Generate random strings

(Or at least pseudorandom strings…)

Base64 character set, with openssl

openssl rand -base64 LENGTH | tr -d '\n'

tr -d '\n' strips the trailing newline

Ex:

openssl rand -base64 18 | tr -d '\n'
# aHT+O9wbqNCDpBE5wD8cYvIw

With typical shell utils only

Basic format

tr -dc 'CHARACTER_SET' < /dev/urandom | head -c LENGTH

Passing -dc drops all chars not in the designated set

Examples

20-character alpha-numeric password

tr -dc '[:alnum:]' < /dev/urandom | head -c 20
# FIlex5AKDDacPkgQ2L7M

10-digit random US phone number I guess

tr -dc '[:digit:]' < /dev/urandom | head -c 10
# 5392531251

30-character password with letters, numbers, and typical punctuation characters (sans-quotes)

tr -dc '[:alnum:]!#%&()*+,-./:;<=>?@[\]^_{|}~' < /dev/urandom | head -c 30
# k}FrTv!XdZ%BOKYhX_F7^%kzfby!]h