C: Hi, my code doesn't display the error message properly

September 12, 2022

I wrote a code to create a glossary of the most basic C instructions, their function and some definition (explained in a very simplistic way).

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

int main(void)
{
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

int main(void)
{
        char dv = '"';
        char choice;
        int lsel;
        printf("%s", "C GLOSSARY\nInstructions' syntax list, their function and definitions\n\n----------------------------------------------\n");
        printf("%s", "\nType:\n- 'L' to display the list of instructions currently \n  covered in this glossary.");
        printf("%s", "\n- 'E' to exit the program\n");
        do
        {   
            scanf("%c", &choice);
            choice = toupper(choice);
            if(choice != 'L')
                printf("ERROR: invalid option. Please, try again: ");
        } while(choice != 'L');
        if(choice == 'E')
            return 0; //the code continues...
}

It works, but the message ERROR: invalid option. Please, try again: is displayed two times! Do you know why? If you want to try the code: https://github.com/AndreMarinelli/C-glossary

Thank you 🙂