use imagination

 1 #include <stdio.h>
 2 #include <stdlib.h> //for EXIT_FAILURE,exit()
 3 
 4 int main(void)
 5 {
 6     FILE *fp;
 7     char arr[100];
 8 
 9     // write something to test file
10     fp = fopen("test","w");
11     if(fp == NULL)
12     {
13         puts("File open failed.");
14         exit(EXIT_FAILURE);
15     }
16     fprintf(fp,"%s","nihaoa");
17     fclose(fp);
18 
19     //output the file,exactually just one line
20     fp = fopen("test","r");
21     if(fp == NULL)
22     {
23         puts("Cannot open the file for reading.");
24         exit(EXIT_FAILURE);
25     }
26     if(fgets(arr,100,fp) != NULL)
27         puts(arr);
28     fclose(fp);
29 
30     return 0;
31 }