Hello there.

I'm trying do make a script capable of verifying if a given script is running at the moment in the environment, and if does, forbid it to execute.

So, I've coded this so far:

#!/bin/ksh
set CUR_SHELL="/bin/ksh"
set V1="VAR1"
set V2="VAR2"

ps -e -o args | grep "$CUR_SHELL $1" | tr -s " " | cut -d" " -f1 | 
while read -r V1 V2
do
    if [ "$V1" = "$CUR_SHELL" ]; then
        echo "Error - Program is already running."
        echo "V1 -> $V1"
        exit 1
    fi 
done
echo "V1 -> $V1"
echo "V2 -> $V2"

if [ -z "$V1" ]; then
    echo "V1 IS NULL"
fi

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.

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
}

Don't do:
set var="string"
in ksh. It's just
var="string"

Using set doesn't make the code more readable ?

Well, I've heard about some solutions using a temporary file as well, but
my "boss" said to avoid this option if I can.

So I'm trying to figure out a different solution...
But I didn't thaught about using the PID ... it may be a good point...

Thanks anyway !

Using set makes the code wrong.
var="string"
will set $var to the value "string". On the other hand,
set var=string
does not affect a variable called var. Instead it clobbers the arguments and sets $1 to the value "var=string". Try it,
set var="string"
echo $var
echo $1

So...
What's actually the purpose of the set command ?