What is the return value from printf() function?

printf function always returns the number of characters printed. Let us understand this with an example:

main()
{
int a=10;
printf("%d",printf("%d %d %d", a,a,a));
}

In this above program the inner printf is first called which prints value of a, three times with space between each value, 10 10 10. Total 5 characters get printed (3 value of 10 and 2 spaces).

As explained earlier the inner printf after printing the values, returns the number of characters printed, 5 which is printed by the outer printf.

The output of the above program is

10 10 10 5

A function always returns a value and printf function returns the number of characters successfully printed.