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Re: /dev/tcp/localhost/finger

From: Wilhelm Mueller
Subject: Re: /dev/tcp/localhost/finger
Date: 14 May 2001 16:30:49 +0200

    Adam>       However, I can't get it to work with bash.
    Adam>       (and what would be the syntax for that matter)

    Adam> cmd < file.in > file.out 

This will open two different sockets, which is not what fingerd
expects. (Actually, inetd will even start two copies of fingerd.)

    Adam> echo hi | cat < /dev/tcp/localhost/finger    

    Adam>       does not seem to do trick, like few other commands
    Adam>       I tried.

Sure, it can't: first, the pipe is assigned to fd0, then this is
replaced by the socket: you still have just one fd open for reading.

    Adam> suggestions?

Sure --

 ( cat 1>&3 2>/dev/null & cat 0<&3 ) 3<>/dev/tcp/localhost/finger

does what you want. The redirection of stderr is becaus fingerd
will shutdown the socket when it has sent its output, so the second
cat gets an EOF on stdin, but the first an IO error on stdout.

But I don't yet know why 

  { cat 1>&3 2>/dev/null & cat 0<&3; } 3<>/dev/tcp/localhost/finger

does *not* work...


   Wilhelm Müller          Baumanagement Bremen GmbH
   Schlachte 32               Tel: +49-421-361-10629
   D-28195 Bremen, Germany    Fax: +49-421-361-2295

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