[SOLVED] Making the program to wait for keyboard input.

stf92 · 04-12-2015, 03:18 PM

Within a loop I want the program to wait the <Enter> key being pressed. I tried with

fflush(stdin);
getc(stdin);

but the control does not stop at the instruction. I don't have my C programs with me, to copy from them (and do have Little practice with C). Could somebody tell me how to accomplish this job?

T3RM1NVT0R · 04-12-2015, 03:50 PM

It will be good if you can share the program, though I am not good at C but here is the program which I wrote and it stops for user input before continuing with the rest of the loop. Basically you will need a condition to stop.

Program:

Code:

#include <stdio.h>
int main()
{
    int x;
    char a;
    for ( x = 0; x <= 10; x++ )
    {
        if (x == 5)
        {
                printf("You have reached mid of the loop, press C to continue=");
                scanf("d",&a);
                if (a == 99)
                {
                        continue;
                }
        }
        printf( "%d\n", x );
    }
}

Once it prompt me to hit c to continue and if I enter c it will check ASCII value and compare it against 99 and if it is true it will continue.

stf92 · 04-12-2015, 05:54 PM

The program is this:

Code:

#include <stdio.h>
#include <stdlib.h>

main(){
    char buf[90];
    int n1,n2,i,j,aux;
    
    n1=n2=1; j=2;
    while(1){
        for(i=0; i<10; i++){
            printf("d   %d\n", j,n2);
	    aux= n2;
            n2= n1 + n2;
	    n1= aux;
	    j++;
        }
    


    fflush(stdin);
    getc(stdin);
//    scanf("%s\n", buf);
    } 
}

I mistankenly put the getc outside the while scope. Sorry for that.

ntubski · 04-12-2015, 09:49 PM

Quote:

Originally Posted by T3RM1NVT0R

Once it prompt me to hit c to continue and if I enter c it will check ASCII value and compare it against 99 and if it is true it will continue.

Just use 'c', not a literal 99. The compiler generates the same code, and humans can read it more easily.

NevemTeve · 04-12-2015, 11:31 PM

never use scanf. fgets + sscanf is the usable way.

veerain · 04-13-2015, 12:24 AM

@stf92: The third post by you works perfectly in my system.

In linux with glibc waiting for input is the default behaviour unless you use low level terminal functions to return immediately if a key press is not available.

T3RM1NVT0R · 04-13-2015, 05:01 AM

Quote:

Originally Posted by ntubski

Just use 'c', not a literal 99. The compiler generates the same code, and humans can read it more easily.

Yes that is correct basically I am getting the character input but performing a integer scan which will automatically translate it to 99. Though I haven't code it to work with capital C

millgates · 04-16-2015, 03:30 PM

Also, please note that fflush serves to flush output buffer to a file. For an input stream, the behaviour is undefined (even though it will probably work on most systems).