Thread: Need to do an infinite loop until I press a key to stop it

Need a bit of guidance here. A simple program I wrote before I add in my complicated robot control command. I need to make this program keep repeating itself until I press a key to stop it. It's like keep commanding the robot to move until I want it to stop. Please do look at my simple program first. Thanks in advance.

Code:

#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>
#include <ctype.h>

int kbhit(void)
{
	struct termios oldt, newt;
	int ch;
	int oldf;
	
	tcgetattr(STDIN_FILENO, &oldt);
	newt = oldt;
	newt.c_lflag &= ~(ICANON | ECHO);
	tcsetattr(STDIN_FILENO, TCSANOW, &newt);
	oldf = fcntl(STDIN_FILENO, F_GETFL, 0);
	fcntl(STDIN_FILENO, F_SETFL, oldf | O_NONBLOCK);

	ch = getchar();

	tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
	fcntl(STDIN_FILENO, F_SETFL, oldf);

	if(ch !=EOF)
	{
		ungetc(ch, stdin);
		return 1;
	}
	return 0;
	}

int main()
{
	char ch;
	int asc;	
	while(!kbhit())
	scanf("%c",&ch);
	asc=toascii(ch);
	if (asc==119)
	{
	 printf("\n move front \n");
	}
	else if (asc==97)
	{
	 printf("\n move left \n");
	}
	else if (asc==115)
	{
	 printf("\n move back \n");
	}
	else if (asc==100)
	{
	 printf("\n move right \n");
	}
	else if (asc==104)
	{
	 printf("\n H \n");
	}
	else
	{
	printf("\n stop \n");
	}
	return 0;
}

Well, that's not going to do it for you.

You should build a very small "snake" type of game, so you can see what you're going to get with your current logic. It's not at all what you want.

You need something like getche() to get the key you press, you can't get an unbuffered keypress with scanf(). And for getche() you need to include conio.h, or use ncurses library, or use Windows API.

Do you have Turbo C or some C compiler that includes the conio.h header?

If you're not already set with a conio.h compatible compiler, I'd recommend using the Windows API for this. It's more complicated, but the basic functionality of your robot program should be good for years to come, so why not take the trouble to make it up with an up to date compiler and on the Windows OS, instead of the older DOS type commands in conio.h? I know they work in Windows up to XP, but I don't know if they'll work in Windows 7 or beyond.

Also, look at the last example here. You will see that your kbhit function is not quite right either.

As an aside, why are you doing the following?

Code:

asc=toascii(ch);
	if (asc==119)
	{
	 printf("\n move front \n");
	}
	else if (asc==97)

You could skip using toascii() altogether, and do your tests like this:

Code:

if(ch == 'w') {
            printf("\n move front \n");
}

And so on. In this way, you are not using magic numbers, and the code should be easier to read.

Yes. All the time until a certain key is pressed to stop the program.

I was a windows user but my robot needs linux terminal/Mac to communicate with the robot. It would be trouble for me to switch to windows again since I don't have much time left. I tried conio.h but somehow I got an error saying that it couldn't find conio.h. Maybe my gcc compiler is not up for conio.h.

I think you should use threads. One thread that includes a while loop...

Code:

while (flag == 0) {

// do movement stuff...

}

...and another thread that waits for user input...

Code:

do {

     scanf("%c", &ch);

     if (ch == 'w') {

          flag = 1;
          // do more stuff

     }

} while (ch != 27);  // 27 is for ESC