File.writef

void writef(alias fmt, A...)(A args) if (isSomeString!(typeof(fmt)))

Writes its arguments in text format to the file, according to the format string fmt.

`fmt`	The format string. When passed as a compile-time argument, the string will be statically checked against the argument types passed.
`args`	Items to write.

Exception if the file is not opened.

ErrnoException on an error writing to the file.

void writef(Char, A...)(in Char[] fmt, A args)

ditto