PS finds a ghost? - UNIX for Dummies Questions & Answers

jguirao · #1 (**permalink**) 02-28-2001

Hello,

I have problems executing a script in ksh with this script named
process.sh:

Code:

ps -ef | grep process.sh | grep -v grep | wc -l | read a
if [ $a -gt 1 ]
then
 echo "The script is running" 
exit 0
fi

The problem is that when I execute the script, sometimes it shows the
message "The script is running", when I think it's impossible.
The reason that I write "wc -l|read a" is that
the count returns 1 because the "ps" is executed in the same script.
My idea is that nobody execute 2 times the same script, only on time.

Is something wrong?

Thanks in advance.

added code tags for readability --oombera

PxT · #2 (**permalink**) 02-28-2001

How about:

Code:

#!/bin/ksh

ps -ef | grep "[p]rocess.sh" 1> /dev/null 2>&1
if [$? -eq 0]
then
	echo "script is running"
	exit 0
fi
exit 1

added code tags for readability --oombera

jguirao · #3 (**permalink**) 02-28-2001

The script is always running 1 time, I must insert the code in the same script to control if someone will execute the script again.

PxT · #4 (**permalink**) 02-28-2001

Ok, I understand now. Why don't you make the script test for a lockfile when it starts?

if [ -a /tmp/process.lock ]; then
exit
fi

touch /tmp/process.lock
# rest of script
rm /tmp/process.lock

jguirao · #5 (**permalink**) 02-28-2001

Your idea is good, but I need to implement it in a lot of scripts (77 aprox), a lot of them running at the same time.

What I don't want is to use 77 different names for each temporary file.

PxT · #6 (**permalink**) 02-28-2001

Ok, third time's a charm...

What about:

Code:

#!/bin/ksh
NUM=`ps -ef | grep "[p]rocess.sh" | wc -l
if [ $NUM -gt 1 ] 
then 
            echo "The script is running" 
            exit 0 
fi

added code tags for readability --oombera

mib · #7 (**permalink**) 03-01-2001

Quote:

#!/bin/ksh
NUM=`ps -ef | grep "[p]rocess.sh" | wc -l

Script is perfect.

But it lost closing quote. isn't it?

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