Programming Forums > Application Development > C

Sane · Nov 4th, 2006, 9:50 AM

Quote:

Originally Posted by Jessehk

Sane, you really should stop ending all your C code in system( "pause" ).
It destroys any portability, as other OSs use other commands.

I think using getchar() would work just as well.

 c Syntax (Toggle Plain Text) 
#include <stdio.h>
 
int main( void ) {
    puts( "Press any key to exit..." );
    getchar();
 
    return 0;
}
#include <stdio.h>

int main( void ) {
    puts( "Press any key to exit..." );
    getchar();

    return 0;
}

Jessehk, there are two problems with that code:

If there's something in the buffer (IE. After some instances of scanf), then it will skip right past the prompt.

You need to press enter after typing in a character.

Both of these issues leave it to not behave the same way as system ("pause"), which is the desirable requirement in most instances.

The system ("pause") is just meant to be there as an informal way to add a break to the end of the program. If the code was going to be serious enough to require portability, it would arguably never even need a break at the end in the first place. But if you wanted to replicate its behaviour, you would need to combine an event flush with something like GetAsyncKeyState, in order to remove the need to hit return. Which, I believe... is windows inclusive?

If it's not windows inclusive, is that the best way to handle keystrokes without waiting for return, it seems a little extraneous? Never bothered to look up any alternatives to system ("pause"). I see no need really.

Yeah, it's still Windows inclusive. Ain't it?

Gimme a cheap way out of it!

 c Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <windows.h>
#include <time.h>
 
void waitForRelease (char lower, char upper) {
        int key, hasPressed;
        do {
                hasPressed = 0;
                for (key=lower; key<=upper; key++) {
                        while (GetAsyncKeyState (key)) {
                                hasPressed = 1;
                        }
                }
        } while (hasPressed);        
}
 
int getSeconds () {
        return clock () / CLOCKS_PER_SEC;    
}
 
int waitForKeyStroke (char lower, char upper, int maxWait) {
        int key, start = getSeconds ();
        while (1) {
                for (key=lower; key<=upper; key++) {
                        if (GetAsyncKeyState (key)) {
                                return key;
                        }
                }
                if (maxWait && (getSeconds () - start) >= maxWait) {
                        return -1;
                }
        }
}
 
int systemPause (int maxWait) {
        waitForRelease ('\n', 'z');
        printf ("Press any key to continue . . .");
        return waitForKeyStroke ('\n', 'z', maxWait);
}
 
int main () {
        printf ("Hello World!\n\n");
        systemPause (15);
        return 0;
}
#include <stdio.h>
#include <windows.h>
#include <time.h>

void waitForRelease (char lower, char upper) {
        int key, hasPressed;
        do {
                hasPressed = 0;
                for (key=lower; key<=upper; key++) {
                        while (GetAsyncKeyState (key)) {
                                hasPressed = 1;
                        }
                }
        } while (hasPressed);        
}

int getSeconds () {
        return clock () / CLOCKS_PER_SEC;    
}

int waitForKeyStroke (char lower, char upper, int maxWait) {
        int key, start = getSeconds ();
        while (1) {
                for (key=lower; key<=upper; key++) {
                        if (GetAsyncKeyState (key)) {
                                return key;
                        }
                }
                if (maxWait && (getSeconds () - start) >= maxWait) {
                        return -1;
                }
        }
}

int systemPause (int maxWait) {
        waitForRelease ('\n', 'z');
        printf ("Press any key to continue . . .");
        return waitForKeyStroke ('\n', 'z', maxWait);
}

int main () {
        printf ("Hello World!\n\n");
        systemPause (15);
        return 0;
}

grumpy · Nov 4th, 2006, 6:17 PM

Jessehk's point was not to use system("pause") in code you post on forums. Posting it liberally in forums like this one implicitly encourages newbies to use it, and it is never a good idea to encourage non-portable techniques unless they are absolutely needed. Furthermore, in most of the examples where you use it, it is completely irrelevant to the problem at hand. Which means you are posting unnecessary information that implicitly encourages newbies to adopt bad practices.

As to a cheap solution under windows, that's easy. When you are creating an executable, all compilers create them in some directory (usually the path of your project, or some other directory that you configure, so you know where it is). I then do the following (assuming I have windows installed, with the windows directory being C:\WINNT and the path of executable being created being C:\whatever)

1) Create a desktop shortcut to C:\WINNT\System32\CMD.exe

2) Change properties of the shortcut so the directory it starts in is C:\whatever.

To use that shortcut;

1) Doubleclick it.

2) Type in the name of the executable and hit Enter. The output from the executable will be displayed in the command window, even after the program exits.

