On 08/12/2011 06:51 AM, Greg Wooledge wrote:
On Thu, Aug 11, 2011 at 11:56:10PM -0700, Linda Walsh wrote:
**Exception**
declare -i a
a=0
--
As a is declared to be an integer, it has the results evaluated
at assignment time. a=0 is an integer expression that doesn't set
$?=1
Neither should:
((a=0))
a=0 is an assignment. Assignments always return 0.
No they don't.
readonly a
a=0
sets $? to non-zero.
imadev:~$ ((a=0)); echo $?
1
And here, the same thing, but we return false, because the value was 0.
This is the thing about which you are complaining. This is also one
of the things I mention on http://mywiki.wooledge.org/BashFAQ/105 in
which I describe how horrible and useless set -e is.
And that point has been made several times in this thread. 'set -e' is
a historical wart - bash has it because POSIX requires it. If you want
to use bash extensions, then _don't_ use 'set -e', and you don't have to
worry about how the unintuitive behavior interacts with extensions.
Greg, you missed one other useful form:
a=$((0))
This is an assignment (sets $? to 0 for all but errors like assigning to
a readonly variable) of arithmetic expansion. Also POSIX, and slightly
shorter than
: $((a=0))
--
Eric Blake ebl...@redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
