I use a command called “hc12-console” to connect to 68HC12 microcontrollers over a serial port. The command takes two arguments: the name of a microcontroller to connect to and a file to load. I only have two microcontrollers called “dragon1″ and “dragon2″. Therefore, I want to be able to tab complete the first argument to one of those values only. The second argument should be the name of a file that ends in “.load”.

I do this with a function that checks the argument number and then completes it based on a specified list or by limiting the types of files that will be listed.

_hc12console ()
{
	local cur

	COMPREPLY=()
	cur=${COMP_WORDS[COMP_CWORD]}

	# First argument completes with either dragon1 or dragon2
	if [[ $COMP_CWORD -eq 1 ]] ; then
		COMPREPLY=( $( compgen -W "dragon1 dragon2" -- $cur ) )
		return 0
	fi

	# Second argument completes with only files matching *.load
	if [[ $COMP_CWORD -eq 2 ]] ; then
		COMPREPLY=( $( compgen -f -X '!*.load' -- $cur ) )
		return 0
	fi

	# All other arguments will not auto-complete
	return 0
}
complete -F _hc12console hc12-console

I added the script above to a file that my bashrc sources. It associates the function with the shell command, and then instead of manually typing out:

hc12-console dragon1 file.load <enter>

I can type:

hc12<tab> <tab>1 <tab> <enter>

# Source global definitions
[ -f /etc/bashrc ]      && source /etc/bashrc
[ -f /etc/bash.bashrc ] && source /etc/bash.bashrc
# enable programmable completion features
if [ -z "$BASH_COMPLETION" \
    -a -r ~/.configuration/bash/bash_completion.caliban ]; then
    BASH_COMPLETION=~/.configuration/bash/bash_completion.caliban
    source $BASH_COMPLETION
fi

First, I source the global definitions, Ubuntu uses /etc/bashrc, and Fedora uses /etc/bash.bashrc. After that, if the bash_completion script was already sourced, $BASH_COMPLETION will be set. I check to see if it is zero length (-z) and then source my own copy of it if it is. Now I have advanced bash completion on both Ubuntu and Fedora.