NAME
flopen, flopenat
— Reliably open and lock a
file
LIBRARY
library “libutil”
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);
int
flopenat(int
fd, const char
*path, int
flags);
int
flopenat(int
fd, const char
*path, int flags,
mode_t mode);
DESCRIPTION
Theflopen()
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.
The
flopenat()
function is equivalent to the flopen() function
except in the case where the path specifies a relative
path. In this case the file to be opened is determined relative to the
directory associated with the file descriptor fd
instead of the current working directory. If
flopenat() is passed the special value
AT_FDCWD in the fd parameter,
the current working directory is used and the behavior is identical to a
call to flopen().
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
AUTHORS
The flopen function and this manual page
were written by Dag-Erling Smørgrav
<des@FreeBSD.org>.