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rcmd(3)
NAME
  rcmd,	 rcmd_r - Allow execution of commands on a remote host

LIBRARY
  Standard C Library (libc.a)

SYNOPSIS
  #include <sys/types.h>
  #include <netdb.h>
  #include <unistd.h>

  int rcmd(
	  char **host,
	  u_short port,
	  char *local_user,
	  char *remote_user,
	  char *command,
	  int *err_file_desc);

  The following function is supported in order to maintain backward
  compatibility with previous versions of the operating system.

  int rcmd_r(
	  char **host,
	  u_short port,
	  char *local_user,
	  char *remote_user,
	  char *command,
	  int *err_file_desc,
	  struct hostent_data *host_data);

PARAMETERS
  host	    Specifies the name of a remote host that is listed in the
	    /etc/hosts file.  The function sets the host parameter to be the
	    fully qualified hostname.

  port	    Specifies the well-known port to use for the connection.  The
	    /etc/services file contains the DARPA Internet services, their
	    ports, and socket types.

  local_user
	    Points to usernames that are valid at the local host.  Any valid
	    username can be given.

  remote_user
	    Points to usernames that are valid at the remote host.  Any valid
	    username can be given.

  command   Specifies the name of the command to be executed at the remote
	    host.

  err_file_desc
	    Points to an address used by rcmd() to store a pointer to the
	    file descriptor for a channel used by the remote process to write
	    stderr messages and to accept bytes as signal numbers to be
	    forwarded to the process group of the command.

	    If a null pointer is specified, the standard error (stderr) of
	    the remote command is the same as the standard output (stdout).
	    No provision is made for sending arbitrary signals to the remote
	    process.  However, it is possible to send out-of-band data to the
	    remote command.

  host_data Per-thread data for reentrant version.

DESCRIPTION
  The rcmd() (remote command) function allows execution of certain commands
  on a remote host.  For example, the rcmd() function is used by rsh and
  rlogin, among others.

  The rcmd() function looks up a host via the name server or, if the local
  name server is not running, via the /etc/hosts file.	If the connection
  succeeds, a socket in the Internet domain of type SOCK_STREAM is returned
  to the calling process and given to the remote command as standard input
  (stdin) and standard output (stdout).

  Always specify the host name.	 If the local domain and remote domain are
  the same, specifying the domain parts is optional.  The rcmd() function
  returns the fully qualified hostname in the host parameter. To reuse the
  host name in another rcmd() call, you should make a string copy of the host
  parameter.  For example:

       rcmd ( &host, .... );
       first_host = strdup(host);
       ...
       rcmd ( &host, .... );

  Only processes with an effective user ID of root user can use the rcmd()
  function.  An authentication scheme based on remote port numbers is used to
  verify permissions.  Ports in the range from 0 to 1023 can only be used by
  a root user.

NOTES
  The rcmd_r() function is the reentrant version of rcmd(). It is supported
  in order to maintain backward compatibility with previous versions of the
  operating system.

  The netdb.h header file defines the hostent_data structures.

RETURN VALUES
  Upon successful completion, the rcmd() function returns a valid socket
  descriptor.  The function returns a value of -1 if the effective user ID of
  the calling process is not root user, if the function fails to resolve the
  host, or if it encounters a socket connection error.

FILES
  /etc/services
	    Contains the service names, ports, and socket types.

  /etc/hosts
	    Contains hostnames and their addresses for the hosts in a
	    network.

  /etc/resolv.conf
	    Contains the name server and the domain name.


RELATED INFORMATION
  Functions: gethostname(2), rresvport(3), ruserok(3), sethostname(2).

  Commands: rlogin(1), rsh(1).

Index for Section 3

Alphabetical listing for R

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