DragonFly On-Line Manual Pages

FLOPEN(3)             DragonFly Library Functions Manual             FLOPEN(3)

NAME
     flopen -- 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);

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
     Smorgrav <des@FreeBSD.org>.

DragonFly 5.1                    June 6, 2009                    DragonFly 5.1