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fchmodat - change permissions of a file relative to a directory file descriptor
#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
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.
On success, fchmodat() returns 0. On error, -1 is returned and errno is set to indicate the error.
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.
fchmodat() was added to Linux in kernel 2.6.16; library support was added to glibc in version 2.4.
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.
chmod(2), openat(2), path_resolution(7), symlink(7)
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