How to resolve the algorithm Determine if only one instance is running step by step in the UNIX Shell programming language
Published on 12 May 2024 09:40 PM
How to resolve the algorithm Determine if only one instance is running step by step in the UNIX Shell programming language
Table of Contents
Problem Statement
This task is to determine if there is only one instance of an application running. If the program discovers that an instance of it is already running, then it should display a message indicating that it is already running and exit.
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Determine if only one instance is running step by step in the UNIX Shell programming language
Source code in the unix programming language
# (c) Copyright 2005 Mark Hobley
#
# This is free software. This file can be redistributed or modified
# under the terms of version 1.2 of the GNU Free Documentation Licence
# as published by the Free Software Foundation.
#
singleinstance ()
{
if [ -d $SRUNDIR ] ; then
if [ -w $SRUNDIR ] ; then
if [ -d $SRUNDIR/$APPNAME ] ; then
echo "Process Already Running" >& 2
return 221
else
mkdir $SRUNDIR/$APPNAME
if [ "$?" -ne 0 ] ; then
if [ -d $SRUNDIR/$APPNAME ] ; then
echo "Process Already Running" >& 2
return 221
else
echo "Unexpected Error" >& 2
return 239
fi
fi
return 0 ; # This is a unique instance
fi
else
echo "Permission Denied" >& 2
return 210
fi
else
echo "Missing Directory" >& 2
return 199
fi
}
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