if statement on multiline string not working

I'm trying to force the restart of my rsyslog server. I have sanitary reboot during the day, and sometimes the restart fails, so I want to restart it until the restart is a success.

At this point I'm trying to check if the output of the restart matches the output it is supposed to give when the restart is good.

But I don't understand why the if statement below doesn't work. It always goes to the else statement whether I put a == or != in the test condition.

Is there a way to check if a multi-line string is equal to another predefined multi-line string?

#!/bin/sh
endv=0
testv="Shutting down system logger: [ OK ]
Starting system logger: [ OK ]"
startv="$(/etc/init.d/rsyslog restart)"
while [ $endv == 0 ]; do echo "$startv" if [[ "$startv" != "$testv" ]]; then startv="$(/etc/init.d/rsyslog restart)" echo THEN else echo ELSE endv=1 fi
done

1 Answer

A few preliminaries:

1. You should probably be moving away from invoking SysV init scripts directly; you are at least one and likely two steps behind the curve ( SysV init was replaced by upstart and then by systemd). For example:

   systemctl restart rsyslog.service

2. Whichever init interface you use, it's likely that you can use the command's EXIT_STATUS directly rather than capturing its output and testing string equality. For example:

   systemctl restart rsyslog.service
   if [ $? -ne 0 ]; then ...
   fi

   (in any case, as @choroba poined out in comments, the '[OK]' message may in fact be going to standard error rather than standard output).

3. In Ubuntu, /bin/sh is not bash: see DashAsBinSh. Among other things, that means it won't support the [[ . . . ]] extended test syntax.

Having got those out of the way, bash does indeed support string equality tests on multiline strings e.g.

$ str1='This is
a string'
$ str2='That is
a string'
$ str3='This is
a string'
$
$ [[ "$str1" != "$str1" ]] && echo "No match" || echo "Match"
Match
$ [[ "$str1" != "$str2" ]] && echo "No match" || echo "Match"
No match
$ [[ "$str1" != "$str3" ]] && echo "No match" || echo "Match"
Match