$(hostname) doesn't work in cronjob

Question

I have a simple backup script with this line to come up with a name for the backup:

backup=$(/bin/date +'%Y-%m-%d_%H:%M_%S')_$(hostname).gz

It works great when I run it under the root user. Unfortunately when I set it to run as a cronjob, the $(hostname) part is always empty and I don't get the hostname. Why isn't it working, and how can I get the hostname in a cron job?

I'm running ubuntu 18.04

Since you specify /bin/date with an explicit path: Is PATH set correctly to contain hostname? — DonHolgo, Sep 04 '19 at 14:40
Is that a line from the actual cron schedule? % is special in crontabs, and must be escaped. See e.g. How can I execute `date` inside of a cron tab job? — Kusalananda, Sep 04 '19 at 15:04
@DonHolgo You are exactly right! I don't know why I didn't think of that! Works perfect once I add the full path. — user3413723, Sep 04 '19 at 15:59

score 2 · Answer 1 · answered Sep 04 '19 at 15:53

2

Crontab has its own variables lists for path etc...you might use them or run from crontab a bash script instead of a shell-like commad.

This is how to use crontab

VARIABLE=value
PATH=/bin:/path/to/doanything
0 0 * * * doanything.sh $VARIABLE

answered Sep 04 '19 at 15:53

francois P

1,219

score 1 · Accepted Answer · answered Sep 04 '19 at 18:09

1

hostname doesn't seem to be in the PATH in your script. Either put /bin/hostname there, like you did for date, or set PATH to include /bin (inside the script or in the crontab).

answered Sep 04 '19 at 18:09

DonHolgo

620

It would be better to investigate why the root user's PATH is wrong, which indicates a deeper issue with the system. – Kusalananda Mar 08 '23 at 07:00

$(hostname) doesn't work in cronjob

2 Answers2