Re: confused by the wierd "q" option of "string.format".

[Sam Roberts <vieuxtech@...>]

>> however,  under some special cases (e.g. debugging output), I usually need
>> to print the result on a limited screen area and hope not to make mess of
>> other outputs.

%q does what it says it does, but it doesn't give a quoted printable
version of a string in the form I want, either. I use this to quote
strings. Note that it treats \n specially, but not \a\f\t\v\r..etc.
(they all get transformed to decimal escapes).

function quote(_)
    local fmt = string.format
    local _ = fmt("%q", _)

    _ = string.gsub(_, "\\\n", "\\n")
    _ = string.gsub(_, "[%z\1-\31\127-\255]", function (x)
        return fmt("\\%03d",string.byte(x))
    end)

    return _
end

s = "---null=\0,space=\32,nl=\n,quote=\"/\',del=\127,bs=\\,high=\200,low=\6,vt=\v---"

print(string.format("%%q=<%q>\nquote=<%s>", s, quote(s)))


Output:

% lua q.lua
%q=<"---null=\000,space= ,nl=\
,quote=\"/',del=,bs=\\,high=�,low=,vt=
                                      ---">
quote=<"---null=\000,space=
,nl=\n,quote=\"/',del=\127,bs=\\,high=\200,low=\006,vt=\011---">



Cheers,
Sam