1. Add the line set -vx in the beginning of the script. The shell script will then start debug output. You can disable the debug message by adding set +vx from that point onwards debug messages will be disabled
   
2. Or doing sh -x shellscriptfilename (best option out the lot)
   
3. This is similar to the first one except it will be applicable for the complete shell script. By adding

   #!/bin/sh -vx

   to the beginning of the shell script
   

#!bin/sh

PROCCHECKDELAY=1
RUNCHECKDELAY=2
PAGEROWS=80
PROCNAME=$1
PROCID=

if [ $# -ne 1 ]
then
        echo give program name to watch;
        exit 1;
fi

stat_process()
{
    PROCID=
    _mypid=
    while [ true ]
    do
        _mypid=`ps -e 2>/dev/null|grep $1|head -n1|awk '{ print $1 }'`;
        if [ -z "$_mypid" ]
        then
            echo "$1 is not running"
        else
            break;
        fi
        echo "recheck after $RUNCHECKDELAY seconds";
        sleep $RUNCHECKDELAY;
    done
    PROCID=$_mypid;
}

i=$PAGEROWS;
while true;
do
stat_process $PROCNAME;
if [ $i -eq $PAGEROWS ] ;
then
        i=0;
        UNIX95= ps -p $PROCID -o vsz,pid,ruser,args 2>/dev/null
else
        UNIX95= ps -p $PROCID -o vsz,pid,ruser,args 2>/dev/null|tail +2
fi
if [ ! -z "$PROCID" ]
then
    i=`expr $i + 1`;
fi
sleep $PROCCHECKDELAY;
done;