struct string variable assignment in C

July 11, 2022

#include <stdio.h>

struct Student {
    char name[10];
    int age;
    double gpa;
};

int main(void)
{
    struct Student s1;
    s1.age = 20;
    s1.gpa = 4.3;
    s1.name[10] = "Tom";

    printf("%s", s1.name);

    return 0;
}

I know ‘strcpy’ function or other way to assign string. but Why doesn’t it work above code..?
Please help me.

Specially, s1.name[10] = "Tom";

Thanks.

>Solution :

There are few issues with this statement:

s1.name[10] = "Tom";

In C array (of length n) indexing starts with 0 and ends at n-1. Accessing any elements out side of 0 to n-1 (both inclusive) will cause undefined behaviour. s1.name[10] is out of bound access and not valid.

Another problem is that you cannot assign a string literal to an array using assignment operator except when it is used in the initializer. You have to use strcpy to copy a string literal to a char array. Make sure length of string literal must not exceed the size of the array (make sure there is a room for \0).