pub get

Get is one of the commands of the pub tool. Learn more about pub.

$ pub get [--offline]

This command gets all the dependencies listed in the pubspec.yaml file in the current working directory, as well as their transitive dependencies, and places them in a packages directory located next to the pubspec. For example:

$ pub get
Got dependencies!

Once the dependencies are acquired, they may be referenced in Dart code. For example, if a package depends on unittest:

import "package:unittest/unittest.dart;

When pub get gets new dependencies, it writes a lockfile to ensure that future gets will use the same versions of those dependencies. Application packages should check in the lockfile to source control; this ensures the application will use the exact same versions of all dependencies for all developers and when deployed to production. Library packages should not check in the lockfile, though, since they’re expected to work with a range of dependency versions.

If a lockfile already exists, pub get uses the versions of dependencies locked in it if possible. If a dependency isn’t locked, pub will get the latest version of that dependency that satisfies all the version constraints. This is the primary difference between pub get and pub upgrade, which always tries to get the latest versions of all dependencies.

Getting a new dependency

If a dependency is added to the pubspec and then pub get is run, it will get the new dependency and any of its transitive dependencies and place them in the packages directory. However, it won’t change the versions of any already-acquired dependencies unless that’s necessary to get the new dependency.

Removing a dependency

If a dependency is removed from the pubspec and then pub get is run, it will remove the dependency from the packages directory, thus making it unavailable for importing. Any transitive dependencies of the removed dependency will also be removed, as long as no remaining immediate dependencies also depend on them. Removing a dependency will never change the versions of any already-acquired dependencies.

Linked packages directories

Every entrypoint in a package needs to be next to a packages directory in order for it to import packages acquired by pub. However, it’s not convenient to put every entrypoint at the top level of the package alongside the main packages directory. You may have example scripts or tests that you want to be able to run from subdirectories.

pub get solves this issue by creating additional packages directories that link to the main packages directory at the root of your package. It assumes your package is laid out according to the package layout guide, and creates a linked packages directory in bin/, test/, and example/, as well as their subdirectories.

The system package cache

Dependencies are not physically stored in the packages directory that pub creates. Dependencies downloaded over the internet, such as those from Git and pub.dartlang.org, are stored in a system-wide cache and linked to from the packages directory. This means that if multiple packages use the same version of the same dependency, it will only need to be downloaded and stored locally once. It also means that it’s safe to delete the packages directory without worrying about re-downloading packages.

By default, the system package cache is located in the .pub-cache subdirectory of your home directory. However, it may be configured by setting the PUB_CACHE environment variable before running Pub.

Getting while offline

If you don’t have network access, you can still run pub get. Since pub downloads packages to a central cache shared by all packages on your system, it can often find previous-downloaded packages there without needing to hit the network.

However, by default, pub will always try to go online when you get if you have any hosted dependencies so that it can see if newer versions of them are available. If you don’t want it to do that, pass the --offline flag when running pub. In this mode, it will only look in your local package cache and try to find a set of versions that work with your package from what’s already available.

Keep in mind that pub will generate a lockfile after it does this. If the only version of some dependency in your cache happens to be old, this will lock your app to that version. The next time you are online, you will likely want to run pub upgrade to upgrade to a later version.

Options

For options that apply to all pub commands, see Global options.