On 2/10/11 11:08 PM, Daniel Villeneuve wrote:
> I'm using GNU bash, version 4.1.2(1)-release (i386-redhat-linux-gnu).
>
> Following the change of semantics of "set -e" in bash 4,"man bash" seems to
> imply that the following script should exit after the for command (from the
> text "or one of the commands executed as part of a command list enclosed
> by braces" where "one of the commands" should match a "for" command) .
> However it does not.
>
>
> set -e
> {
> for i in a b c; do
> [ -z "$i" ] && echo "null"
> done
> echo "'for' return code = $?"
> }
> echo "brace return code = $?"
>
>
> For reference, I've consulted
> http://thread.gmane.org/gmane.comp.standards.posix.austin.general/282,
> http://thread.gmane.org/gmane.comp.shells.bash.bugs/13465 and
> the current public POSIX spec I have access to which still says:
>
> *-e*
> When this option is on, if a simple command fails for any of the
> reasons listed in Consequences of Shell Errors
> <ref to V3_chap02.html#tag_18_08_01>
> or returns an exit status value >0, and is not part of the compound
> list following a *while*, *until*, or *if* keyword, and is not a
> part of an AND or OR list, and is not a pipeline preceded by the *!*
> reserved word, then the shell shall immediately exit.
>
>
> Question 1: Is it the case that the bash 4 behavior is as intended here and
> that it's the documention of "set -e" in bash 4 that is imprecise
> ("commands" being too broad)?
I think the key is that the (new and as yet unpublished) Posix description
includes this sentence:
Additionally if the
failed command is a compound command whose exit status was
derived from a command that is one of the aforementioned
exceptions, the shell shall not exit.
That appears to cover this case.
>
> Also, note that the man page section on "trap ERR" says that the trap is
> triggered if a "simple command" returns >0 (sharing exceptions with "set
> -e"). It seems however that the trigger is the same as for "set -e", as in
>
> trap 'echo "error caught ($?), exiting"; exit 1' ERR
> (exit 2)
> echo done
>
> Question 2: Are "set -e" and "trap ... ERR" triggered by the same events?
Yes, that's the intent.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
