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Similarly to set -e performs an exit on "uncaught" $? != 0, I'd like to have this event trigger the execution of another command, e.g. a logger call. How can this be done?

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As hinted at in this question, the answer is setting up a trap on the ERR signal - basically set -e corresponds to trap 'exit' ERR. So to e.g. log errors but continue execution, use

trap 'logger -t myscriptname "Command $BASH_COMMAND exited with code $?"' ERR

In bash, the variable $BASH_COMMAND contains the offending command. $? contains the exit code of the last command executed - note that if you want to perform multiple actions, e.g. logger ...; echo $? the $? will contain logger's exit code, not $BASH_COMMAND's one, so you may have to store it in a variable first, e.g.

trap 'EXITCODE=$?; logger -t "Command $BASH_COMMAND exited with code $EXITCODE"; echo "$BASH_COMMAND at line $LINENO exited with code $EXITCODE"' ERR

Of course you might be better off declaring a function and passing it the $? and $BASH_COMMAND instead of such a long line!

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@Gilles It's a bit sneaky to edit in a ksh into the question to require this edit :P But while you're at it, is there a similar variable in ksh and are there other important differences? –  Tobias Kienzler Nov 15 '13 at 7:49

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