Flush Input Buffer C

Question

Note: fflush(stdin) did not work.

Problem:
I'm entering numbers in as a while loop using scanf (inb4 depreciated). When I enter one, the buffer fills the rest in with blank lines.

Code:

double input, total;

for(i=0; i<COUNT; i++){
     printf("\nNumber %d: ", i+1);
     scanf("%d", &input);
     total += input;
}
printf("\nAverage: %f\n", total/COUNT);

Output:

Please enter 5 decimal numbers: 
Number 1: 1.0

Number 2: 
Number 3: 
Number 4: 
Number 5: 
Average: 0.000000

Why are you using `%d` to take a float value in scanf? Use `%f`. — Anirudh Ramanathan, Jan 28 '14 at 06:06
As usual, you forgot to add "\n" to the scanf format (and it should be "%f" and not "%d"). Try using "%f\n" and you should see a better result. — kuroi neko, Jan 28 '14 at 06:16
scanf needs to be told when a newline occurs. "\n" allows to skip the end of line and be ready to read the next value. See any man page for detail, or do a search here on SO. The question has been answered like half a million times. — kuroi neko, Jan 28 '14 at 06:20
@kuroineko My bad. Assumed it was unnecessary here. You're right. — Anirudh Ramanathan, Jan 28 '14 at 06:27
@FabianHarmsen it is defined at the top of the file. `#define COUNT (x number here)` — Goodies, Jan 28 '14 at 06:27
@kuroineko Need not `"\n"` adds if you type in succession number. It is ignored by default. Further, it should be `%lf` instead of `%d`. — BLUEPIXY, Jan 28 '14 at 08:03
@BLUEPIXY Except if the input does not match as a float. Anyway, this has been documented here on SO a million times or more... — kuroi neko, Jan 28 '14 at 09:27
@BLUEPIXY Sure, but if you count the OP's comments, you can bet it's somewhere between 1 and 10 millions ;) — kuroi neko, Jan 28 '14 at 09:40
@kuroineko see http://stackoverflow.com/questions/21404191/scanf-requires-more-inputs-than-requested Effect immediately. — BLUEPIXY, Jan 28 '14 at 11:49

score 2 · Answer 1 · answered Jan 28 '14 at 06:23

2

 if(scanf("%d", &input) != 1)
 {
      /* If scanf failed to read a number clear the input buffer */
      while((c = getchar()) != '\n' && c != EOF);
 }

answered Jan 28 '14 at 06:23

Devolus

20,356
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duckvader · Answer 2 · 2014-01-28T09:09:47.863

0

Use flushall() before taking the input Also you have used %d to store in double,use %lf, or declare input as int

edited Jan 28 '14 at 09:09

answered Jan 28 '14 at 06:17

duckvader

71
12

1

`flushall` is non-standard. – Anirudh Ramanathan Jan 28 '14 at 06:19

Flush Input Buffer C

2 Answers2