My "Bread and Butter" Process Keep Alive Perl Script.... Post: 302883288

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Top Forums UNIX for Beginners Questions & Answers Answers to Frequently Asked Questions Tips and Tutorials My "Bread and Butter" Process Keep Alive Perl Script.... Post 302883288 by MadeInGermany on Monday 13th of January 2014 05:33:45 AM

01-13-2014

Registered User

Now the haute cuisine:
a shell daemon that polls /proc every 30 seconds:

Code:

#!/bin/bash

# name of the daemon to watch
pname=named
pstart=/usr/sbin/$pname

# this script
me=${0##*/}
# e.g. me=named_watcher.sh

export PATH=/bin:/usr/bin:/usr/sbin:/sbin

# sh sends SIGHUP on exit, we need to continue
trap 'echo "SIGHUP captured"' HUP

# no interactions, log all output and errors
mkdir -p /var/log
exec </dev/null >/var/log/${me%.*}.log 2>&1

# Solaris needs -z option
zopt=`{ zonename; } 2>/dev/null`
zopt=${zopt:+"-z $zopt"}

echo "$me started with pid $$"
sleep 3
# initiate the pid variables
pid=`pgrep $zopt -x $pname`
[ -n "$pid" ] || exec echo "no $pname process - exiting"
echo "$me watching $pname[$pid]"

# endless loop
while :
do
 sleep 30
 if [ \! -d /proc/$pid ]; then
  echo "`date` $me $pid is gone!"
  sleep 1
  echo "starting $pname"
  date
  eval $pstart
  sleep 3
  # renew the pid variables
  pid=`pgrep $zopt -x $pname`
  [ -n "$pid" ] || exec echo "no $pname process - exiting"
  echo "$me watching $pname[$pid]"
 fi
done

The script should be background-started (with &) in the start section of the process (here: named) init script, *after* the process is started.
And killed in the stop section of the process start script, *before* the process is killed.

Last edited by MadeInGermany; 01-13-2014 at 03:46 PM..

MadeInGermany

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LEARN ABOUT SUSE

crontab

CRONTAB(1)						      General Commands Manual							CRONTAB(1)

NAME

       crontab - maintain crontab files for individual users (ISC Cron V4.1)

SYNOPSIS

       crontab [-u user] file
       crontab [-u user] [-l | -r | -e]

DESCRIPTION

       Crontab	is  the  program  used	to install, deinstall or list the tables used to drive the cron(8) daemon in ISC Cron.	Each user can have
       their own crontab, and though these are files in /var, they are not intended to be edited directly.

       If the cron.allow file exists, then you must be listed therein in order to be allowed to use this command.  If the cron.allow file does not
       exist  but  the	cron.deny  file does exist, then you must not be listed in the cron.deny file in order to use this command.  If neither of
       these files exists, only the super user will be allowed to use this command.

       If the -u option is given, it specifies the name of the user whose crontab is to be tweaked.  If this option is not given, crontab examines
       "your"  crontab,  i.e.,	the  crontab of the person executing the command.  Note that su(8) can confuse crontab and that if you are running
       inside of su(8) you should always use the -u option for safety's sake.

       The first form of this command is used to install a new crontab from some named file or standard input  if  the	pseudo-filename  ``-''	is
       given.

       The -l option causes the current crontab to be displayed on standard output.

       The -r option causes the current crontab to be removed.

       The -e option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR environment variables.  After you exit
       from the editor, the modified crontab will be installed automatically.

SEE ALSO

       crontab(5), cron(8)

FILES

       /etc/cron.allow
       /etc/cron.deny

STANDARDS

       The crontab command conforms to IEEE Std1003.2-1992 (``POSIX'').  This new command syntax differs from previous versions of Vixie Cron,	as
       well as from the classic SVR3 syntax.

DIAGNOSTICS

       A fairly informative usage message appears if you run it with a bad command line.

AUTHOR

       Paul Vixie <vixie@isc.org>

4th Berkeley Distribution					 29 December 1993							CRONTAB(1)