mjhjmtu

I am writing a shell script to check if mongod server is running and if not, to start it. To acheive that I am using the below command:

systemctl is-active --quiet mongod

This does the job as expected. But it's possible my script will run on systems that do not have systemd, so I am interested in knowing whether there is a more portable way to do this.

This is not perfect, but will work on many systems. Note that the pgrep approach is suboptimal since the name might be slightly different, or you might pass a name that is a substring of another name, but it's a start.

#!/usr/bin/sh

if systemctl is-active --quiet "$1" > /dev/null 2>&1; then
 echo "Running! (systemctl)"
elif service "$1" status 2>&1 | grep -Eq 'is running|: active (running)'; then
 echo "Running! (service)"
elif pgrep "$1" > /dev/null 2>&1 ; then
 echo "Running (pgrep)"
else
 echo "Not running"
fi

Save that as checkIfRunning and run it like this:

checkIfRunning mongod

There is no one, portable way of achieving that. But many current Linux distributions have old, legacy service command that behaves as a proxy to systemctl if run on systemd powered OS.

So you can run the command like this:

# service sshd status
Redirecting to /bin/systemctl status sshd.service
● sshd.service - OpenSSH server daemon
 Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled)
 Active: active (running) since Wed 2019-02-20 12:16:17 UTC; 1 weeks 2 days ago
 Docs: man:sshd(8)
 man:sshd_config(5)
 Main PID: 3388 (sshd)
 CGroup: /system.slice/sshd.service
 └─3388 /usr/sbin/sshd -D