Is there a way to insert a backspace character while writing to the terminal? I'd like to remove the space character that is automatically inserted between two calls of \message{}:
\message{.}\message{.}\message{.}
\bye
is written as . . . to the terminal but I want ....
The texio library provided by luatex provides more control over message formatting and does not insert a space:
\def\mymessage#1{\directlua{texio.write("\luaescapestring{#1}")}}
\mymessage{.}\mymessage{.}\mymessage{.}
\bye
The result is:
grendel:io sharpie$ luatex io.tex
This is LuaTeX, Version beta-0.60.2-2010071218 (TeX Live 2010) (rev 3736)
(./io.tex... )
No pages of output.
This space is, as far as I know, impossible to avoid between two separate \messages. The solution would be to first combine all the contiguous material in one macro (adding material with \edef\foo{\foo <material>}), and then doing \message{\foo}.
To really know where the space comes from, look in tex.web, documented source code of TeX. The relevant procedure seems to be procedure issue_message;, which calls @<Print string |s| on the terminal@>, defined as follows.
@ @<Print string |s| on the terminal@>=
begin if term_offset+length(s)>max_print_line-2 then print_ln
else if (term_offset>0)or(file_offset>0) then print_char(" ");
slow_print(s); update_terminal;
end
I think that print_char(" ") is the culprit. A related question on \write rather than \message was answered by @TH. last January, and he introduced me to reading tex.web.
