#!/usr/bin/env sh

which() {
    local path

    if [ $# -gt 0 ]; then
        for path in $(IFS=: && echo ${PATH}); do
            [ -x "${path}/${1}" ] && echo -n "${path}/${1}" && return 0
        done

        return 1
    else
        echo >&2 "Usage: which COMMAND"
        echo >&2 "Writes the full path of COMMAND to standard output"

        return 255
    fi
}