Question

I have a simple bash script which calls a php script every 10 minutes thats performs some maintenance. Every once in a while this php script terminates while it’s running and when this happens the bash script exits.

I’d like to make it so the bash script keeps on looping even if the php script falters. Can anyone point me in the right direction? I’ve been searching for a while but I can’t seem to find the answer, maybe I’m not using the right search terms.

#!/bin/sh
set -e    
while :    
do    
    /usr/bin/php /path/to/maintenance/script.php
    sleep 600    
done

Answer 1

The:

set -e

line sets the shell’s “exit on error” flag, which tells it that if a program it runs exits with a non-zero status, the shell should also exit:

set -e
false
echo if this prints, your shell is not honoring "set -e"

There are exceptions for programs whose status is being tested, of course, so that:

set -e
if prog; then
    echo program succeeded
else
    echo program failed
fi
echo this will still print

will work correctly (one or or the other echo will occur, and then the last one will as well).

Back in the Dim Time, when /bin/sh was non-POSIX and was written in Bournegol, there was a bug in some versions of sh that broke || expressions:

set -e
false || true
echo if this prints, your shell is OK

(The logic bug applied to && expressions internally as well, but was harmless there, since false && anything is itself false which means the whole expression fails anyway!) Ever since then, I’ve been wary of “-e”.