scanf() question.

This is a discussion on scanf() question. within the C Programming forums, part of the General Programming Boards category; Before my program quits, I would like a user to press enter before the program ends. I want to do ...

  1. #1
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    scanf() question.

    Before my program quits, I would like a user to press enter before the program ends. I want to do something similiar to simple:
    getchar();
    but with using scanf();
    Is there anyway of doing it like that ?

    Regards,
    apacz.

  2. #2
    Code Goddess Prelude's Avatar
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    >Is there anyway of doing it like that ?
    I suppose:
    Code:
    scanf ( "%*c" );
    But why do you what to use scanf? It's for formatted input, and this task implies unformatted input. getchar is better suited in principle and in practice.
    My best code is written with the delete key.

  3. #3
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    because I have sucha code:
    Code:
    #include <stdio.h>
    
    int main()
    {
            int     s;
            scanf("%d\n", &s);
            getchar();
            return  0;
    }
    and it doesn't work neither if there is '\n' in scanf or not.

  4. #4
    and the hat of wrongness Salem's Avatar
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    Which is why we usually suggest fgets() + sscanf() rather than trying to cope with the randomness which simple scanf() leaves behind.
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  5. #5
    Code Goddess Prelude's Avatar
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    >and it doesn't work neither if there is '\n' in scanf or not
    Using scanf to read a single character won't save you from that either because you're simulating the functionality of getchar. The effect is identical. Now, the proper solution is to use fgets for reading a line and then parsing the line in memory. This avoids the "whitespace stuck in the stream" problem:
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int main ( void )
    {
      char buf[BUFSIZ];
      int x;
    
      printf ( "Enter a whole number: " );
      fflush ( stdout );
    
      if ( fgets ( buf, sizeof buf, stdin ) != NULL ) {
        if ( sscanf ( buf, "%d", &x ) != 1 ) {
          fprintf ( stderr, "Invalid input\n" );
          return EXIT_FAILURE;
        }
    
        printf ( "You entered: %d\n", x );
      }
    
      getchar();
    
      return EXIT_SUCCESS;
    }
    Alternatively, you can "flush" the stream with an ugly hack:
    Code:
    int ch;
    
    while ( ( ch = getchar() ) != EOF && ch != '\n' )
      ;
    I don't recommend that.
    My best code is written with the delete key.

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    Thank you very much .

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    Quote Originally Posted by apacz
    Before my program quits, I would like a user to press enter before the program ends. I want to do something similiar to simple:
    getchar();
    but with using scanf();
    Is there anyway of doing it like that ?

    Regards,
    apacz.
    ya..there is a way..
    just decalre a variable of type char and use scanf to read it..i think it will work..u can also do with int

  8. #8
    ATH0 quzah's Avatar
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    You don't need a variable. There's a format specifier modifer that allows the discarding of what you read. However, your solution wouldn't work any better than just a single getchar call. More than one character in the stream would have the same problem. There are format specifiers that allow you to read a everything up to a newline, so you'd need that.

    It doesn't make it a good solution. But you could do it.


    Quzah.
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    Instead of using getchar(), there is another way to make the program stop before quitting and wait for the user to type anykey.
    The answer is... using : system("pause"); at the end of your code.

    Just try!

  10. #10
    {Jaxom,Imriel,Liam}'s Dad Kennedy's Avatar
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    No, don't EVER use system() anything if you can help it. . .

  11. #11
    Code Goddess Prelude's Avatar
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    >The answer is... using : system("pause"); at the end of your code.
    This isn't recommended because it's neither portable nor secure.
    My best code is written with the delete key.

  12. #12
    Reverse Engineer maxorator's Avatar
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    Quote Originally Posted by Prelude
    >The answer is... using : system("pause"); at the end of your code.
    This isn't recommended because it's neither portable nor secure.
    Yeah... Windows specific function
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  13. #13
    Frequently Quite Prolix dwks's Avatar
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    For more information on system("pause") and the alternatives, read these FAQs:

    BTW, using getchar() is greatly preferable to using system("pause"), although you may have to put it into a loop (as the second FAQ link does) if there's something in the input buffer.
    dwk

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