pgrep searches through the currently running processes, pkill will send the specified signal (by default SIGTERM) to each process instead of listing them on stdout.
Syntax pgrep [-flvx] [-d delimiter] [-n|-o] [-P ppid,...] [-g pgrp,...] [-s sid,...] [-u euid,...] [-U uid,...] [-G gid,...] [-t term,...] [pattern] pkill [-signal] [-fvx] [-n|-o] [-P ppid,...] [-g pgrp,...] [-s sid,...] [-u euid,...] [-U uid,...] [-G gid,...] [-t term,...] [pattern] Key pattern An Extended Regular Expression to match process names or command lines. -d delimiter Set the string used to delimit each process ID in the output (by default a newline). (pgrep only.) -f The pattern is normally only matched against the process name. When -f is set, the full command line is used. -g pgrp,... Only match processes in the process group IDs listed. Process group 0 is translated into pgrep's or pkill's own process group. -G gid,... Only match processes whose real group ID is listed. Either the numerical or symbolical value may be used. -l List the process name as well as the process ID. (pgrep only.) -n Select only the newest (most recently started) of the matching processes. -o Select only the oldest (least recently started) of the matching processes. -P ppid,... Only match processes whose parent process ID is listed. -s sid,... Only match processes whose process session ID is listed. Session ID 0 is translated into pgrep's or pkill's own session ID. -t term,... Only match processes whose controlling terminal is listed. The terminal name should be specified without the "/dev/" prefix. -u euid,... Only match processes whose effective user ID is listed. Either the numerical or symbolical value may be used. -U uid,... Only match processes whose real user ID is listed. Either the numerical or symbolical value may be used. -v Negates the matching. -x Only match processes whose name (or command line if -f is specified) exactly match the pattern. -signal Defines the signal to send to each matched process. Either the numeric or the symbolic signal name can be used. (pkill only.)
All the criteria have to match.
For example, pgrep -u root sshd will only list the processes called sshd AND owned by root.
On the other hand, pgrep -u root,daemon will list the processes owned by root OR daemon.
Example 1: Find the process ID of the named daemon:
$ pgrep -u root named
Example 2: Make syslog reread its configuration file:
$ pkill -HUP syslogd
Example 3: Give detailed information on all xterm processes:
$ ps -fp $(pgrep -d, -x xterm)
Example 4: Make all netscape processes run nicer:
$ renice +4 'pgrep netscape'
1. One or more processes matched the criteria.
2. No processes matched.
3. Syntax error in the command line.
4. Fatal error: out of memory etc.
“Somebody should tell us, right at the start of our lives, that we are dying. Then we might live life to the limit, every minute of every day. Do it! I say. Whatever you want to do, do it now! There are only so many tomorrows” - Pope Paul VI
ps - List running processes (returns PID)
kill - Stop a process from running
killall - Kill processes by name
bg - Put a process in the background
fg - Put a process in the foreground
Equivalent Windows command: KILL - Remove a program from memory