Question

I have one cron job where I want to send its output to /dev/null but in case an error happens then it should send an email.

Otherwise I get an email daily of the output of cron and it’s difficult for me to see when errors occured or not.

Answer 1

How about

59 23 * * * { tmpFile=/tmp/yourCmdErrs.$$ ; export tmpFile ; yourCommand > /dev/null 2>${tmpFile}; if [ -s ${tmpFile} ] ; then mailx -s"errors in yourCommand" < ${tmpFile} ; /bin/rm ${tmpFile} ; fi ; }

Exploded, it is

# set whatevery your time/days are # 59 23 * * * 
# my superstition to use open and closing # { }
# set a tmpFile var # tmpFile=/tmp/yourCmdErrs.$$ ; export tmpFile ;
# run yourCmd save STDERR to file # yourCommand > /dev/null 2>${tmpFile}; 
# check if tmpFile has anything in it # if [ -s ${tmpFile} ] ; then 
# obvious, hopefully # mailx -s"errors in yourCommand" < ${tmpFile} 
#  cleanup tmpFile # /bin/rm ${tmpFile} ;
#  fi 
# note that closing ';' is a must when using {} pairs ; }

The actual call to mail/mailx may be slightly funky, I don’t have a way to test it right now.

I hope this helps.