Imported from ../bash-2.04.tar.gz.

[thirdparty/bash.git] / COMPAT

This document details the incompatibilites between this version of bash,
bash-2.04, 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

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'