How to Lock the Script? Post: 302876531

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Top Forums UNIX for Dummies Questions & Answers How to Lock the Script? Post 302876531 by rbatte1 on Monday 25th of November 2013 08:45:40 AM

11-25-2013

Moderator

To respond to the suggestions from RavinderSingh13

The problem with looking for a process of the right name is that someone could be editing a file of the same/similar name, or using more to browse the script. They will all get detected as an in-use condition.

It would be neater written as:-

Code:

if [ `ps -ef | grep -c [t]est.ksh` -ne 1 ]
then

... although I'm probably breaking all sorts of rules about back-ticks inside a test.

For a single use script, you could create a lock file in your code:-

Code:

#!/bin/ksh

if [ -f /tmp/my_lock_file ]
then
   cat /tmp/my_lock_file
   exit
fi

# I've got here, so it's not locked by anyone else, so I will lock it

echo "`date` : This script is being run by $USER" >/tmp/my_lock_file

# Do what your script needs to do
# Do what your script needs to do
# Do what your script needs to do
# Do what your script needs to do

# Tidy up lock file
rm /tmp/my_lock_file

It's not pretty, but it works in a clunky way.

You can add more to it to reduce the risk of someone else getting in between you checking and creating the lock file, but it's more complex and doesn't work if you switch user:-

Code:

if [ -f /tmp/my_lock_file ]
then
   echo "Sorry, but \c"
   cat /tmp/my_lock_file
   exit 99
fi
echo "$USER started updates at `date '+%H:%M:%S on %d/%m/%Y'`">/tmp/my_lock_file
sleep 1
cat /tmp/my_lock_file|read luserid rest
if [ $luserid != $USER ]
then
   echo "Very unlucky. \c"
   cat /tmp/my_lock_file
   exit 99
fi


# I've got here, so it's not locked by anyone else, so I will lock it

echo "`date` : This script is being run by $USER" >/tmp/my_lock_file

# Do what your script needs to do
# Do what your script needs to do
# Do what your script needs to do
# Do what your script needs to do

# Tidy up lock file
rm /tmp/my_lock_file

Code:

if [ `ps -ef | grep -c [t]est.ksh` -ne 1 ]
then

... although I'm probably breaking all sorts of rules about back-ticks inside a test.

I hope that this helps
Robin
Liverpool/Blackburn
UK

Last edited by rbatte1; 11-25-2013 at 09:51 AM..

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