cosmopolitan/libc/calls/openat.c

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "libc/calls/calls.h"
#include "libc/calls/internal.h"
#include "libc/sysv/consts/at.h"
#include "libc/sysv/errfuns.h"
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/**
* Opens file, the modern way.
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*
* @param dirfd is normally AT_FDCWD or an open relative directory thing
* @param file is a UTF-8 string, preferably relative w/ forward slashes
* @param flags should be O_RDONLY, O_WRONLY, or O_RDWR, and can be or'd
* with O_CREAT, O_TRUNC, O_APPEND, O_EXCL, O_CLOEXEC, O_TMPFILE
* @param mode is an octal user/group/other permission signifier, that's
* ignored if O_CREAT or O_TMPFILE weren't passed
* @return number needing close(), or -1 w/ errno
* @asyncsignalsafe
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*/
int openat(int dirfd, const char *pathname, int flags, ...) {
va_list va;
unsigned mode;
va_start(va, flags);
mode = va_arg(va, unsigned);
va_end(va);
if (!pathname) return efault();
if (dirfd == AT_FDCWD) {
return open(pathname, flags, mode);
} else {
return openat$sysv(dirfd, pathname, flags, mode);
}
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}