access(2) - NetBSD Manual Pages

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ACCESS(2)                 NetBSD Programmer's Manual                 ACCESS(2)


NAME

     access - check access permissions of a file or pathname


LIBRARY

     Standard C Library (libc, -lc)


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) are used in place of the
     effective ID for verifying permission.

     If a process has super-user privileges and indicates success for R_OK or
     W_OK.  the file may not actually have read or write permission bits set.
     If a process has super-user privileges and indicates success for X_OK, at
     least one of the user, group, or other execute bits is set.  (However,
     the file may still not be executable.  See execve(2).)


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 request-
                   ed 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 exe-
                   cute 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 re-
                   spect to the ``other'' mode bits.

     [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.


SEE ALSO

     chmod(2), execve(2), stat(2)


STANDARDS

     The access() function conforms to IEEE Std 1003.1-1990 (``POSIX'').


CAVEAT

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

NetBSD 1.5                       April 1, 1994                               2