Bash Completion script to complete file path after certain arguments options

Alternatively if you do not have the bash-completion-lib, I looked at the source of the _filedir() function and was able to get full bash completion using comptopt -o along with compgen -f:

if [[ ${prev} == --*file ]] || [[ ${prev} == --out ]]; then
    comptopt -o filenames 2>/dev/null
    COMPREPLY=( $(compgen -f -- ${cur}) )
elif ...

However, you do not get the functionality of resolving ~usernames or case-insensitivity that _filedir() provides.

You can use compgen -f to complete filenames, like this:

if [[ ${prev} == --*file ]] || [[ ${prev} == --out ]]; then
    COMPREPLY=( $(compgen -f -- ${cur}) )
elif ...

However, compgen -f isn't great at completing filenames because it doesn't honour spaces in filenames.

A better way is to use the _filedir function available in bash-completion-lib. It might already be available on your system (type: declare -f _filedir to check).

Using _filedir, your completion function becomes:

if [[ ${prev} == --*file ]] || [[ ${prev} == --out ]]; then
    _filedir
elif ...