Ben's blog

Not all cron jobs are created equal, and some of them can afford to fail sporadically before we need to worry about them. Maybe they rely on a third party server, and we don’t want the occasional fail to pollute our inbox.

Here is a little cron job wrapper I created that will suppress stderr but keeps track of the job’s returned exit codes. Above a certain threshold of consecutive abnormal exits it doesn’t suppress stderr anymore.

# if the counter file doesn't already exist we create/initialize it
if [ ! -f /tmp/counter_ri7g3 ] ;
then
    echo 0 > /tmp/counter_ri7g3 ;
fi ;

# we pull the current counter
counter=`cat /tmp/counter_ri7g3` ;

# if the counter is still small, we send stderr to /dev/null
if [ $counter -lt 5 ] ;
then
    $1 > /dev/null 2>&1 ;
# otherwise stderr will follow its normal path and find its way to email
else
    $1 > /dev/null ;
fi ;

# lastly if running the $1 resulted in an abnormal exit, the counter is incremented
if [ ! $? = 0 ] ;
then
    counter=`cat /tmp/counter_ri7g3` ;
    echo "$counter+1" | bc > /tmp/counter_ri7g3 ;
# and if $1 exited normally, we reset the counter
else
    echo 0 > /tmp/counter_ri7g3 ;
fi ;

a cron entry calling it looks as such:

30 * * * *      root      /usr/local/bin/cron_wrapper "/path/to/script arg_1 arg_2"