How can I replace multiple empty lines with a single empty line in bash?

Question

I have a file that contains:

something



something else

something else again

I need a bash command, sed/grep w.e that will produce the fo

Answer 1

Use awk:

awk '{ /^\s*$/?b++:b=0; if (b<=1) print }' file

Breakdown:

/^\s*$/?b++:b=0
    - ? :       the ternary operator
    - /^\s*$/   matches a blank line
    - b         variable that counts consecutive blank lines (b++).
                however, if the current line is non-blank, b is reset to 0.


if (b<=1) print
    print if the current line is non-blank (b==0)
          or if there is only one blank line (b==1).

By adjusting the regex, you can generalize it to other scenarios like squeezing multiple blank lines (">") in email: https://stackoverflow.com/a/59189823/12483961