Let me know (mail me) when there’s an error

September 5, 2018

I’ve got a shell script where I’d like to know when an error happens. Typically when that happens, something gets written to stdout or stderr – and I’d like to see that. But when things are just peachy, I don’t want to be bothered.

Here’s an easy way to achieve that. At the beginning of my script, I have:

WEATHEROUT=`/bin/mktemp`
WEATHERERR=`/bin/mktemp`

(Did I mention this is a script for a weather station? Yep.)

Then in the body of the script, I have:

/usr/local/bin/do-the-thing > ${WEATHEROUT} 2> ${WEATHERERR}
/usr/local/bin/do-the-other-thing >> ${WEATHEROUT} 2>> ${WEATHERERR}

Finally, at the end of the script, there’s:

if [ -s ${WEATHERERR} -o -s ${WEATHEROUT} ]; then
   cat ${WEATHEROUT} ${WEATHERERR} | /usr/bin/mail -s "Weather command error" me@myaddr
fi

That’s all!

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