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/* Copyright (C) 1992-2020 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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* 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:
__set_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);
}
weak_alias (__flock, flock)
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