Bash version 4.0 released
Bourne-again shell (Bash) version 4.0 has been released and includes several fixes to serious bugs from the 3.x releases and some significant new features. Bash 4.0, a free software Unix/Linux shell written for the GNU Project, is released under version 3 of the GNU General Public License and is the default shell for most Linux systems.
New features in Bash 4 include two new redirection operators;
&>> which sends standard output and standard errors to a named file, and
|&, synonymous with
2>&1 |, which redirects standard error to a pipe. Associative arrays can now be created using
declare -A name, which allows for arrays to be indexed by arbitrary strings.
** expansion operator has been added; where
* would expand to all files and directories in the current directory,
** expands to all files in the current directory and all directories below it. However, this feature is only enabled when the
globstar option is enabled. Other options include a
dirspell option which when enabled, corrects spelling errors during file name tab completion.
The new version is more rigorous about parsing commands inside command substitutions, fixing a Posix non-compliance issue. Changes were made to
ulimit to make it more Posix compliant when in Posix mode.
Version 4.0 of Bash is available and is on the GNU FTP servers now and, unlike previous releases, the tar file also includes all of the formatted documentation. An updated FAQ for Bash 4.0 can be found here.