generate random strings

random-string.sh

#!/usr/bin/env bash
##
##  Usage: random-string [length] [lines] [pattern]
##    Generates a random string using /dev/urandom
##
##  Default:
##    length: 32
##     lines: 1
##   pattern: 'a-zA-Z0-9'
##
##  Examples:
##    > random-string
##    qW8uYmDZ3Z3Yv811HuZlketieWpCLWtW
##
##    > random_string 40 3
##    HXR5yc32y01dfE3Db60X1g43qgYaZNdizcYOX8N4
##    jQTKKdgPti1pOpkwsxzKG0wxQkKV1WWp0QAkd3kv
##    grpLs2CO8X5g741BCWY7JPAs3EwSOodYXLZeezTY
##
##    > random_string 40 1 'a-z'
##    ejobgsixxrwhgigwmccryezbzisgwvprrzxflwce
##
##    > random_string 40 1 '0-9'
##    4576764404246601394987469772076603834655
##

LC_CTYPE=C tr -dc "${3:-'a-zA-Z0-9'}" < /dev/urandom \
  | fold -w "${1:-32}" \
  | head -n "${2:-1}"

# REFERENCES
#  http://www.2uo.de/myths-about-urandom/
#  http://stackoverflow.com/questions/101362/how-do-you-generate-passwords
#  https://gist.github.com/earthgecko/3089509