Question

Returns a formatted version of its variable number of arguments
following the description given in its first argument (which must be a string).
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.
The q option formats a string in a form suitable to be safely read
back by the Lua interpreter:
the string is written between double quotes,
and all double quotes, newlines, embedded zeros,
and backslashes in the string
are correctly escaped when written.
For instance, the call

 string.format('%q', 'a string with "quotes" and \n new line')

will produce the string:

 "a string with \"quotes\" and \
 new line"

The options c, d, E, e, f,
g, G, i, o, u, X, and x all
expect a number as argument,
whereas q and s expect a string.

This function does not accept string values
containing embedded zeros.