Linux pgrep Command: Find Process IDs by Name or Criteria

pgrep finds the process ID of running processes based on conditions such as process name and user. It is a command to check the target PID and does not terminate the process by itself.

What is the pgrep command?

The basic pattern is applied to the process name using a regular expression. Use -x if the entire name must match exactly, and -f to check the full command line. -f can match more broadly, so be sure to verify the results.

Basic syntax

pgrep [option] pattern

Installed implementations and options may vary depending on the distribution. Check the description on the current system with man pgrep.

Examples

Search PID by name

Outputs matching PIDs line by line.

pgrep sshd

View name and PID together

Displays which tasks are selected to reduce mistakes.

pgrep -a sshd

Exact name restriction with user

Narrow the scope to avoid selecting processes with the same name of other users.

pgrep -u alice -x python3

Reason why search results show as PID

pgrep outputs the PID of processes that match the conditions. Using -a shows both the PID and the full command line, making it easier to check.

pgrep -a sshd

Example output (on a system where the process is running):

1234 /usr/sbin/sshd -D

If no lines appear, there may be no matching process, or there could be permission or condition issues. By default, the search targets the process name, and to search the full command line, use -f. Broad patterns may include unexpected processes, so check the results before passing them to termination commands.

Main Options and Format

Precautions when using

The process name may differ from the visible command line, and long names may be affected by the internal limits of the implementation. -f may find more jobs than expected. Before passing the found PID to kill, double-check with ps -p PID -o cmd= or similar.

Frequently Asked Questions

Is it an error if there are no results from pgrep?

It usually means that there are no processes matching the condition and the exit status may not be 0. To confirm the service status, also check the execution time and search conditions.

Official Documentation

You can check the exact behavior of the options and implementation differences in the official pgrep documentation.