Writing a bash completion script similar to scp - bash

Question

I have a script I thought I would allow completions via Bash completion.
The script takes a quoted string argument and then a file or server e.g.
my_cmd "something" stuff
I thought I could leverage the same completion as the scp command by:
have my_cmd &&
_my_cmd()
{
. /usr/share/bash-completion/completions/scp >/dev/null 2>&1 && complete -F _scp $1 && return 124
} && complete -F _my_cmd my_cmd
Which works, however this appends a colon to known servers. Not really knowing much about how the bash-completion works have you any better ideas to accomplish this?

Answer 1

If you look in the scp completion, it's using _known_hosts_real from /usr/share/bash-completion/bash-completion:
# Helper function for completing _known_hosts.
# This function performs host completion based on ssh's config and known_hosts
# files, as well as hostnames reported by avahi-browse if
# COMP_KNOWN_HOSTS_WITH_AVAHI is set to a non-empty value. Also hosts from
# HOSTFILE (compgen -A hostname) are added, unless
# COMP_KNOWN_HOSTS_WITH_HOSTFILE is set to an empty value.
# Usage: _known_hosts_real [OPTIONS] CWORD
# Options: -a Use aliases
# -c Use `:' suffix
# -F configfile Use `configfile' for configuration settings
# -p PREFIX Use PREFIX
# Return: Completions, starting with CWORD, are added to COMPREPLY[]
So, what you probably want is:
_my_cmd() {
local cur prev words cword
_init_completion || return
_known_hosts_real -a "$cur"
} && complete -F _my_cmd my_cmd
This works for me, at least. I admit, I don't generally write these, but it seems consistent with how other completions work. Here is another related example if you want to do some more shell foo with your completions:
https://unix.stackexchange.com/questions/136351/autocomplete-server-names-for-ssh-and-scp
Edited:
Here's for hosts and files, mostly inspired by what _scp_local_files does:
_my_cmd() {
local cur prev words cword
_init_completion || return
_known_hosts_real -a "$cur"
COMPREPLY+=( $( ls -aF1dL $cur* 2>/dev/null | \
sed -e 's/[*#|=]$//g' -e 's/[^\/]$/& /g' -e "s/^/$prefix/") )
} && complete -F _my_cmd my_cmd
Again, this is just taking the stuff you want from the _scp completion and making your own. This works for me, but the directory name completion is a little wonky.