High performance implementation of a subset of wc -l. Counts the number of \n that appear in a file... and nothing more.

Seems to be nearly 3x faster than wc -l on a 4.2GB CSV with 28 million lines.

Usage:

$ command | line-counter
1234
$ line-counter file1.txt file2.txt
1234 file1.txt
4321 file2.txt