printf whitespace control

This is a discussion on printf whitespace control within the C++ Programming forums, part of the General Programming Boards category; Hi guys I need to now that I can control the white spaces in the printf("%5d") defined by 5. In ...

  1. #1
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    printf whitespace control

    Hi guys I need to now that I can control the white spaces in the printf("%5d") defined by 5.

    In my program I need to control it to implement or decrement. So instead of using %5 what can I use.

    I need ideas, thanks for help!

  2. #2
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    You can create the format string on the fly:
    Code:
    char format[100];
    sprintf(format, "%%%dd", 5); // or snprintf if available
    printf(format, some_int);

  3. #3
    and the hat of wrongness Salem's Avatar
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    Quote Originally Posted by man page
    A field width or precision, or both, may be indicated by an asterisk `*'
    or an asterisk followed by one or more decimal digits and a `$' instead
    of a digit string. In this case, an int argument supplies the field
    width or precision. A negative field width is treated as a left adjust-
    ment flag followed by a positive field width; a negative precision is
    treated as though it were missing. If a single format directive mixes
    positional (nn$) and non-positional arguments, the results are undefined
    Eg.
    Code:
    printf( "%*d\n", 5, some_int );
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    C++まいる!Cをこわせ! Elysia's Avatar
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    Is this C or C++? This is C code, yet is posted in the C++ section.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    actually I am trying to control

    sprintf(*form, "%s", "%5d");

    in this line %5d must be controlled by a variable!

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    and it is c++ but we're not using its GUI

  7. #7
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    in this line %5d must be controlled by a variable!
    What are you doing? You have already been given code to accomplish exactly this.

    and it is c++ but we're not using its GUI
    What GUI? If you are using C++, then you can also do this the C++ way.
    Code:
    std::cout << std::setw(5) << i << std::endl;

  8. #8
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    sorry it is

    sprintf(form, "%s", "%5d");

    not *form

  9. #9
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    Quote Originally Posted by komacan View Post
    and it is c++ but we're not using its GUI
    If you're using C++, why not use cout and iomanip's setw?

  10. #10
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    but this must be controlled by a variable "%5d" part must be controlled

    and also I am obligated to write in C but in c++ file

  11. #11
    and the Hat of Guessing tabstop's Avatar
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    So you should read the man page on printf/sprintf/etc, and note how to use a variable to control the precision.

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    I ve already read but nothing founr so I am here!

  13. #13
    and the Hat of Guessing tabstop's Avatar
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    Then you need to read better.

    Quote Originally Posted by man 3 printf
    A field width or precision, or both, may be indicated by an asterisk `*'
    or an asterisk followed by one or more decimal digits and a `$' instead
    of a digit string. In this case, an int argument supplies the field
    width or precision. A negative field width is treated as a left adjust-
    ment flag followed by a positive field width; a negative precision is
    treated as though it were missing.

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