faccessat — check user's permissions of a file relative to a directory file descriptor
#define _ATFILE_SOURCE #include <fcntl.h> #include <unistd.h>
int
faccessat( |
int | dirfd, |
const char * | pathname, | |
int | mode, | |
int | flags) ; |
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.
On success, (all requested permissions granted)
faccessat
() returns 0. On
error, −1 is returned and errno
is set to indicate the error.
The same errors that occur for access(2) can also occur
for faccessat
(). The following
additional errors can occur for faccessat
():
dirfd
is not
a valid file descriptor.
Invalid flag specified in flags
.
pathname
is
relative and dirfd
is a file
descriptor referring to a file other than a
directory.
This system call is non-standard but is proposed for inclusion in a future revision of POSIX.1.
See openat(2) for an
explanation of the need for faccessat
().
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.
access(2), openat(2), euidaccess(3), credentials(7), path_resolution(7)
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