A very simple command, pgrep, can quickly locate the PID of a process that contains a keyword; using this command, no longer use PS aux to go to which process PID
-l parameter, which can display PID and process name; no-l show PID only, who knows what process PID
# pgrep HTTPD
# pgrep-l HTTPD
Of course, the use of pgrep is not only so, interested students can study, but in my case, the application of a limited scope, in line with the principle of application, did not do too much study of pgrep.