Get the nth line from the bottom "safely"

Question

Given a file:

dept4.abc.edu
dept3.abc.edu
dept2.abc.edu
dept1.abc.edu

I know how to get the 3rd line from the bottom using the command:

tail -3 file | head -1

This is okay as long as the file length is greater or equal 3 lines [ $(wc -l < file) -gt 3 ]. So tail -4 file | head -1 is still fine, but tail -5 file | head -1 is not what I really want.

I am wondering if there is a better way and cleaner way in getting the nth line safely, by saying safely I mean if it is not there, just return me an empty string or error. Any ideas?

if you know the line number, you can use `sed 'NUMq;d' file` — Fredrik Pihl, Jun 17 '14 at 15:03
...or reverse the file using `tac` first, and then use `sed '3q;d'` — Fredrik Pihl, Jun 17 '14 at 15:05
Thanks, it works! `tac file | sed '5q;d'` (given there must be an empty line in the end of the file) — Daniel, Jun 17 '14 at 15:09

score 4 · Accepted Answer · edited May 23 '17 at 12:27

4

There are many ways to get the nth line from a file, see e.g. Bash tool to get nth line from a file

The simplest way to get the nth line from the bottom of the file is to use tac (inverse of cat) to reverse the file. Something like this:

tac file | sed '3q;d'

edited May 23 '17 at 12:27

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answered Jun 17 '14 at 15:13

Fredrik Pihl

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Get the nth line from the bottom "safely"

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