NAME
flopen - Reliably open and lock a file
LIBRARY
Utility functions from BSD systems (libbsd, -lbsd)
SYNOPSIS
#include <sys/fcntl.h>
#include <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
Smørgrav 〈des@FreeBSD.org〉.