pgrep httpd

pgrep
It is a command to search for process ID using a pattern that represents process name, user group, terminal name, etc. among running processes. You can use exetnded regular expression(10th) for patterns.

You can also use the pidof command to find the process ID from the command name.

[vagrant@localhost tests]$ pgrep httpd
1779
2082
2083
2084
2085
2086
2087
2088
2089

この数字はプロセスIDですな。