"while" question

This is a discussion on "while" question within the C Programming forums, part of the General Programming Boards category; Code: # include <stdio.h> main() { int c, n1; n1 = 0; while (( c = getchar()) != EOF) if ...

  1. #1
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    "while" question

    Code:
    # include <stdio.h>
    
    main()
    
    {
    	int c, n1;
            n1 = 0;
            while (( c = getchar()) != EOF)
                  if ( c == '\n')
                           ++n1;
            printf("%d\n", n1);
    }
    ** it returns**
    % gcc while.c -o while
    % while
    %while: too few arguments.

    however when i do this:

    % gcc while.c
    % a.out

    the programs runs why?

  2. #2
    Massively Single Player AverageSoftware's Avatar
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    I bet you're using a Unix shell of some sort, in which 'while' is a shell command.

    If you want to run your 'while', try ./while
    There is no greater sign that a computing technology is worthless than the association of the word "solution" with it.

  3. #3
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    in an ironic twist, there is something wrong with your number of arguments as well: they're undefined. Main definition should be:
    Code:
    int main(void)

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    There was a thread here a while ago where someone (MacGyver, I think) showed that int main() is actually better than int main(void).

    In any case, the implicit int rule is deprecated in newer versions of C, and so the OP should use int. Returning zero is probably a good idea too.
    dwk

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    Captain Crash brewbuck's Avatar
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    Don't name your programs after other commonly used words (like "while"), and do NOT put "." in your path. To run a program in the current directory you should always run it as "./program"

  6. #6
    Frequently Quite Prolix dwks's Avatar
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    If you do put "." into your path, it might make it easier to run programs -- you don't have to type "./" all of the time. But, of course, it causes problems when programs are named after shell commands. It also creates a security risk: if someone put a program called ls in a directory which did something completely different from what ls is supposed to do, you'd run that ls instead of /bin/ls if you just typed "ls".
    dwk

    Seek and ye shall find. quaere et invenies.

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  7. #7
    Deathray Engineer MacGyver's Avatar
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    Quote Originally Posted by dwks View Post
    There was a thread here a while ago where someone (MacGyver, I think) showed that int main() is actually better than int main(void).
    Yikes, no!

    From the FAQ:

    http://faq.cprogramming.com/cgi-bin/...&id=1043284376

    The only versions of main() that has the blessing of the C standard for both C89/C90 and C99 is this:

    Code:
    int main(void);
    int main(int argc, char *argv[]);
    Unfortunately, I do not believe the C++ standard allows void to be a type of C++ that main() can accept, because C and C++ have totally different meaning with regard empty arguments in a function. C takes an empty argument function to mean that the function has an unknown number of arguments and C++ takes it to mean that the function has no arguments.

    Hence the only true versions of main() in C++ is:

    Code:
    int main();
    int main(int argc, char *argv[]);
    So hence, the only version of main() which I think fits for both C89/C90, C99, and C++ is this:

    Code:
    int main(int argc, char *argv[]);
    Now someone contradicted me the last time I stated this, but I don't remember the particulars. If someone has something definite on any of this, that would be great.

    Since compilers are usually pretty loose with regard to main()'s return type and parameters, some will, no doubt, feel perfectly fine with arbitrary declarations of main().

    Quote Originally Posted by dwks View Post
    In any case, the implicit int rule is deprecated in newer versions of C, and so the OP should use int. Returning zero is probably a good idea too.
    Agreed.

  8. #8
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by dwks View Post
    There was a thread here a while ago where someone (MacGyver, I think) showed that int main() is actually better than int main(void).
    It was me. int main() has a slight advantage in environments where the "typical" C calling convention of caller-cleans is not used. It's a fairly obscure argument. If you asked me for my personal opinion I'd say I don't think it matters too much. Getting the return type correct is more immediately important.

  9. #9
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by dwks View Post
    It also creates a security risk: if someone put a program called ls in a directory which did something completely different from what ls is supposed to do, you'd run that ls instead of /bin/ls if you just typed "ls".
    That's a strong enough reason to never use it, IMHO. Since "." is not a fixed location, it's like having a wildcard in your path, which obviously can lead to all sorts of awful things.

  10. #10
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    Quote Originally Posted by dwks View Post
    There was a thread here a while ago where someone (MacGyver, I think) showed that int main() is actually better than int main(void).
    Using obsolescent practices is not better, hackish at best, but never better.
    Quote Originally Posted by ISO 9899 6.11.6
    The use of function declarators with empty parentheses (not prototype-format parameter
    type declarators) is an obsolescent feature.

  11. #11
    Deathray Engineer MacGyver's Avatar
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    Quote Originally Posted by brewbuck View Post
    It was me. int main() has a slight advantage in environments where the "typical" C calling convention of caller-cleans is not used. It's a fairly obscure argument. If you asked me for my personal opinion I'd say I don't think it matters too much. Getting the return type correct is more immediately important.
    What system would not have main() declared as using the stdcall convention, or not provide some means to allow main() to work just as gracefully using some other convention?

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    Here's the "int main()" vs. "int main(void)" thread. I'll have to bookmark this since it keeps coming up.

    i need help with sorting an array

  13. #13
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by MacGyver View Post
    What system would not have main() declared as using the stdcall convention, or not provide some means to allow main() to work just as gracefully using some other convention?
    Actually, it's __stdcall that causes the problem. In that convention the callee cleans the stack, which means that the called function has to know certainly what arguments ARE on the stack, so it can clean them. If you declare main(void), this implies there will be no arguments on the stack, even though the runtime DOES push argc and argv there. So as main returns it corrupts the stack.

    Again, you don't normally declare main() as __stdcall so I said this argument is obscure. The standard in fact does state that "int main(void)" is okay, so...

  14. #14
    Deathray Engineer MacGyver's Avatar
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    Indeed, perhaps I should have though a little more when I wrote my last post. IMO, main() should always be stdcall or some equivalent convention where the caller is doing the cleaning.

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