Bash – Why bash disables autocompletion for some commands and how can I enable it

autocompletebash

It often happens to me that bash disables auto completion for certain commands. This forces me to add random symbol to name of command, use autocompletion, and than fix the command name. This is rather annoying. For example:

# I type:
openvpn s<tab>
# Nothing happens, so I add x
openvpnx s<tab>
# Now this expands to
openvpnx somepath

# Same with ./configure or many other commands...

Is there a way to disable the disabling so that auto-completion ALWAYS works?

Best Answer

Listing completions

You can see what Bash/Readline uses for completing a command using complete -p command, e.g., if I run complete -p openvpn, I get

bash: complete: openvpn: no completion specification

This shows that Readline used by my shell doesn’t have any specific completion for the openvpn command so it defaults to the traditional form of completion, i.e., filenames.

Another example (to demonstrate a defined completion):

$ complete -p dillo
complete -F _filedir_xspec dillo

This indicates that a function named _filedir_xspec is used to provide completions for the dillo command.

Removing completions

To remove a defined completion, use the -r option with the complete builtin:

complete -r openvpn

Related Solutions

How to get the shell functions to make use of existing autocompletion in zsh

To request that a command be completed like another command that is already known to the completion system, you can use the compdef my_command=known_command form of compdef.

compdef s=ssh
compdef {cxterm,uxterm,xterm-color}=xterm

Under the hood, this is basically equivalent to _comps[s]=$_comps[ssh].

Some completion commands apply to a family of functions and read the first word of the command line to determine which particular command to complete. For example, the commands ssh, scp, sftp and a few more are all completed by the function _ssh. In that case, you need to tell the completion function which “service” your function is like (by default, the service is the executable name, here your function's name).

_s () {
  local service=ssh
  _ssh "$@"
}
compdef _s s

Bash Autocomplete – How to Output String Completions to stdout

You can use the following function, which use the same way sudo auto-completion generate the completion list:

comp() {
    local COMP_LINE="$*"
    local COMP_WORDS=("$@")
    local COMP_CWORD=${#COMP_WORDS[@]}
    ((COMP_CWORD--))
    local COMP_POINT=${#COMP_LINE}
    local COMP_WORDBREAKS='"'"'><=;|&(:"
    # Don't really thing any real autocompletion script will rely on
    # the following 2 vars, but on principle they could ~~~  LOL.
    local COMP_TYPE=9
    local COMP_KEY=9
    _command_offset 0
    echo ${COMPREPLY[@]}
}
comp git config ''

where _command_offset is defined in bash-completion (package).

NOTE: the function need to be run in a interactive shell (i.e. if it is in a file, the file need to be sourced instead of just run.) or the necessary completion rules/functions will not be defined.

PS. compgen -A only works for builtin actions, what you should have tried (but doesn't work either) is compgen -F (or actually compgen -o bashdefault -o default -o nospace -F _git). The reason this doesn't work (and doc for bash built-in commands including compgen/complete) can be found in bash(1).