int ab[2], bc[2], ca[2];
pipe(ab); pipe(bc); pipe(ca);

pid_t pid[3];
int n;

pid[0]=fork();
if(pid[0] == 0)
{
        // Process A reads from process C
        dup2(ca[0], STDIN_FILENO);
        // Process A writes to process B
        dup2(ab[1], STDOUT_FILENO);
        // Essential: close all other pipes and copies of pipes
        for(n=0; n<2; n++)
        { close(ab[n]); close(bc[n]); close(ca[n]); }

        // do whatever you want
        ...
        // quit so your child doesn't end up in the main program
        exit(0);
}

pid[1]=fork();
if(pid[1] == 0)
{
        // Process B reads from process A
        dup2(ab[0], STDIN_FILENO);
        // Process B writes to process C
        dup2(bc[1], STDOUT_FILENO);
        // Essential: close all other pipes and copies of pipes
        for(n=0; n<2; n++)
        { close(ab[n]); close(bc[n]); close(ca[n]); }

        // do whatever you want
        ...
        // quit so your child doesn't end up in the main program
        exit(0);
}

pid[2]=fork();
if(pid[2] == 0)
{
        // Process C reads from process B
        dup2(bc[0], STDIN_FILENO);
        // Process C writes to process A
        dup2(ca[1], STDOUT_FILENO);
        // Essential: close all other pipes and copies of pipes
        for(n=0; n<2; n++)
        { close(ab[n]); close(bc[n]); close(ca[n]); }

        // do whatever you want
        ...
        // quit so your child doesn't end up in the main program
        exit(0);
}

// Only the parent will be running outside of those if statements.
// Essential: close all other pipes and copies of pipes
for(n=0; n<2; n++)
{ close(ab[n]); close(bc[n]); close(ca[n]); }

for(n=0; n<3; n++)
{
        int status;
        waitpid(pid[n], &status, 0);
        printf("Child %d exited with status %d\n", n, WEXITSTATUS(status));
}