27.读文件时通过两种方式判断文件结尾-优快云博客

 1 //判断读到文件末尾
 2 #include <stdio.h>
 3 #define F_PRINT_ERR(e)\
 4 do\
 5 {\
 6     if(e == NULL)\
 7     {\
 8       printf("open error");\
 9       exit(-1);\
10     }\
11 }\
12 while(0)
13 int main(int argc,char* argv[])
14 {
15 
16     FILE* pf = fopen("G:/qtcode/pfw.txt","w+");
17     F_PRINT_ERR(pf);
18 //往文件里写几个字符进去
19     char ch;
20     for(ch = 'a';ch <= 'd';ch++)
21     {
22         putchar(fputc(ch,pf));
23     }
24     putchar(10);
25     rewind(pf);
26 //尝试通过两种方式判断读到文件末尾
27 #if 0
28     //错误用法
29     while(!feof(pf))//
30     {
31         ch = fgetc(pf);
32         printf("%x->%c\n",ch,ch);
33     }
34 #endif
35 
36 #if 0
37     //正确用法，先读再判断
38     while((ch = fgetc(pf)) && (!feof(pf)))
39     {
40         printf("%x->%c\n",ch,ch);
41     }
42 #endif
43 
44 #if 0
45     //正确用法，先读再判断
46     ch = fgetc(pf);
47     while(!feof(pf))
48     {
49         printf("%x->%c\n",ch,ch);
50         ch = fgetc(pf);
51     }
52 #endif
53 
54 #if 1
55     while((ch = fgetc(pf)) != EOF)
56     {
57         printf("%x->%c\n",ch,ch);
58     }
59 #endif
60 
61     return 0;
62 }