#include<stdio.h> int main(void) { char *file = "hoge.dat"; FILE *fp; fp = fopen(file, "w"); if (fp == NULL) { printf("open error %s", file); } else { setbuf(fp, NULL); int i = 0; for (i = 0; i < 0x7FFFFFFF; i++) { fprintf(fp, "%d\n", i); } } fclose(fp); }