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FLOPEN(3)		     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,  ex-
     cept  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 work-
     ing 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 re-
     turns -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 ports 15.quarterly	  July 28, 2017 		       FLOPEN(3)

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