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access(2)                   BSD System Calls Manual                  access(2)


NAME

     access, faccessat -- check access permissions of a file or pathname


SYNOPSIS

     #include <unistd.h>

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

     int
     faccessat(int fd, const char *path, int mode, int flag);


DESCRIPTION

     The access() function checks the accessibility of the file named by path
     for the access permissions indicated by amode.  The value of amode 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) are used in place of the
     effective ID for verifying permission.

     The faccessat() system call is equivalent to access() except in the case
     where path specifies a relative path.  In this case the file whose acces-
     sibility is to be determined is located relative to the directory associ-
     ated with the file descriptor fd instead of the current working direc-
     tory.  If faccessat() is passed the special value AT_FDCWD in the fd
     parameter, the current working directory is used and the behavior is
     identical to a call to access().  Values for flag are constructed by a
     bitwise-inclusive OR of flags from the following list, defined in
     <fcntl.h>:

     AT_EACCESS
             The checks for accessibility are performed using the effective
             user and group IDs instead of the real user and group ID as
             required in a call to access().

     Even if a process has appropriate privileges and indicates success for
     X_OK, the file may not actually have execute permission bits set.  Like-
     wise for R_OK and W_OK.


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 and the global integer variable
     errno is set to indicate the error.  Otherwise, a 0 value is returned.


ERRORS

     Access to the file is denied if:

     [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.

     [EFAULT]           Path points outside the process's allocated address
                        space.

     [EINVAL]           An invalid value was specified for amode.

     [EIO]              An I/O error occurred while reading from or writing to
                        the file system.

     [ELOOP]            Too many symbolic links were encountered in translat-
                        ing the pathname.

     [ENAMETOOLONG]     A component of a pathname exceeded {NAME_MAX} charac-
                        ters, or an entire path name exceeded {PATH_MAX} char-
                        acters.

     [ENOENT]           The named file does not exist.

     [ENOTDIR]          A component of the path prefix is not a directory.

     [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 that is presently being executed.

     Also, the faccessat() system call may fail if:

     [EBADF]            The path argument does not specify an absolute path
                        and the fd argument is neither AT_FDCWD nor a valid
                        file descriptor.

     [EINVAL]           The value of the flag argument is not valid.

     [ENOTDIR]          The path argument is not an absolute path and fd is
                        neither AT_FDCWD nor a file descriptor associated with
                        a directory.


SEE ALSO

     chmod(2), stat(2)


STANDARDS

     The access() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1'').  The
     faccessat() system call is expected to conform to POSIX.1-2008 .


CAVEAT

     access() is a potential security hole and should never be used.

4th Berkeley Distribution        April 1, 1994       4th Berkeley Distribution

OS X 10.10 - Generated Thu Oct 30 08:00:12 CDT 2014