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.\"     @(#)access.2	8.2 (Berkeley) 4/1/94
.\"
.Dd April 1, 1994
.Dt ACCESS 2
.Os
.Sh NAME
.Nm access
.Nd check access permissions of a file or pathname
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn access "const char *path" "int mode"
.Sh DESCRIPTION
The
.Fn access
function checks the accessibility of the file named by
.Fa path
for the access permissions indicated by
.Fa mode .
The value of
.Fa mode
is the bitwise inclusive
.Tn OR
of the access permissions to be checked
.Pf ( Dv R_OK
for read permission,
.Dv W_OK
for write permission, and
.Dv X_OK
for execute/search permission) or the existence test,
.Dv F_OK .
All components of the pathname
.Fa path
are checked for access permissions (including
.Dv F_OK ) .
.Pp
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.
.Pp
Even if a process has appropriate privileges and indicates success for
.Dv X_OK ,
the file may not actually have execute permission bits set.
Likewise for
.Dv R_OK
and
.Dv W_OK .
.Sh RETURN VALUES
If
.Fa 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.
.Sh ERRORS
Access to the file is denied if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded
.Dv {NAME_MAX}
characters, or an entire path name exceeded
.Dv {PATH_MAX}
characters.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EROFS
Write access is requested for a file on a read-only file system.
.It Bq Er ETXTBSY
Write access is requested for a pure procedure (shared text)
file presently being executed.
.It Bq Er 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
.Dq owner
read, write, and execute mode bits, members of the file's group other
than the owner have permission checked with respect to the
.Dq group
mode bits, and all others have permissions checked with respect to the
.Dq other
mode bits.
.It Bq Er EFAULT
.Fa path
points outside the process's allocated address space.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er EINVAL
An invalid value was specified for
.Ar mode .
.El
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr stat 2
.Sh STANDARDS
The
.Fn access
function conforms to
.St -p1003.1-90 .
.Sh CAVEATS
.Fn access
is a potential security hole and should never be used.