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Le Ray
Le Ray

Reputation: 387

Script not executing properly when using /bin/sh

My script doesnt function properly when I execute using just sh, it used to function fine before until today. Even in cronjob it used to execute without a problem.

/bin/sh process_check.sh

But it seems to execute fine when I execute using the following way

./process_check.sh

Script (checks if a process is running, executes the process if it's not running)

#/bin/sh
     $service=xxx

    if (( $(/bin/ps -ef | grep $service | wc -l) > 1 ))
      then
         true
      else
         echo "$service is not running!!!"
         /usr/sbin/xxx
      fi

Also, any ways to make this much more efficient? I have a compiled program that I am trying to ensure is always running.

Upvotes: 1

Views: 2038

Answers (2)

John1024
John1024

Reputation: 113994

One problem is this line:

$service=xxx

This likely should be:

service=xxx

Also, the following is inherently unreliable:

(( $(/bin/ps -ef | grep $service | wc -l) > 1 ))

The number of processes found this way in a multitasking system depends on accidents of timing. A more reliable approach is to use pgrep:

pgrep "$service"

This will list PIDs for $service without the possibility of matching the grep process.

Because pgrep sets a useful return code all by itself, there is no need for math test. Thus, replace:

if (( $(/bin/ps -ef | grep $service | wc -l) > 1 ))

With:

if pgrep -q "$service"

where -q tells pgrep to just set the exit code without listing the PIDs to stdout.

If your pgrep does not support the -q option, then use:

if pgrep "$service" >/dev/null

Upvotes: 1

TEVD
TEVD

Reputation: 31

In the first line of the script, you used #/bin/sh instead of #!/bin/sh. When you use ./process_check.sh it uses /bin/bash instead of /bin/sh.

Upvotes: 2

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