Runtime equivalent to fmt.format?

As a spin-off to More efficient way to substitue values in ‘string’; I wonder if there’s a runtime equivalent to the std.fmt.format interface for formatting and printing strings. For example, if I want the user of my program to provide the format specifiers (say to format floats like “{d:.2}”). I could use std.c.printf but really would prefer to stay in pure Zig land.