bash-completion-gen

Bash Completion Generator

Generate a bash completion script for any CLI command by discovering its full subcommand tree and options, then building and validating a completion script.

Input

The user provides a command name. The agent must be able to locate and execute the command.

Step 1 — Locate the Command

Find the command binary:

which <command> || find /usr /home -name '<command>' -type f 2>/dev/null | head -10

If the command is not in PATH, use the full path for all subsequent steps. If the command cannot be found at all, stop and inform the user.

Step 2 — Check for Built-in Completion Generator

Many modern CLI tools can generate their own completion scripts. Try these variants in order — if any succeeds, follow its output/instructions and skip to Step 6 (Install):

<command> completion bash
<command> completions bash
<command> --completion bash
<command> --completions bash
<command> generate-completion bash

If none of these work, proceed to manual discovery.

Step 3 — Discover Subcommands and Options

This is a recursive process. Start with the top-level command and work down the subcommand tree.

3a — Top-level Help

Run the command's help:

<command> --help 2>&1
<command> -h 2>&1

From the output, extract:

1. Global options — flags and options that apply to the command itself (e.g., --verbose, --version, -h)
2. Subcommands — named sub-commands listed in the help output
3. Option arguments — which options take values vs. are boolean flags
4. Enum values — options with a fixed set of allowed values (e.g., --format table|json|yaml)

3b — Recurse into Each Subcommand

For each discovered subcommand, run:

<command> <subcommand> --help 2>&1
<command> <subcommand> -h 2>&1

Extract the same information: sub-subcommands, options, option arguments, and enum values.

Continue recursing until there are no deeper subcommands. Most CLIs are 2–3 levels deep.

Efficiency tip: Batch multiple subcommand help calls into a single shell invocation to reduce round-trips: