Why doesn't getchar() receive any input?

Question

I made a program to see what your name is, if you were a male or female, how old you are, and if I should call you as Mrs, Ms, Mr, or just by your full name depending on the previous conditions. When I pick my gender as female and enter a first name, last name, and a age that's over or equal to 20 I ask if that person is married, however for whatever reason the program skips over the getchar, and just finishes the program.

Here is the code:

#include <stdio.h>
#include <string.h>

int main()
{
    char gender;
    char fName[15]; 
    char lName[15];
    char mar;
    char str[] = "Then I shall call you";
    int age = 0;

    printf("What is your gender (M or F): ");
    gender = getchar();

    printf("First name: ");
    scanf("%s", fName);
    //fgets(fName, 16, stdin);
    //fName[strcspn(fName, "\n")] = 0;

    printf("Last name: ");
    scanf("%s", lName);
    //fgets(lName, 16, stdin);
    //lName[strcspn(lName, "\n")] = 0;

    printf("Age: ");
    scanf("%d", &age);

    puts("");

    if(gender == 'F' || gender == 'f')
    {
        if(age >= 20)
        {   
            printf("Are you married, %s (y or n)?: ", fName);

            //scanf("%c", &mar);
            mar=getchar();

            printf("%c\n", mar); 

            if(mar == 'Y' || mar == 'y')
                printf("%s Mrs. %s.\n", str, lName);

            else if(mar == 'n' && age >= 20|| mar == 'N' && age >= 20)
                printf("%s Ms. %s.\n", str, lName);
        }

        else
            printf("%s %s %s.\n", str, fName, lName);
    }

    else if(gender == 'M' || gender == 'm')
    {
        if(age >= 20)
            printf("%s Mr. %s.\n", str, lName);

        else
            printf("%s %s %s.\n", str, fName,lName);
    }   

    return 0;
}

And the output:

What is your gender (M or F): F
First name: Jane
Last name: Doe
Age: 25

Are you married, Jane (y or n)?:

I also have another question as to when I used fgets instead of scanf to read the string. As I heard to typically stay away from scanf when reading strings I tried fgets but the output wasn't as I wanted it to be.

Here is the output when I used fgets instead of scanf:

What is your gender (M or F): M 
First name: Last name: Joe
Age: 23

Then I shall call you Mr. Joe.

The output should be as it was when I used the scanf so that The last name is underneath the first name.

Your problems come from mixing single character getchar() with multi-char input in scanf or fgets. When you press Enter, that produces a character as well, which you have to handle. — Bo Persson
Use either scanf(" %c", &mar); or getchar(); mar=getchar(). The problem is because of the newline character left over by the previous scanf. — Spikatrix
when calling the system function: scanf(), 1) always check the returned value (not the parameter value) to assure the operation was successful. 2) when using a input/format string that does not automatically skip over white space, insert a space into the format string before the (for instance) %s, so any leading white space is automatically consumed. 3) when using the format %s always use the max length modifier (which needs to be 1 less than the actual input buffer length) I.E. %14s for a 15 char input buffer. — user3629249

chux - Reinstate Monica chux - Reinstate Monica · Accepted Answer · 2015-09-05T17:06:32

Why doesn't getchar() receive any input?

Code has 2 problems:

1) It got the left-over '\n' from the previous line, use scanf(" %c", &mar); (note space) or better yet, replace all input with fgets()

2) It did not report unexpected input. Code should detect and report unexpected input and handle all possible paths of logic. Example:

    {   
        printf("Are you married, %s (y or n)?: ", fName);
        mar=getchar();
        printf("%c\n", mar); 
        if(mar == 'Y' || mar == 'y')
            printf("%s Mrs. %s.\n", str, lName);
        else if(mar == 'N' || mar == 'n') {
           if (age >= 20)
             printf("%s Ms. %s.\n", str, lName);
           else 
             printf("%s ??? %s.\n", str, lName);
        }
        else { 
          printf("Unexpected input char:'%c' code:%d\n", mar, mar);
        }  
    }

Why doesn't getchar() receive any input?

2 Answers