From: Gennady <gfb@...>
Date: 2004-06-18T01:26:11+09:00
Subject: Re: Bidirectional named pipes on Linux


On Jun 16, 2004, at 22:48, Scott Rubin wrote:

> Phil Tomson wrote:
>> I've got two programs which need to communicate (which eliminates 
>> un-named pipes).  Information needs to be sent in both directions 
>> such that one program (say it's called the master) sends a couple of 
>> bytes to and then waits for a response from the other program (say 
>> it's called the slave) and so on.  It looks like if you open the pipe 
>> (or FIFO file) from both sides in read/write mode that the pipe is 
>> opened non-blocking so what ends up happening is that the side which 
>> sends first just keeps sending and doesn't wait for a response.  
>> ...yeah, I should probably be using sockets, but this is a sort of 
>> 'legacy' system.
>> phil
>
> Phil,
>
> I'm doing this exact same thing on a linux system so that a ruby 
> process and a C process can communicate.  It works perfectly, here is 
> generally how I did it.  First, pipes are one way. You can have one 
> end reading and one end writing at the same time, but both sides may 
> not write simultaneously and both ends may not read simultaneously. 
> Pipes are strictly fifos, that's why the command to make named ones is 
> mkfifo. One way in, one way out. So you can

Actually, the original command for making fifos (as well as other types 
of special files) is mknod (it is in /etc on some systems, in /bin or 
/sbin on others):

mknod <fifo file name> p

;-)

Sincerely,
Gennady Bystritsky