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C Programming: Simple application closes after input.

This is a discussion on C Programming: Simple application closes after input. within the C Programming forums, part of the General Programming Boards category; Hey guys, I'm just starting to learn C, and I was trying some of the tutorials. I started experimenting in ...

  1. #1
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    C Programming: Simple application closes after input.

    Hey guys, I'm just starting to learn C, and I was trying some of the tutorials. I started experimenting in CodeBlocks. When I build and run it inside of CodeBlocks, it's fine. It will come up with a command prompt screen, then at the end, it will say "Press any key to continue."

    I tried getchar(); but it still won't work. Here is what I have.

    Also, I've searched for other solutions, but all of them are for C++.

    Code:
    #include <stdio.h>int main()
    
    
    {
        int pizza;
    
    
        printf("How many slices of pizza do you have right now?\n");
        scanf("%d", &pizza);
    
    
    if (pizza <=2) {
        printf("Get more pizza!\n");
        }
    
    
    else if (pizza <=8) {
        printf("You should have enough pizza...\n");
        }
    else {
        printf("YOU HAVE WAY TO MUCH PIZZA. GIVE ME SOME I'LL GET RID OF IT FOR YOU.\n");
        }
        getchar();
        return 0;
    }
    So how do I make it so that when I put in a number, and press enter, it doesn't close automatically?

    Please explain this to me like I'm 5 years old.

    Thanks.

  2. #2
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    Please explain this to me like I'm 5 years old.
    To a child: I asked for one slice of pizza, but you gave me two and I'm going to bed as a result.

    To an adult: Your "scanf()" will read an integer from the input buffer, but when you press 'enter', there are actually two things in the input buffer; the number you entered, and a newline. For instance:

    Code:
    5\n
    There are several ways to deal with this. A quick fix would be to place a "getchar()" directly after the "scanf()" to eat up the newline. Keep the other "getchar()" at the end of your code if you want to wait until you press 'enter' to close the program.
    dpaksoni likes this.

  3. #3
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    Welcome to the forum, DevSun!

    Lots of ways to do this, but the simplest may be to just add another getchar(), right after the scanf().

    That will clear out the newline which is left behind by scanf(), so that the SECOND getchar() will stop as you want it to. There is a while() that is more robust and pulls off several char's from the input buffer, if present, but it's a bit more difficult to grok.

    You've been reading my mind again, Matticus - that's uncanny!
    Matticus likes this.

  4. #4
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    Oh great thanks! And for future reference, whenever I have a scanf(), do I put a getchar(); after it?

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    You've almost given me a heart Adak!
    But seriously, I love your never ending patience with these things. You're definitely a great asset to this community!

  6. #6
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    Quote Originally Posted by DevSun View Post
    Oh great thanks! And for future reference, whenever I have a scanf(), do I put a getchar(); after it?
    The greatest thing about programming is that you can see for yourself.

    Code:
    #include <stdio.h>
    
    int main(void)
    {
        int x;
    
        printf("Enter an integer:  ");
        scanf("%d",&x);
        printf("You entered %d\n",x);
    
        getchar();  // <--- does it work as you expect?
    
        return 0;
    }
    Code:
    #include <stdio.h>
    
    int main(void)
    {
        char x;
    
        printf("Enter a character:  ");
        scanf("%c",&x);
        printf("You entered %c\n",x);
    
        getchar();  // <--- does it work as you expect?
    
        return 0;
    }
    Code:
    #include <stdio.h>
    
    int main(void)
    {
        float x;
    
        printf("Enter a floating point number:  ");
        scanf("%f",&x);
        printf("You entered %f\n",x);
    
        getchar();  // <--- does it work as you expect?
    
        return 0;
    }
    rags_to_riches likes this.

  7. #7
    TEIAM - problem solved
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    You can ask to read another character (i.e. '\n') and do nothing with it by using "%*c"

    i.e.
    Code:
    scanf("%d%*c", &pizza);

  8. #8
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    scanf just sucks for that reason.
    I would use the following:
    Code:
    char buf[100];
    ...
    printf("How many slices of pizza do you have right now?\n");
    gets(buf);
    sscanf(buf, "%d", &pizza);
    ... but people will point out that 'buf' can be overflowed by malicious intent if the user types in too many characters that exceed its allotted length. There are other functions that read a maximum amount.

  9. #9
    Registered User hk_mp5kpdw's Avatar
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    Of course you mean fgets and not gets right nonoob?
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  10. #10
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    Possibly. but if Kernighan and Ritchie hadn't intended for us to use gets() they wouldn't have invented it.

  11. #11
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    If gets() is such a good function why did they remove it from the current standard (C11)?

    Bye, Andreas
    christop and laserlight like this.

  12. #12
    TEIAM - problem solved
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    Quote Originally Posted by AndiPersti View Post
    If gets() is such a good function why did they remove it from the current standard (C11)?

    Bye, Andreas
    I believe that it's because it that it has no checks with the string size - This leads to a situation where code is susceptible to buffer overflows
    Last edited by Click_here; 08-30-2012 at 06:52 PM.

  13. #13
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Click_here
    I believe that it's because it that it has no checks with the string size - This leads to a situation where code is susceptible to buffer overflows
    Yeah, but I'm fairly certain AndiPersti knew that: the question was rhetorical. That said, I suspect nonoob was just being silly to begin with
    AndiPersti likes this.
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  14. #14
    TEIAM - problem solved
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    Sorry, I processed that sentence differently in my head the first time around - I completely missed the tone.

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