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From sebb <seb...@gmail.com>
Subject Re: [Telnet] how to determine the prompt?
Date Tue, 03 Jun 2008 15:04:15 GMT
On 03/06/2008, Uwe Fischer <mistuwefischer@web.de> wrote:
> Hello Sebb,
>
>  maybe we misunderstood one another...
>  I was talking about the telnet client example, where the input stream is read as long
as a defined "prompt" character is found.
>  E.g., http://www.informit.com/guides/content.aspx?g=java&seqNum=40
>
>  In this example a command like 'ls -l > output.txt' would not be handled properly
(of course only if ">" is defined to be the prompt too).
>

In which case, turn off echo.

Or just look for > at or near the start of a line.

As I wrote (twice) before, how does a human know when input is expected?

>  I hope I do not confuse you. Actually I'm just looking for another way to find out when
a command has been executed. Isn't the telnet standard offering anything like this? I mean,
does the client get some kind of status about the remote machine (something like "busy" or
"waiting for command" or similar).

No, AFAIK telnet does not address that.

Besides, some OSes allow one to type-ahead, so even when the system is
"busy" it will accept input (though this is usually fairly limited in
size).

>
>  Cheers,
>  Uwe
>
>
>
>
>
>  > On 03/06/2008, Uwe Fischer <mistuwefischer@web.de> wrote:
>  > > Hi Sebb,
>  > >
>  > >  your idea to change the prompt sounds good. However, how would I identify
the very first appearance of the prompt in order to change it? Also, is this (changing the
prompt) possible for Windows based telnet servers aswell?
>  > >
>  >
>  > It's not the telnet server that provides the prompt, it's the
>  > application you are talking to, in that case presumably DOS.
>  >
>  > You either need to know what the prompt is in advance, or wait for a timeout.
>  >
>  > As I wrote before: how does a human know the system is ready for input?
>  >
>  > >  Concerning your question, the problem with output redirection is that the
program would stop reading from the input stream, due to the appearance of ">" which would
indicate that the prompt has been reached. AFAIK.
>  >
>  > That does not make sense to me.
>  >
>  > If you telnet to a Unix system and issue the command:
>  >
>  > ls -l >list.txt
>  >
>  > the shell prompt will be issued as soon as the ls program has finished.
>  >
>  > >  Cheers,
>  > >  Uwe
>  > >
>  > >
>  > >
>  > >  > -----Ursprüngliche Nachricht-----
>  > >  > Von: "sebb" <sebbaz@gmail.com>
>  > >  > Gesendet: 03.06.08 14:40:16
>  > >
>  > > > An: "Commons Users List" <user@commons.apache.org>
>  > >  > Betreff: Re: [Telnet] how to determine the prompt?
>  > >
>  > >
>  > >  > On 03/06/2008, Uwe Fischer <mistuwefischer@web.de> wrote:
>  > >  > > Hello Pierre,
>  > >  > >
>  > >  > >  thanks for your answer.
>  > >  > >  Yes, I did what you mention. But it's not "really" solving my
issue. The problem I face is that the devices I attach to can have the "#" or ">" characters
maintained in a user welcome messages when logging in. E.g., the following welcome message
is displayed when logging on to the device:
>  > >  > >  ############################################
>  > >  > >  Welcome at "hostname". In case of any issues contact Uwe
>  > >  > >  ############################################
>  > >  > >
>  > >  > >  How can one distinguish the "#" character when used in a comment
and when used to indicate the prompt?
>  > >  > >
>  > >  >
>  > >  > Can you set the prompt to a string that is not likely to be seen elsewhere?
>  > >  > Maybe even include a control character such as ^G (bell).
>  > >  >
>  > >  > If not, you are probably going to have to use timeouts to decide when
>  > >  > output has finished.
>  > >  >
>  > >  > >  Another problem could occur when somebody would redirect stdout
of a Unix system to a file, e.g.:
>  > >  > >  ls -l > output_list.txt
>  > >  > >
>  > >  > >  Any ideas?
>  > >  >
>  > >  > How would a human know when output has finished?
>  > >  >
>  > >  > >  Thanks and best regards,
>  > >  > >  Uwe
>  > >  > >
>  > >  > >
>  > >  > >  > -----Ursprüngliche Nachricht-----
>  > >  > >  > Von: "Pierre Brico" <pierre.brico@tsdsoftware.eu>
>  > >  > >  > Gesendet: 03.06.08 11:11:37
>  > >  > >  > An: "Commons Users List" <user@commons.apache.org>
>  > >  > >  > Betreff: Re: [Telnet] how to determine the prompt?
>  > >  > >
>  > >  > >
>  > >  > >
>  > >  > >  > Hello Uwe,
>  > >  > >  >
>  > >  > >  > Did you try to change the command prompt before executing
the command. You
>  > >  > >  > just should send commands to the shell like this:
>  > >  > >  >
>  > >  > >  > PS1="#>"
>  > >  > >  > export PS1
>  > >  > >  >
>  > >  > >  > And you will get the "#>" as prompt.
>  > >  > >  >
>  > >  > >  > Pierre
>  > >  > >  >
>  > >  > >  > On Tue, Jun 3, 2008 at 10:50 AM, Uwe Fischer <mistuwefischer@web.de>
wrote:
>  > >  > >  >
>  > >  > >  > > Hello all,
>  > >  > >  > >
>  > >  > >  > > I'm looking for a solution to a problem that bothers
me for quite some time
>  > >  > >  > > now and I hope somebody here can help me out.
>  > >  > >  > > I'm using the telnet api to connect to various systems,
which works fine.
>  > >  > >  > > The problem I face is, how can I determine that a command
has run to its
>  > >  > >  > > end if there is no static "prompt" character like "#"
or ">", but
>  > >  > >  > > dynamically changing prompt characters?
>  > >  > >  > >
>  > >  > >  > > I have read through the Telnet specification but couldn't
find anything
>  > >  > >  > > that deals with this kind of problem. But surely there
must be a solution to
>  > >  > >  > > this. I have found another thread in this mailing list
concerning a similar
>  > >  > >  > > issue, posted by: Anthony Webster Thu, 28 Feb 2008 10:54:35
GMT.
>  > >  > >  > > Unfortunately none has answered it yet.
>  > >  > >  > >
>  > >  > >  > > Thanking in advance,
>  > >  > >  > > U.F.
>  > >  > >  > >
>  > >  > >  > >
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