07 Jan

crontab not working with dynamic date filename – rhel linux

I have done it for so many times, setting a cronjob.
Today I was tring to set a simple cronjob which will output the log file with timestamp attached filename.

Hourly running cron entry was:

0 * * * * perl demo.pl > demo-out_`date "+%Y-%m-%d_%H-%M"`.log

Running the same command on shell prompt was working fine. Execute permissions and path were proper. But it kept on failing to create the proper log!!

I changed the crontab as follows, added \ before % to escape and voila!!

Things worked !!

0 * * * * perl test.pl > test-out_`date "+\%Y-\%m-\%d_\%H-\%M"`.log

A quick lesson.

Good to note some of the date changers in linux for finding yesterdays and tomorrows and so on:
date –date=”1 days ago”
date –date=”yesterday”
date –date=”next day”
date –date=”-1 day”
date –date=’tomorrow’
date –date=’1 day’
date –date=’10 day’
date –date=’10 week’
date –date=’10 month’
date –date=’10 year’
date –date=”next Friday”
To escape problems you should learn to escape “special characters” – Krex
P.S.:This works in real life as well 😉

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-- Kedar Vaijanapurkar --