Bash: what does "-eq" mean?
<p>I would like to know what <code>-eq</code> does in a bash script (as in the below example):</p>

<pre><code>LINES=`ps -p $PID`
    PIDRET=$?
    if [ $PIDRET -eq 0 ];
    then
        export PID
        return 0;
    fi
    rm -f "$CATALINA_PID" 
</code></pre>