My understanding is that DEL is a control character and that it should
be (essentially) ignored when written to a screen.
This is the case for old versions of xterm (e.g. XFree86 4.0.1(139) on
Red Hat Linux 7.0).
This is not the case for newer versions (e.g. XFree86 4.2.0(165) on
Red Hat Linux 8.0 or XFree86 4.3.99.5(179) on Fedora Core 1). DEL
seems to be displayed as a SPace.
An easy test is to run the following bash command:
echo -e 'X\177Y'
I think that the output should be:
XY
On the newer systems, the output appears to be:
X Y
I care about this because it introduces a bug in JOVE (an editor that
actually predates xterm!).
Interestingly enough, the DEL is output by JOVE to work around a bug
in xterm that was fixed in about this timeframe. Still, I don't wish
to remove the workaround since JOVE continues to work on systems which
need the workaround.
Supporting evidence that DEL should be ignored:
- the copy of the official VT100 manual at
<http://vt100.net/docs/vt100-ug/>
says so in
<http://vt100.net/docs/vt100-ug/table3-10.html>
- The vt102 manual at
<http://vt100.net/docs/vt102-ug/>
does not list DEL is table 5-2, so the following rule from
<http://vt100.net/docs/vt102-ug/chapter5.html#S5.4>
applies:
All other control characters are ignored.
I think that xterm is supposed to emulate VT102.
- the vt202 manual specifies about DEL, in
<http://vt100.net/docs/vt220-rm/table4-1.html>
Mnemonic Code Name Action Taken
...
DEL 7/15 Delete Ignored when received. Note: May not be used as a
time fill character.
I think that xterm follows vt202 sometimes.
Thomas: do you agree with this analysis? I suspect the change was
made by you. What was the intent?
Thanks for all your contributions!
Hugh Redelmeier
[EMAIL PROTECTED] voice: +1 416 482-8253
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