How to write from n-th row to a file using perl

Question

I have a source text in a file and looking for a code that would take the second (or n-th - in general) row from this file and print to a seperate file.

Any idea how to do this?

Answer 1

You can do this natively in Perl with the flip-flop operator and the special variable $. (used internally by ..), which contains the current line number:

# prints lines 3 to 8 inclusive from stdin:
while (<>)
{
    print if 3 .. 8;
}

Or from the command line:

perl -wne'print if 3 .. 8' < filename.txt >> output.txt

You can also do this without Perl with: head -n3 filename.txt | tail -n1 >> output.txt