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Bash-5.0-beta available for FTP

From: Chet Ramey
Subject: Bash-5.0-beta available for FTP
Date: Tue, 18 Sep 2018 09:56:03 -0400

The first beta release of bash-5.0 is now available with the URL


and from the bash-5.0-testing branch in the bash git repository       

This tar file includes the formatted documentation (you should be able to
generate updated versions yourself).

This release fixes several outstanding bugs in bash-4.4 and introduces several
new features.  The most significant bug fixes are an overhaul of how
nameref variables resolve and a number of potential out-of-bounds memory
errors discovered via fuzzing. There are a number of changes to the
expansion of $@ and $* in various contexts where word splitting is not
performed to conform to a Posix standard interpretation.

The most notable new features are several new shell variables: BASH_ARGV0,
EPOCHSECONDS, and EPOCHREALTIME. The `history' builtin can remove ranges of
history entries and understands negative arguments as offsets from the end
of the history list. There is an option to allow local variables to inherit
the value of a variable with the same name at a preceding scope. There is
a new shell option that, when enabled, causes the shell to attempt to
expand associative array subscripts only once (this is an issue when they
are used in arithmetic expressions).  The `globasciiranges' shell option
is now enabled by default; it can be set to off by default at configuration

There are a few incompatible changes between bash-4.4 and bash-5.0. The
changes to how nameref variables are resolved means that some uses of
namerefs will behave differently, though I have tried to minimize the
compatibility issues. By default, the shell only sets BASH_ARGC and
BASH_ARGV at startup if extended debugging mode is enabled; it was an
oversight that it was set unconditionally and caused performance issues
when scripts were passed large numbers of arguments.

`bashbug' may be used to report bugs with this version.  It will send
mail to address@hidden if the shell's `release status' is alpha or

As always, thanks for your help.


+========== CHANGES ==========+
This document details the changes between this version, bash-5.0-beta, and
the previous version, bash-5.0-alpha.

1.  Changes to Bash

a. Fixed a bug that allowed subshells to "inherit" enclosing loops -- this
   is where POSIX says the subshell is not "enclosed" by the loop.

b. Added more UTF-8-specific versions of multibyte functions, and optimized
   existing functions if the current locale uses UTF-8 encoding.

c. In POSIX mode, assignments preceding regular builtins should not persist
   when the builtin completes.

d. Added additional checks to special array assignment (e.g., BASH_ALIASES)
   so it can't be used to bypass validity checks performed in other places.

e. The `!!' history expansion now refers to the previous history entry as
   expected, even if used on the second or subsequent line of a multi-line
   history entry.

f. Fixed a bug that could cause the shell to dereference a NULL pointer if
   the environment (`environ') is set to NULL.

g. Bash uses slightly better integer overflow handling for brace sequence
   expansion on systems where ints are 32 bits and intmax_t is 64 bits.

h. Fixed a bug setting attributes for a variable named as an argument to
   `declare' that also appears as a nameref in the temporary environment.

i. Fixed several bugs that could cause assignments to namerefs to create
   variables with invalid names.

j. Fixed a bug that could result in the SIGINT handler being set incorrectly
   in asynchronous subshells.

k. Fixed a bug that could cause `bash -t' to not execute the specified command.

l. Fixed several bugs that caused the shell to operate on the wrong variable
   when using namerefs with the same name as a global variable in shell

m. Internal changes to how the shell handles variables with invalid names in
   the initial environment and to prevent variables with invalid names from
   being added to the environment instead of passing them on to children.

n. Changes to make sure that an expansion that results in a quoted null string
   is reflected in the expansion, even if the word expands to nothing.

o. Changes to make sure that $* and ${array[*]} (and $@/address@hidden) expand
   the same way after the recent changes for POSIX interpretation 888.

p. Saving and restoring the positional parameters at function entry and exit
   is considerably more efficient; noticeably so when there are large numbers
   of positional parameters.

q. Fixed a bug that caused `lastpipe' and `pipefail' to return an incorrect
   status for the pipeline if there was more than one external command in a
   loop body appearing in the last pipeline element.

r. Fixed a bug that caused value conversion errors with the printf builtin's
   %u and %f conversion specifications and invalid constants.

2.  Changes to Readline

a. Added more UTF-8-specific versions of multibyte functions, and optimized
   existing functions if the current locale uses UTF-8 encoding.

b. Fixed a problem with bracketed-paste inserting more than one character and
   interacting with other readline functions.

c. Fixed a bug that caused the history library to attempt to append a history
   line to a non-existent history entry.

d. If using bracketed paste mode, output a newline after the \r that is the
   last character of the mode disable string to avoid overwriting output.

e. Fixes to the vi-mode `b', `B', `w', `W', `e', and `E' commands to better
   handle multibyte characters.

f. Fixed a redisplay problem that caused an extra newline to be generated on
   accept-line when the line length is exactly the screenwidth.

3.  New Features in Bash

a. Bash no longer allows variable assignments preceding a special builtin that
   changes variable attributes to propagate back to the calling environment
   unless the compatibility level is 44 or lower.

b. You can set the default value for $HISTSIZE at build time in config-top.h.

c. The `complete' builtin now accepts a -I option that applies the completion
   to the initial word on the line.

d. The internal bash malloc now uses mmap (if available) to satisfy requests
   greater than 128K bytes, so free can use mfree to return the pages to the

e. The shell doesn't automatically set BASH_ARGC and BASH_ARGV at startup
   unless it's in debugging mode, as the documentation has always said, but
   will dynamically create them if a script references them at the top level
   without having enabled debugging mode.

f. The localvar_inherit option will not attempt to inherit a value from a
   variable of an incompatible type (indexed vs. associative arrays, for

g. The `globasciiranges' option is now enabled by default; it can be set to
   off by default at configuration time.

4.  New Features in Readline

a. The history expansion library now understands command and process
   substitution and extended globbing and allows them to appear anywhere in a

b. The history library has a new variable that allows applications to set the
   initial quoting state, so quoting state can be inherited from a previous

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://tiswww.cwru.edu/~chet/

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