Reputation: 1820
I was wondering why the outcome of this program is 5621?
#include <stdio.h>
main()
{
int i=56;
printf("%d\n",printf("%d",printf("%d",i)));
getch();
}
Upvotes: 5
Views: 595
Reputation: 106102
The printf()
function returns the number of characters that it prints on console.
For example after the following printf call, num_chars
will have the value 10
as string "Hi haccks\n"
consistes of 10 non-nul characters that will be print on screen.
num_chars = printf("Hi haccks\n");
// ^^^^^^^^^ ^
// 12345678910
Note: \n
is single 10th char. So in above code returned value from printf assigned to num_chars
variable.
In your code, in the given statement, inner printf()
prints the values and then return number of chars that value printed by outer printf as shown below:
// 1 2 3
printf("%d\n", printf("%d", printf("%d",i))); // Here i = 56
^ ^ ^
print: 1 print: 2 print: 56
returns: 1 returns: 1 returns: 2
// 3 2 1 <--Order of printf called
So it outputs 5621
Upvotes: 1
Reputation: 1572
It's equivalent to
#include <stdio.h>
main()
{
int n, i = 56;
n = printf("%d",i);
n = printf("%d", n);
n = printf("%d\n", n);
}
printf returns the number of characters written.
Upvotes: 6
Reputation: 21089
printf()
returns the number of characters printed:
printf("%d",i)
outputs the value 56
.
printf("%d",printf("%d",i))
outputs 56
and then 2
, the number of characters in 56
.
printf("%d\n",printf("%d",printf("%d",i)))
outputs 56
, then 2
, then the number of characters in 2
, which is 1
.
Upvotes: 6
Reputation: 117836
printf
returns the amount of characters it has printed.
So first the most inner printf
gets called with 56, printing 56
. Then it returns the amount of characters it has printed (2) to the middle printf
, printing 2
. Then finally the amount of characters printed (1) gets passed into the outer printf
, which then gets printed to procude 5621
.
Upvotes: 22
Reputation: 42205
From the printf
man page
Return value
Upon successful return, these functions return the number of characters printed (excluding the null byte used to end output to strings).
56
is printed for the inner printf
2 characters were printed so the argument to the next %d
format specifier is 2
1 character was printed by the middle printf
so the argument to the outer %d
format specifier is 1
Only the outer printf
includes a newline so the preceding calls output one after another on the same line, giving 5621\n
.
Upvotes: 9