Return value of printf in C?

Question

My Code:

int main() {
  int x = 10, y;
  y = printf("x = %d\n", x);
  printf("y = %d\n", y);
  return 0;
}

Output:

x = 10
y = 7

I know printf returns the number of character when we print string. But why is returning 7 when printing 10. what is the return value of printf when it prints int ?

Possible Duplicate: Return value of printf() function in C

How is it 3? "x =" has 3 characters. "x = " has 4, "x = 1" has 5, ... — William Pursell, Jul 05 '13 at 14:15
@user1762571 I think you are assuming ,scape and new line char are not counted and `10` is single char that is actually two — Grijesh Chauhan, Jul 05 '13 at 14:36
@ Grijesh Chauhan - Thank you for this information. i didnt know before — user1762571, Jul 06 '13 at 05:43

jh314 · Answer 1 · 2013-07-05T14:37:57.950

5

Like you said, "printf returns the number of character when we print string".

"x = 10\n" has 7 chars. (Namely, these: 'x',' ','=',' ','1','0','\n').

Thus, y is set to 7.

edited Jul 05 '13 at 14:37

answered Jul 05 '13 at 14:15

jh314

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Grijesh Chauhan · Accepted Answer · 2013-07-05T15:01:54.447

3

Read: int printf ( const char * format, ... );

On success, the total number of characters written is returned.

for x = 10 in your code first printf:

printf("x = %d\n", x);

prints seven chars x = 10\n, and return 7 that is received in y:

    x = 10\n
    1234567 
     ^ ^  ^- new line char \n
     | |--spaces

remember \n (new line)is single char, and space is single char.

edited Jul 05 '13 at 15:01

answered Jul 05 '13 at 14:23

Grijesh Chauhan

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*prints 7 chars that is received in `y`* -- I think you should rather write *returns 7( i.e the no. of chars) that is received in `y`*. – 0decimal0 Jul 05 '13 at 14:29
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@PHIfounder Thanks! Yet I think `@jh314` explained better than me :) – Grijesh Chauhan Jul 05 '13 at 14:38
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yes of course that's why I voted up for him even before you :) – 0decimal0 Jul 05 '13 at 14:40

MasterHD · Answer 3 · 2013-07-05T14:21:20.623

1

The length of the string:

"x = 10\n"

(not including double quotes) is 7 characters. That is what is being stored in y. The white spaces and '\n' are also each just 1 character.

edited Jul 05 '13 at 14:21

answered Jul 05 '13 at 14:15

MasterHD

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score -1 · Answer 4 · answered Jul 05 '13 at 14:27

"x = %d\n" Of course there are 7 characters. Notice there are 2 "space",1 "%" and 1"d", remember "\n" is a whole . You can try other sentences. such as z = printf("x = %d,asd\n",x); or sth. like that. The answer is 11. I think such questions can be done by just one more line codes .

Return value of printf in C?

4 Answers4