pidof

Overview

pidof prints the PIDs of running programs matched by name. It is a quick alternative to pgrep -x for simple lookups and remains common in init scripts and one-liners. For flexible pattern matching, prefer pgrep.

Syntax

pidof [options] program [program...]

Common Options

Option	Description
-s	Single PID only (first/one)
-c	Only processes with same root (chroot)
-x	Also match scripts (by script name)
-o omitpid	Omit PID(s); often -o %PPID or self
-z	Skip zombies (when supported)

Options vary slightly between implementations (sysvinit-utils vs others).

Examples with Explanations

Basics

pidof nginx
pidof sshd
pidof bash

Single PID

pidof -s nginx
kill -HUP "$(pidof -s nginx)"

Scripts

pidof -x backup.sh
pgrep -f backup.sh          # often clearer for scripts

Existence gate

if pidof dockerd >/dev/null; then
  echo docker running
fi

Omit PIDs

pidof -o $$ bash            # other bashes, not this script’s shell if named bash
pidof -o %PPID nginx

Feed to kill

kill $(pidof myapp)
# safer with pgrep:
pgrep -x myapp | xargs -r kill

Compare tools

pidof nginx
pgrep -x nginx
pgrep -a nginx
systemctl status nginx

Notes / Pitfalls

• Name matching is not always exact across threads/workers — verify with ps.
• Multiple PIDs print space-separated — quote carefully in scripts.
• Race: process may exit between pidof and kill.
• Containers: only sees processes in the same PID namespace.
• Prefer systemctl for supervised services instead of raw PID kills.

2026-relevant notes

• systemd units: systemctl show -p MainPID nginx.
• pgrep/pkill from procps are more expressive for modern scripts.
• Rootless stacks may have multiple same-named processes per user — be specific.

Related Commands

• pgrep / pkill — pattern match / signal
• kill / killall — signal by PID / name
• ps — detailed process list
• systemctl — service PIDs
• pidwait / pwait — wait for PID exit (if installed)

Additional Resources

• man pidof