How to check if a shell is already running ? Post: 302597832

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Operating Systems Solaris How to check if a shell is already running ? Post 302597832 by agama on Sunday 12th of February 2012 11:35:47 AM

02-12-2012

Registered User

I assume you have a long running script and are wanting to prevent a second copy from starting if the first is running. What is probably happening is that your test is seeing 'itself' in the output from ps and is claiming that another copy is already running.

When I have to ensure that the invocation of a script is the only one running I use a marker directory in /tmp. Only one process can create a directory, so if two are started at the same time then only one will 'win' and continue running. Further, I add some information to the directory so that when another detects one already running, it can verify that it is still running and allows itself to start if it finds a marker, but doesn't find an associated process.

Here's an example:

Code:

#!/usr/bin/env ksh

trap "rm -fr \${solo_mark:-nosuchfile}" EXIT            # remove our marker stuff at exit

cmd=${0##*/}
solo_mark=/tmp/$cmd.solo
if ! mkdir $solo_mark 2>/dev/null       # if two started at the same time only one will be successful
then
    sleep 1                             # if there was a collision, allow winner to set the info file
    read rinfo <$solo_mark/info
    echo "verification that '$rinfo' is still running"
    if ps -e -o pid,command |awk -v rinfo="$rinfo" '
        BEGIN { split( rinfo, a, " " ); }
        $1 == a[1] {
            if( rinfo == $0 )
                exit( 1 );
            next;
          }'
    then
        echo "marker exists, but not running; we continue"
    else
        echo "already running"
        exit 1;
    fi
else
    echo "not running"
fi
ps -o pid,command | grep "^[ ]*$$" >$solo_mark/info     # save our info for others to verify
 


# ------- do intended work here -----------------

The bit of extra work to save the info, and verify it, makes things easier following a system crash, or someone killing the process in such a way that the marker doesn't get removed.

Hope this helps.

Last edited by agama; 02-12-2012 at 12:39 PM.. Reason: formatting

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LEARN ABOUT SUSE

ivman-launch

IVMAN-LAUNCH(8) 					      System Manager's Manual						   IVMAN-LAUNCH(8)

NAME

       ivman-launch - launch script for Ivman

SYNOPSIS

       ivman-launch [ --exit-with-session <cmd> ] [ OPTIONS ] [ COMMAND [ ARGS... ]]

DESCRIPTION

       ivman-launch  is a simple script used to launch Ivman.  Its sole purpose is to ensure Ivman is closed at the end of a user's login session.
       You can use it if your session manager does not properly close Ivman when you log out.

       ivman-launch supports the same command-line options as Ivman, and one additional option: --exit-with-session.   Thus,  there  is  no  point
       using ivman-launch if you do not need to use this option.

       If  you supply a COMMAND (with optional ARGS), the the specified command will be run after ivman is started, and ivman will be killed after
       that command exits.

OPTIONS

       --exit-with-session <cmd>
	      ivman-launch will block until the command 'cmd' terminates, at which point it will kill Ivman and exit itself.  If the command 'cmd'
	      is  not  running when ivman-launch is started, Ivman will exit immediately.  Note that this option implies Ivman will be called with
	      the '--nofork' option.  option.

       --debug --nofork --system
	      These flags be passed to the launched ivman command.

EXAMPLES

       ivman-launch --exit-with-session xinit &
	      The ivman process will be started, then the xinit process is watched.  When the xinit process exits, ivman is killed.  Placing  this
	      command  in  an  ~/.xinitrc  file would cause Ivman to launch in the background when your session begins, and exit when your session
	      ends:

       ivman-launch /usr/bin/x-window-manager
	      The ivman process is launched, then /usr/bin/x-window-manager is run, when x-window-manager exits, ivman	is  killed.   This  is	an
	      example of how ivman might be launched from Xsession in order to chain several programs together in one session.

SEE ALSO

       ivman(8) Xsession(5)

CREDITS

       This script was written by Daniele Favara.

								 10 February 2006						   IVMAN-LAUNCH(8)

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