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Full Discussion: How to check if a shell is already running ?
Operating Systems Solaris How to check if a shell is already running ? Post 302597988 by zionassedo on Monday 13th of February 2012 05:48:55 AM
Old 02-13-2012
Thanks for the help, but as you said, the problem with the 'test&set' method is the reinit after system crash or manual killing.
My problem is that I see 2 lines, the shell process id and it's parent, I must be able to make the difference between the parent and an other process.
What I dont understand also is that i do it on 2 different machines and I get 2 differents outputs.
On the 1rst machine (spark v210) I get
root 14550 14543 0 10:40:48 pts/2 0:00 /usr/bin/ksh test.sh
root 14543 14016 0 10:40:45 pts/2 0:00 /usr/bin/ksh test.sh
As you can see these 2 lines are in fact related to the same process, the first line is in fact the parent process of the process appearing in the 2nd line.
the real solution is to store the PID and the PPID in 2 different arrays and build an algorythm that will be able to understand this situation.
On the second machine (spark v120) i get a single line.
I think that it is because that the first one got 2 processors and the 2nd one a single processor.

---------- Post updated at 12:48 PM ---------- Previous update was at 11:24 AM ----------

I think I got something :
here is how to manage the 'Parent process' case

Code:
set -A pids Dum
set -A fpids Dum
ps -ef| grep $0 | grep -v grep > $LOGDIR/$0.pid

i=0
j=0
while read filename
do
  pids[i]=$(echo $filename | awk '{printf "%s ",$2}') # I store the pid
  fpids[i]=$(echo $filename | awk '{printf "%s ",$3}') # I store the parent pid
#  echo "pids fpids index $i =" ${pids[i]} ${fpids[i]}

  (( i=i+1 ))
done < $LOGDIR/$0.pid

while [[ $j -lt $i ]]
do

if [[ ${pids[$j]} -ne $$ ]] # if the considered pid is not me
then
if [[ ${fpids[$j]} -ne $$ ]] # and even not my parent
then
print " $0 is already running. Exiting" #well it is a stranger
exit 0
fi
fi
(( j=j+1 ))
done

Last edited by DukeNuke2; 02-13-2012 at 08:13 AM..
 

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LEARN ABOUT MINIX

pidof

PIDOF(8)						Linux System Administrator's Manual						  PIDOF(8)

NAME

       pidof -- find the process ID of a running program.

SYNOPSIS

       pidof [-s] [-c] [-n] [-x] [-o omitpid[,omitpid..]]  [-o omitpid[,omitpid..]..]  program [program..]

DESCRIPTION

       Pidof  finds  the  process  id's (pids) of the named programs. It prints those id's on the standard output. This program is on some systems
       used in run-level change scripts, especially when the system has a System-V like rc structure. In that case these scripts  are  located	in
       /etc/rc?.d, where ? is the runlevel. If the system has a start-stop-daemon (8) program that should be used instead.

OPTIONS

       -s     Single shot - this instructs the program to only return one pid.

       -c     Only  return  process ids that are running with the same root directory.	This option is ignored for non-root users, as they will be
	      unable to check the current root directory of processes they do not own.

       -n     Avoid stat(2) system function call on all binaries which are located on network based file systems like NFS.  Instead of using  this
	      option the the variable PIDOF_NETFS may be set and exported.

       -x     Scripts too - this causes the program to also return process id's of shells running the named scripts.

       -o omitpid
	      Tells  pidof  to omit processes with that process id. The special pid %PPID can be used to name the parent process of the pidof pro-
	      gram, in other words the calling shell or shell script.

EXIT STATUS

       0      At least one program was found with the requested name.

       1      No program was found with the requested name.

NOTES

       pidof is actually the same program as killall5; the program behaves according to the name under which it is called.

       When pidof is invoked with a full pathname to the program it should find the pid of, it is reasonably safe. Otherwise it is  possible  that
       it  returns  pids  of  running programs that happen to have the same name as the program you're after but are actually other programs. Note
       that that the executable name of running processes is calculated with readlink(2), so symbolic links to executables will also match.

SEE ALSO

       shutdown(8), init(8), halt(8), reboot(8), killall5(8)

AUTHOR

       Miquel van Smoorenburg, miquels@cistron.nl

								    01 Sep 1998 							  PIDOF(8)
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