Thread: switch problem

#include <stdio.h>


int main(void)
{
int ch;
char buf[BUFSIZ];

puts("Flushing input");

while ((ch = getchar()) != '\n' && ch != EOF);

printf ("Enter some text: ");

if (fgets(buf, sizeof(buf), stdin))
{
printf ("You entered: %s", buf);
}
return 0;
}


got few noob question, what does the

Code:

puts("Flushing input");
  
  while ((ch = getchar()) != '\n' && ch != EOF);

what it flushed?and why it need to be flushed?

if (fgets(buf, sizeof(buf), stdin))<=== the stdin means what?

Originally Posted by matsp

flushing input means just that - removing anything in the input buffer. There is a slight flaw in this particular piece of code in that it will wait for the user to type enter if there isn't something in the input already.

Edit: stdin is the "standard input", which normally means your keyboard/console input channel.

--
Mats

ok i try the "How to convert char to int tutorial"

#include <stdio.h>

Code:

main(void)
{
	int choice = 0;

	while(choice != 4)
	{
		printf("key in a value");
		
		choice = getchar();



		
			switch(choice)
		{

			case 1:
				printf("yes");
				break;

			case 2:
				printf("double yes");
				break;

			case 3:
				printf("trileple yes");
				break;

			case 4:
				printf("byebye");
				break;
			default:
				printf("wtf");
	}
	}

}

how come when i enter 1,2,3,4 its nvr show according to the cases

Stdin usually refers to the input stream from the keyboard however, that input stream can be redirected - say to a file, for instance.

When you scanf("%c") for a char, the char is pulled off the keyboard buffer, by scanf, but the "enter" key will leave behind it's newline ('\n'), char, in the keyboard buffer. If a subsequent scanf("%c") is in your code, scanf() will see the newline char in the buffer, and take it as it's designated input, not waiting for any more input from the user. It has the effect of making it seem like the scanf() line of code was somehow "skipped" over.

If you change your scanf() calls for a single char, from this: scanf("%c"), to this scanf(" %c") (just adding that one space before the % sign), the "skipping" will be greatly reduced.

lolx so back to the question.. what should i do to make the while loop run once only when the user key in a junk ?

what method should i go for with my noob skills?

i read the flush things.. it just the away the making "123456acb" to "1234" somthing like that.. so how i do use this flush things into my code?

You don't want the while loop to run only once if the user keys in junk. If the user keys in junk 20 times, you want it to loop 21 times asking for their choice.

I'd put that flush code, right at the very bottom of the while loop, just before it loops back up to get input again, if needed.