bash: check if file size is zero before doing some action

[marchello_lippi2]

Hi all,
I'm sending some log to my inbox on regular basis using crontab. Sometimes log is empty and I would like to skip it in this case if possible.

59 0 * * * rm /tmp/rejectlog_filtered.txt; less /var/log/exim4/rejectlog | grep -v "junkemailfilter" > /tmp/rejectlog_filtered.txt; mpack -s "rejectlog_filtered.txt" /tmp/rejectlog_filtered.txt user@example.com

Another question is, how do I send mentioned log file as message body instead of attachment? (less important for me, but still would like to solve)
Please advise.

[sudodus]

Test with test -s

test -s filename

If size=0, the test returns 1, otherwise if size>0 test returns 0.

You find more details about test in bash by the command

help test

[marchello_lippi2]

Hi sudodus,
Thanks, I tested it and it should work for me.
I don't know when it returns 0 and when 1, but below command returns size=0 properly (if file is empty indeed) :

$ if test -s /tmp/test.txt; then echo -e "size>0"; else echo -e "size=0"; fi
size=0

Upd:

$ less /home/user/rejectlog_email.sh
if [ -f "/tmp/rejectlog_filtered.txt" ]; then rm /tmp/rejectlog_filtered.txt; fi

less /var/log/exim4/rejectlog | grep -v "junkemailfilter" > /tmp/rejectlog_filtered.txt

if test -s /tmp/rejectlog_filtered.txt; then mpack -s "some subject" /tmp/rejectlog_filtered.txt user@example.com; fi

[sudodus]

Returning zero means true (or success) while 1 means false (or failure). I think you got it right.

Please notice that [ something ] is the same as test something

[marchello_lippi2]

Thanks sudodus.