14 replies to this topic

[Drakkcon]

I want to use SDL functions in my program, but I also want to be able to use the Command Prompt. Could someone tell me how to allow stdio to use the console window?

[Simian Man]

If you use Visual C++ just select "Win32 Cosole Application". That works fine for me.

[swinchen]

Hmm, right now I dont have access to a compiler or I would test this:

in the SDL source code:

#ifndef NO_STDIO_REDIRECT

So maybe you can:

#define NO_STDIO_REDIRECT


Then again, this may be something you have to do when you compile SDL.

I hope this helps.

p.s. in linux it is pretty easy if I remember correctly using close(stdout); and then opening it with 0 I think.

On windows I am not sure.

[thugkilla]

Does this have anything to do with input/ and output?because in allegro you can't really do use allegro functions in a console window so thats probable the same thing with SDL not sure so don't flame if I'am wrong.

[swinchen]

Well I installed dev-cpp on this computer and the define didnt work :(

So I was thinking I would be clever..

FILE* oldStdout;
*oldStdout = *stdout; //causes the application to crash :(

SDL_Init(....)

.....

fclose(stdout);
*stdout = *oldStdout;



I thought for sure this would work... alas, I was wrong.

If you are using windows, microsoft claims:
STDOUT 1 Output to the Command Prompt window source

If you find an answer let me know :)

If I think of anything else I will give it a try.

[Drakkcon]

Ugh. Nothing yet, I really wish there was something in the SDL documentation. Thanks for the help to far though, I'm going to look some more through the SDL header files.

[Oluseyi]

Quote:

Original post by Drakkcon Could someone tell me how to allow stdio to use the console window?

It's platform specific, so the following is Windows only.

1. Create a new console window if your app is a "Win32 Application." AllocConsole is the API you want.


2. Once you have your console, retrieve its standard input (or, possibly in the future, standard output) stream handle. You want GetStdHandle.


3. You then want to get a C file descriptor corresponding to said handle. Windows provides the _open_osfhandle API for exactly this purpose.


4. Now retrieve a FILE * for that file descriptor: call _fdopen.


5. Finally, redirect the standard I/O stream pointer with code like the following:
   

   *stdin = *conin;
   *stdout = *conout;

   where conin and conout are the FILE *s that correspond to the input and output handles of your console, respectively.


6. One extra step is to eliminate I/O buffering, so any data printed to stdout shows up immediately (if you want). Call setvbuf with the appropriate parameters.

You can save a lot of time by analyzing and copying the relevant bits of code from this excellent article.

Alternatively, if you're up to rebuilding SDL entirely, pass --disable-stdio-redirect as a compilation parameter.

Happy hacking.

[Drakkcon]

Thank you very much oluseyi! Trying it now...

[Oluseyi]

/me bows

[swinchen]

Sorry about the cross-post Oluseyi. It was before I we got your answer. I thought someone in that group might have a good idea.

[Drakkcon]

void ActivateConsole()
{
    AllocConsole();
    
    HANDLE newConsoleInput = GetStdHandle(STD_INPUT_HANDLE);
    HANDLE newConsoleOutput = GetStdHandle(STD_OUTPUT_HANDLE);
    
    int inFd = _open_osfhandle((long)newConsoleInput, _O_TEXT);
    int outFd = _open_osfhandle((long)newConsoleOutput, _O_TEXT);
    
    FILE* consoleIn = _fdopen(inFd, "r");
    FILE* consoleOut = _fdopen(outFd, "w");
    
    setvbuf(consoleIn, NULL, _IONBF, 0);
    setvbuf(consoleOut, NULL, _IONBF, 0);
    
    *stdin = *consoleIn;
    *stdout = *consoleOut;
}

Here's my console activation function. The only problem is, I still don't get a console [sad]. What I'm probably doing wrong involves HANDLEs probably, since I don't know what a handle is a typedef of. when I use _open_osfhandle(newConsoleInput, _0_TEXT); I get an error: invalid conversion from `void*' to `long int'. I have tried casting it to many things.

Any ideas?

[Drakkcon]

Ah, nevermind! I fixed it, I was forgetting to call my ActivateConsole() function.

Me <--- Embarresed.

Thanks a lot oluseyi, it works!

PS: What is a file descriptor?

[Oluseyi]

Quote:

Original post by Drakkcon PS: What is a file descriptor?

Streams and File Descriptors.

[Drakkcon]

Thanks!

I also found this,
which tells me how to use them.