Hello friends! i am writing a code in which i take inputs (numbers) from user and count the total number of positive, negative and zeros entered. I need to clear my standard input buffer before scanf() command. My compiler is completely ignoring the fflush(stdin) command. its not even showing any error!. I am using Linux(ubunto) platform. Help!
#include<stdio.h>
int main()
{
int pos=0,neg=0,zeros=0;
float num;
char ans='y';
while(ans=='y')
{
printf("Enter a number : ");
scanf("%f",&num);
if(num>0)
{
pos++;
}
else if(num<0)
{
neg++;
}
else
{
zeros++;
}
printf("Wanna enter another number ? (y/n)\n");
fflush(stdin);
scanf("%c",&ans);
if(ans=='n')
{
printf("positive number : %d \n Negative numbers : %d \n Zeros : %d",pos,neg,zeros);
}
}
return 0;
}
It certainly is showing error but you're not looking for it. That's what scanf()'s return value is for, it returns 0 if it reads no values, 1 if it found 1 value, 2 for 2, etc. Each %... code counts as one "value".
The buffering thing is a known issue with scanf(). It's a "feature" -- it stops scanning at the first bad character -- which is pretty useless if you're not building a compiler.
fflush should work, if you tell it which stream to flush, which you are not. But the proper way to avoid these buffer problems is to not use scanf().
You can still use sscanf though, which is just as good without the problems! It scans a string, and has no buffer to leave things in.
Here's the usual way to do it:
while(ans=='y')
{
char line[512];
float val;
// Quit the loop if the file hits EOF
if(fgets(line, 512, stdin) == NULL) break;
// sscanf returns 1 if it reads one value, 2 if it found 2 values, etc.
if(sscanf(line, "%f", &val) != 1)
{
fprintf(stderr, "'%s' is not a number\n", line);
continue; // Skip back to top of 'while'
}
// Quit the loop if the file hits EOF
if(fgets(line, 512, stdin) == NULL) break;
if(sscanf(line, "%c", &ans) != 1)
{
fprintf(stderr, "Couldn't read Y/N\n");
continue;
}
}