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From: Bryan Henderson <bryanh@giraffe-data.com>
Newsgroups: gnu.bash.bug
Subject: Re: Backspace echoed incorrectly with TERM=garbage
Date: 19 Jun 2020 02:30:35 +0000
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> Try the xev program. It will show X events and may reveal the keypresses
> you're interested in.

Thanks.  The mystery here is on the other side - things received by the
terminal, not keys pressed.

But I thought of 'strace'.  I attached that to the Bash process and
clearly saw it sending only space characters, no backspaces:

pselect6(1, [0], NULL, NULL, NULL, {[], 8}) = 1 (in [0])
read(0, "q", 1)                         = 1
write(2, " ", 1)                        = 1
pselect6(1, [0], NULL, NULL, NULL, {[], 8}) = 1 (in [0])
read(0, "q", 1)                         = 1
write(2, " ", 1)                        = 1

Compared to the better Bash 4 behavior:

read(0, "q", 1)                         = 1
write(2, "\10 \10", 3)                  = 3
read(0, "q", 1)                         = 1
write(2, "\10 \10", 3)                  = 3

(N.B. "q" is the "erase" character for this experiment).
(N.B. "\10" is ASCII backspace (ctl-H) in octal)


I see what is probably the crucial difference between my working Bash 4 and
my nonworking Bash 5:  Different Ncurses shared libraries.  The former uses
libncurses.so.5 _and_ libtinfo.so.5, while the latter uses only
libtinfo.so.6.

Still doesn't explain why this is a problem only for me, though.

-- 
Bryan Henderson                                   San Jose, California