pipe.c

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

void ensure(int x) {
  if (!x) {
    printf("ensure failed, exiting\n");
    exit(-1);
  }
}

#define N 10

int main(void) {
  int pipefd[2];
  int res = pipe(pipefd);
  ensure(res == 0);
  int pid = fork();
  ensure(pid >= 0);
  if (pid == 0) {
    res = close(pipefd[1]);
    ensure(res == 0);
    int n = 0;
    for (int i = 0; i < N; i++) {
      char c;
      res = read(pipefd[0], &c, 1);
      ensure(res == 1);
      ensure(c == i + 77);
      n++;
    }
    printf("child process read %d bytes\n", n);
  } else {
    res = close(pipefd[0]);
    ensure(res == 0);
    int n = 0;
    for (int i = 0; i < N; i++) {
      char c = i + 77;
      res = write(pipefd[1], &c, 1);
      ensure(res == 1);
      n++;
    }
    printf("parent process wrote %d bytes\n", n);
  }
  return 0;
}