FACCESSATSection: Linux Programmer's Manual (2)
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NAMEfaccessat - 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);
DESCRIPTIONThe 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:
- Perform access checks using the effective user and group IDs. By default, faccessat() uses the real IDs (like access(2)).
- If pathname is a symbolic link, do not dereference it: instead return information about the link itself.
RETURN VALUEOn success, (all requested permissions granted) faccessat() returns 0. On error, -1 is returned and errno is set to indicate the error.
ERRORSThe 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.
VERSIONSfaccessat() was added to Linux in kernel 2.6.16.
CONFORMING TOThis system call is non-standard but is proposed for inclusion in a future revision of POSIX.1.
NOTESSee openat(2) for an explanation of the need for faccessat().
Glibc NotesThe 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 ALSOaccess(2), openat(2), euidaccess(3), path_resolution(7)