How to use printf() and scanf() in C without going to the next line?

Question

I want to get date of birth in one line:

#include <stdio.h>

int main()
{
    int BirthYear,BirthMonth,BirthDay;
    printf("Please enter your birth date: ");
    scanf("%d",&BirthYear);
    printf("/");
    scanf("%d",&BirthMonth);
    printf("/");
    scanf("%d",&BirthDay);
    return 0;
}

This is my output:

Please enter your birth date: YYYY
/MM
/DD

But I want to get something like this:

Please enter your birth date: YYYY/MM/DD

In output, it goes to next line after each scanf() without using \n. I use VS Code for IDM.

Answer 1

Here is a workaround using ansi control characters. I would not do like this, but just to show that it is possible:

#define PREVLINE "\033[F"
#define MSG "Please enter your birth date: "

int main(void) {
    int BirthYear,BirthMonth,BirthDay;
    
    printf(MSG);
    scanf("%d",&BirthYear);
    printf(PREVLINE MSG "%d/", BirthYear);
    scanf("%d",&BirthMonth);
    printf(PREVLINE MSG "%d/%d/", BirthYear, BirthMonth);
    scanf("%d",&BirthDay);
    printf("You entered: %d/%d/%d\n", BirthYear, BirthMonth, BirthDay);
}

Please note that this is not portable. The terminal needs to support this in order to work. AFAIK there's no 100% portable way to achieve this.

If you want to do this stuff for real, then I recommend taking a look at the ncurses library

Note:

Always check the return value for scanf to detect errors.

Note2:

It may be a good idea to add fflush(stdout); after each printf statement.

I actually wrote another answer today about ascii control characters. It might be interesting: https://stackoverflow.com/a/64549313/6699433

Answer 2

You can explicitly specify that the three input numbers should be separated by a '/' character by adding that character in the format specifier for the scanf function.

Then, you can ensure that the user gave valid input by checking the value returned by scanf (which will be the number of items successfully scanned and assigned); if that value is not 3, then you will (probably) need to clear any 'leftover' characters in the input buffer, using a getchar() loop until a newline (or end-of-file) is found:

#include <stdio.h>

int main()
{
    int BirthYear, BirthMonth, BirthDay;
    int nIns = 0, ch;
    while (nIns != 3) {
        printf("Enter D.O.B. (as YYYY/MM/DD): ");
        nIns = scanf("%d/%d/%d", &BirthYear, &BirthMonth, &BirthDay);
        while ((ch = getchar() != '\n') && (ch != EOF))
            ; // Clear remaining in-buffer on error
    }
    printf("Entered data were: %d %d %d!\n", BirthYear, BirthMonth, BirthDay);
    return 0;
}