FLOPEN(3) BSD Library Functions Manual FLOPEN(3)NAMEflopen — 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 an fcntl() F_SETLK or F_SETLKW operation with
lock type F_WRLCK, 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 fcntl(2) and open(2).
SEE ALSOerrno(2), fcntl(2), open(2)HISTORY
The flopen() function first appeared in FreeBSD 6.3.
AUTHORS
The flopen function and this manual page were written by Dag-Erling
Smørgrav ⟨des@FreeBSD.org⟩.
BSD December 27, 2008 BSD
