---
title: Shell completions
description: Tab completion for subcommands, namespaces, and flags is included out of the box. The source generator emits lookup tables at compile time (same model...
url: https://docs-v3-preview.elastic.dev/argh/features/completions
---

# Shell completions
Tab completion for subcommands, namespaces, and flags is included out of the box. The source generator emits **lookup tables** at compile time (same model as routing and `--help`), and a small `__complete` handler answers the shell with one candidate per line.
<note>
  `--completions` is not reserved. Use `__completion` / `__complete` only for Argh's integration.
</note>


## Commands


| Command                                  | Purpose                                                                |
|------------------------------------------|------------------------------------------------------------------------|
| `myapp __completion bash\|zsh\|fish`     | Print an install snippet (substitutes your executable name).           |
| `myapp __complete <shell> -- <words...>` | Return completion candidates; `words` are argv after the program name. |


## Installation

```bash
eval "$(myapp __completion bash)"
```

Add to `~/.bashrc` to persist.
```bash
source <(myapp __completion zsh)
```

Add to `~/.zshrc` to persist.
Fish 3.4+ required (for `commandline -opc`):
```sh
mkdir -p ~/.config/fish/completions
myapp __completion fish > ~/.config/fish/completions/myapp.fish
```


## How it works

The generator emits completion lookup tables alongside routing and help printers. When the shell invokes `__complete`, the handler walks the command tree using the provided context words and returns matching candidates, one per line.
Completions cover:
- Subcommand and namespace names
- Flag names (including aliases)
- Enum values for typed parameters