Lua, Ascii String From Binary Value

Question

I have been reading THIS PAGE (among others) but still can't find my answer.

I'm trying to get Lua to convert an 8 bit value (i.e., an integer from 0 to 255) into a 2 Byte Ascii representation of the corresponding Hex chars

The only Lua syntax that I know how to use for this purpose is this one...

 MyString =  string.format("%1x", That_Number  )  

... but, when the number is 0 to 15, that syntax gives me: 1 2 3 4 5 6 7 8 9 a b c d e f

... while this is what I really want: 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

My Question: Is there a simple syntax to guarantee me a "two digit" Ascii representation ?

("simple" means that it's already built into the syntax; not a function that I have to write)

p.s., it would be nice if I could get the A, B, C, D, E, F characters as upper case.

Answer 1

string.format("%02X", 14))

0 for padding zeros instead of spaces. 2 for a forced width of two characters (not 1 as in your example). X for upper case letter output instead of lower case.

It should be pointed out that essentially none of this answer is Lua specific as those are printf standard sequences and format options.

The Lua reference manual says:

The format string follows the same rules as the printf family of standard C functions. The only differences are that the options/modifiers *, l, L, n, p, and h are not supported and that there is an extra option, q.

so we can infer that the x and X format specifiers are available with the usual width and leading zero modifiers intact.

The same principle applies to a number of Lua library functions. You will often need to refer to the related standard C runtime library function mentioned in the Lua reference to get a complete understanding.