Bash One-Liners: Flip a Coin and Generate Random Passwords with /dev/urandom

Sometimes you need quick, cryptographically sound random output directly in your terminal without installing extra tools or opening a browser.

Here are two quick Bash one-liners powered by /dev/urandom.

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1. Flip a Coin in Terminal

Add this quick function to your .bashrc or run it directly in shell:

flipcoin(){ (($(od -An -N1 /dev/urandom) % 2)) && echo heads || echo tails; }

How it works:

• od -An -N1 /dev/urandom reads a single raw byte from the kernel random pool and outputs it as an integer.
• Arithmetic evaluation (( byte % 2 )) yields either 0 (false) or 1 (true), printing heads or tails with zero pseudo-random bias.

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2. Generate a Quick Random String (Temporary Tokens)

To generate a fast, random 12-character alphanumeric string for throwaway testing, salt values, or staging tokens:

tr -dc '_A-Z-a-z-0-9' < /dev/urandom | head -c12; echo

Example output:

k9_xM2Qp7L_w

Security Note on Passwords: While quick 12-character CLI strings are handy for temporary tokens or throwaway hashes, they should never be used as primary account passwords. For real-world security, always follow the NIST SP 800-63B Digital Identity Guidelines — prioritising longer multi-word passphrases (16+ characters), dedicated password managers, and multi-factor authentication (MFA/2FA) over short, manually generated strings.

Bonus: Quick Terminal Wisdom

When you just need a quick chuckle or fortune before logging off SSH:

fortune