check access permissions of a file or pathname
#include <unistd.h> intaccess(const char *path, int mode);
function checks the accessibility of the file named by
for the access permissions indicated by
The value of
is the bitwise inclusive
of the access permissions to be checked
.Pf ( Dv R_OK
for read permission,
for write permission, and
for execute/search permission) or the existence test,
All components of the pathname
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,
will always indicate success for
regardless of the actual file permission bits.
if the file has any of the execute bits set and
is not a directory,
will indicate success.
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.
Access to the file is denied if:
A component of the path prefix is not a directory.
A component of a pathname exceeded
characters, or an entire path name exceeded
The named file does not exist.
Too many symbolic links were encountered in translating the pathname.
Write access is requested for a file on a read-only file system.
Write access is requested for a pure procedure (shared text)
file presently being executed.
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
read, write, and execute mode bits, members of the file's group other
than the owner have permission checked with respect to the
mode bits, and all others have permissions checked with respect to the
Write access has been requested and the named file has its immutable
flag set (see
points outside the process's allocated address space.
An I/O error occurred while reading from or writing to the file system.