On Mon, Jan 03, 2022 at 05:25:31AM +0000, Long Wind wrote: > when i type "ifdown wl" and press Tab, it shall complete it with full device > name wlx12345 > i believe it's taken from /etc/network/interfaces > but sometimes it doesn't work in buster
You're describing "programmable completion", which is an optional feature of bash. It's done on a per-command basis. E.g. if you type "cd wlx<TAB>" it will not complete the wlx word using interface names, because there is no such completion defined for the "cd" command. Apparently there is (on your system) for "ifdown" though. By default, Debian installs the bash-completion package, which contains programmable completions for a whole bunch of commands. This is enabled by dotting in a file from ~/.bashrc (the code to do this is at the end of /etc/skel/.bashrc, which becomes the default user ~/.bashrc file if you add users with "adduser"). Unless told otherwise, we're going to assume you're using bash (not zsh) as your shell, and that you've got the standard Debian ~/.bashrc file, so that bash's programmable completion has been enabled. If some programmable completion isn't working the way you expect, then you need to gather some more information. Give us the versions of the bash and bash-completion packages that you've got installed, and then tell us the EXACT command you typed, and what results you got by pressing Tab.
