#!/bin/sh

if [ "$1" = "-n" ] ; then
    template='[:alnum:]'
    shift
else
    template='[:alnum:]+=\-_'
fi


if [ -z "$1" ] ; then
    echo "usage: $0 [-n] length" >&2
    exit 1
fi

LC_ALL=C tr -dc "$template" </dev/urandom | \
    fold -w$1 | head -n1