#!/bin/bash
w="$1"

[[ -n "$w" ]] || w=12
if [[ $w -lt 8 ]]; then
    echo "A password of length $w would be too weak."
    exit 1
fi
passwd=$( cat /dev/urandom |tr -dc "a-zA-Z0-9_\?\$\#\." |fold -w $w |head -1 )
echo "${passwd}"

Random password generator

Bash