libutil.h> (See libbsd(7) for include usage.)
flopen(const char *path, int flags);
flopen(const char *path, int flags, mode_t mode);
flopenat(int fd, const char *path, int flags);
flopenat(int fd, const char *path, int flags, mode_t mode);
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
open(), the additional mode argument is required if flags includes
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() returns a valid file descriptor. Otherwise, it returns -1, and sets errno as described in flock(2) and open(2).
errno(2), flock(2), open(2)
The flopen function and this manual page were written by Dag-Erling Smørgrav <des@FreeBSD.org>.