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

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 );

LIBRARY
  Standard C Library (libc)

PARAMETERS
  host
      Specifies the name of a remote host. 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 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.  A user 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.

  Alternatively, the rcmd() function can use a Secure Shell connection to
  authenticate users. In addition to authenticating users, a Secure Shell
  connection also authenticates the client and server and provides data
  encryption, data integrity, and nonrepudiation. You configure the rcmd()
  function (and the rsh, rlogin, and rcp commands) to automatically use a
  Secure Shell connection by enabling the Secure Shell EnforceSecureRutils
  keyword in the /etc/ssh2/ssh2_config file or in a user's
  $HOME/.ssh2/ssh2_config file. When the EnforceSecureRutils keyword is
  enabled:

    ·  The sshd daemon runs and spawns the srcmd child process; the rshd and
       rlogind daemons do not run.

    ·  The rcmd() function can use only Secure Shell host-based
       authentication to authenticate users.

  See Security Administration for more information about configuring Secure
  Shell host-based authentication and the EnforceSecureRutils keyword.

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.

  $HOME/.rhosts
      Specifies remote users that can use a local user account.

  /etc/ssh2/ssh2_config
      Specifies Secure Shell client configuration information.

  /etc/ssh2/sshd2_config
      Specifies Secure Shell server configuration information.

SEE ALSO
  Functions: gethostname(2), rresvport(3), rresvport_af(3), ruserok(3),
  sethostname(2)

  Commands: rlogin(1), rsh(1)

Index for Section 3

Alphabetical listing for R

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