ACCESS(2) OpenBSD Programmer's Manual ACCESS(2)NAME
access - check access permissions of a file or pathname
SYNOPSIS
#include <unistd.h>
int
access(const char *path, int mode);
DESCRIPTION
The access() function checks the accessibility of the file named by path
for the access permissions indicated by mode. The value of mode is the
bitwise inclusive OR of the access permissions to be checked (R_OK for
read permission, W_OK for write permission, and X_OK for execute/search
permission) or the existence test, F_OK. All components of the pathname
path are checked for access permissions (including F_OK).
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 R_OK and W_OK, regardless of the actual file
permission bits. Likewise, for X_OK, if the file has any of the execute
bits set and path is not a directory, access() will indicate success.
RETURN VALUES
If path cannot be found or if any of the desired access modes would not
be granted, then a -1 value is returned; otherwise a 0 value is returned.
ERRORS
Access to the file is denied if:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG]
A component of a pathname exceeded {NAME_MAX} characters,
or an entire path name exceeded {PATH_MAX} characters.
[ENOENT] The named file does not exist.
[ELOOP] Too many symbolic links were encountered in translating the
pathname.
[EROFS] Write access is requested for a file on a read-only file
system.
[ETXTBSY] Write access is requested for a pure procedure (shared
text) file presently being executed.
[EACCES] Permission bits of the file mode do not permit the
requested access, or search permission is denied on a
component of the path prefix. The owner of a file has
permission checked with respect to the ``owner'' read,
write, and execute mode bits, members of the file's group
other than the owner have permission checked with respect
to the ``group'' mode bits, and all others have permissions
checked with respect to the ``other'' mode bits.
[EPERM] Write access has been requested and the named file has its
immutable flag set (see chflags(2)).
[EFAULT] path points outside the process's allocated address space.
[EIO] An I/O error occurred while reading from or writing to the
file system.
[EINVAL] An invalid value was specified for mode.
SEE ALSOchmod(2), stat(2)STANDARDS
The access() function conforms to IEEE Std 1003.1-1990 (``POSIX'').
CAVEATSaccess() should never be used for actual access control. Doing so can
result in a time of check vs. time of use security hole.
OpenBSD 4.9 June 10, 2008 OpenBSD 4.9