Question

Please help me write down a program to check email address valid or not.
Tip:parse the string and count the special characters like '@', '.' .and at least one character.
Suggested libc functions: printf()
1.Have to be by the argc/argv of main function
2.Connot use scanf/getchar and other user input functions
3.Please explain the details and steps for me cause I'm a beginner hhhhhh
Thank you soooo much for helping me！

Answer 1

Note:

The program has been written in C as you didn't specify the language.

Code:

#include<stdio.h>

int main(int argc, char**argv)

{

    // If email is not passed as the command argument

    if(argc==1)

    {

        // Printing the message onto the console that email is not entered

        printf("Email not entered\n");

    }

    // If more than one command argument is passed to the program (excluding the object file name)

    else if(argc>2)

    {

        // Printing the message onto the console that too many arguments have been passed

        printf("Too many arguments passed to the program\n");

    }

    // Else, parse the email

    else

    {

        // This variable is used to keep track of current index of the email string

        int email_char_index = 0;

        // This variable is used to keep track of how many special characters have been found

        int special_characters = 0;

        // This variable is used to keep track of how many characters have been found

        int characters = 0;

        // Iterating over the string until end is reached

        while(argv[1][email_char_index]!= '\0')

        {

            

            // If the value at argv[1][email_char_index] is an lowercase alphabet, then it is a character

            if(argv[1][email_char_index] >= 'a' && argv[1][email_char_index] <= 'z'){++characters;}

            // If the value at argv[1][email_char_index] is an uppercase alphabet, then it is a character

            else if(argv[1][email_char_index] >= 'A' && argv[1][email_char_index] <= 'Z'){++characters;}

            // If the value at argv[1][email_char_index] is an digit, then it is a character

            else if(argv[1][email_char_index] >= '0' && argv[1][email_char_index] <= '9'){++characters;}

            // If the value at argv[1][email_char_index] is none of the above, then it is a special character

            else{++special_characters;}

            // Pre incrementing the email_char_index

            ++email_char_index;

        }

        // According to the given tip, the email should have more than one character and zero or more special charcters.

        // So if those two conditions are passed, then the email is valid

        if(special_characters >= 0 && characters > 0)

        {

            printf("Entered email is %s and it is a valid email\n",argv[1]);

        }

        // Else, the email is invalid

        else

        {

            printf("Entered email is %s and it is not a valid email\n",argv[1]);

        }        

    }

    return 0;

}

Sample Output: