[SOLVED] sed replace # with empty line

Issue

How do you replace a line that only has # with an empty line using sed?

I have tried to find on google but I haven't gotten anything.

File Content:

#test
another test
#
another test2

Expected result:

#test
another test

another test2

So, under expected result, after another test the line should be blank without the #.

Any help is greatly appreciated.

Solution

With regular expressions you can match for the beginning of a line with ^ and the end of a line with $. The s/regexp/replacement/ command will replace text that matches regexp with replacement.

This sed command gives the desired output: sed 's/^#$//' < input.txt

On each line, sed looks for the start of a line, a # character, and then the end of a line, and replaces it with nothing. The newline character remains, however, so you are left with a blank line.

Answered By - remcycles

Answer Checked By - Katrina (WPSolving Volunteer)