I'm having trouble with my Backspace key on the tmux command prompt. The backspace deletes previous characters (as expected) within tmux but not on the tmux command prompt. For example, <PREFIX>:lists<DEL> will not delete the 's' character. Using C-h instead of the Delete key does delete the 's' character in this situation. C-? does NOT delete the 's' character. Some debugging I've done within the tmux window:
$TERM=screen-256color
infocmp reports kbs=\177 (good)
appres XTerm | grep backarrowKeyIsErase reports as true (good)
appres XTerm | grep ptyInitialErase reports as true (good)
stty -a | grep erase reports as "^H" (bad, I think I want ^?)
I've also tried binding the Backspace key in the .tmux.conf as shown below to both C-h and C-?, neither work. :list-keys within tmux confirms that the mapping is occurring.
bind-key -n BSpace send-keys C-?
I've done a stty erase ^? as well, both before and after invoking tmux and that does not affect the behavior. Finally, I've removed my .tmux.conf entirely and still get the same behavior.
Does the command line use a different set of key bindings that would affect BSpace functionality?
The problem was because there was a mismatch between my $TERM settings, my .Xdefaults, the keybindings for the terminal (I use konsole) and whatever tmux was sending. My specific fix required getting Backspace set to ^? everywhere and NOT ^h. Additionally, tmux's $TERM is best set to screen-256colors or tmux-256colors so you need to ensure that those terminal modes can see the right key mappings.
In my .Xdefaults, note that this is for all VT100 and not just XTerm*VT100 because I want screen, tmux, and konsole to see these entries:
*VT100.Translations: #override \n\
<Key>BackSpace: string(0x7F) \n\
<Key>Delete: string("\033[3~")
*ttyModes: erase ^?
I also had to fix my bindkeys in my ~/.cshrc:
bindkey -a "\e[3~" delete-char
stty erase ^?
... and also add a similar entry to an ~/.inputrc file (which konsole reads):
"\e[3~": delete-char