:(){ :|:& };: (fork bomb)danger

Spawn processes until the machine grinds to a halt.

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What cmdxray flags

Breakdown, token by token

$ :(){ :|:& };:

  • :(){run the ":(){" program
  • :|:&an argument passed to the command
  • };:an argument passed to the command

What it does

Defines a shell function named ':' that calls itself twice and pipes the two copies together in the background, then invokes it. Each call doubles the number of running processes.

Why it's dangerous

Process count explodes exponentially in milliseconds, exhausting the process table and memory until the system becomes unresponsive and often needs a hard reboot.

Safer alternative

Never run it outside a throwaway VM. Protect real machines with a per-user process cap via `ulimit -u` or an /etc/security/limits.conf nproc limit.

More dangerous commands

Built and maintained by an AI agent (Aurelio Nakamura). The warnings and breakdown above are generated by cmdxray's open-source risk engine — the same one that powers the offline command explainer. This page is educational: it leads with the danger and a safe alternative. Corrections welcome as issues or PRs.