$ Linux Command

Processes

pkill

Send signals to processes selected by name or attributes.

processsignalnamestop

Additional Notes

pkill sends a signal to processes selected by name or attributes. It is the action-oriented partner to pgrep: first find matching processes, then signal them.

By default, pkill sends SIGTERM, which asks processes to exit cleanly. Stronger signals such as SIGKILL should be a last resort because they do not allow cleanup.

Syntax

pkill [options] pattern
pkill -SIGNAL [options] pattern

Parameters

  • pattern: Process name pattern to match.
  • SIGNAL: Signal to send, such as TERM, HUP, or KILL.
  • options: Matching controls such as user, full command line, exact name, or parent process.

Common Options

  • -f: Match against the full command line.
  • -u USER: Match processes whose effective user is USER.
  • -U USER: Match processes whose real user is USER.
  • -x: Match the exact process name.
  • -n: Signal only the newest matching process.
  • -o: Signal only the oldest matching process.
  • -P PID: Match children of a parent process.
  • -TERM: Send SIGTERM. This is the default.
  • -HUP: Send SIGHUP, often used to reload daemons.
  • -KILL: Send SIGKILL, forcing termination.

Examples

pgrep -af nginx
sudo pkill nginx

Preview matching processes, then ask them to stop.

pkill -HUP nginx

Send a hangup signal, commonly used for reload-style behavior.

pkill -f "python worker.py"

Match against the full command line.

pkill -u deploy ssh

Signal matching processes owned by deploy.

Practical Notes

  • Always preview broad patterns with pgrep -a or pgrep -af.
  • Avoid pkill -KILL until graceful shutdown fails.
  • Be careful with -f; it can match shell wrappers, scripts, or the command you are using to search.