debian man page for flopen

FLOPEN(3)						   BSD Library Functions Manual 						 FLOPEN(3)

NAME
     flopen -- reliably open and lock a file

LIBRARY
     Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS
     #include <sys/fcntl.h>
     #include <bsd/libutil.h>

     int
     flopen(const char *path, int flags);

     int
     flopen(const char *path, int flags, mode_t mode);

DESCRIPTION
     The flopen() function opens or creates a file and acquires an exclusive lock on it.  It is essentially equivalent with calling open() with
     the same parameters followed by flock() with an operation argument of LOCK_EX, except that flopen() will attempt to detect and handle races
     that may occur between opening / creating the file and locking it.  Thus, it is well suited for opening lock files, PID files, spool files,
     mailboxes and other kinds of files which are used for synchronization between processes.

     If flags includes O_NONBLOCK and the file is already locked, flopen() will fail and set errno to EWOULDBLOCK.

     As with open(), the additional mode argument is required if flags includes O_CREAT.

RETURN VALUES
     If successful, flopen() returns a valid file descriptor.  Otherwise, it returns -1, and sets errno as described in flock(2) and open(2).

SEE ALSO
     errno(2), flock(2), open(2)

AUTHORS
     The flopen function and this manual page were written by Dag-Erling Smorgrav <des@FreeBSD.org>.

BSD
								   June 6, 2009 							       BSD