[lug] RE: reference/tutorial for connecting to port 23

[matthew.w.mcillece at lmco.com]

This helps tremendously!  Thanks much!

> -----Original Message-----
> From:	Alan Robertson [SMTP:alanr at suse.com]
> Sent:	Wednesday, July 26, 2000 12:50 PM
> To:	lug at lug.boulder.co.us
> Cc:	clue-talk at clue.denver.co.us
> Subject:	CLUE-Talk: Re: [lug] reference/tutorial for connecting to
> port 23
> 
> matthew.w.mcillece at lmco.com wrote:
> > 
> > Does anyone know where I might find an explanation of how to
> automatically
> > pass the output of a distinct process to (and through) a connection such
> as
> > telnet?  I've always expected telnet to be tied to the keyboard that
> > initiated the connection, but now need to pass characters generated by
> > another process through without user intervention, if possible.  I've
> been
> > reading an IRIX Network Programming Guide but the discussion is not what
> I
> > can use.  I've also grepped through all the Linux HOWTO's, but haven't
> found
> > anything quite on topic.
> 
> Here's some GPLed code I wrote a week or so ago to do that: 
> /*
>  * Start a process with its stdin and stdout redirected to pipes
>  * so the parent process can talk to it.
>  */
> int
> StartProcess(const char * cmd, int * readfd, int * writefd)
> {
>         pid_t   pid;
>         int     wrpipe[2];      /* The pipe the parent process writes to
> */
>                                 /* (which the child process reads from) */
>         int     rdpipe[2];      /* The pipe the parent process reads from
> */
>                                 /* (which the child process writes to) */
>  
>         if (pipe(wrpipe) < 0) {
>                 perror("cannot create pipe\n");
>                 return(-1);
>         }
>         if (pipe(rdpipe) < 0) {
>                 perror("cannot create pipe\n");
>                 close(wrpipe[0]);
>                 close(wrpipe[1]);
>                 return(-1);
>         }
>         switch(pid=fork()) {
>  
>                 case -1:        perror("cannot StartProcess cmd");
>                                 close(rdpipe[0]);
>                                 close(wrpipe[1]);
>                                 close(wrpipe[0]);
>                                 close(rdpipe[1]);
>                                 return(-1);
>  
>                 case 0:         /* We are the child */
>  
>                                 /* Redirect stdin */
>                                 close(0);
>                                 dup2(wrpipe[0], 0);
>                                 close(wrpipe[0]);
>                                 close(wrpipe[1]);
>  
>                                 /* Redirect stdout */
>                                 close(1);
>                                 dup2(rdpipe[1], 1);
>                                 close(rdpipe[0]);
>                                 close(rdpipe[1]); 
>                   
>                                 execlp("/bin/sh", "sh", "-c", cmd, NULL);
>                                 perror("cannot exec shell!");
>                                 exit(1);
>  
>                 default:        /* We are the parent */
>                                 *readfd = rdpipe[0];
>                                 close(rdpipe[1]);
>  
>                                 *writefd = wrpipe[1];
>                                 close(wrpipe[0]);
>                                 return(pid);
>         }
>         /*NOTREACHED*/
>         return(-1);
> }                                               
> 
> 
> Hope this helps...  [I specifically use it with telnet...]
> 
> 	-- Alan Robertson
> 	   alanr at suse.com