Question

I’m trying to write a bash script that takes a file name, and return lines that have one word. Here is sample text:

This has more than one word
There
is exactly one word in above line.
         White-space
in the start of the above line doesn't matter.
Need-some-help.

Output:

There
         White-space
Need-some-help.

I’m looking into using a combination SED and Regex.

Note: I cannot using anything else (it has to be a bash script, without custom modules), so suggesting that wouldn’t help.

Answer 1

If words can contain any non-whitespace characters, then:

grep -E '^\s*\S+\s*$'

or

sed -E '/^\s*\S+\s*$/!d'

or

sed -n -E '/^\s*\S+\s*$/p'