Re: The backspace key can only move forward and cannot delete characters

[Chet Ramey]

On 3/20/24 11:54 AM, G. Branden Robinson wrote:
> At 2024-03-20T09:12:20-0400, Chet Ramey wrote:
> > On 3/19/24 9:38 PM, 高剑平 wrote:
> > > May I ask how to bound to `delete-char' instead of
> > > `backward-delete-char'.
> >
> > This is backward; it sounds like you want to bind it to
> > backward-delete-char.
> >
> > 1. Find out what key sequence your backspace key emits. This is
> >     terminal- specific, but you might be able to find it in your
> >     terminal app's settings. Let's say it's \033[3~
>
> (I'll speak of Bash rather than readline in this message; that is
> because the readline library is bundled with Bash and Chet maintains
> them together.  Formally, Bash is merely a readline application.)

Yes, though bash exercises more of readline's features than most other
applications, with the possible exception of gdb.


> I would add that there are a couple of approaches you can take to this.

These are all valid.

> > 2. Bind that sequence to the desired command in ~/.inputrc
> >
> > "\033[3~":backward-delete-char

Keep in mind that the ^ shorthand for control needs to be \C- in readline
key bindings. For instance, if you want to bind what terminfo (and the tty
driver) shows as ^?, you need to use \C-?.


> [1] As I understand it, Bash has for a long time shipped its own
>      "vendored" version of the GNU termcap library (which has been
>      unmaintained for about 30 years), but it supports using the termcap
>      API of the system's curses library if it offers one (ncurses does).

A last-ditch default so that bash links successfully. It probably works ok
if the termcap entry is in the TERMCAP environment variable.

>      (This probably can't be taken for granted; the X/Open Curses
>      standard withdrew the termcap API in Issue 7--2009--but I reckon
>      System V Unix vendors lazily kept right on doing whatever they'd
>      been doing for years, offering the termcap API or not.  Chet likely
>      has more insight into what deployments look like thanks to Bash
>      configuration/bug reports from relevant OSes.)

Most distros make readline depend on ncurses, which continues to provide
the termcap compatibility functions.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/