C，获得（）与fgets（）

Question

char s1[100]; 
char s2[100]; 
gets(s1); 
fgets(s2,sizeof(s2),stdin); 
printf("%d,%d\n",strlen(s1),strlen(s2)); 

运行后，我输入 “ABCD” 两次， ，结果我得到的是：4,5 这是为什么？

Answer 1

从gets/fgets手册页：

The fgets() function reads at most one less than the number of characters 
specified by n from the given stream and stores them in the string s. 
Reading stops when a newline character is found, at end-of-file or error. 
The newline, if any, is retained. If any characters are read and there 
is no error, a `\0' character is appended to end the string. 

The gets() function is equivalent to fgets() with an infinite n and a 
stream of stdin, except that the newline character (if any) is not stored 
in the string. It is the caller's responsibility to ensure that the 
input line, if any, is sufficiently short to fit in the string. 

fgets保持换行符，这是字符数5，但gets没有。 此外，养成一直使用fgets的习惯，因为在使用gets时无法防止缓冲区溢出。

Answer 2

因为fgets返回的字符串结尾为'\n'而gets不是。

Answer 3

从gets() man page：

的gets()函数等效于fgets()具有无限n和的stdinstream，不同之处在于换行字符（如果有的话）不存储在的字符串中。