From: ian AT cygnus DOT com
Subject: Re: Pipe with TCL/TK
7 Apr 1998 09:43:12 -0700
Message-ID: <199804062057.QAA22686.cygnus.gnu-win32@tweedledumb.cygnus.com>
References: <199804060717 DOT JAA16572 AT hermes7 DOT cst DOT cnes DOT fr>
To: genesis AT hermes9 DOT cst DOT cnes DOT fr
Cc: gnu-win32 AT cygnus DOT com

In gnu-win32 genesis AT hermes9 DOT cst DOT cnes DOT fr (Utilisateur genesis) writes:

>I use TCK/TK with GNUWIN32-B19. My application use Tcl functions libraries to send Tcl and Tk commands.
>I use pipe to interprocess communication, and I want to detect when a pipe may be read.
>For that I created pipe with "pipe" function, and started a function handler "action_pipe" (for execute a callback when pipe may be read).

>   int fid[2];
>   Tcl_Channel pipe_channel;
>#ifdef _WIN32
>   HANDLE pipe_handle;
>#else
>   int pipe_fd;
>#endif


>   pipe (fid);
>#ifdef _WIN32
>   pipe_fd = get_osfhandle(fid[0]);
>#else
>   pipe_fd = fid[0]; 
>#endif
>   pipe_channel = Tcl_MakeFileChannel ( pipe_fd TCL_READABLE );
>   Tcl_CreateChannelHandler ( pipe_channel, TCL_READABLE,          
>                               action_pipe, (ClientData) fid[0] );

>I've the same source code for SUN Solaris 2.5 and Windows NT GNUWIN32-B19. I've TCL/TK 8.0 on both platforms. I use -D_WIN32 compilation option on Windows. 

>I've no problem on SUN platform, the handler "action_pipe" is activate when a pipe may be read.
>On Windows platform my application block when the TCl/TK event loop is started.


Windows pipes are really lame.  There is no way to get them to send
you a message when there is some data to read, so you have to set up a
separate thread to sit around trying to read from them.  That's the
point behind all the code I added to tclWinPipe.c.

The problem with what you are trying to do is that you are treating a
pipe as a file, by calling Tcl_MakeFileChannel.  That won't work.  On
Windows, pipes are not files.

The code I added to tclWinPipe.c will only help if you create a Tcl
pipe.

What you should do is look at the expect program, at
expect/exp_event.c, where I had to get a similar thing to work.  Look
particularly at make_pipe_channel and friends.  That will show you how
to make a pipe channel that will work on Windows.  It's pretty hairy.

Ian
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