Getting the line number of the nth match

If we're aiming to find the line number of the nth match, we might think to use grep and parse it's output.

Take this markdown document for example, where we want to find the line number of the second occurrence of ---:

input.md

---
title: some frontmatter
--- <-- We want the line number of this line

# Some content

grep '^---$' -m 2 -n input.md | tail -1 | cut -d ":" -f 1

This gets the job done, but it invokes a number of subshells, reducing performance. An alternative using awk may be less I/O intensive:

awk '/^---$/ && (++c == 2) { print NR; exit }' input.md

Source