rexec

Purpose

     Allows command execution on a remote host.

Library

     Sockets Library (libsock.a)

Syntax

     int rexec (host, port, user, passwd, command, errfdp)

     char **host;
     int port;
     char *user, *passwd, *command;
     int *errfdp

Description

     The  rexec  subroutine  allows  the  calling  process  to
     execute commands on a remote host.

     The host  parameter contains  the name  of a  remote host
     that is  listed in the  /etc/hosts file.  If the  name of
     the host is not found in this file, the rexec fails.

     The  port   parameter  specifies  the   well-known  DARPA
     Internet port  to use for  the connection.  A  pointer to
     the  structure that  contains the  necessary port  can be
     obtained by issuing the following call:

          getservbyname("exec", "tcp")

     The protocol for the connection is described in detail in
     the  discussion of  rexecd in  Interface Program  for use
     with TCP/IP.

     The user  and passwd  parameters point to  a user  ID and
     password valid at the host.   If these parameters are not
     supplied,  the  rexec   subroutine  takes  the  following
     actions until finding  a user ID and password  to send to
     the remote host:

     1.  Searches the current environment  for the user ID and
         password on the remote host.

     2.  Searches the user's home  directory for a file called
         .netrc that contains a user ID and password.

     3.  Prompts the user for a user ID and password.

     The command parameter  points to the name  of the command
     to be executed at the remote host.

     If  the connection  succeeds,  a socket  in the  Internet
     domain  of type  SOCK_STREAM is  returned to  the calling
     process and  is given to  the remote command  as standard
     input and standard output.

     If errfdp  is not  0, an auxiliary  channel to  a control
     process is set  up, and a descriptor for it  is placed in
     *errfdp.  The control  process provides diagnostic output
     from the remote command on  this channel and also accepts
     bytes as  signal numbers to  be forwarded to  the process
     group of  the command.  This diagnostic  information does
     not include remote authorization failure, since this con-
     nection is set up after authorization has been verified.

     If errfdp  is 0,  then the standard  error of  the remote
     command is the same as  standard output, and no provision
     is  made  for sending  arbitrary  signals  to the  remote
     process.  In  this case, however,  it may be  possible to
     send out-of-band data to the remote command.

Return Value

     The rexec subroutine fails and  a value of -1 is returned
     if the specified host name does not exist.

Related Information

     In this book:  "rcmd, rresvport, ruserok."

     The  discussion of  rexecd  and  /etc/hosts in  Interface
     Program for use with TCP/IP.