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Full Discussion: The "read" command
Top Forums UNIX for Advanced & Expert Users The "read" command Post 43181 by google on Wednesday 12th of November 2003 04:18:13 PM
Old 11-12-2003
I had created a function awhile back to create a lock file based upon the process number of the shell. The function takes two arguments, one for the name of the log file and the other is $$. The script creates a lock file in the /tmp directory. This file holds the process ID of the shell that created it. If you attempt to execute the script while another instance was running, this function will prevent the second instance from running. Works well for me. Feel free to use if you so choose.
Code:
CreateLockFile () {

unset PROCESS_ID
unset ID
LFILE=${TEMP_PATH}/${1}_${TODAYS_DATE}.LCK
ID=$2

if [ -r ${LFILE} ]
 then
    OPID=`cat ${LFILE}` 2> /dev/null
    if [ -z ${OPID} -eq 0 ] #Make Sure OPID contains a value
     then
	 exit ${FAILURE} "ERROR-APP-->: `basename ${LFILE}` exists but contains no Process ID" | tee -a ${INLOG}
     else
        PROCESS_ID=`ps -p ${OPID} | grep ADD-SCRIPT-NAME-HERE | awk -F" " '{print $1}'  2> /dev/null`

        if [ ${PROCESS_ID} ]  #Lock File is there, check if process is actually running
         then
           echo "WARNING-->: ${1} Script Is Currently Running [PID=${OPID}], Exiting. ${DATE_TIME}" | tee -a ${INLOG}
           exit ${SUCCESS}
        else
	  echo "INFO-->: Old Lock File with PID= [ ${OPID} ] Exists But Process Is Not Running. " >> ${INLOG}
	  echo "INFO-->: Overwriting Old PID with New PID Value of [ ${ID} ] " >> ${INLOG}
          echo "$ID" > ${LFILE}
        fi 
     fi
else
  echo "$ID" > ${LFILE}

    if [ $? -ne 0 ]
      then 
        exit ${FAILURE} "ERROR-APP-->: Could Not Create Lock File - Exiting " | tee -a ${INLOG}
    fi
fi
}

added code tags for readability --oombera

Last edited by oombera; 02-21-2004 at 02:19 AM..
 

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SETUID(1)                                                     General Commands Manual                                                    SETUID(1)

NAME
setuid - run a command with a different uid. SYNOPSIS
setuid username|uid command [ args ] DESCRIPTION
Setuid changes user id, then executes the specified command. Unlike some versions of su(1), this program doesn't ever ask for a password when executed with effective uid=root. This program doesn't change the environment; it only changes the uid and then uses execvp() to find the command in the path, and execute it. (If the command is a script, execvp() passes the command name to /bin/sh for processing.) For example, setuid some_user $SHELL can be used to start a shell running as another user. Setuid is useful inside scripts that are being run by a setuid-root user -- such as a script invoked with super, so that the script can execute some commands using the uid of the original user, instead of root. This allows unsafe commands (such as editors and pagers) to be used in a non-root mode inside a super script. For example, an operator with permission to modify a certain protected_file could use a super command that simply does: cp protected_file temp_file setuid $ORIG_USER ${EDITOR:-/bin/vi} temp_file cp temp_file protected_file (Note: don't use this example directly. If the temp_file can somehow be replaced by another user, as might be the case if it's kept in a temporary directory, there will be a race condition in the time between editing the temporary file and copying it back to the protected file.) AUTHOR
Will Deich local SETUID(1)
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