Input Validation for a String in C-CodePudding

I'm trying to make a loop that does not stop until the user inputs a string. For ex. if the user inputs a number or a letter it will say Invalid input until the user enters a string.

But for some strange reason, when I run my code and I input a string, the program continues to loop the block of code. Here's the output

#include <stdio.h>

int main() {
    char name[100];
    char letter[100];

  lt:
    printf("\033[0;33m");
    printf("\nEnter your Name:\ni.e. Miguel\n");
    printf("\033[0m");
    scanf("%s", name);
    if (name != letter) {
       printf("\033[0;31m");
       printf("Invalid input");
       printf("\033[0m");
       goto lt;
    }
    return0;
}

I've tried the goto function to loop the code but seems like that isn't working.

CodePudding user response：

Uninitialized variables:

char letter[100];

letter is used uninitialized in your code. It's contents are indeterminate. Variables declared with automatic storage aren't implicitly initialised to 0.

Comparing strings:

if (name != letter)

This only compares the pointer addresses (and I believe it invokes undefined behavior), not the contents of the what those pointers point to.

The C standard library provides a function strcmp that compares two strings. Note: It's declared in string.h.

Buffer overflow vulnerability:

scanf("%s", name);

is equivalent to using gets. scanf will happily continue to read input and potentially overflow the buffer.

Use a field width to limit input:

scanf("