title	Shell Integration
sidebar_position	12
description	Hooks, completions, and PATH management

Shell Integration

Hooks, Completions, and PATH Management

This guide covers OMG's shell integration features including the shell hook, completions, and ultra-fast shell functions.

🎯 Overview

OMG provides deep shell integration that:

Automatically updates PATH when you change directories
Detects version files and activates the correct runtime
Provides instant completions for all commands
Exposes ultra-fast functions for shell prompts

🔧 Shell Hook Installation

What the Hook Does

The shell hook:

Runs on every directory change (cd)
Runs on every prompt (to catch pushd, popd, etc.)
Detects version files (.nvmrc, .python-version, etc.)
Prepends correct runtime bin directories to PATH
Provides fast package count functions

Installation by Shell

Zsh

Add to ~/.zshrc:

eval "$(omg hook zsh)"

Reload:

source ~/.zshrc
# or
exec zsh

Bash

Add to ~/.bashrc:

eval "$(omg hook bash)"

Reload:

source ~/.bashrc
# or
exec bash

Fish

Add to ~/.config/fish/config.fish:

omg hook fish | source

Reload:

source ~/.config/fish/config.fish
# or
exec fish

Verifying Installation

# Test hook output
omg hook zsh

# Check if hook is active
type _omg_hook

# Test version detection
cd /path/to/project/with/.nvmrc
echo $PATH | grep omg

📝 How Version Detection Works

Detection Order

When you enter a directory, OMG checks for version files in this order:

Current directory
Parent directories (walking up to filesystem root)
Global default (~/.local/share/omg/versions/<runtime>/current)

Supported Version Files

File	Runtime	Priority
`.node-version`	Node.js	1 (highest)
`.nvmrc`	Node.js	2
`.bun-version`	Bun	1
`.python-version`	Python	1
`.ruby-version`	Ruby	1
`.go-version`	Go	1
`go.mod`	Go	2
`.java-version`	Java	1
`rust-toolchain.toml`	Rust	1
`rust-toolchain`	Rust	2
`.tool-versions`	Multiple	3
`.mise.toml`	Multiple	3
`.mise.local.toml`	Multiple	2
`mise.toml`	Multiple	4
`package.json`	Node/Bun	4 (engines/volta)

Version File Formats

Simple Version Files

.nvmrc, .python-version, .go-version, etc.:

20.10.0

Or with v prefix:

v20.10.0

Or aliases (Node.js):

lts/*
lts/hydrogen

rust-toolchain.toml

[toolchain]
channel = "stable"  # or "nightly" or "1.75.0"
components = ["rustfmt", "clippy"]
targets = ["wasm32-unknown-unknown"]
profile = "minimal"

Or simple rust-toolchain file:

stable

.tool-versions (asdf format)

node 20.10.0
python 3.12.0
rust stable
go 1.21.0

.mise.toml

[tools]
node = "20.10.0"
python = "3.12.0"
rust = "stable"
deno = "1.40.0"

[tools.node]
version = "20"

[tools.python]
version = "3.12"

package.json

{
  "engines": {
    "node": ">=18 &lt;21",
    "bun": ">=1.0"
  },
  "volta": {
    "node": "20.10.0",
    "bun": "1.0.25"
  }
}

Priority: engines > volta

🚀 Ultra-Fast Shell Functions

The hook provides cached package count functions for shell prompts.

Cached Functions (Sub-Microsecond)

These read from a cached status file updated by the daemon:

Function	Returns
`omg-ec`	Explicit package count
`omg-tc`	Total package count
`omg-oc`	Orphan count
`omg-uc`	Updates count

Fresh Functions (~1ms)

These read the status file directly:

Function	Returns
`omg-explicit-count`	Explicit package count
`omg-total-count`	Total package count
`omg-orphan-count`	Orphan count
`omg-updates-count`	Updates count

