pkill command sends any specified signal, or by default the termination signal, to processes based on a matching pattern. Similar to the pgrep command, but actually sends a signal instead of printing to stdout. For example, if you start top in one terminal, and then issue pkill top in another terminal, you’ll see that top terminates. The command matched a name pattern rather than a process ID.
Syntax
The syntax of this command is:
# pkill [options] {pattern}
The kill and pkill commands send signals to processes directing them to terminate. Each signal has a number, name, and an associated event. Below are some of the most commonly used signals with their functionalities.
| Number | Name | Description |
|---|---|---|
| 1 | SIGHUP | Reload Configuration File |
| 2 | SIGINT | Interrupt by keyboard (ctrl+c) |
| 9 | SIGKILL | kill process |
| 15 | SIGTERM | End process immediately. (Terminate a process in controlled manner so cleanup is possible) |
| 18 | SIGCONT | Continue the process stopped with STOP |
| 19 | STOP | Stop process |
pkill Command Examples
1. Kill all processes which match:
# pkill "process_name"
2. Kill all processes which match their full command instead of just the process name:
# pkill -f "command_name"
3. Force kill matching processes (can’t be blocked):
# pkill -9 "process_name"
4. Send SIGUSR1 signal to processes which match:
# pkill -USR1 "process_name"
5. Kill the main `firefox` process to close the browser:
# pkill --oldest "firefox"
6. The pkill command can be used to send a signal to processes running from a specific controlling Terminal, as shown in the following syntax:
# pkill -t [terminal_name] -U UID [command_pattern]