Gnarly Sed

Last night I wrote a script to compute a Table of Contents for Markdown documents and insert it into the document. It handles both syntaxes for heading blocks. (I also wrote a git hook to run this script on commit.)

It contains what is probably the most gnarly sed script I’ve ever written. I am so glad we’ve moved beyond sed.

(However, sed is also everywhere without having to install other tools on almost any system, which is why I used sed and awk instead of something more modern.)

Anyway, for your reading pleasure (or torture), here it is:

/^#/ {
        s/^\(#*\) */\1|/
        p
        }
        /^--*/ {
        x
        s/^/##|/
        p
        }
        /^==*/ {
        x
        s/^/#|/
        p
        }
        h