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RCMD(3)                    Library Functions Manual                    RCMD(3)

     rcmd, orcmd, rcmd_af, orcmd_af, rresvport, rresvport_af, iruserok,
     ruserok, iruserok_sa -- routines for returning a stream to a remote

     Standard C Library (libc, -lc)

     #include <&lt;unistd.h>&gt;

     rcmd(char **ahost, int inport, const char *locuser, const char
     *remuser, const char *cmd, int *fd2p);

     orcmd(char **ahost, int inport, const char *locuser, const char
     *remuser, const char *cmd, int *fd2p);

     rcmd_af(char **ahost, int inport, const char *locuser, const char
     *remuser, const char *cmd, int *fd2p, int af);

     orcmd_af(char **ahost, int inport, const char *locuser, const char
     *remuser, const char *cmd, int *fd2p, int af);

     rresvport(int *port);

     rresvport_af(int *port, int family);

     iruserok(uint32_t raddr, int superuser, const char *ruser, const char

     ruserok(const char *rhost, int superuser, const char *ruser, const char

     iruserok_sa(const void *raddr, int rlen, int superuser, const char
     *ruser, const char *luser);

     The rcmd() function is available for use by anyone to run commands on a
     remote system.  It acts like the orcmd() command, with the exception that
     it makes a call out to the rcmd(1) command, or any other user-specified
     command, to perform the actual connection (thus not requiring that the
     caller be running as the super-user), and is only available for the
     ``shell/tcp'' port.  The orcmd() function is used by the super-user to
     execute a command on a remote machine using an authentication scheme
     based on reserved port numbers.  While rcmd() and orcmd() can only handle
     IPv4 address in the first argument, rcmd_af() and orcmd_af() can handle
     other cases as well.  The rresvport() function returns a descriptor to a
     socket with an address in the privileged port space.  The rresvport_af()
     function is similar to rresvport(), but you can explicitly specify the
     address family to use.  Calling rresvport_af() with AF_INET has the same
     effect as rresvport().  The iruserok() and ruserok() functions are used
     by servers to authenticate clients requesting service with rcmd().  All
     six functions are present in the same file and are used by the rshd(8)
     server (among others).  iruserok_sa() is an address family independent
     variant of iruserok().

     The rcmd() function looks up the host *ahost using gethostbyname(3),
     returning -1 if the host does not exist.  Otherwise *ahost is set to the
     standard name of the host and a connection is established to a server
     residing at the well-known Internet port inport.

     If the connection succeeds, a socket in the Internet domain of type
     SOCK_STREAM is returned to the caller, and given to the remote command as
     stdin and stdout.  If fd2p is non-zero, then an auxiliary channel to a
     control process will be set up, and a descriptor for it will be placed in
     *fd2p.  The control process will return diagnostic output from the
     command (unit 2) on this channel, and will also accept bytes on this
     channel as being UNIX signal numbers, to be forwarded to the process
     group of the command.  If fd2p is 0, then the stderr (unit 2 of the
     remote command) will be made the same as the stdout and no provision is
     made for sending arbitrary signals to the remote process, although you
     may be able to get its attention by using out-of-band data.

     rcmd_af() and orcmd_af() take address family in the last argument.  If
     the last argument is PF_UNSPEC, interpretation of *ahost will obey the
     underlying address resolution like DNS.

     The protocol is described in detail in rshd(8).

     The rresvport() and rresvport_af() functions are used to obtain a socket
     with a privileged address bound to it.  This socket is suitable for use
     by rcmd() and several other functions.  Privileged Internet ports are
     those in the range 0 to 1023.  Only the super-user is allowed to bind an
     address of this sort to a socket.

     The iruserok() and ruserok() functions take a remote host's IP address or
     name, respectively, two user names and a flag indicating whether the
     local user's name is that of the super-user.  Then, if the user is NOT
     the super-user, it checks the /etc/hosts.equiv file.  If that lookup is
     not done, or is unsuccessful, the .rhosts in the local user's home
     directory is checked to see if the request for service is allowed.

     If this file does not exist, is not a regular file, is owned by anyone
     other than the user or the super-user, or is writable by anyone other
     than the owner, the check automatically fails.  Zero is returned if the
     machine name is listed in the ``hosts.equiv'' file, or the host and
     remote user name are found in the ``.rhosts'' file; otherwise iruserok()
     and ruserok() return -1.  If the local domain (as obtained from
     gethostname(3)) is the same as the remote domain, only the machine name
     need be specified.

     If the IP address of the remote host is known, iruserok() should be used
     in preference to ruserok(), as it does not require trusting the DNS
     server for the remote host's domain.

     While iruserok() can handle IPv4 addresses only, iruserok_sa() and
     ruserok() can handle other address families as well, like IPv6.  The
     first argument of iruserok_sa() is typed as void * to avoid dependency
     between <unistd.h> and <sys/socket.h>.

     RCMD_CMD    When using the rcmd() function, this variable is used as the
                 program to run instead of rcmd(1).

     The rcmd() function returns a valid socket descriptor on success.  It
     returns -1 on error and prints a diagnostic message on the standard

     The rresvport() and rresvport_af() function return a valid, bound socket
     descriptor on success.  They return -1 on error with the global value
     errno set according to the reason for failure.  The error code EAGAIN is
     overloaded to mean ``All network ports in use.''

     rcmd(1), rlogin(1), rsh(1), intro(2), rexec(3), hosts.equiv(5),
     rhosts(5), rexecd(8), rlogind(8), rshd(8)

     The orcmd(), rresvport(), iruserok() and ruserok() functions appeared in
     4.2BSD, where the orcmd() function was called rcmd().  The (newer) rcmd()
     function appeared in NetBSD 1.3.  rcmd_af() and rresvport_af() were
     defined in RFC2292.

NetBSD 6.1.5                    March 30, 2005                    NetBSD 6.1.5