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rcmd(3x)							      rcmd(3x)

Name
       rcmd,  rresvport, ruserok - routines for returning a stream to a remote
       command

Syntax
       rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);
       char **ahost;
       u_short inport;
       char *locuser, *remuser, *cmd;
       int *fd2p;

       s = rresvport(port);
       int *port;

       ruserok(rhost, superuser, ruser, luser)
       char *rhost;
       int superuser;
       char *ruser, *luser;

Description
       The subroutine is used by the superuser	to  execute  a	command	 on  a
       remote  machine	using  an authentication scheme based on reserved port
       numbers.	 The subroutine is a routine that returns a  descriptor	 to  a
       socket with an address in the privileged port space.  The subroutine is
       a routine used by servers to authenticate  clients  requesting  service
       with  All  three functions are present in the same file and are used by
       the server (among others).

       The subroutine looks up the host *ahost using returning -1 if the  host
       does  not  exist.  For further information, see 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	call succeeds, a socket of type SOCK_STREAM is returned to the
       caller and given to the remote command as stdin and stdout.  If fd2p is
       nonzero, 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 chan‐
       nel, 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 sig‐
       nals to the remote process, although you may be able to get its	atten‐
       tion by using out-of-band data.

       The protocol is described in detail in

       The  subroutine	is  used  to obtain a socket with a privileged address
       bound to it.  This socket is suitable for use by and several other rou‐
       tines.	Privileged addresses consist of a port in the range 0 to 1023.
       Only the superuser is allowed to bind an address	 of  this  sort	 to  a
       socket.

       The  subroutine	takes  a remote host's name, as returned by a routine,
       two user names and a flag indicating if the local user's	 name  is  the
       superuser.   It	then checks the files and in the user's home directory
       to see if the request for service is allowed.  A 0 is returned  if  the
       machine	name  is  listed in the file, or the host and remote user name
       are found in the file.  Otherwise returns -1.  If the superuser flag is
       1, the checking of the file is bypassed.

See Also
       rlogin(1c),    rsh(1c),	  gethostent(3n),    rexec(3x),	   rexecd(8c),
       rlogind(8c), rshd(8c)

								      rcmd(3x)
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