Julia Packages and Environments

Installing Packages: The Typical Approach

Most often, if we want to install a Julia package, we install it via the REPL

] #the ] command enters the Pkg REPL
add PackageName

This will install PackageName from the Julia Package Registry. If we want to install multiple packages, we just write them out with a space between them

]
add PackageName OtherPackageName

Installing Unregistered Packages

If a package isn’t registered, we can just add the URL of the Git repository:

pkg> add https://github.com/OWNER/REPO.jl

Installing a Local/In-Development Package

If you want to install a local, in-development package, use dev instead of add

pkg> dev MyPkg

This assumes that MyPkg is in the ~/.julia/dev directory, but we can change this via the environment variable JULIA_PKG_DEVDIR

Creating an Environment

By default, Julia installs packages to your global/default environment, which is denoted by the Julia version name. It’s usually better practice to have a dedicated environment for each project (to help better manage dependencies).

To create an environment, use the activate command from the Pkg REPL. First, navigate to your project directory

cd path/to/MyPkg

Then activate the project from the Julia Pkg REPL:

]
activate .

You’ll get a message saying that project has been activated, but you won’t see any new files yet. The Pkg REPL prompt will change, though, to look like:

(MyPkg) pkg>

And then when you add a package, Julia will create a Project.toml and Manifest.toml file in the project root.

Installing a Project’s Dependencies

If we use someone else’s project (e.g. if we clone a repo from Github), we want to be able to ensure we have all of the dependencies as well. Julia’s instantiate handles this for us. So once we navigate to a project we’ve cloned a project:

git clone https://github.com/OWNER/MyPkg.jl.git
cd MyPkg.jl

And activated it locally:

]
pkg> activate .

We can instantiate it to install any dependencies:

(MyPkg) pkg> instantiate