3) Repeat step 2 whenever you want to run the executable.

4) Close the command window when no longer required.

It takes a bit more effort to do this than using system("pause") in your program, but it only needs to be setup (at most) once for every project.

Game_Ender · Nov 5th, 2006, 3:12 AM

I agree with all the portability issues grumpy said above. Don't most IDE's do this automatically, I mean run the program in such a way that is "pauses" after execution.

lectricpharaoh · Nov 5th, 2006, 4:41 AM

Quote:

Originally Posted by grumpy

Jessehk's point was not to use system("pause") in code you post on forums. Posting it liberally in forums like this one implicitly encourages newbies to use it, and it is never a good idea to encourage non-portable techniques unless they are absolutely needed. Furthermore, in most of the examples where you use it, it is completely irrelevant to the problem at hand. Which means you are posting unnecessary information that implicitly encourages newbies to adopt bad practices.

Agreed. If I want something like this in my code, I generally write a waitKey() function that uses a platform-specific method to wait for a key. It's generally fairly trivial to implement something like this, and even if it's non-portable, a programmer who sees the function call can usually figure out what it does, and why it's there.

Quote:

Originally Posted by grumpy

As to a cheap solution under windows, that's easy. When you are creating an executable, all compilers create them in some directory (usually the path of your project, or some other directory that you configure, so you know where it is). I then do the following (assuming I have windows installed, with the windows directory being C:\WINNT and the path of executable being created being C:\whatever)

1) Create a desktop shortcut to C:\WINNT\System32\CMD.exe

2) Change properties of the shortcut so the directory it starts in is C:\whatever.

To use that shortcut;

1) Doubleclick it.

2) Type in the name of the executable and hit Enter. The output from the executable will be displayed in the command window, even after the program exits.

You could do all that, or you could be lazy like me, and get the 'open command prompt here' PowerToy from Microsoft's site. It's a shell extension that adds an option to the right-click menu in Explorer, so you can open a command prompt in a folder of your choice. This, along with TweakUI, are a couple on my list of must-haves.

grumpy · Nov 6th, 2006, 4:26 AM

Quote:

Originally Posted by lectricpharaoh

You could do all that, or you could be lazy like me, and get the 'open command prompt here' PowerToy from Microsoft's site. It's a shell extension that adds an option to the right-click menu in Explorer, so you can open a command prompt in a folder of your choice. This, along with TweakUI, are a couple on my list of must-haves.

Each to their own. I use Microsoft's powertoys, but installing a program to achieve what I can do with two or three mouse clicks (the "open command prompt here" powertoy still needs to be supplied with path information) is not exactly lazy. I could be a member of the olympic laziness team, and beat you in this instance.

And, Game_Ender, the reason this comes up as an issue is that most IDE's do not run a console application in a way that pauses after they finish execution. Hence the common workaround is to get the program to wait for input; unfortunately the method that people tend to wish for is equivalent to the microsoft "pause" command, and there is no portable way (but plenty of non-portable ways) to achieve that in C/C++.

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Nov 4th, 2006, 6:17 PM	#12
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,260 Rep Power: 5	Jessehk's point was not to use system("pause") in code you post on forums. Posting it liberally in forums like this one implicitly encourages newbies to use it, and it is never a good idea to encourage non-portable techniques unless they are absolutely needed. Furthermore, in most of the examples where you use it, it is completely irrelevant to the problem at hand. Which means you are posting unnecessary information that implicitly encourages newbies to adopt bad practices. As to a cheap solution under windows, that's easy. When you are creating an executable, all compilers create them in some directory (usually the path of your project, or some other directory that you configure, so you know where it is). I then do the following (assuming I have windows installed, with the windows directory being C:\WINNT and the path of executable being created being C:\whatever) 1) Create a desktop shortcut to C:\WINNT\System32\CMD.exe 2) Change properties of the shortcut so the directory it starts in is C:\whatever. To use that shortcut; 1) Doubleclick it. 2) Type in the name of the executable and hit Enter. The output from the executable will be displayed in the command window, even after the program exits. 3) Repeat step 2 whenever you want to run the executable. 4) Close the command window when no longer required. It takes a bit more effort to do this than using system("pause") in your program, but it only needs to be setup (at most) once for every project.

Nov 5th, 2006, 3:12 AM	#13
Game_Ender Professional Programmer Join Date: May 2006 Location: Maryland, USA Posts: 306 Rep Power: 3	I agree with all the portability issues grumpy said above. Don't most IDE's do this automatically, I mean run the program in such a way that is "pauses" after execution.

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Programming Forums > Application Development > C

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