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Re: set -e ignored in subshell if part of command list
From: |
Chet Ramey |
Subject: |
Re: set -e ignored in subshell if part of command list |
Date: |
Wed, 13 Nov 2019 10:07:44 -0500 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 |
On 11/13/19 5:24 AM, Shaun Crampton wrote:
Bash Version: 5.0
Patch Level: 3
Release Status: release
Description:
I was trying to get a function to return early if a command
fails by putting
the body of the function in a subshell and using set -e inside
the subshell.
If I run a subshell on its own, this works, but when I try to combine it
into a larger program, the set -e gets ignored.
Repeat-By:
Managed to boil it down to this smaller example:
# On its own, subshell behaves as expected:
$ ( set -ex; false; echo here )
+ false
# In a list, behaviour changes, "echo here" gets executed:
$ ( set -ex; false; echo here ) && echo there
+ false
+ echo here
here
there
The subshell command is part of an and-or list, so the -e is ignored for
that command:
"The -e setting shall be ignored when executing the compound list following
the while, until, if, or elif reserved word, a pipeline beginning with the
! reserved word, or any command of an AND-OR list other than the last."
(from
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_25_03)
The subshell inherits this state (being part of an and-or list) from its
parent.
# If the subshell is executed in the background, it works
$ ( set -e; false; echo here ) & pid=$!; wait $pid && echo there
In this command, the subshell is not part of an and-or list.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/