Shell Programming and Scripting

#!/bin/ksh
while hour=$(date +%H)
do      if [ $hour -ge 6 ] && [ $hour -lt 19 ]
        then    exit 20
        fi
        all_found=1
        while IFS="," read group file X
        do      if [ -f "$file" ]
                then    time=$(ls -l "$file" | nawk '{print $6,$7,$8}')
                        printf "%s,%s,%s,YES\n" "$group" "$file" "$time"
                else    all_found=0
                        printf "%s,%s,NO\n" "$group" "$file" 
                fi
        done < list.txt
        if [ $all_found -eq 1 ]
        then    exit 0
        else    sleep 900
        fi
done