Re: why bash completion sometimes doesn't work?

[Greg Wooledge <greg@wooledge.org>]

On Mon, Jan 03, 2022 at 08:12:50PM +0000, Long Wind wrote:
> Thank Greg!  i use bash 5.0-4 and bash-completion 1:2.8-6

> i type "ifdown wl" and press Tab, nothing happens
> there's only one wireless device in /etc/network/interfaces
> it shall complete command to "ifdown wlx12345" 
> 
> i've read /etc/skel/.bashrc, programmable completion seems enabled by default
> and it works for other commands, e.g. i type "dhclient enp" and Tab, it becomes "dhclient enp0s1" 

Well.  In this package, the completions for ifdown and dhclient
are very different.  E.g. in dhclient's completion, there's code that
looks like this:

    if [[ "$cur" == -* ]]; then
        COMPREPLY=( $( compgen -W '-p -d -q -1 -r -lf -pf -cf -sf -s -g -n -nw
            -w' -- "$cur" ) )
    else
        _available_interfaces

The ifdown completion, on the other hand, has:

    if [[ $cword -eq 1 ]]; then
        _configured_interfaces
        COMPREPLY=( $(compgen -W '${COMPREPLY[@]}' -- "$cur") )

I wonder what the difference between _available_interfaces and
_configured_interfaces is.  Looks important.