🚀 go-pugleaf

This program should fill pipe buffer till it's full (after it must be killed
pressing ^C):
the last printf displayed should contain "ITERATION #" where # is equal to
the value of pipe buffer size.
I've read on man pages that "fpathconf(child2parent[1],_PC_PIPE_BUF)" gives
this value but I've tried to run this program and the last iteration has
# bigger than pipe buffer size:

     fpathconf returns 4096 bytes but
               # = 65536 on Debian, Knoppix 3.81 and 3.9 (derived from
                                     Debian) and Ufficio Zero 0.4.2 (derived
                                     from Arch Linux)
               # = 4096 on Pentoo 2005.1 (derived from Gentoo) and
                                   SimplyMepis 3.3.1 (derived from Debian)

Why??????
fpathconf doesn't returns pipe buffer size or it does but write writes more
than once _PC_PIPE_BUF bytes???

PLEASE REPLY ME VIA MAIL BECAUSE I CAN'T CHECK ALL THESE NEWSGROUPS.
THANKS!!!



#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <limits.h>
#include <unistd.h>

inline void sys_err(char *str)
{
     perror(str);
     exit(1);
}

int main()
{
     int child2parent[2],pid,i;
     char ch='\0';
     if (pipe(child2parent)<0)
          sys_err("\nPipe creation error!\n");
     printf("\nFather has PID %d\n",getpid());
     if ((pid=fork())<0)
          sys_err("\nFork error!\n");
     if (pid==0)
     {
          close(child2parent[0]);
          for (i=1;;i++)
          {
               if (write(child2parent[1],&ch,sizeof(ch))<=0)
                    sys_err("\nWrite error!\n");
               if (i==_POSIX_PIPE_BUF || i==_POSIX_PIPE_BUF+1 ||
                   i==PIPE_BUF || i>=PIPE_BUF+1)
               {
                    printf("\nChild has PID %d and father with ",getpid());
                    printf("PID %d   (ITERATION %d)\n\t",getppid(),i);
                    printf("_POSIX_PIPE_BUF=%d\t",_POSIX_PIPE_BUF);
                    printf("PIPE_BUF=%d\t",PIPE_BUF);
                    printf("fpathconf on _PC_PIPE_BUF returns=%ld\n",\
                             fpathconf(child2parent[1],_PC_PIPE_BUF));
               }
          }
     }
     close(child2parent[1]);
     wait(0);
     return 0;
}