Why does this always return one?

Question

#include <stdio.h>

int main() {  
    int i;  
    printf("%d",scanf("%d",&i));// > What does this explain

    return 0;
}

It returns 1 every time. How?

What does scanf return? That's what gets printed. For fun, add something else to the format string, it'll magically print 2. — Retired Ninja, Jul 20 '17 at 01:47
Value returned by scanf function in c https://stackoverflow.com/questions/10469643/value-returned-by-scanf-function-in-c — inferno, Jul 20 '17 at 01:50
Please, read ***Return Value*** section here: https://linux.die.net/man/3/scanf — Dmitriy Kalugin-Balashov, Jul 20 '17 at 01:50

score 1 · Answer 1 · answered Jul 20 '17 at 01:55

scanf() return the number of input items successfully matched and assigned, which can be fewer than provided for, or even zero in the event of an early matching failure.

The value EOF is returned if the end of input is reached before either the first successful conversion or a matching failure occurs. EOF is also returned if a read error occurs, in which case the error indicator for the stream (see ferror(3)) is set, and errno is set indicate the error.

Please read the man: https://linux.die.net/man/3/scanf

score 0 · Answer 2 · answered Jul 20 '17 at 01:48

You're printing out the return value of scanf()-- which returns the number of items formatted.

Try:

#include <stdio.h>

int main() {
  int i;
  scanf("%d", &i);
  printf("%d", i);
  return 0;
}

As another commenter mentioned, however, you should look up the documentation on these functions and experiment with them instead of immediately asking for help on something so easy to answer. Take a look at this website: http://www.cplusplus.com/reference/cstdio/scanf/

Why does this always return one?

2 Answers2