Cron filename with date is passing Y_m_d not actual date

Question

Using cron to backup mysql to a folder everyday. So tried to schedule cron with below code in linux server. related post

0 0 * * * <username> mysqldump -u<mysql username> -p<mysql password> <database name> > /home/<username>/Db_BackUp/expense_$( date +"\℅Y_\℅m_\℅d" ).sql

above cron is working but generated file name is like

expense_\.Y_\.m_\.d.sql

I need cron to create filename as expense_2016_04_05.sql

how to do this in cron?

related answer from SO Post

addition info about cron restart SO Post

score 4 · Accepted Answer · answered Apr 05 '16 at 04:59

4

Since cron is not a shell, it doesn't execute items in $() wrapper within the cron line in the way a shell does. However some crons like Vixie Cron will allow you to define variables before your command:

YMD=/bin/date +%Y_%m_%d
0 0 * * * /path/to/command > /home/username/Db_BackUp/expense_$($YMD).sql

If that doesn't work, you might have to write a helper script and run it via cron instead. For example:

mysqldump_helper.sh

#!/bin/bash
YMD=`/bin/date +%Y_%m_%d`
/path/to/command > /home/username/Db_BackUp/expense_$YMD.sql

crontab

* * * * * /path/to/mysqldump_helper.sh

answered Apr 05 '16 at 04:59

David White

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but i'm using `crontab` from `RHEL7`. do you think it will work? – Syed Nizamudeen Apr 05 '16 at 05:05
You'll just have to try it. RHEL7 may use "cronie", which may allow the same variable assignment that the first solution above shows. In any case, however, the second solution will work with any cron program. – David White Apr 05 '16 at 05:11
Thanks! @David White anyway i wrote shell script and its working great – Syed Nizamudeen Apr 06 '16 at 03:11
1

@DavidWhite, Saved me. I was making sure the command that has $(date..) runs in the shell but wondering why it's not running from CRON properly. Now I got it :) Hard lessons for a Windows -> Linux user – Joy George Kunjikkuru Sep 09 '20 at 01:26
Glad it helped, @JoyGeorgeKunjikkuru ! – David White Sep 10 '20 at 02:06

Cron filename with date is passing Y_m_d not actual date

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