|-s||Single shot - this instructs the program to only return one pid.|
|-c||Only return process ids that are running with the same root directory. This option does not make sense for non-root users, as they will be unable to check the current root directory of processes they do not own.|
|-x||Scripts too - this causes the program to also return process ids of shells running the named scripts.|
|-o||Tells pidof to omit processes with that process id. The special pid %PPID can be used to name the parent process of the pidof program, in other words the calling shell or shell script.|
When pidof is invoked with a full pathname to the program it should find the pid of, it is reasonably safe. Otherwise it is possible that it returns pids of running programs that happen to have the same name as the program youre after but are actually other programs.