Yep, that's exactly what it's doing. You typically don't want to do a kill on
a process if you don't have a process id... hence the check if it's empty.
Why, then, doesn't it just do this?
if [ "$pid" != "" ]
Well, this takes me back a bit so my memory might not be 100% accurate here.
Say $pid is empty, though. What this would look like is:
if [ "" != "" ]
Modern shells can handle this just fine. Older shells (like the original
Bourne shell) got confused by this. So as a matter of practice, you would
put a guaranteed non-NULL character in both sides of the string. If the
environment variable was null, then it would look like so:
if [ "X" != "X" ];
which is the same as "" != "".
As I said, though, it's been a while since I learned to do that so my memory
could be shot.
On Monday 31 July 2006 14:36, David wrote:
> What is the point of the below in a script? This snippage is in the
> 'stop' portion of an init script. I just dont see the point of the if
> statement. It almost looks like it's just making sure $pid isn't empty.
>
>
> ------begin snippet------
>
> pid=`/bin/ps -e | grep process_name | grep -v mon | grep -v grep |
> sed -e 's/^ *//' -e 's/ .*//' | head -1`
> if [ "X$pid" != "X" ]
> then
> /bin/kill $pid
> echo "**process_name** interface stopped"
> fi
> ------end snippet------
>
> Thanks,
> David
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