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 is ignored for non-root users, as they will be unable to check
the current root directory of processes they do not own.
-q
Quiet mode, suppress any output and only sets the exit status
accordingly.
-w
Show also processes that do not have visible command line (e.g. kernel
worker threads).
-x
Scripts too - this causes the program to also return process id's of
shells running the named scripts.
-o omitpid
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.
-S separator
Use separator as a separator put between pids. Used only when more
than one pids are printed for the program. The -d option is an
alias for this option for sysvinit pidof compatibility.
When using the -x option, pidof only has a simple method for
detecting scripts and will miss scripts that, for example, use env. This
limitation is due to how the scripts look in the proc filesystem.