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FLOPEN(3)	       FreeBSD Library Functions Manual		     FLOPEN(3)

NAME
     flopen, flopenat -- Reliably open and lock	a file

LIBRARY
     System Utilities Library (libutil,	-lutil)

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
     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, mail-
     boxes 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 in-
     cludes 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
     errno(2), flock(2), open(2)

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

FreeBSD	13.0			 July 28, 2017			  FreeBSD 13.0
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | AUTHORS

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