#!/bin/zsh
# crontab usage:
#* * * * * minutemaid 9 cd repo; git pull # runs every nine minutes

local offset=0 opt=
while getopts 'o:h' opt; do
    case $opt in
    o)  offset="$OPTARG";;
    ?)  local fd=0
        [ $opt = h ] && fd=0 || fd=2
        echo -E "usage: $0 [-o offset] {interval} [{command} [{args...}]]" >&$fd
        [ $opt = h ] && return 0 || return 1;;
    esac
done
shift $((OPTIND-1))

local interval="${1:?no interval specified}"
shift

local sec="$(date +%s)"
let min=sec/60+offset
let mod=min%interval
if [ $# -gt 0 ]; then
    local cmd="${1}"
    shift

    [ $mod -eq 0 ] && "$cmd" "$@"
else
    [ $mod -eq 0 ] && return 0 || return 1
fi