Tab completion for hosts from Ansible inventory for ansible, ssh, scp, rsync

Greetings!

If you work frequently with hosts via Ansible, typing their names in full quickly becomes tedious or you end up opening the inventory to copy a name. It would be nice to get a list of available hosts by pressing Tab.

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Below is an instruction on how to set up host auto-completion from Ansible inventory using the Tab key when using commands like ssh, scp, rsync, ansible, and ansible-playbook.

Sample data

Suppose you have ~/Ansible/inventory.yml:

YAML

all:
  children:
    test:
      children:
        test_hosts_1:
          hosts:
            test-1.r4ven.me:
              ansible_host: 192.168.122.140

            test-2.r4ven.me:
              ansible_host: 192.168.122.141
              ansible_port: 22

            test-3.r4ven.me:
              ansible_host: 192.168.122.142
              ansible_port: 22

        test_hosts_2:
          hosts:
            test-4.r4ven.me:
              ansible_host: 192.168.122.143

            test-5.r4ven.me:
              ansible_host: 192.168.122.144
              ansible_port: 22

            test-6.r4ven.me:
              ansible_host: 192.168.122.145
              ansible_port: 22
Click to expand and view more

And ~/.ssh/config

BASH

Host orangepi
    HostName 10.10.10.12
    User orange
    Port 22
    IdentityFile ~/.ssh/id_ed25519
    Compression yes

Host router
    HostName 10.10.10.13
    User root
    Port 22
    IdentityFile ~/.ssh/id_ed25519
    Compression yes

Host proxmox
    HostName 10.10.10.15
    User root
    Port 22
    IdentityFile ~/.ssh/id_ed25519
Click to expand and view more

Gif demo

Watch a short gif demo to see what we’re talking about:

Snippets for Zsh and Bash

If you use the wonderful ZSH, open .zshrc with vim and add the following snippet:

BASH

vim ~/.zshrc
Click to expand and view more

BASH

_ansible_inventory_hosts() {
    local inv="${ANSIBLE_INVENTORY:-$HOME/Ansible/inventory.yml}"
    [[ -r "$inv" ]] || return 0
    grep -oP '^\s*\K[^:#\s]+(?=:\s*$)' "$inv" 2>/dev/null \
        | grep -vxE 'all|hosts|children|vars|ansible_.*' | sort -u
}

if [[ -r "${ANSIBLE_INVENTORY:-$HOME/Ansible/inventory.yml}" ]]; then
    zstyle -e ':completion:*:(ssh|scp|sftp|rsync):*' hosts 'reply=(
        ${(f)"$(_ansible_inventory_hosts)"}
        ${=${${${(M)${(f)"$(cat /dev/null ~/.ssh/config(N))"}:#(#i)Host *}#(#i)Host }:#*[*?]*}}
        ${(@)${=${${(M)${(f)"$(cat /dev/null {/etc/ssh/ssh_,$HOME/.ssh/}known_hosts(N))"}:#[^|#]*}%%[[:space:]]*}//,/ }}
    )'

    _ansible_hosts_completion() {
        local -a hosts
        if [[ $words[CURRENT-1] == (-l|--limit) ]] ||
           [[ $service == ansible && $CURRENT -eq 2 && $words[CURRENT] != -* ]]; then
            hosts=( ${(f)"$(_ansible_inventory_hosts)"} )
            if (( ${#hosts} )); then
                _describe 'ansible hosts' hosts
                return
            fi
        fi
        _default
    }
    (( $+functions[compdef] )) && compdef _ansible_hosts_completion ansible ansible-playbook
fi
Click to expand and view more

If your shell is the equally wonderful Bash, then edit .bashrc:

BASH

vim ~/.bashrc
Click to expand and view more

BASH

_ansible_inventory_hosts() {
    local inv="${ANSIBLE_INVENTORY:-$HOME/Ansible/inventory.yml}"
    [[ -r "$inv" ]] || return 0

    grep -oP '^\s*\K[^:#\s]+(?=:\s*$)' "$inv" 2> /dev/null \
        | grep -vxE 'all|hosts|children|vars|ansible_.*' | sort -u
}

if [[ -r "${ANSIBLE_INVENTORY:-$HOME/Ansible/inventory.yml}" ]]; then
    declare -A _ansible_orig_comp

    _ansible_hosts_augmented() {
        local fn=${_ansible_orig_comp[$1]}
        if [[ -n $fn ]] && declare -F "$fn" &>/dev/null; then
            "$fn" "$@"
        fi

        local cur=${COMP_WORDS[COMP_CWORD]}
        if [[ $cur != -* ]]; then
            local hosts
            hosts=$(_ansible_inventory_hosts)
            [[ -n $hosts ]] && COMPREPLY+=( $(compgen -W "$hosts" -- "$cur") )
        fi
    }

