fgets函数

sip2011

1.执行如下代码
test.c ：
     1 #include <stdio.h>
      2 #include <stdlib.h>
      3 #include <string.h>
      4 #define  MAX 81
      5 int main(void)
      6 {
      7     char name[MAX];
      8     char *ptr;
      9
     10     printf("Hi,what's your name?\n");
     11     ptr=fgets(name,MAX,stdin);
     12     printf("%s? AH! %s!\n",name,ptr);
     13
     14     return 0;

[root@redhat code_C]#gcc test.c -o test.out
[root@redhat code_C]#./test.out
Hi,what's your name?
yzh
yzh
? AH! yzh
!


2.修改代码后执行（MAX改为4）：
test.c ：
     1 #include <stdio.h>
      2 #include <stdlib.h>
      3 #include <string.h>
      4 #define  MAX 4
      5 int main(void)
      6 {
      7     char name[MAX];
      8     char *ptr;
      9
     10     printf("Hi,what's your name?\n");
     11     ptr=fgets(name,MAX,stdin);
     12     printf("%s? AH! %s!\n",name,ptr);
     13
     14     return 0;

[root@redhat code_C]#gcc test.c -o test.out
[root@redhat code_C]#./test.out
Hi,what's your name?
yzh
yzh? AH! yzh!
[root@redhat code_C]#


请问1中fgets的第二个参数为81时为什么结果与预期不一致，我的理解是fgets的第二个参数是限定从流中输入的字符个数，只要该值大于我所需要输入的字符个数就行了，那为什么太过大了又不行呢？

linux_c_py_php

1. 
   
2. NAME
   
3.        fgets - get a string from a stream
   
4. 
   
5. SYNOPSIS
   
6.        #include <stdio.h>
   
7. 
   
8.        char *fgets(char *restrict s, int n, FILE *restrict stream);
   
9. 
   
10. DESCRIPTION
    
11.        The fgets() function shall read bytes from stream into the array pointed to by s, until n-1 bytes are read, or a <newline> is read  and  trans-
    
12.        ferred to s, or an end-of-file condition is encountered. The string is then terminated with a null byte.
    
13. 
    
14.        The  fgets()  function may mark the st_atime field of the file associated with stream for update. The st_atime field shall be marked for update
    
15.        by the first successful execution of fgetc(), fgets(), fgetwc(), fgetws(), fread(), fscanf(),  getc(),  getchar(),  gets(),  or  scanf()  using
    
16.        stream that returns data not supplied by a prior call to ungetc() or ungetwc().
    
17. 
    
18. RETURN VALUE
    
19.        Upon  successful completion, fgets() shall return s. If the stream is at end-of-file, the end-of-file indicator for the stream shall be set and
    
20.        fgets() shall return a null pointer.  If a read error occurs, the error indicator for the stream shall be set,  fgets()  shall  return  a  null
    
21.        pointer,  and shall set errno to indicate the error.

复制代码

sip2011

回复 2# pmerofc


    原来回车符\n也读进去了，知道了，谢谢！