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RedHat 9 (Linux i386) - man page for rcmd (redhat section 3)

RCMD(3) 			   BSD Library Functions Manual 			  RCMD(3)

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

SYNOPSIS
     #include <unistd.h>

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

     int
     rresvport(int *port);

     int
     iruserok(u_int32_t raddr, int superuser, const char *ruser, const char *luser);

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

DESCRIPTION
     The rcmd() function is used by the super-user to execute a command on a remote machine using
     an authentication scheme based on reserved port numbers.  The rresvport() function returns a
     descriptor to a socket with an address in the privileged port space.  The iruserok() and
     ruserok() functions are used by servers to authenticate clients requesting service with
     rcmd().  All four functions are present in the same file and are used by the rshd(8) server
     (among others).

     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 connec-
     tion 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.

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

     The rresvport() function is 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, respec-
     tively, 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 direc-
     tory 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 writeable 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(2)) 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.

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

     The rresvport() function returns a valid, bound socket descriptor on success.  It returns -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.''

SEE ALSO
     rlogin(1), rsh(1), intro(2), rexec(3), rexecd(8), rlogind(8), rshd(8)

HISTORY
     These functions appeared in 4.2BSD.

4.2 Berkeley Distribution		   June 4, 1993 		4.2 Berkeley Distribution


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