How to add unique id to file name in cron job?

Question

My cronjob looks like this:

5 3 * * * mysqldump -u root test > /srv/backup/mysql_daily.dump

How can I make filename unique for every time when cronjob writes mysql_daily.dump?

Answer 1

For bash, maybe:

... > /srv/backup/mysql_daily-$(date -u +\%Y\%m\%dt\%H\%M\%S).${RANDOM}.dump

Personally, i generally only put simple commands in my crontab. I'd put this in a little script and use the script in the crontab. This would have the benefit of not requiring the % characters to be escaped (a common crontab pitfall).

Answer 2

Try

5 3 * * * mysqldump -u root test > /srv/backup/mysql_daily.$(/bin/date +\%Y\%m\%d).dump

which will put the current date in the format YYYYMMDD into the filename.

Answer 3

The general practice for this is to use a timestamp using date +%s to generate something useful to mark the file (I used seconds as an example but you can use any date format). It's really not necessary to have a truly unique file name as long as the file name doesn't conflict.

5 3 * * * mysqldump -u root test > /srv/backup/mysql_daily_`date +\%s`.dump