[bash][shell] password generator

genpasswd.sh

#!/bin/bash
#+ Password Generator
#+ Author: misha@sawangwan.me

#+ Utilizes the entropy pool to generate a password. If no length
#+ is specified, a default length of 20 is used.

#+ Execute with './' prefix or add to PATH (recommended).

#+ Usage:
#+      genpasswd [pw_length_int_value] OR genpasswd

#+ Example:
#+      ~$ genpasswd 32

#+ More Info: /dev/urandom or /dev/random

len=$1
[ "$1" == "" ] && len=20
RESULT=$(tr -dc A-Za-z0-9_ < /dev/urandom | head -c ${len}; echo)

echo ""
echo "[ +] Password: $RESULT"
echo ""