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    SubjectRe: How do I make a circular pipe?
    Date
    Can't you do it like this?
    # mkfifo fifo
    # pppd notty < fifo | pppoe -I eth1 >fifo
    /Johan

    ----- Original Message -----
    From: Rob Landley <telomerase@yahoo.com>
    To: <linux-kernel@vger.kernel.org>
    Sent: Saturday, April 14, 2001 3:05 AM
    Subject: How do I make a circular pipe?


    > How do I do the following:
    >
    > # --> pppd notty | pppoe -I eth1 | --
    > |_________________________________|
    >
    > I.E. connect the stdout of a process (or chain
    > thereof) to its own stdin?
    >
    > So I wrote a program to do it, along the lines of:
    >
    > sixty-nine /bin/sh -c "pppd notty | pppoe -I eth1"
    >
    > With an executable approximately along the lines of
    > (warning, pseudo-code, the other machine isn't hooked
    > up to the internet at the moment for obvious reasons):
    >
    > int main(int argc, char *argv[], char *envp[])
    > {
    > int fd[2];
    > pipe(fd);
    > dup2(fd[0],0);
    > dup2(fd[0],1);
    > execve(argv[1],argv+1,envp);
    > fprintf(stderr,"Bad.\n");
    > exit(1);
    > }
    >
    > And it didn't work. I made a little test program that
    > writes to stdout and reads from stdin and reports to
    > stderr, and it gets nothing. Apparently, the pipe
    > fd's evaporate when the process does an execve.
    >
    > What do I do? (If anybody else knows an easier way to
    > get pppoe working, that would be helpful too.
    >
    > Rob
    >
    > (P.S. WHY does pppd want to talk to a tty by default
    > instead of stdin and stdout? Were the people who
    > wrote it at all familiar with the unix philosophy?
    > Just curious...)
    >
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