Red Hat Bugzilla – Bug 55205
bash 2.04.21/2.05.8 env var incompatibility
Last modified: 2008-05-01 11:38:01 EDT
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Description of problem:
Create the following shell script:
When run on bash 2.04.21, this produces
When run on bash 2.05.8, it produces
My understanding is that setting the value of a variable on the
command line is supposed to temporarily affect the environment
for that command only. This would mean the 2.04 behavior is
correct, and the 2.05 behavior is wrong. I see no mention of the
change in the bash FAQ or COMPAT file.
As a practical matter, this incompatibility between the two
versions caused an existing shell script to fail, so there's
an existence proof that the change in behavior matters to at
least one user. :-)
Version-Release number of selected component (if applicable):
Steps to Reproduce:
See Description field above.
I'm not sure whether or not this change is intentional (might be, because a
function is not actually a separate process).
I've sent a message to the base maintainer, waiting for reply.
From: Chet Ramey <email@example.com>
Feature. POSIX.2, section 3.9.5, says:
When a function is executed, it shall have the syntax-error and
variable-assignment properties described for special built-in
utilities in the enumerated list at the beginning of 3.14.
Section 3.14 says, in part:
Variable assignments specified with special built-in utilities
shall remain in effect after the built-in completes...
Note that bash behaves this way only when in posix mode.
Note that this was a real incompatibility that cost me an afternoon to track
down (after upgrading from RH7.1 to 7.2). The shell script in my case was
invoked by /sbin/ifup-local. Since the shell behaves differently in POSIX
mode, the circumstantial evidence points to some change in the way ifup-local
is invoked between 7.1 and 7.2 -- perhaps it's now posixly-correct when it wasn't
before. It might be nice to understand what changed, so that no other breakage
occurs as a result of the same incompatibility...