Shell Programming and Scripting

I'm new in Shell Programming and Scripting, I would like to ask some questions.

Code:

ps -ef | grep $appNAme | grep -v grep <-- what will it return when it find a process is running? return 1 or 0

if [ $? -ne 1 ]
then
      exit 1  <--- if  = 0 , run this ?
else
      continue <---  if  = 1 , run this ?
fi

Am I right? Thank you for your attention.

Moderator's Comments:

Please use code tags when posting code, data or logs etc., thanks.

When it finds a process with "grep" in it, it will be always 0, no matter what process you are looking for.
You should 1st use grep -v grep to filter out the line and then check for that process. You will then get the correct return code you are looking for.

1) In case of a pipeline, the exit status is that of the last command (unless the shell supports the pipefail option and that is set). So, the exit status is that of grep -v grep, which will be 0 if it anything passes through this grep command to standard output.
In short, if the process is running, this will return a 0 (success).

2) No. That means if not 1 which might not be the same as if 0.

3) Yes.

1) If you have commands like pgrep/pkill then use it. This should be better.

2) $? is not always 1 or 0.(As pointed above)

3) And you can use simply like this..

Code:

if [[ $(pgrep "$process_name" ]]
then
echo "process running"
else
echo "process not running"
fi

Thanks all guys......

You can also use pidof "process"
If its anything but 0, then its running