Question

I tried doing it with cat and then after I type the second file I added | head -$line | tail -1 but it doesn’t work because it performs cat first.

Any ideas? I need to do it with cat or something else.

Answer 1

I’d probably use sed for this job:

line=3
sed -e "${line}r file2" file1

If you’re looking to overwrite file1 and you have GNU sed, add the -i option. Otherwise, write to a temporary file and then copy/move the temporary file over the original, cleaning up as necessary (that’s the trap stuff below). Note: copying the temporary over the file preserves links; moving does not (but is swifter, especially if the file is big).

line=3
tmp="./sed.$$"
trap "rm -f $tmp; exit 1" 0 1 2 3 13 15
sed -e "${line}r file2" file1 > $tmp
cp $tmp file1
rm -f $tmp
trap 0