pipes in c

hi,
i am trying to connect a maximum of up to three processes in c using pipes as the means of communication, each process should be forked from a single parent process but i'm having trouble with the pipes. I can find plenty of examples where a parent process foks a child and communicates with it through a pipe but nothing using anymore than that, ie i need an array of pipes(i think!). Any examples or pointers to how to go about this would be great.

thanks very much.

Here is a quick modification of the first pipe example in "Unix Nextwork Programming" by W. Richard Stevens, to handle arrays. His example is just a quick demonstration of pipes. I modified it quickly and crudely to work with an array, with a slight variation on his error logging, to use standard prinf instead.

Code:

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#include <stdio.h>
#include <stdlib.h>

int main( void )
{
        int pipefdarray[3][2], n,p;
        char buff[3][100];

        for( n = 0; n < 3; n++ )
                if( pipe( pipefdarray[n] ) < 0 )
                {
                        printf( "Error calling pipe on %d.\n", n );
                        exit( EXIT_FAILURE );
                }

        for( n = 0; n < 3; n++ )
                printf("read fd[%d] = %d, write fd[%d] = %d\n",
                        n, pipefdarray[n][0], n, pipefdarray[n][1] );

        for( n = 0; n < 3; n++ )
                if( write( pipefdarray[n][1], "hello world\n", 12 ) != 12 )
                        printf( "Error writing on pipe %d\n", pipefdarray[n][1] );

        for( n = 0; n < 3; n++ )
                if( (p=read( pipefdarray[n][0], buff[n], sizeof( buff[n] ) ) ) <= 0 )
                        printf( "Error reading on pipe %d\n", pipefdarray[n][0] );

        for( n = 0; n < 3; n++ )
                write( 1, buff[n], p );


        return 0;
}

---

Quick copy/paste from vi, so the formatting may not be to your liking. However, it demonstrates an array of pipes, which is what you were looking for. Very simple really.

On an aside, I would highly recommend the book I mentioned.

Quzah.

Hey Quzah,

That book you mentioned is most likely way beyond where I am at right now, but still I am curious - I just did a quick check on amazon and they list a few different editions - looks like there is more than one volume - is yours a multi-volume set?

Quote:

---

Originally posted by kermit
Hey Quzah,

That book you mentioned is most likely way beyond where I am at right now, but still I am curious - I just did a quick check on amazon and they list a few different editions - looks like there is more than one volume - is yours a multi-volume set?

---

Vol 2 is for IPC, so I guess that's the one Quzah's refering to. They're listed on Stevens' home page here:
http://www.kohala.com/start/

I have the earlier single volume work. Hard cover, just called "Unix Network Programming". I haven't picked up the new three piece set. It's (the original) actually quite good. You can get it fairly inexpensively also, compared to what it originally retailed for. It's worth a read. Not overly complex, and he's a good author with good examples.

Quzah.

sorry to bump a really old thread, but how would you implement this using dup2s and closes?

Just because you are sorry for bumping an old thread doesn't make it ok or right