The truth is most systems return CRLF (CR to make it go to left column,
LF to make it go down one line) but often you don't see this. Unix
usually only stores the LF part in files and the CR is added after the
fact by the termio routines. However when you read input from a real
application that connects like this you may see both. If you want to
make the stuff you're collecting fit Unix, you'll need to purposefully
throw away the extra CR. In short you'll have to scan the data taken in
from read() and remove the CR programatically. A pain, but not too
difficult.
Good luck. I'm off to Interop.
- Matt
JM wrote:
>
> Matt, Thank you very much for your help. I coded according
> to your pseudo-code and it really works!!!
>
> I still have one last question, though. The output of the telnet
> pipes back to parent which has a c/r (ASCII carriage return)
> appended at the end of everyline in my Text widget window.
> I am using motif 1.2 with text widget window to show all output
> from telnet. If I replaced execl() of telnet to other command (ls or ps)
> then it is OK. For some reasons, my Text widget window
> displays all hidden characters of the telnet output.
>
> Login: c/r
> Passwd: c/r
> c/r
> $
>
> Thanks again for your help.
>
> John
>
> ----- Original Message -----
> From: Matt Fahrner <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Wednesday, May 03, 2000 11:03 AM
> Subject: Re: Telnet program
>
> > Ok then, the best I can do is give some pseudo-code:
> >
> > - Program starts.
> > - Create two pipes with pipe() calls.
> > - fork()
> > - Child chooses one pipe and dup2()'s the read end over descriptor 0
> > (stdin)
> > - Child takes other pipe and dup2()'s the write end over descriptor 1
> > (stdout)
> > and maybe descriptor 2 (stderr).
> > - Child (to be clean) close all the pipe()'s since they're now
> > replacing stdin
> > and stdout.
> > - Parent (to be clean) closes the same ends that were dup2()'ed (since
> > those
> > technically belong to the child only.
> > - Child does an execv(), execl(), or your exec of choice of
> > "telnet". Child
> > has now been officially replaced. You may or may not choose to
> > pass an argument
> > that is the host to telnet (you can write "open XXXX" to it
> > later instead if you
> > want.
> > - Parent continues.
> > - Start parsing input and output.
> > - Parent read()s from other end of pipe duped to child's descriptor 1
> > until it
> > sees "login:", when it does it write()s the usename to the
> > other end of the pipe
> > duped to child's descriptor 0.
> > - Parent read()s until it sees "password:", when it does it
> > write()s
> > the password. You may want to use regular expressions to do matching
> > so
> > its more portable. You may also want to use select() or poll()
> > to check
> > for read() or write()ability so you don't block (probably not in this
> > particular scenario though).
> > - Parent read()s until it sees the shell prompt (or output
> > indicating the shell
> > in use is ready for input), then writes any command(s) it
> > wants to execute.
> > - Continue to read() and write() whatever's necessary to control what
> > you're
> > doing.
> > - When done wait3() for the child to complete (ie: exit).
> >
> > "telnet" may not be happy with a pipe() as stdin and stdout. In which
> > case you'll have to use pseudo-terminals (a whole nother ball of wax).
> > You may have to read character by character and do your own buffering
> > too. If you're lucky, the above will work.
> >
> > - Matt
>
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