Group filenames fed to stdin into wildcard patterns (e.g. "*.txt", "*.pdf")

to-file-extension-patterns.awk

#! /usr/bin/awk -f
# Copyright (C) 2009 Sebastian Pipping <[email protected]>
# Licensed under GPLv3 or later
# 2009-04-09
#
# Input
#   one.txt
#   two.pdf
#   three.txt
#
# Output
#   *.txt
#   *.pdf
#
BEGIN {
	FS = "/"
}

{
	dotPartsCount = split($NF, dotParts, "\\.")
	if (dotPartsCount <= 1) {
		next
	}

	fileExtension = dotParts[dotPartsCount]
	if (length(fileExtension) < 1) {
		next
	}

	if (fileExtensionsSeenBefore[fileExtension]) {
		next
	}

	fileExtensionsSeenBefore[fileExtension] = 1
	print "*." fileExtension
}