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Full Discussion: Help scripting to start, check, and restart processes
Top Forums Shell Programming and Scripting Help scripting to start, check, and restart processes Post 302533478 by neutronscott on Thursday 23rd of June 2011 06:37:39 PM
Old 06-23-2011
I thought using screen -ls was more elegant. This is what I came up with:

Code:
#!/bin/sh
# chkscreen: checks if a screen session is running.
WORKINGDIR=/home/mute/test
PIDFILE=cb.pid
SESSION="server1"
DAEMON="/home/mute/test/java-daemon.sh"

is_running()
{
    pid=$1
    name=$2
    [ -z "$pid" ] && return 1
    [ ! -d /proc/$pid ] &&  return 1
    cmd=`cat /proc/$pid/cmdline | tr "\000" "\n"|tail -n 1 |cut -d : -f 1`
    [ "$cmd" != "$name" ] &&  return 1
    return 0
}

# does the session exist?
#screen -S $SESSION -ls -q 2>&1 >/dev/null

# check java-daemon.sh's pid instead?
pid=$(cat $PIDFILE 2>/dev/null)
is_running "$pid" "$DAEMON"

if [ $? != 0 ]; then
        echo "Restarting $DAEMON"
        screen -d -m -S $SESSION $DAEMON
fi

Code:
#!/bin/sh
# java-daemon.sh: keeps restarting a buggy server... ;)

WORKINGDIR=/home/mute/test
PIDFILE=cb.pid

cd $WORKINGDIR
echo $$ >$PIDFILE

while true; do
top
done


or a more simple way without checking that it is the correct command running (it's not often the PIDs wrap around and get used for something else...?)

Code:
# check java-daemon.sh's pid instead?
pid=$(cat $PIDFILE 2>/dev/null)
kill -0 $pid 2>/dev/null

if [ "$?" != 0 ]; then
        echo "Restarting $DAEMON"
        screen -d -m -S $SESSION $DAEMON
fi

This User Gave Thanks to neutronscott For This Post:
MacG32
 

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LEARN ABOUT MINIX

uuidd

UUIDD(8)						       System Administration							  UUIDD(8)

NAME

       uuidd - UUID generation daemon

SYNOPSIS

       uuidd [options]

DESCRIPTION

       The  uuidd  daemon is used by the UUID library to generate universally unique identifiers (UUIDs), especially time-based UUIDs, in a secure
       and guaranteed-unique fashion, even in the face of large numbers of threads running on different CPUs trying to grab UUIDs.

OPTIONS

       -d, --debug
	      Run uuidd in debugging mode.  This prevents uuidd from running as a daemon.

       -F, --no-fork
	      Do not daemonize using a double-fork.

       -k, --kill
	      If currently a uuidd daemon is running, kill it.

       -n, --uuids number
	      When issuing a test request to a running uuidd, request a bulk response of number UUIDs.

       -P, --no-pid
	      Do not create a pid file.

       -p, --pid path
	      Specify the pathname where the pid file should be written.  By default, the pid file is written to /run/uuidd/uuidd.pid.

       -q, --quiet
	      Suppress some failure messages.

       -r, --random
	      Test uuidd by trying to connect to a running uuidd daemon and request it to return a random-based UUID.

       -S, --socket-activation
	      Do not create a socket but instead expect it to be provided by the calling process.  This  implies  --no-fork  and  --no-pid.   This
	      option is intended to be used only with systemd(1).  It needs to be enabled with a configure option.

       -s, --socket path
	      Make  uuidd use this pathname for the unix-domain socket.  By default, the pathname used is /run/uuidd/request.  This option is pri-
	      marily for debugging purposes, since the pathname is hard-coded in the libuuid library.

       -T, --timeout number
	      Make uuidd exit after number seconds of inactivity.

       -t, --time
	      Test uuidd by trying to connect to a running uuidd daemon and request it to return a time-based UUID.

       -V, --version
	      Output version information and exit.

       -h, --help
	      Display help screen and exit.

EXAMPLE

       Start up a daemon, print 42 random keys, and then stop the daemon:

	      uuidd -p /tmp/uuidd.pid -s /tmp/uuidd.socket
	      uuidd -d -r -n 42 -s /tmp/uuidd.socket
	      uuidd -d -k -s /tmp/uuidd.socket

AUTHOR

       The uuidd daemon was written by Theodore Ts'o <tytso@mit.edu>.

SEE ALSO

       uuid(3), uuidgen(1)

AVAILABILITY

       The uuidd daemon is part of the util-linux package and is available from the Linux Kernel  Archive  <https://www.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux							     July 2014								  UUIDD(8)
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