Shell Programming and Scripting

!#/bin/sh
main="/home/arm/my_folder"

for file in $( find $main -type f | awk -F "/" '{ print $NF}' | cut -c1-3 )
do

case $file in
f01) start=$( find $main -type f -name "$file*" | sort | cut -c13-16 | head -1)
     end=$( find $main -type f -name "$file*" | sort | cut -c13-16 | tail -1 )
     diff=$(( $end - $start ))
     miss=$file*diff*
     echo $miss

f02) start=$( find $main -type f -name "$file*" | sort | cut -c13-16 | head -1)
     end=$( find $main -type f -name "$file*" | sort | cut -c13-16 | tail -1 )
     diff=$(( $end - $start ))
     miss=$file*diff*
     echo $miss
esac

done