Thread: how to stop this proccess prematurely..

i need to enter numbers in a row
of certain length.
if i deside size =3
then i have to input 3 2 7
if i press enter in the middle of the proccess it doesnt stop'
it just enters a new line and continues from there
i want it to sent an error instead.
so if i will press 3 2 enter
it will return an error
i tried to do it here // in the commented line "\n line"
its now working??

Code:

#include <stdio.h>
int read_array(int input[],int i,int size);
 
int main()
{
	int i;
    int input[40];
    printf("%d\n",read_array(input,0,8));
  for(i=0;i<8;i++)
  {
    printf("%d ",input[i]);  
  }
   printf("\n");
}
int read_array(int input[],int i,int size)
{
	int flag,rt;
       
	if (i==size)
	{
     
	   return 1;
	}
     flag=scanf("%d",&input[i]);  "\n line"
	 if (input[i]=='\n')
	 {
        return 0;
	 }
	 if (flag==0)
	 {
		 return 0;
	 }
	 else
	 {
	 }
     rt=read_array(input,i+1,size); 
	 return rt;
}

Again, transgalactic2, you will be much better off if you write a function to get a line of input from a stream, a reusable function that will work with files and stdin (the keyboard). You only have to write the function once and you can use it in everything you write where you are trying to get a line of input. Then you can sscanf the line if you want or modify the function.

Instead, you waste more time trying to make scanf work in ways that it will not.

Code:

	 if (input[i]=='\n')
	 {
        return 0;
	 }

This if-statement will be true when you enter 10 as the number, not when you hit enter.

There is no reasonable way that you can read a number from input with scanf() and see if "nothing was entered, just a newline", since part of scanf is to ignore newlines, spaces, tabs, etc from the input.

--
Mats

so how to change it so it
wont ignore enter??

i tried to add another base case
but its not working
i cant use sscanf

Code:

#include <stdio.h>
int read_array(int input[],int i,int size);
 
int main()
{
	int i;
    int input[40];
    printf("%d\n",read_array(input,0,8));
  for(i=0;i<8;i++)
  {
    printf("%d ",input[i]);  
  }
   printf("\n");
}
int read_array(int input[],int i,int size)
{
	int flag,rt;
       
	 if (input[i]=='\n')
	 {
        return 0;
	 }
	if (i==size)
	{
     
	   return 1;
	}
     flag=scanf("%d",&input[i]);  
	
	 if (flag==0)
	 {
		 return 0;
	 }
	 else
	 {
	 }
     rt=read_array(input,i+1,size); 
	 return rt;
}

scanf() [when using numeric input formats, such as %d, %x, %i, %f, %lf, %u, etc] will ALWAYS ignore enter. The only option, if you want to know if the following digit is a newline or not is to read a string first, then use sscanf() and other string operations to determine the amount of input actually there.

--
Mats

Originally Posted by transgalactic2

can i use getchar() ??
i saw in the loop
stuff like
x=getchar() !='\0'

If you read a number at a time, you could use getchar() after the scanf(), since you are guaranteed that scanf will not until there is something terminating the numeric input.

However, if the input is absolutely empty, you don't get out of scanf until a number has been entered.

--
Mats

Well, you check if getchar() gives you a space or a newline after reading a number - if it's a newline, then that was the end of that line.

--
Mats

i wrote this code
it does stops prematurely
when i input
1 2 3 4 5 enter it stops and return 0 ( )

but on the other hand
when i input
1 2 3 4 5 6 7 8 enter
it returns zero too
why??

Code:

#include <stdio.h>
int read_array(int input[],int i,int size);

int main()
{
	int i;
    int input[40];
    printf("%d\n",read_array(input,0,8));
  for(i=0;i<8;i++)
  {
    printf("%d ",input[i]);
  }
   printf("\n");
   return 0;
}
int read_array(int input[],int i,int size)
{
	int flag,rt,ch;
    ch=getchar();
    if ((ch=='\n')&&(i!=size))
    {
       return 0;
    }
	if (i==size)
	{

	   return 1;
	}
     flag=scanf("%d",&input[i]);

	 if (flag==0)
	 {
		 return 0;
	 }
	 else
	 {
	 }
     rt=read_array(input,i+1,size);
	 return rt;
}

Think about the order of things you do in your code.

--
Mats

And if you enter 9 elements?

--
Mats