fchmodat (2)

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NAME

fchmodat - change permissions of a file relative to a directory file descriptor

SYNOPSIS

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

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

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

fchmodat():

Since glibc 2.10:

_XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L

Before glibc 2.10:

_ATFILE_SOURCE

DESCRIPTION

The fchmodat() system call operates in exactly the same way as chmod(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 chmod(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 chmod(2)).

If pathname is absolute, then dirfd is ignored.

flags can either be 0, or include the following flag:

AT_SYMLINK_NOFOLLOW

If pathname is a symbolic link, do not dereference it: instead operate on the link itself. This flag is not currently implemented.

RETURN VALUE

On success, fchmodat() returns 0. On error, -1 is returned and errno is set to indicate the error.

ERRORS

The same errors that occur for chmod(2) can also occur for fchmodat(). The following additional errors can occur for fchmodat():

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.

ENOTSUP

flags specified AT_SYMLINK_NOFOLLOW, which is not supported.

VERSIONS

fchmodat() 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 fchmodat().

The GNU C library wrapper function implements the POSIX-specified interface described in this page. This interface differs from the underlying Linux system call, which does not have a flags argument.

SEE ALSO

chmod(2), openat(2), 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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