How Do I Check for a Status Bit on a Running Process?
Ok, Here's My Dilemma, I'm Running Headless Ubuntu Server 18.04.3 Lts on a Dell Poweredge T710 Server, and I'm Writing a Bash Script So That I Can Easily...
OK, here's my dilemma, I'm running headless Ubuntu server 18.04.3 LTS on a Dell PowerEdge T710 server, and I'm writing a bash script so that I can easily change the Apache PHP Mod versions without having to keep manually using:-
a2dismod php<version>
a2enmod php<version>
systemctl restart apache2
The beginning of the script uses an if condition to check if the user is logged in as a user account or a root account using the status bit of UID, ie:-
if ((UID)); then
something here
elif ((!UID)); then
something here
fi
using ((UID)) to check if the bit is true and using ((!UID) to check if the bit is false, but here's the problem, I want to add a little bit more checking to make sure apache is actually in a running state, I would rather use boolean true or false than to use something like:-
systemctl status apache2
which gives a lot of output. Is there a status bit for apache? Then I can do a check to make sure apache is actually running before continuing the phpmod version change.
This is the script I have so far:
IT not only needs the checking for apache running, but also a check for the various apache PHP modules to make sure they are actually installed before attempting to enable the correct module, and if not, then the script would execute:-
apt install libapache2-mod-php<version>
2 Answers
You can use the is-active unit command of systemctl which “[r]eturns an exit code 0 if at least one [unit] is active, or non-zero otherwise”:
if systemctl is-active --quiet apache2; then
echo running
else
echo not running
fi
If you’d rather use a parameter there’s $? holding the exit code of the last command, you can simply test for it being 0:
systemctl is-active --quiet apache2
if [ $? -eq 0 ]; then
echo running
else
echo not running
fi
Further reading
Defining own exit codes still uses the same logic as @Dessert describes in his answer.
#!/bin/bash
systemctl is-active -q apache2 && status=TRUE || status=FALSE
case $status in
TRUE)
echo do something ;;
FALSE)
echo do sothing else ;;
esac
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