Hi,
thanks a lot for your quick (and useful) answer Rich.
There are lots of translation modes available at the terminal level,
controllable with the stty command. There may be one to enable
translation of carriage return characters (the enter key) to CR+LF
combinations rather than just NL (LF). Otherwise, you could disable
the translation entirely and just press enter followed by ^J at the
end of each line...
Sounds good, I never thought about it. I think changing such a low-level
behavior just for a specific telnet usage is a little bit overkill. But
it would do the job.
Note that this only matters for interactive use, which is hopefully a
rare thing.
You're right, I forgot to tell that all of this happens in interactive
usage of telnet. It's just a convenient way of trying things with a SMTP
server, and understand a little bit how it works.
Also, any SMTP server I've ever used accepts NL-only (with
no CR) input, so for interactive use rather than script use (wherein
the latter you would want to be fully robust against strict servers),
it probably doesn't matter anyway...
I'm experimenting with a gmail server at the moment. It works well until
I enter the DATA step. At this moment, the server fails to recognize the
termination line (ie. the line containing a single dot), and I get stuck
there with no way out. I figured out it's because of the missing CR
character.
Another solution would be to use sed 's/$/^M/' | telnet ... (where ^M
is a literal carriage return in the command line) so that telnet is
reading from a pipe rather than a terminal, and sed is adding CR's for
you...
Yep ! That's great, exactly what I was looking for. I tried this
solution, and I had a little bit more trouble than expected, but it
worked in the end.
The first thing is that, for interactive use, you don't want sed to
buffer the data. And this feature is not implemented in busybox sed, so
you need another implementation of sed.
The second thing is that there is this nasty piece of code in busybox
telnet.c source:
else if (c == '\r')
outbuf[j++] = '\0'; /* CR -> CR NUL */
Hell ! For some reason, every CR has a NUL appended to it. So I had to
remove that, and then everything works fine. Any idea about the reason
for this stuff ? I read the comment above but it doesn't make sense to
me...
Anyway, in the end the right command is:
$ sed --unbuffered 's/$/\r/' | telnet ...
Arnaud
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