printf not printing

This is a discussion on printf not printing within the C Programming forums, part of the General Programming Boards category; As with my previous question this is also some confusion about an example or two from K&R. Both of these ...

  1. #1
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    printf not printing

    As with my previous question this is also some confusion about an example or two from K&R. Both of these programs are supposed to produce the same answers and I can follow the code easily enough but when I run the program it doesn't print the results. I am guessing that it is supposed to print the no. of characters that I input.

    Program 1:
    Code:
    #include <stdio.h>
    
    main()
    {
        long nc;
        nc = 0;
        while (getchar() != EOF)
            ++nc;
        printf("%ld\n", nc);
    
    }
    Program 2:
    Code:
    #include <stdio.h>
    
    main()
    {
        double nc;
        for (nc = 0; getchar() != EOF; ++nc)
            ;
        printf ("%.0f\n", nc);
    }
    Why would they not print? Or is my assumption that they should print something wrong?

  2. #2
    CSharpener vart's Avatar
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    Works for me
    Code:
    1 1 1 1
    123
    123
    ^Z
    17
    Note that K&R style is outdated
    Code:
    #include <stdio.h>
    
    int main(void)
    {
        long nc = 0;
        while (getchar() != EOF)
            ++nc;
        printf("&#37;ld\n", nc);
        return 0;
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
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    Hi,
    Thanks a lot. You are my saviour.
    It works for me too.
    I now understand your CTRL-Z.
    After Ctrl-Z I have to press return.

    I thought that it would print the result immediately after I press return (without entering Ctrl-Z).

    Not getting this would have meant the rest of the chapter would have been confusing. Thank you very much.

  4. #4
    CSharpener vart's Avatar
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    to print result after enter you need to modify code in the following way:
    Code:
    #include <stdio.h>
    
    int main(void)
    {
        long nc = 0;
        int ch;
        while ((ch =getchar()) != EOF && ch != '\n')
            ++nc;
        printf("&#37;ld\n", nc);
    	return 0;
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  5. #5
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    Thanks again. That code works perfectly for me and with a bit of testing I understand that "ch != '\n'" is the reason it prints the result after enter. Why does this make such a difference?

    Also looking at your previous results and mine too where did the number 17 come from?

    1 1 1 1
    123
    123
    ^Z
    17
    I retried your numbers and got the same result. But I am guessing how to count them.
    First line has 9 characters: 4x1, 4xspace and \n . Maybe that's right.
    Next two lines have four characters each including newline and the total is 17?

  6. #6
    CSharpener vart's Avatar
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    I suppose so
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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