faccessat (2)

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NAME

faccessat - check user's permissions of a file relative to a directory file descriptor

SYNOPSIS

#include <fcntl.h>           /* Definition of AT_* constants */
#include <unistd.h>

int faccessat(int dirfd, const char *pathname, int mode, int flags);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

faccessat():

Since glibc 2.10:

_XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L

Before glibc 2.10:

_ATFILE_SOURCE

DESCRIPTION

The faccessat() system call operates in exactly the same way as access(2), except for the differences described in this manual page.

If the pathname given in pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by access(2) for a relative pathname).

If pathname is relative and dirfd is the special value AT_FDCWD, then pathname is interpreted relative to the current working directory of the calling process (like access(2)).

If pathname is absolute, then dirfd is ignored.

flags is constructed by ORing together zero or more of the following values:

AT_EACCESS

Perform access checks using the effective user and group IDs. By default, faccessat() uses the real IDs (like access(2)).

AT_SYMLINK_NOFOLLOW

If pathname is a symbolic link, do not dereference it: instead return information about the link itself.

RETURN VALUE

On success, (all requested permissions granted) faccessat() returns 0. On error, -1 is returned and errno is set to indicate the error.

ERRORS

The same errors that occur for access(2) can also occur for faccessat(). The following additional errors can occur for faccessat():

EBADF

dirfd is not a valid file descriptor.

EINVAL

Invalid flag specified in flags.

ENOTDIR

pathname is relative and dirfd is a file descriptor referring to a file other than a directory.

VERSIONS

faccessat() was added to Linux in kernel 2.6.16; library support was added to glibc in version 2.4.

CONFORMING TO

POSIX.1-2008.

NOTES

See openat(2) for an explanation of the need for faccessat().

Warning: faccessat() is subject to the same kinds of races as access(2) and euidaccess(3).

Glibc notes

The AT_EACCESS and AT_SYMLINK_NOFOLLOW flags are actually implemented within the glibc wrapper function for faccessat(). If either of these flags are specified, then the wrapper function employs fstatat(2) to determine access permissions.

SEE ALSO

access(2), openat(2), euidaccess(3), credentials(7), path_resolution(7), symlink(7)

COLOPHON

This page is part of release 3.54 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

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