Compare with "gr what-is-it -r here-you-go". I do not have to remember all that argument hell.

Probably slower than the go version, but more flexible since you have more over the files processed.

        # bash
	# find/replace
	function fr {
		local pattern=$1
		local replacement=$2
		local program

		if [[ -z "$replacement" ]]
		then
			program="grep $pattern"
		else
			program="sed -i s/$pattern/$replacement/g"
		fi

		while read line
		do
			$program "$line"
		done
	}

	# usage
	find . | fr find-this
	find . | fr replace-this with-that

Well, one can write an one-line shell alias (or script) instead of reinventing the wheel by rewriting the whole thing anew in Go. (Which is certainly good as learning experience for Go, but the end result is easier to achieve with the shell)

When you start adding coloring, nice output, .hg/.gitignore support, it becomes just a big mess. Been there, done that.

coloring is already supported by grep, .hg/.gitignore support is just a few lines

Just do it then.

A C wrapper around `sed -e "s/what-is-it/here-you-go/" would be a little more efficient, and a lot simpler. Reinventing the wheel is bad for X+Y+Z reasons, where X, Y and Z are the bugs, options, and features in the last wheel.