[OS] Numerical Names

#!/bin/bash
if [ $# -ne 2 ]
then
    echo "USAGE: `basename $0` source_folder some_name.txt"
    exit 1
fi
FROM=$1
result=$2
#recursively list even the deepest documents in the argument#1 folder, then leave only the names of the .txt files that include a \n1n2n3n4\ pattern
files=`ls -R $FROM | grep ^- | awk 'print $9' | grep \'\'[0-9][0-9][0-9][0-9]\'\'.*\.txt$`
for f in $files
do
    #get the 4 digit number in the file's name and print the file's insides in the argument#2 file
    digitcode=` echo $f | awk -F'\' {print $2}`
    echo "============= $digitcode ============="
    echo "cat ${FROM}${f}" >> $result
    echo "============= $digitcode ============="
done
cat $result