Test if a systemd unit is active in a bash script

Question

I'm writing a script to automatically install a bind server on a CentOs 7 distribution.

I'm stuck with systemctl status, because it does not produce an error code (it's right, since a status is not an error) I can use.

What I want is to check whether the service is started (active). What is the best and efficient way to do this?

Indigestive

Actually systemctl status does return a status - as I found when doing systemctl status openvpn@<>. Where the values are 0 for running, and 3 for stopped. However, this command is interactive :(. Hence the @lars suggested systemctl is-active is the way to go, and better att the -q as suggested by @palswim – Googly

Answer 1

The best way to check if a service is active is with the systemctl is-active command:

# systemctl start sshd
# systemctl is-active sshd >/dev/null 2>&1 && echo YES || echo NO
YES
# systemctl stop sshd
# systemctl is-active sshd >/dev/null 2>&1 && echo YES || echo NO
NO

Byway

Thanks, that's exactly what i was looking for! it seems i missed it in the manual. ^^' – Indigestive

You can also use the -q switch so that you don't have to redirect output: systemctl -q is-active sshd – Dickens

Answer 2

If you want to check in a shell script, you can do:

if (systemctl -q is-active some_application.service)
    then
    echo "Application is still running."
    exit 1
fi

To check if a application is not running just add a exclamation mark in the condition.

Fabrice

This if statement always resolved to true because the strings "active" and "inactive" are both true. – Diggs

The script works fine in my production machines. If an application is running the script exits, else it continues the script. – Fabrice

looks like the script is checking the return code of systemctl not the string returned. So it works. – Yetta

"This if statement always resolved to true because the strings "active" and "inactive" are both true." -> I tested and it worked for me. – Khelat

For the pair with -q flag it's better to check explicitly for status code. e.g. ` systemctl -q is-active some_application.service\n if [ $? -eq 0 ]; then\n echo 'App running'\n exit 0\n fi ` p.s. sorry for the mess with code block, it's impossibru to use newline for comments. – Article