Originally Posted by Hko
Also I now noticed that the syntax of printf with parenthesis is accepted and works, though the man page of awk says it is a statement and show printf without parenthesis. So this may be a GNU-awk-only feature.
It is not a Gnu-awk specific feature but actually a correct POSIX syntax.
I would recommend using it as it makes boundaries clearer and let the printf command looks like the C language equivalent.