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Imported from ../bash-3.2.tar.gz.

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Jari Aalto 2006-10-10 14:15:34 +00:00
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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.)
This document details the incompatibilities between this version of bash,
bash-3.2, and the previous widely-available versions, bash-1.14 (which is
still the `standard' version for a few Linux distributions) and bash-2.x.
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)
@ -184,42 +184,92 @@ and bash-2.0 were significant.)
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
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.
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 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.
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.
15. Bash no longer auto-exports the HOME, PATH, SHELL, TERM, HOSTNAME,
HOSTTYPE, MACHTYPE, or OSTYPE variables. If they appear in the initial
environment, the export attribute will be set, but if bash provides a
default value, they will remain local to the current shell.
16. Bash no longer initializes the FUNCNAME, GROUPS, or DIRSTACK variables
to have special behavior if they appear in the initial environment.
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.
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.
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.
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.
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.
21. A number of variables have the integer attribute by default, so the +=
assignment operator returns expected results: RANDOM, LINENO, MAILCHECK,
HISTCMD, OPTIND.
22. Bash-3.x is much stricter about $LINENO correctly reflecting the line
number in a script; assignments to LINENO have little effect.
23. By default, readline binds the terminal special characters to their
readline equivalents. As of bash-3.1/readline-5.1, this is optional and
controlled by the bind-tty-special-chars readline variable.
24. The \W prompt string expansion abbreviates $HOME as `~'. The previous
behavior is available with ${PWD##/*/}.
25. The arithmetic exponentiation operator is right-associative as of bash-3.1.
26. The rules concerning valid alias names are stricter, as per POSIX.2.
27. The Readline key binding functions now obey the convert-meta setting active
when the binding takes place, as the dispatch code does when characters
are read and processed.
28. The historical behavior of `trap' reverting signal disposition to the
original handling in the absence of a valid first argument is implemented
only if the first argument is a valid signal number.
29. In versions of bash after 3.1, the ${parameter//pattern/replacement}
expansion does not interpret `%' or `#' specially. Those anchors don't
have any real meaning when replacing every match.
30. Beginning with bash-3.1, the combination of posix mode and enabling the
`xpg_echo' option causes echo to ignore all options, not looking for `-n'
31. Beginning with bash-3.2, bash follows the Bourne-shell-style (and POSIX-
style) rules for parsing the contents of old-style backquoted command
substitutions. Previous versions of bash attempted to recursively parse
embedded quoted strings and shell constructs; bash-3.2 uses strict POSIX
rules to find the closing backquote and simply passes the contents of the
command substitution to a subshell for parsing and execution.
32. Beginning with bash-3.2, bash uses access(2) when executing primaries for
the test builtin and the [[ compound command, rather than looking at the
file permission bits obtained with stat(2). This obeys restrictions of
the file system (e.g., read-only or noexec mounts) not available via stat.
33. Beginning with bash-3.1/readline-5.1, the readline key binding code obeys
the current setting of the `convert-meta' variable.