Printing a char in ANSI C

Question

I've used getchar and putchar to succeessfully print my entered char to the screen before, however I've changed the code slightly and now it prints my entered char twice in a row. Code:

#include <stdio.h>

int main()
{
    int charInput;
    printf("Enter a char >> ");
    charInput = getchar();
    printf("%c", putchar(charInput));

    return 0;
}

I know I could just use putchar without the printf but I wanted to experiment with them. The output I get is:

Enter a char >> a
aa

2 chars are printed to the screen?

Answer 1

The function putchar(charInput) itself print char 'a' and return decimal equivalent of char (e.g ascii) that is printed as char using printf() so total printed two a.

Read Manual page:

int putchar(int c);

The functions, fputc(), putc(), putchar(), putc_unlocked(), and putchar_unlocked() return the character written. If an error occurs, the value EOF is returned. The putw() function returns 0 on success; EOF is returned if a write error occurs, or if an attempt is made to write a read-only stream.

So you can assume:

printf("%c", putchar(charInput));
//      ^            ^ first `a` 
//      | second `a`

is equivalent to:

temp = putchar(charInput);  // first `a`
printf("%c", temp);         // second `a`