How to unpack a package's sourcecode

To unpack a package into current directory, one may use following script.

#!/bin/sh

# Unpacks the target
unpack () {
	local curSrc="$1"
	local friendlyName="$2"
	test -z "$curSrc" && return 2
	case "$curSrc" in
		*.tar) tar xvf $curSrc ;;
		*.tar.gz|*.tgz|*.tar.Z) gzip -d < $curSrc | tar xvf - ;;
		*.tar.bz2|*.tbz2) bzip2 -d < $curSrc | tar xvf - ;;
		*.zip) unzip $curSrc ;;
		*) if test -d "$curSrc" ; then
				if test -n "$friendlyName" ; then
					cp -prvd "$curSrc" "./$friendlyName"
				else
					cp -prvd "$curSrc" .
				fi
			else
				echo "source archive $curSrc has unknown type" >&2
				return 1
			fi ;;
	esac
}

# Fetches the tarball into a store
fetch () {
	nix-build "<nixpkgs>" -A $1.src --show-trace
}

unpack `fetch $1` $1

Copy it to a directory which is listed in the PATH, name it nix-unpack. Then, to obtain, say, Midnight Commander's sources, run:

nix-unpack mc

Thanks goes to Mark Weber, Llu�s Batlle, Yury G. Kudrya