uudecode in POSIX sh

uudecode.sh

uudecode_sh() {
	if command -v uudecode >/dev/null; then
		uudecode -p
		return
	fi

	bs=0
	while read -rs t ; do
		if [ "$bs" -eq 1 ] ; then
			if [ "a$t" = "aend" ] ; then
				bs=2
			else
				set $(printf "%d " "'${t:0:1}" "'${t:1:1}" "'${t:2:1}" "'${t:3:1}" "'${t:4:1}" "'${t:5:1}" "'${t:6:1}" "'${t:7:1}" "'${t:8:1}" "'${t:9:1}" "'${t:10:1}" "'${t:11:1}" "'${t:12:1}" "'${t:13:1}" "'${t:14:1}" "'${t:15:1}" "'${t:16:1}" "'${t:17:1}" "'${t:18:1}" "'${t:19:1}" "'${t:20:1}" "'${t:21:1}" "'${t:22:1}" "'${t:23:1}" "'${t:24:1}" "'${t:25:1}" "'${t:26:1}" "'${t:27:1}" "'${t:28:1}" "'${t:29:1}" "'${t:30:1}" "'${t:31:1}" "'${t:32:1}" "'${t:33:1}" "'${t:34:1}" "'${t:35:1}" "'${t:36:1}" "'${t:37:1}" "'${t:38:1}" "'${t:39:1}" "'${t:40:1}" "'${t:41:1}" "'${t:42:1}" "'${t:43:1}" "'${t:44:1}" "'${t:45:1}" "'${t:46:1}" "'${t:47:1}" "'${t:48:1}" "'${t:49:1}" "'${t:50:1}" "'${t:51:1}" "'${t:52:1}" "'${t:53:1}" "'${t:54:1}" "'${t:55:1}" "'${t:56:1}" "'${t:57:1}" "'${t:58:1}" "'${t:59:1}" "'${t:60:1}")
				l=$(($1 -32 & 63 ))
				shift
				while [ $l -gt 0 ] ; do
					i0=$(($1 -32 & 63))
					shift
					i1=$(($1 -32 & 63))
					shift
					i2=$(($1 -32 & 63))
					shift
					i3=$(($1 -32 & 63))
					shift
					if [ $l -gt 2 ] ; then
						echo -ne "\0$(($i0 >> 4))$(($i0 >> 1 & 7))$(($i0 << 2 & 4 | $i1 >> 4))\0$(($i1 >> 2 & 3))$(($i1 << 1 & 6 | $i2 >> 5))$(($i2 >> 2 & 7))\0$(($i2 & 3))$(($i3 >> 3 & 7))$(($i3 & 7))"
						true
					elif [ $l -eq 2 ] ; then
						echo -ne "\0$(($i0 >> 4))$(($i0 >> 1 & 7))$(($i0 << 2 & 4 | $i1 >> 4))\0$(($i1 >> 2 & 3))$(($i1 << 1 & 6 | $i2 >> 5))$(($i2 >> 2 & 7))"
						true
					else
						echo -ne "\0$(($i0 >> 4))$(($i0 >> 1 & 7))$(($i0 << 2 & 4 | $i1 >> 4))"
						true
					fi
					l=$(($l-3))
				done
			fi
		elif [ "${t:0:5}" = "begin" ]; then
			bs=1
		fi
	done
}

This is from a comment in this thread:

http://www.weeklywhinge.com/?p=108