#include <
stdio.h>
int main()
{
char s[20];
FILE *fp;
fp=fopen("file.txt", "w");
if(fp == NULL) return 0;
fprintf(fp, "%s", "hello world!");
fclose(fp);
fp=fopen("file.txt", "r");
if(fp == NULL) return 0;
fscanf(fp, "%s", s);
fclose(fp);
printf("%s", s);
return 0;
}