fgets函數(shù)

sip2011

1.執(zhí)行如下代碼
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.修改代碼后執(zhí)行（MAX改為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]#


請問1中fgets的第二個參數(shù)為81時為什么結(jié)果與預期不一致，我的理解是fgets的第二個參數(shù)是限定從流中輸入的字符個數(shù)，只要該值大于我所需要輸入的字符個數(shù)就行了，那為什么太過大了又不行呢？

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.

復制代碼

sip2011

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