    _ansible_augment_hosts_completion() {
        local cmd spec fn
        
        for cmd in "$@"; do
            if ! complete -p "$cmd" &>/dev/null; then
                if declare -F _comp_load &>/dev/null; then
                    _comp_load "$cmd" 2>/dev/null
                elif declare -F _completion_loader &>/dev/null; then
                    _completion_loader "$cmd" 2>/dev/null
                fi
            fi
            
            fn=""
            spec=$(complete -p "$cmd" 2>/dev/null) || spec=""
            
            if [[ $spec =~ \ -F\ ([^\ ]+) ]]; then
                fn=${BASH_REMATCH[1]}
            fi
            
            _ansible_orig_comp[$cmd]=$fn
            complete -o default -F _ansible_hosts_augmented "$cmd"
        done
    }

    _ansible_augment_hosts_completion ssh scp sftp rsync
    _ansible_cli_completion() {
        local cur=${COMP_WORDS[COMP_CWORD]} prev=${COMP_WORDS[COMP_CWORD-1]}
        COMPREPLY=()
        
        if [[ $prev == -l || $prev == --limit ]] ||
           [[ $1 == ansible && $COMP_CWORD -eq 1 && $cur != -* ]]; then
            COMPREPLY=( $(compgen -W "$(_ansible_inventory_hosts)" -- "$cur") )
        fi
    }

    complete -o default -F _ansible_cli_completion ansible ansible-playbook
fi
Click to expand and view more

Note that it’s important to correctly specify the path to your inventory file. By default, the snippet looks for the inventory at $HOME/Ansible/inventory.yml. If your path is different, you can either redefine it in the snippet itself or use the ANSIBLE_INVENTORY environment variable:

BASH

export ANSIBLE_INVENTORY=/path/to/your/inventory.yml
Click to expand and view more

Applying changes in the current session

For Zsh:

BASH

exec zsh
Click to expand and view more

For Bash:

BASH

exec bash
Click to expand and view more

Completion will load automatically on the first Tab press.

Testing the setup

BASH

ssh <TAB><TAB>

scp <TAB><TAB>

rsync -e ssh ivan@<TAB><TAB>

ansible <TAB><TAB>

ansible-playbook -l <TAB><TAB>
Click to expand and view more

It should output a list of all hosts from the inventory plus those in ~/.ssh/config and known_hosts. If nothing appears, check that the inventory file is readable and actually contains hosts in YAML format.

In practice, using this snippet will save a lot of time, especially if you have many hosts with long names 🤯.

Why is the bash code three times longer than zsh?

The difference in size is actually not about the language, but about the architecture of completion systems in the two shells.

In zsh-compsys, an extension point is built in from the start. The standard completers _ssh/_scp/_rsync don’t hardcode host sources - they ask for them from a common function _hosts, which in turn reads the configuration via zstyle. The result: to inject your own hosts, you need literally one zstyle -e call, without loading other functions or wrapping.

In bash-completion, everything is simpler and more modest. A system of conventions: one function per command, registration via complete -F, and you’re done. No configuration layers, no shared host storage. So to add to completion without overwriting the native registration, you need:

First load the original completer. bash-completion is lazy - it registers completers only on first Tab. You have to explicitly call _comp_load (newer versions) or _completion_loader (older versions), then parse the output of complete -p to extract the function name.
Save the original. If you simply call complete -F new_function ssh, you overwrite the native registration. You need an associative array to remember the name of the original function and call it first.
Merge results. Pass through the original function, then append your hosts to COMPREPLY via compgen.

Plus there’s a second factor - the density of zsh as a language. Single-line parameter expansions like ${(f)...} and ${(M)...:#...} replace entire loops with grep and sed. In bash, you’d have to spell all that out explicitly, but there’s no point - _ssh from bash-completion can already do it, why duplicate.

To be honest, the zsh code is “small” also because the complexity just lives elsewhere. The functions _hosts and all of compsys are thousands of lines of framework maintained upstream. In bash there’s no such infrastructure, so part of the plumbing ended up in the config. A typical trade-off: a rich framework gives short extensions, a thin convention requires DIY wrapping for everyone.

👨‍💻And…

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💬 All the best ✌️

That should be it. If not, check the logs 🙂

Tab completion for hosts from Ansible inventory for ansible, ssh, scp, rsync

🖐️Hey!

Sample data

Gif demo

Snippets for Zsh and Bash

Applying changes in the current session

Testing the setup

Why is the bash code three times longer than zsh?

👨‍💻And…

Copyright Notice

Table of Contents

🖐️Hey!

Sample data

Gif demo

Snippets for Zsh and Bash

Applying changes in the current session

Testing the setup

Why is the bash code three times longer than zsh?

👨‍💻And…

Copyright Notice

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