Test if postfix is running

Question

I'm searching for a reliable way to test if postfix is running from inside a bash script.

My first attempt was simply trying pidof postfix, which doesn't work.

Then I tried to get the postfix status:

POSTFIX_LOCATION=/var/packages/MailServer/target/sbin/postfix # location of postfix
result=`$POSTFIX_LOCATION status`
if [ -z $result ]; then
    echo "Error: No status output from postfix"
elif [[ "$result" == *"is running"* ]]; then
    echo "postfix is running!"
else echo "postfix is not running!"
fi

But even though the status is reported to the console, the result variable stays empty. This is the console output:

postfix/postfix-script: the Postfix mail system is running: PID: 11996
Error: No status output from postfix

I finally found a way to test if postfix is running by getting the process name of PID: 11996, which is "master". So the following does work:

pidof master

But this is not very verbose and I'm not sure if this is a reliable way to test if postfix is running.

So my questions are:

• How can I get the output of postfix status from inside a bash script? - Anything I'm doing wrong there?
• Is there a better reliable way to test if postfix is running from inside a bash script?

Answer 1

Debian or Ubuntu

sudo service postfix status

Answer 2

To check whether Postfix is running or not:

sudo /etc/init.d/postfix status

To start the Postfix:

sudo /etc/init.d/postfix start

To stop the postfix:

sudo /etc/init.d/postfix stop

Answer 3

A reliable way to test if postfix is running:

if /var/packages/MailServer/target/sbin/postfix status; then
    echo "postfix is running!"
else echo "postfix is not running!"
fi

An alternative that essentially does the same:

if /var/packages/MailServer/target/libexec/master -t 2>/dev/null; then
    echo "postfix is not running!"
else echo "postfix is running!"
fi

---

Reasoning

After doing some more research, it turned out that testing for ps | grep [p]ostfix is not reliable at all to verify if postfix is running.

It seems the reason why /var/packages/MailServer/target/sbin/postfix status does not output anything useful is, because postfix uses the internal postlog binary for the output. The relevant code can be found in the bash script /var/packages/MailServer/target/libexec/postfix-script:

LOGGER="$command_directory/postlog -t $MAIL_LOGTAG/postfix-script"
INFO="$LOGGER -p info"

Checking for the exit code of postfix status does work fine on the other hand. The postfix-script is actually called behind the scenes by the postfix binary and cannot be called directly. But luckily the script also includes the code to test if postfix is running:

status)
    $daemon_directory/master -t 2>/dev/null && {
        $INFO the Postfix mail system is not running
        exit 1
    }
    $INFO the Postfix mail system is running: PID: `sed 1q pid/master.pid`
    exit 0
    ;;

The variable $daemon_directory gets set by the calling postfix binary. On my system it resolves to /var/packages/MailServer/target/libexec/.