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timeout Command Cheat Sheet

timeout runs a command with a time limit. If the command runs longer than the specified duration, timeout kills it.

Synopsis

timeout [OPTION] DURATION COMMAND [ARG]...

Basic Usage

Limit Execution Time

Run ping for 5 seconds, then kill it.

timeout 5 ping google.com

With Units

  • s: seconds (default)
  • m: minutes
  • h: hours
  • d: days
timeout 1m script.sh

Signals

Custom Signal (-s)

By default, timeout sends SIGTERM. You can send SIGKILL (9) or SIGINT (2).

timeout -s SIGKILL 10s hung_process

Kill After Timeout (-k)

If the command catches SIGTERM and refuses to die, send SIGKILL after a grace period.

# Send SIGTERM after 10s. If still running after 15s (10+5), send SIGKILL.
timeout -k 5s 10s long_process.sh

Exit Status

  • 124: Command timed out.
  • 125: internal error.
  • 126: command found but cannot be invoked.
  • 127: command not found.
  • Other: The exit status of the command itself (if it finished in time).

Preserve Status (--preserve-status)

By default, timeout returns 124 on timeout. Use this to return the command's own exit status (even if killed).

timeout --preserve-status 5s command

Notes

  • Foreground: timeout normally runs in the background. Use --foreground if the command needs to interact with the TTY.