On 06/28/2010 01:22 AM, Cristian Ionescu-Idbohrn wrote: >> Has bash's behaviour changed recently (I'm using an ancient >> version)? Yes - bash 4.1 tries harder to be compliant with the recent Austin Group interpretations (and more like ksh). > > bash 3.2.39 and 4.0.37 are behaving as dash without the suggested > patch. Still. What is the correct behaviour? That should be the > essential matter IMO, not what others do. So, why should this fail: > > $ dash -c 'set -e; false; echo here' > > and this succeed? > > $ dash -c 'set -e; (false); echo here' According to the Austin Group: http://austingroupbugs.net/view.php?id=52 the desired behavior is: Replace the description of -e with: -e When this option is on, when any command fails (for any of the reasons listed in [xref to 2.8.1] or by returning an exit status greater than zero) the shell immediately shall exit with the following exceptions: 1) The failure of any individual command in a multi-command pipeline shall not cause the shell to exit. Only the failure of the pipeline itself shall be considered. 2) 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. 3) If the exit status of a compound command other than a subshell command was the result of a failure while -e was being ignored, then -e shall not apply to this command. This requirement applies to the shell environment and each subshell environment separately. For example, in set -e; (false; echo one) | cat; echo two the false command causes the subshell to exit without executing echo one; however, echo two is executed because the exit status of the pipeline (false; echo one) | cat is zero. Per these rules, both 'set -e; false; echo here' and 'set -e; (false); echo here' are silent in bash 4.1. The fact that dash is not silent when a subshell exits with non-zero status is at odds with the above Austin Group ruling. -- Eric Blake eblake@xxxxxxxxxx +1-801-349-2682 Libvirt virtualization library http://libvirt.org
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