Thread: Why should i use the system

Just wondering why this code doesn't display the last print statement. In place of getchar i have to use a system call.

Code:

system("pause")

.

here it is. What is the logic i'm missing.

Code:

/* scanf used properly */

#include <stdio.h>

int main()

{

    int sum;
    char letter;
    float money;

    printf("Please enter an integer ");
    scanf("%d", &sum);

    printf("Please enter a character ");
    /* leading space before the %c ignores whitespace in input */
    scanf(" %c", &letter);

    printf("Please enter a float variable ");
    scanf("%f", &money);

    printf("\nThe values you entered were\n");
    printf("Sum = %d, letter = %c, money = %.2f\n", sum, letter, money);

    getchar();
    return 0;

}

It prints the last statement, you just can't blink or you may miss it. Change this:

Code:

scanf("%f", &money);

to this:

Code:

scanf(" %f", &money);

>/* scanf used properly */
Not really. For even remotely proper scanf usage, you need to check the return value. Basically anything that takes outside input that has a chance of failure (interactive input meets both of these requirements), you should check for errors.

Not too sure what you were saying thantos. Can you let me know again.

also prelude:

Code:

scanf("  %f", &money)

doesn't that ignores leading whitespace. I haven't tested to see if it works but curious about what else it does that i am not aware of.


in regards to

Code:

scanf("%d", x)

x being that math symbol i can't find on my keyboard - i swear to god i tried to edit the code, but it look fine like so

Code:

scanf("%d", &sum) /* this is not how it is supposed to look */

wonder what i did?

okay this is freaky. I just previed my reply and when i do the ampersand and then sum it prints out this &sum. If i leave out a space it prints out this

Code:

& sum

. WTF?

btw prelude just tested your code, and it still flashes w/o me being able to see the results. Also yeah, i'm aware the comments from the code is a lie. I really should have validated the user input with the stdlib and ctypes.h I did this mainly to test the arguments and errors scanf would return. I don't understand why the iso/ainsi committee even kept this. What is its purpose other than to get the user to start accepting user input right away?
A point that is echoed seemingly here.

>doesn't that ignores leading whitespace
Yes.

>and it still flashes w/o me being able to see the results
You have an exceptionally annoying implementation of scanf then. You'll need to either clear out the stream somehow, or double up your getchar calls if you're sure that there's only a newline left in stdin. Really all you have to remember is that the only input function that works well with scanf is scanf. Anything else requires you to jump through hoops to get it working.

>I don't understand why the iso/ainsi committee even kept this.
To keep old code from breaking. Pre-standard programs used scanf religiously, so the ISO standard had little choice but to keep it. Also consider that stdin can be redirected to a file stream. In those cases scanf is correct, safe, and slightly more convenient than fscanf.

>WTF?
These forums act funny with &<some specific character sequence>.