mark54g:
Could it be that grep is limited to certain line numbers. When I had close to 1/2 million columns I did not have a problem. BUT, now that I have that many rows, grep does not seem to work.


treedroppings:
Yes I have tried the man pages since I know very little about unix.

why don't you use the below code,

for line in `cat file1`
do
grep -w "$line" file2 >>file3
done

Could you feed it to cat and then use xargs to append the file?

Maybe this will work:

cat file1 | while read LINE
do
grep -e $LINE file2 >> file3
done

mark54g and apsprabhu;

You were very helpful. THANK YOU!. This code works:

file="file1.txt"
while read line
do
grep $line file2 >> file3
done < $file