|ACCESS(2)||System Calls Manual||ACCESS(2)|
char *path, int
fd, const char
*path, int amode,
access() function checks the accessibility of the file named by path for the access permissions indicated by amode. The amode argument is either the bitwise OR of one or more of the access permissions to be checked (
R_OKfor read permission,
W_OKfor write permission, and
X_OKfor execute/search permission) or the existence test,
F_OK. All components of the pathname path are checked for access permissions (including
The real user ID is used in place of the effective user ID and the real group access list (including the real group ID) is used in place of the effective ID for verifying permission.
If the invoking process has superuser privileges,
access() will always indicate success for
W_OK, regardless of
the actual file permission bits. Likewise, for
if the file has any of the execute bits set and path
is not a directory,
access() will indicate
faccessat() function is equivalent to
access() except that where
path specifies a relative path, the file whose
accessibility is checked is determined relative to the directory associated
with file descriptor fd instead of the current working
faccessat() is passed the special value
AT_FDCWD (defined in
<fcntl.h>) in the
fd parameter, the current working directory is used.
If flag is also zero, the behavior is identical to a
The flag argument is the bitwise OR of zero or more of the following values:
NAME_MAXcharacters, or an entire pathname (including the terminating NUL) exceeded
faccessat() will fail
AT_FDCWDnor a valid file descriptor.
faccessat() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).
access() first appeared as an internal kernel function in Version 1 AT&T UNIX and was reimplemented in C before the release of Version 4 AT&T UNIX. It was first promoted to a system call in the Programmer's Workbench (PWB/UNIX), which was later ported to Version 7 AT&T UNIX and 2BSD.
faccessat() function appeared in
access() kernel function in C.
faccessat() should never be used for actual access control. Doing so can result in a time of check vs. time of use security hole.
|January 19, 2015||OpenBSD-current|