Bash – Is it possible to (re)define what readline (embedded in bash) defines as a word

The bash documentation states:

backward-kill-word (M-Rubout)

Kill the word behind point. Word boundaries are the same as those used by backward-word.

And

backward-word (M-b)

Move back to the start of the current or previous word. Words are composed of alphanumeric characters (letters and digits).

The handling of backward-word in Bash 4.2 is done in the bundled libreadline code (text.c:rl_backward_word). The word break is based on rl_alphabetic, which itself relies on the isalnum function. This is locale-dependent, but not configurable directly in bash.

Note that Bash 4.0 introduced another "word" type with the shell-forward-word and shell-backward-word actions (and kill equivalents). These break only on shell meta-characters (()<>;&|") and blanks (possibly locale dependant via isblank), handled in the main bash code (bashline.c).

The question I'd ask would be why would anyone want to do that?

You can disable some aspects of interactive shells like:

• PS1= PS2= to disable the prompts
• set +m to disable job control
• disable history in some shells
• you may be able to unload the zle and all completion modules in zsh.

But if you want the shell to stop being interactive, you could instead do:

. /some/file; exit

To tell it to get the rest of the commands from /some/file (replace with /dev/tty if you still want the commands to be read from the tty device), though there would still be some differences from non-interactive shells, like for the behaviour of return or the fact that it would still do job control or:

exec myshell /dev/tty

To replace your current interactive shell with a non-interactive one that still reads commands from the tty device.

Note that with bash 4.4, set +i returns with a bash: set: +i: invalid option like in most other shells.