a daemon pid file
() writes a file containing the process ID
of the program to the /var/run
file name has the form /var/run/basename.pid
argument is NULL,
will determine the program name and use
The pid file can be used as a quick reference if the process needs to be sent a
signal. When the program exits, the pid file will be removed automatically,
unless the program receives a fatal signal.
() returns 0 on success and -1 on failure.
function call appeared in
() is called multiple times with
, only the last pidfile
will be removed upon exit.
() to ensure the pidfile is unlinked at
program exit. However, programs that use the
() function (for example, in signal
handlers) will not trigger this behaviour.