scanf help

homerz · 11-11-2003, 04:41 AM

I want to make a C program in emacs. The program should read several strings from the user at one time and do stuff with the strings. Between each string and the other there exist a space. What function should i use and how can i use it so when the scanff reaches a space it will know that the first string has ended and start with the second string. Thanks.

jim mcnamara · 11-11-2003, 05:24 AM

Code:

#include <stdio.h>

int main(){
 char word1[80],word2[80];
 memset(word1,0x00,sizeof(word1));
 memset(word2,0x00,sizeof(word2));
 printf("enter two words: ");
 scanf("%s %s",word1,word2);
 printf("word1=%s word2=%s \n",word1,word2);

 return 0;
}

This reads two "words" separated by spaces from stdin (the keyboard in this case).

scanf is NOT a safe function because it does not check the size of the data item being input. scanf usage in older programs is a source of vulnerability.

MartinN · 11-11-2003, 05:48 AM

Now that we're talking vulnerabilities...

Never EVER write this kind of code:

printf(word1);

always do it like this: (like jim mcnamara did)

printf("%s", word1);

The first style is vulnerable to a user (or a hacker) entering strings with '%' characters.

Martin