在C中的scanf（）函数有问题吗？

Question

#include<stdio.h>
void main()  
 {  
  int i;  
   char a[20];   
   char b[20];   
   scanf("%d",&i);  
    gets(a);   
    puts(a);  
gets(b);  
puts(b); 

}

Here,after entering the value of 'a' it is printing the value of i and a.It is not taking the value of 'b'.How i can insert the value of 'b'?

Answer 1

1) Never use gets , it has been removed from the C standard, and is unsafe. Use fgets instead, (eg, fgets(a, sizeof a, stdin); ). Note that fgets doesn't remove the newline from the end of the string.

2) The return type of main is int , not void .

3) The scanf does not consume the newline after reading i , so gets(a) results in a being the empty string because it reads the newline that was buffered from when the user pressed return after typing the number. Then gets(b) reads what you thought was a . (Print some prompts before reading each value and you'll see. Or try the input: 1 a Enter b Enter )

Suggested solution: use fgets to read i into a buffer, then, eg, atoi or strtol to convert it to an integer. (Or you could do an extra fgets after scanf , or getchar in a loop until you've read a newline, but, seriously, the fgets solution is a lot more robust and worth learning now.)

Answer 2

  gets(a);   

Don't use gets it is evil. Try fgets

#include<stdio.h>
int main()   //declare here `int main()`
 {  
     int i;  
     char a[20],c[10];   
     char b[20];   
     fgets(c,sizeof c,stdin);
     i=atoi(c);         
     fgets(a,sizeof a,stdin);   
     puts(a);  
     fgets(b,sizeof b,stdin);  
     puts(b); 
     return 0;
 }