variables, and no longer attempts to discover whether or + not it has been invoked by sshd in order to run the startup files. + +18. Bash no longer requires that the body of a function be a group command; + any compound command is accepted. + +19. As of bash-3.0, the pattern substitution operators no longer perform + quote removal on the pattern before attempting the match. This is the + way the pattern removal functions behave, and is more consistent. + +20. After bash-3.0 was released, I reimplemented tilde expansion, incorporating + it into the mainline word expansion code. This fixes the bug that caused + the results of tilde expansion to be re-expanded. There is one + incompatibility: a ${paramOPword} expansion within double quotes will not + perform tilde expansion on WORD. This is consistent with the other + expansions, and what POSIX specifies. |