ACCESS(2)		  FreeBSD System Calls Manual		     ACCESS(2)

NAME
     access, eaccess -- check accessibility of a file

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     access(const char *path, int mode);

     int
     eaccess(const char *path, int mode);

DESCRIPTION
     The access() and eaccess() system calls check the accessibility of the
     file named by the path argument for the access permissions indicated by
     the mode argument.  The value of mode is either 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).

     For additional information, see the File Access Permission section of
     intro(2).

     The eaccess() system call uses the effective user ID and the group access
     list to authorize the request; the access() system call uses the real
     user ID in place of the effective user ID, the real group ID in place of
     the effective group ID, and the rest of the group access list.

     Even if a process's real or effective user has appropriate privileges and
     indicates success for X_OK, the file may not actually have execute per-
     mission bits set.	Likewise for R_OK and W_OK.

RETURN VALUES
     Upon successful completion, the value 0 is returned; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

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 255 characters, or

			an entire path name exceeded 1023 characters.

     [ENOENT]		The named file does not exist.

     [ELOOP]		Too many symbolic links were encountered in translat-

			ing 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.

     [EFAULT]		The path argument points outside the process's allo-

			cated address space.

     [EIO]		An I/O error occurred while reading from or writing to

			the file system.

SECURITY CONSIDERATIONS
     The access() system call is a potential security hole due to race condi-
     tions and should never be used.  Set-user-ID and set-group-ID applica-
     tions should restore the effective user or group ID, and perform actions
     directly rather than use access() to simulate access checks for the real
     user or group ID.	The eaccess() system call likewise may be subject to
     races if used inappropriately.

     access() remains useful for providing clues to users as to whether opera-
     tions make sense for particular filesystem objects (e.g. 'delete' menu
     item only highlighted in a writable folder ... avoiding interpretation of
     the st_mode bits that the application might not understand -- e.g. in the
     case of AFS).  It also allows a cheaper file existence test than stat(2).

SEE ALSO
     chmod(2), intro(2), stat(2)

STANDARDS
     The access() system call is expected to conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').

HISTORY
     The access() function appeared in Version 7 AT&T UNIX.

FreeBSD 7.2		       February 11, 2008		   FreeBSD 7.2

NAME - LIBRARY - SYNOPSIS - DESCRIPTION - RETURN VALUES - ERRORS - 
SECURITY CONSIDERATIONS - SEE ALSO - STANDARDS - HISTORY -