fwriteで試した.c

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/time.h>
#include <assert.h>

int main(void) {
  size_t a = 2;
  int b = 10;
  {  // read
    FILE* f = fopen("data.log", "rb+");
    if (f) {
      size_t ra;
      int rb;
      int cnt = 0;
      for (;;) {
        size_t a_nread = fread(&ra, 1, sizeof(ra), f);
        if (a_nread < sizeof(size_t)) { break; }
        //printf("nread: %zd\n", a_nread);
        //printf("a: %zd   ra: %zd\n", a, ra);
        assert(a == ra);

        size_t b_nread = fread(&rb, 1, sizeof(rb), f);
        if (b_nread < sizeof(rb)) {
          printf("read not meat\n");
          break;
        }
        assert(b == rb);
        //printf("nread: %zd\n", b_nread);
        //printf("b: %d   rb: %d\n", b, rb);
        ++cnt;
      }
      printf("%d data read\n", cnt);
    }
  }
  printf("validation success\n");

  {  // append
    FILE* f = fopen("data.log", "wb");
    size_t i;
    for (i = 0; i < 1000; ++i) {
      fwrite(&a, sizeof(a), 1, f);
      fflush(f);
      usleep(1000);
      fwrite(&b, sizeof(b), 1, f);
      fflush(f);
    }
    fclose(f);
  }
  printf("write finished\n");
}