crontab and date

The other day, I wanted to add a script to the crontab and to redirect the output to a file including the current date. Easy. I have used the date command many times in bash script like that:

current_date=$(date +"%Y%m%dT%H%M")

So I added the following to my crontab:

0 1 * * * /usr/local/bin/foo > /tmp/foo.$(date +%Y%m%dT%H%M).log 2>&1

And... it didn't work...

I quickly identified that the script was working properly when run from the crontab (it's easy to get a script working from the prompt, not running from the crontab due to incorrect PATH). The problem was the redirection but I couldn't see why.

I googled a bit but didn't find anything...

I finally looked at the man pages:

$  man 5 crontab

     ...
     The  ``sixth''  field  (the  rest of the line) specifies the command to be run.  The entire command portion of the line, up to a
     newline or % character...

Here it was of course! % is a special character. It needs to be escaped:

0 1 * * * /usr/local/bin/foo > /tmp/foo.$(date +\%Y\%m\%dT\%H\%M).log 2>&1

Lesson to remember: check the man pages before to google!