Bash-4.2 available for FTP

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Chet Ramey

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Feb 14, 2011, 8:37:02 PM2/14/11
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Introduction
============

The first public release of bash-4.2 is now available with the URLs

ftp://ftp.cwru.edu/pub/bash/bash-4.2.tar.gz
ftp://ftp.gnu.org/pub/gnu/bash/bash-4.2.tar.gz

and from the usual GNU mirror sites.

This tar file includes the formatted documentation (postscript, dvi, html,
and nroffed versions of the manual pages).

Diffs from bash-4.1 are not available.

Please use `bashbug' to report bugs with this version. It is built
and installed at the same time as bash.

Installation
============

Please read the README file first.

Installation instructions are provided in the INSTALL file.

New Features
============

This is the second revision to the fourth major release of bash.

This release fixes several outstanding bugs in bash-4.1 and introduces
several new features.

The most notable new features are \u and \U unicode character escapes
for the echo and printf builtins and $'...' quoting, a new mechanism
to declare variables with attributes in the global scope from a shell
function, and new word expansion features. There are also a number of
changes to accommodate recent Posix shell interpretations, changing the
bash posix-mode behavior to align with the newly-intepreted standard.

Read the file NEWS in the bash-4.2 distribution for a complete
description of the new features. A copy of the relevant portions
is included below.

Changes have been made to the Readline library being released at
the same time as bash-4.2, readline-6.2, so that Bash can be
linked against an already-installed Readline library rather than
the private version in lib/readline. Only readline-6.0 and later
versions are able to provide all of the symbols that bash-4.2
requires; earlier versions of the Readline library will not work
correctly.

A complete list of changes between bash-4.1 and bash-4.2 is
available in the file CHANGES; the complete list is too large to
include in this message.

Readline
========

Also available is a new release of the standalone Readline library,
version 6.2, with its own configuration scripts and Makefiles.
It can be retrieved with the URLs

ftp://ftp.cwru.edu/pub/bash/readline-6.2.tar.gz
ftp://ftp.gnu.org/pub/gnu/readline/readline-6.2.tar.gz

and from the usual GNU mirror sites.

Diffs from readline-6.1 are not available.

The formatted Readline documentation is included in the readline
distribution tar file.

A separate announcement listing the changes in Readline is being
distributed.

As always, thanks for your help.

Chet

+========== NEWS ==========+
This is a terse description of the new features added to bash-4.2 since
the release of bash-4.1. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.

1. New Features in Bash

a. `exec -a foo' now sets $0 to `foo' in an executable shell script without a
leading #!.

b. Subshells begun to execute command substitutions or run shell functions or
builtins in subshells do not reset trap strings until a new trap is
specified. This allows $(trap) to display the caller's traps and the
trap strings to persist until a new trap is set.

c. `trap -p' will now show signals ignored at shell startup, though their
disposition still cannot be modified.

d. $'...', echo, and printf understand \uXXXX and \UXXXXXXXX escape sequences.

e. declare/typeset has a new `-g' option, which creates variables in the
global scope even when run in a shell function.

f. test/[/[[ have a new -v variable unary operator, which returns success if
`variable' has been set.

g. Posix parsing changes to allow `! time command' and multiple consecutive
instances of `!' (which toggle) and `time' (which have no cumulative
effect).

h. Posix change to allow `time' as a command by itself to print the elapsed
user, system, and real times for the shell and its children.

j. $((...)) is always parsed as an arithmetic expansion first, instead of as
a potential nested command substitution, as Posix requires.

k. A new FUNCNEST variable to allow the user to control the maximum shell
function nesting (recursive execution) level.

l. The mapfile builtin now supplies a third argument to the callback command:
the line about to be assigned to the supplied array index.

m. The printf builtin has a new %(fmt)T specifier, which allows time values
to use strftime-like formatting.

n. There is a new `compat41' shell option.

o. The cd builtin has a new Posix-mandated `-e' option.

p. Negative subscripts to indexed arrays, previously errors, now are treated
as offsets from the maximum assigned index + 1.

q. Negative length specifications in the ${var:offset:length} expansion,
previously errors, are now treated as offsets from the end of the variable.

r. Parsing change to allow `time -p --'.

s. Posix-mode parsing change to not recognize `time' as a keyword if the
following token begins with a `-'. This means no more Posix-mode
`time -p'. Posix interpretation 267.

t. There is a new `lastpipe' shell option that runs the last command of a
pipeline in the current shell context. The lastpipe option has no
effect if job control is enabled.

u. History expansion no longer expands the `$!' variable expansion.

v. Posix mode shells no longer exit if a variable assignment error occurs
with an assignment preceding a command that is not a special builtin.

w. Non-interactive mode shells exit if -u is enabled and an attempt is made
to use an unset variable with the % or # expansions, the `//', `^', or
`,' expansions, or the parameter length expansion.

x. Posix-mode shells use the argument passed to `.' as-is if a $PATH search
fails, effectively searching the current directory. Posix-2008 change.

2. New Features in Readline

a. The history library does not try to write the history filename in the
current directory if $HOME is unset. This closes a potential security
problem if the application does not specify a history filename.

b. New bindable variable `completion-display-width' to set the number of
columns used when displaying completions.

c. New bindable variable `completion-case-map' to cause case-insensitive
completion to treat `-' and `_' as identical.

d. There are new bindable vi-mode command names to avoid readline's case-
insensitive matching not allowing them to be bound separately.

e. New bindable variable `menu-complete-display-prefix' causes the menu
completion code to display the common prefix of the possible completions
before cycling through the list, instead of after.


--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU ch...@case.edu http://cnswww.cns.cwru.edu/~chet/

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