POSIX Shell reverse oblique confusion

I'm trying to create a wrapper script with simple functionality, but I can't seem to wrap my head around on how to properly handle backslashes. One of my functions looks like this:

#!/bin/sh

func() {
    cmd="$*"
    printf "%s\n" "$cmd"
    echo -e $cmd
}
func '%{NAME}\\n'

      

        
        
        
      

    

This is the correct conclusion as I need it:

%{NAME}\\n
%{NAME}\n

      

        
        
        
      

    

Now the problem is that I cannot use "echo -e" as this script must be run on a * nix system where the echo command does not have the "-e" flag (eg HPUX), this is also why I have to use sh rather than bash. Since I want to make this script as portable as possible, I would not use tr / sed languages ​​or (even worse) script.

The input string format can be chosen arbitrarily. I used% {NAME} for a reason, because if it were just normal characters, something like this would work:

#!/bin/sh

func() {
    cmd="$*"
    printf "%s\n" "$cmd"
    printf $cmd
    echo
}
func 'NAME\\n'

      

        
        
        
      

    

Unfortunately this breaks with characters like "%":

%{NAME}\\n
func.sh: line 6: printf: `{': invalid format character

      

        
        
        
      

    

How can I get the output I want (hopefully) with just printf, which I think is the most portable function to use?