Thread: String - Segmentation Fault

Hi All,

I have a problem with this code. I am using a gcc compiler and when i compile and execute this code i am getting a seg fault. I am just assigning two variables, name_1 as pointer and name_2 as string. When i am trying to provide string input for the two values i am getting a seg fault. This seg fault is always associated with the pointer variable that i am using.

Code:

#include <stdio.h>


int main()
{
char *name_1 ;
char name_2[10] ;


/*      Getting 2 strings as an input from the user
        and is stored in the pointer variable name_1 and name_2*/
scanf("%s",name_1) ;
scanf("%s",name_2) ;


/*      Printing the values of the varibales 
        name_1 and name_2 in string format      */
printf("\n%s",name_1) ;
printf("\n%s",name_2) ;


printf("\n\n") ;
return 0 ;
}

You did not allocate any space for the pointer to point to.

Originally Posted by Raj 89

How i need to allocate a space for it?

That is up to you. For example, you could create another array instead of just using a pointer, or you could use malloc and free.

Another mistake is the failure to specify the field width when reading with scanf using %s. It should be something like:

Code:

#include <stdio.h>

int main(void)
{
    char name_1[10];
    char name_2[10];

    scanf("%9s", name_1);
    scanf("%9s", name_2);

    printf("\n%s\n%s\n\n", name_1, name2);

    return 0;
}

Of course, instead of variables named name_1 and name_2 you could have an array of 2 arrays of char instead.

Keep the field width and enter "Almu'tasimu Billahi Muhibbuddin Tuanku Alhaj Abdul Halim Mu'adzam Shah Ibni Almarhum Sultan Badlishah, Yang di-Pertuan Agong of Malaysia and Sultan of Kedah" as the name. Remove the field width and enter the same name.

Originally Posted by Raj 89

In this case i am not aware that what is the size of the string that is to be inputted. But i am sure the input will surely be less than 20 bytes. If i am using %10s and i am providing HelloWorldDennis as input i am i will be losing Dennis from the input. In such case what am i supposed to do?

You should be using %19s instead. 19 characters + null terminator = 20, i.e., the number of elements of the char array.

... And probably not call laserlight "sir" :P