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This document details the incompatibilites between this version of bash,
bash-2.03, and the previous widely-available version, bash-1.14 (which
is still the `standard' version for many Linux distributions). These
were discovered by users of bash-2.x, so this list is not comprehensive.
1. Bash now 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 keybindings in a form that can be re-read, use `bind -p'
instead. If you were using `bind -v' to list the keybindings, 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 above 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
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