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Arcanist User Guide Article

Guide to Arcanist, a command-line interface to Phabricator.

Arcanists provides command-line access to many Phabricator tools (like Differential, Files, and Paste), integrates with static analysis ("lint") and unit tests, and manages common workflows like getting changes into Differential for review.

A detailed command reference is available by running arc help. This document provides an overview of common workflows and installation.

Arcanist has technical, contributor-focused documentation here: http://www.phabricator.com/docs/arcanist/

Quick Start

A quick start guide is available at Arcanist Quick Start. It provides a much more compact summary of how to get arc set up and running for a new project. You may want to start there, and return here if you need more information.


Arcanist is a wrapper script that sits on top of other tools (e.g., Differential, linters, unit test frameworks, git, Mercurial, and SVN) and provides a simple command-line API to manage code review and some related revision control operations.

For a detailed list of all available commands, run:

$ arc help

For detailed information about a specific command, run:

$ arc help <command>

Arcanist allows you to do things like:

  • get detailed help about available commands with arc help
  • send your code to Differential for review with arc diff (for detailed instructions, see Arcanist User Guide: arc diff)
  • show pending revision information with arc list
  • find likely reviewers for a change with arc cover
  • apply changes in a revision to the working copy with arc patch
  • download a patch from Differential with arc export
  • update Git commit messages after review with arc amend
  • commit SVN changes with arc commit
  • push Git and Mercurial changes with arc land
  • view enhanced information about Git branches with arc branch

Once you've configured lint and unit test integration, you can also:

  • check your code for syntax and style errors with arc lint (see Arcanist User Guide: Lint)
  • run unit tests that cover your changes with arc unit

Arcanist integrates with other tools:

  • upload and download files with arc upload and arc download
  • create and view pastes with arc paste

Arcanist has some advanced features as well, you can:

  • execute Conduit method calls with arc call-conduit
  • create or update libphutil libraries with arc liberate
  • activate tab completion with arc shell-complete
  • install arc as a pre-commit hook with arc svn-hook-pre-commit or arc git-hook-pre-receive
  • ...or extend Arcanist and add new commands.

Except where otherwise noted, these workflows are generally agnostic to the underlying version control system and will work properly in git, Mercurial, or SVN repositories.

Installing Arcanist

Arcanist is meant to be installed on your local machine or development server -- whatever machine you're editing code on. It runs on:

Arcanist is written in PHP, so you need to install the PHP CLI first if you don't already have it. Arcanist should run on PHP 5.2 and newer. If you don't have PHP installed, you can download it from http://www.php.net/.

To install Arcanist, pick an install directory and clone the code from GitHub:

some_install_path/ $ git clone https://github.com/phacility/libphutil.git
some_install_path/ $ git clone https://github.com/phacility/arcanist.git

This should leave you with a directory structure like this

some_install_path/    # Wherever you chose to install it.
  arcanist/           # Arcanist-specific code and libraries.
  libphutil/          # A shared library Arcanist depends upon.

Now add some_install_path/arcanist/bin/ to your PATH environment variable. When you type "arc", you should see something like this:

Usage Exception: No command provided. Try 'arc help'.

If you get that far, you've done things correctly. If you get an error or have trouble getting this far, see these detailed guides:

You can later upgrade Arcanist and libphutil to the latest versions with arc upgrade:

$ arc upgrade

Installing Arcanist for a Team

Arcanist changes quickly, so it can be something of a headache to get it installed and keep people up to date. Here are some approaches you might be able to use:

  • Facebook does most development on development servers, which have a standard environment and NFS mounts. Arcanist and libphutil themselves live on an NFS mount, and the default .bashrc adds them to the PATH. Updating the mount source updates everyone's versions, and new employees have a working arc when they first log in.
  • Another common approach is to write an install script as an action into existing build scripts, so users can run make install-arc or ant install-arc or similar.
  • In general, if this sucks and is causing you pain, let us know (see Give Feedback! Get Support!). We're planning to improve this at some point, but it's somewhat complicated to get right. While it can take a little time to set up, we aren't getting feedback that it's a persistent pain point, so it hasn't been a priority.

Installing Tab Completion

If you use bash, you can set up tab completion by adding something like this to your .bashrc, .profile or similar:

source /path/to/arcanist/resources/shell/bash-completion


Some Arcanist commands can be configured. This configuration is read from several sources:

  1. A customization can force any setting with ArcanistWorkingCopyIdentity::setRuntimeConfig().
  2. User can specify settings for working copy in arc/config file located in VCS directory (e.g. .git/arc/config) in JSON format. This file can also be modified by running arc set-config --local.
  3. Repository can specify its config in .arcconfig in JSON format.
  4. User can specify the settings in ~/.arcrc (JSON) through the config key. This file can be modified also by arc set-config --global.
  5. Machine can specify the settings with /etc/arcconfig (JSON). On Windows, the file path is C:\ProgramData\Phabricator\Arcanist\config.

The first place where the setting is defined wins.

Existing settings can be printed with arc get-config.

Next Steps

Continue by:

Advanced topics are also available. These are detailed guides to configuring technical features of arc that refine its behavior. You do not need to read them to get it working.