Shell Programming and Scripting

file1.txt (There are no duplicates in this file)
1234
3232
4343
3435
6564
6767
1213

file2.txt 
1234,wq,wewe,qwqw
1234,as,dfdf,dfdf
4343,asas,sdds,dsds
6767,asas,fdfd,fdffd

output
file3.txt
3232
3435
6564
1213

awk -F, 'FNR==NR {f2[$1];next} !($0 in f2)' file2.txt file1.txt

Got the below error
awk: Input line cannot be longer than 3,000 bytes.

while read line
do
	search_count=`grep -c $line file2.txt`
	echo $grepped
	if [ $grepped -eq 0 ]; then
       echo $line >> unfetch.txt
	fi
done < file1.txt

cut -d , -f1 file2 | awk 'FNR==NR {f2[$1];next} !($0 in f2)' - file1

sort file1.txt > tmp1
cut -d, -f1 file2.txt | sort | uniq > tmp
diff tmp tmp1 | grep '>' | sed -e 's/> //g' > file3.txt
rm -f tmp1 tmp