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/* Copyright (C) 1992, 1995, 1996, 1997 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/* This file implements the `flock' function in terms of the POSIX.1 `fcntl'
locking mechanism. In 4BSD, these are two incompatible locking mechanisms,
perhaps with different semantics? */
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/file.h>
/* Apply or remove an advisory lock, according to OPERATION,
on the file FD refers to. */
int flock( int fd, int operation)
{
struct flock lbuf;
switch (operation & ~LOCK_NB) {
case LOCK_SH:
lbuf.l_type = F_RDLCK;
break;
case LOCK_EX:
lbuf.l_type = F_WRLCK;
break;
case LOCK_UN:
lbuf.l_type = F_UNLCK;
break;
default:
errno = EINVAL;
return -1;
}
lbuf.l_whence = SEEK_SET;
lbuf.l_start = lbuf.l_len = 0L; /* Lock the whole file. */
return fcntl(fd, (operation & LOCK_NB) ? F_SETLK : F_SETLKW, &lbuf);
}
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