Using in Prompts

Zsh Prompt

# In ~/.zshrc
PROMPT='[📦 $(omg-ec)] %~$ '

# Or with colors
PROMPT='%F{cyan}[$(omg-ec) pkgs]%f %~$ '

# Full example with git
PROMPT='%F{green}%n@%m%f %F{blue}%~%f $(git_prompt_info)[📦 $(omg-ec)]$ '

Bash Prompt

# In ~/.bashrc
export PS1='[\w] $(omg-ec) pkgs$ '

# With colors
export PS1='\[\e[36m\][$(omg-ec) pkgs]\[\e[0m\] \w$ '

Fish Prompt

# In ~/.config/fish/functions/fish_prompt.fish
function fish_prompt
    echo -n (omg-ec)" pkgs "
    set_color blue
    echo -n (prompt_pwd)
    set_color normal
    echo '$ '
end

Performance Comparison

Method	Latency	Use Case
`omg-ec` (cached)	<1μs	Prompts
`omg-explicit-count` (fresh)	~1ms	Scripts
`omg explicit --count`	~<2ms	Commands
`pacman -Qq \| wc -l`	~14ms	Fallback

🔤 Shell Completions

Installation

Zsh

# Create completions directory
mkdir -p ~/.zsh/completions

# Generate completions
omg completions zsh > ~/.zsh/completions/_omg

# Add to fpath in ~/.zshrc (if not already)
fpath=(~/.zsh/completions $fpath)
autoload -Uz compinit && compinit

# Rebuild completion cache
rm ~/.zcompdump
compinit

Bash

# System-wide
sudo omg completions bash > /etc/bash_completion.d/omg

# Or user-only
omg completions bash > ~/.local/share/bash-completion/completions/omg

# Source immediately
source /etc/bash_completion.d/omg

Fish

# User completions
omg completions fish > ~/.config/fish/completions/omg.fish

# System-wide
sudo omg completions fish > /usr/share/fish/vendor_completions.d/omg.fish

Completion Features

OMG provides intelligent completions for:

Commands: All subcommands with descriptions
Package names: From daemon cache (80k+ AUR packages)
Runtime versions: Installed and available versions
Options: All flags with descriptions

Fuzzy Matching

OMG uses Nucleo for ultra-fast fuzzy matching:

omg i frfx<TAB>
# Completes to: firefox

🔄 Hook Behavior Deep Dive

Zsh Hook Internals

The Zsh hook uses precmd and chpwd functions:

_omg_hook() {
  trap -- '' SIGINT
  eval "$(omg hook-env -s zsh)"
  trap - SIGINT
}

typeset -ag precmd_functions
if [[ -z "${precmd_functions[(r)_omg_hook]+1}" ]]; then
  precmd_functions=(_omg_hook ${precmd_functions[@]})
fi

typeset -ag chpwd_functions  
if [[ -z "${chpwd_functions[(r)_omg_hook]+1}" ]]; then
  chpwd_functions=(_omg_hook ${chpwd_functions[@]})
fi

Bash Hook Internals

Bash uses PROMPT_COMMAND:

_omg_hook() {
  local previous_exit_status=$?
  trap -- '' SIGINT
  eval "$(omg hook-env -s bash)"
  trap - SIGINT
  return $previous_exit_status
}

if [[ ! "${PROMPT_COMMAND:-}" =~ _omg_hook ]]; then
  PROMPT_COMMAND="_omg_hook${PROMPT_COMMAND:+;$PROMPT_COMMAND}"
fi

Fish Hook Internals

Fish uses event handlers:

function _omg_hook --on-variable PWD --on-event fish_prompt
  omg hook-env -s fish | source
end

Cache Refresh

The hook includes automatic cache refresh every 60 seconds:

_omg_refresh_cache() {
  local f="${XDG_RUNTIME_DIR:-/tmp}/omg.status"
  [[ -f "$f" ]] || return
  local now=$EPOCHSECONDS
  (( now - _OMG_CACHE_TIME < 60 )) && return
  _OMG_CACHE_TIME=$now
  local data=$(od -An -j8 -N16 -tu4 "$f" 2>/dev/null)
  read _OMG_TOTAL _OMG_EXPLICIT _OMG_ORPHANS _OMG_UPDATES <<< "$data"
}

🛠️ Manual PATH Management

If you prefer manual control over PATH:

Without Hook

# Manually add runtime paths
export PATH="$HOME/.local/share/omg/versions/node/current/bin:$PATH"
export PATH="$HOME/.local/share/omg/versions/python/current/bin:$PATH"
export PATH="$HOME/.local/share/omg/versions/go/current/bin:$PATH"
export PATH="$HOME/.local/share/omg/versions/rust/current/bin:$PATH"

