^^M garbles my terminal output

Question

Contrarily to pdfTeX and XeTeX, which send ^^M to the terminal for the character 13, LuaTeX sends the character 13 itself. This garbles the output of my terminal (bash under Ubuntu 10.04).

\edef\foo{\string\^^M}
\message{\meaning\foo ab}

gives

abcro:->\

i.e., the same as

macro:->\
ab 

but smashed into a single line. How can I tell LuaTeX to output ^^M instead?

Answer 1

As @egreg says, it looks like a bug to me. For writing to files you can modify a lua callback but unfortunately the callback (as documented) is not called when writing to the terminal.

\edef\foo{\string\^^M}

{\catcode`\^=12
\directlua{
callback.register(
"process_output_buffer",
function  (s)
snew, n =  string.gsub(s,"\string\r","^^M")
return snew
end)
}}


\message{\meaning\foo ab}
\newwrite\x
\immediate\openout\x=nnl.out
\immediate\write\x{\meaning\foo ab}

\stop

On the terminal you get

ab )o:->\

but in the file you get:

$ cat nnl.out
macro:->\^^Mab

Answer 2

From LuaTeX Reference, beta 0.70.1, section 2.3 UNICODE text support:

Output to the terminal uses ^^ notation for the lower control range (c < 32), with the exception of ^^I, ^^J and ^^M. These are considered 'safe' and therefore print-as-is.

And in the manual are the terminal/log explicitely excluded for process_output_buffer:

4.1.3.2 process_output_buffer (0.43)
[…] It is only called for output to an actual file (that is, excluding the log, the terminal, and \write18 calls).