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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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SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME
script -- make typescript of terminal session SYNOPSIS
script [-akq] [-t time] [file [command ...]] DESCRIPTION
The script utility makes a typescript of everything printed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1). If the argument file is given, script saves all dialogue in file. If no file name is given, the typescript is saved in the file typescript. If the argument command is given, script will run the specified command with an optional argument vector instead of an interactive shell. The following options are available: -a Append the output to file or typescript, retaining the prior contents. -k Log keys sent to program as well as output. -q Run in quiet mode, omit the start and stop status messages. -t time Specify time interval between flushing script output file. A value of 0 causes script to flush for every character I/O event. The default interval is 30 seconds. The script ends when the forked shell (or command) exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-D (if ignoreeof is not set) for the C-shell, csh(1)). Certain interactive commands, such as vi(1), create garbage in the typescript file. The script utility works best with commands that do not manipulate the screen. The results are meant to emulate a hardcopy terminal, not an addressable one. ENVIRONMENT
The following environment variable is utilized by script: SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most shells set this variable automatically). SEE ALSO
csh(1) (for the history mechanism). HISTORY
The script command appeared in 3.0BSD. BUGS
The script utility places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects. It is not possible to specify a command without also naming the script file because of argument parsing compatibility issues. When running in -k mode, echo cancelling is far from ideal. The slave terminal mode is checked for ECHO mode to check when to avoid manual echo logging. This does not work when in a raw mode where the program being run is doing manual echo. BSD
January 22, 2004 BSD
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