Project-Specific

# Add to project's .envrc (if using direnv)
export PATH="$HOME/.local/share/omg/versions/node/20.10.0/bin:$PATH"

Check Active Versions

# See what's in PATH
echo $PATH | tr ':' '\n' | grep omg

# Check symlinks
ls -la ~/.local/share/omg/versions/node/current

⚙️ Configuration Options

Shims vs Hooks

OMG offers two PATH management methods:

Hooks (Default, Recommended)

Faster runtime switching
PATH modified on directory change
Works with all terminals

Shims

Better IDE compatibility
Wrapper scripts for each binary
Slightly slower execution

Enable shims in ~/.config/omg/config.toml:

shims_enabled = true

Generate shims:

omg shim generate

Runtime Backend

Control runtime resolution:

# In ~/.config/omg/config.toml
runtime_backend = "native-then-mise"

Options:

native — Only OMG's built-in managers
mise — Only mise
native-then-mise — Native first, mise fallback (default)

🔍 Troubleshooting

Hook Not Running

# 1. Check hook is in shell config
grep "omg hook" ~/.zshrc

# 2. Verify hook works
omg hook zsh | head -20

# 3. Check function exists
type _omg_hook

# 4. Force reload
exec zsh

Wrong Version Active

# 1. Check version files
ls -la .nvmrc .python-version .tool-versions

# 2. Check what OMG detects
omg which node

# 3. Check PATH order
echo $PATH | tr ':' '\n' | head -10
# OMG paths should be first

# 4. Force switch
omg use node 20.10.0

Slow Directory Changes

# 1. Ensure daemon is running
omg status

# 2. Check hook-env timing
time omg hook-env -s zsh
# Should be under 10ms

# 3. If slow, the daemon may be down
omg daemon

Completions Not Working

# Zsh
rm ~/.zcompdump
omg completions zsh > ~/.zsh/completions/_omg
compinit

# Check fpath
echo $fpath | tr ' ' '\n' | grep completions

📊 Performance Tips

1. Keep Daemon Running

# Start daemon on login
echo "omg daemon &" >> ~/.zprofile

# Or use systemd
systemctl --user enable omgd

2. Use Cached Functions in Prompts

# Fast (cached)
PROMPT='$(omg-ec) pkgs$ '

# Avoid (hits binary each time)
PROMPT='$(omg explicit --count) pkgs$ '

3. Minimize Version Files

Only place version files in project roots, not deeply nested directories.

4. Combine with Starship/Powerlevel10k

These prompt themes have built-in version display. Combine with OMG:

# OMG handles PATH, Starship handles display
eval "$(omg hook zsh)"
eval "$(starship init zsh)"

📚 See Also

Quick Start — Initial setup
Configuration — Shell and runtime settings
Runtime Management — Version file details
Troubleshooting — Common issues

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Shell Integration

🎯 Overview

🔧 Shell Hook Installation

What the Hook Does

Installation by Shell

Zsh

Bash

Fish

Verifying Installation

📝 How Version Detection Works

Detection Order

Supported Version Files

Version File Formats

Simple Version Files

rust-toolchain.toml

.tool-versions (asdf format)

.mise.toml

package.json

🚀 Ultra-Fast Shell Functions

Cached Functions (Sub-Microsecond)

Fresh Functions (~1ms)

Using in Prompts

Zsh Prompt

Bash Prompt

Fish Prompt

Performance Comparison

🔤 Shell Completions

Installation

Zsh

Bash

Fish

Completion Features

Fuzzy Matching

🔄 Hook Behavior Deep Dive

Zsh Hook Internals

Bash Hook Internals

Fish Hook Internals

Cache Refresh

🛠️ Manual PATH Management

Without Hook

Project-Specific

Check Active Versions

⚙️ Configuration Options

Shims vs Hooks

Hooks (Default, Recommended)

Shims

Runtime Backend

🔍 Troubleshooting

Hook Not Running

Wrong Version Active

Slow Directory Changes

Completions Not Working

📊 Performance Tips

1. Keep Daemon Running

2. Use Cached Functions in Prompts

3. Minimize Version Files

4. Combine with Starship/Powerlevel10k

📚 See Also