# 4. Working with Environments

## Creating your own projects

So far we have added packages to the default project at ~/.julia/environments/v1.0. It is however easy to create other, independent, projects. It should be pointed out that when two projects use the same package at the same version, the content of this package is not duplicated. In order to create a new project, create a directory for it and then activate that directory to make it the "active project", which package operations manipulate:

julia> mkdir("MyProject")

julia> cd("MyProject")
/Users/kristoffer/MyProject

(v1.0) pkg> activate .

(MyProject) pkg> st
Status Project.toml

Note that the REPL prompt changed when the new project is activated. Since this is a newly created project, the status command shows that it contains no packages, and in fact, it has no project or manifest file until we add a package to it:

julia> readdir()
0-element Array{String,1}

(MyProject) pkg> add Example
Updating registry at ~/.julia/registries/General
Updating git-repo https://github.com/JuliaRegistries/General.git
Resolving package versions...
Updating Project.toml
[7876af07] + Example v0.5.1
Updating Manifest.toml
[7876af07] + Example v0.5.1
[8dfed614] + Test

julia> readdir()
2-element Array{String,1}:
"Manifest.toml"
"Project.toml"

julia> print(read("Project.toml", String))
[deps]
Example = "7876af07-990d-54b4-ab0e-23690620f79a"

julia> print(read("Manifest.toml", String))
[[Example]]
deps = ["Test"]
git-tree-sha1 = "8eb7b4d4ca487caade9ba3e85932e28ce6d6e1f8"
uuid = "7876af07-990d-54b4-ab0e-23690620f79a"
version = "0.5.1"

[[Test]]
uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

This new environment is completely separate from the one we used earlier.

## Precompiling a project

The REPL command precompile can be used to precompile all the dependencies in the project. You can for example do

(HelloWorld) pkg> update; precompile

to update the dependencies and then precompile them.

## Using someone else's project

Simply clone their project using e.g. git clone, cd to the project directory and call

(v1.0) pkg> activate .

(SomeProject) pkg> instantiate

If the project contains a manifest, this will install the packages in the same state that is given by that manifest. Otherwise, it will resolve the latest versions of the dependencies compatible with the project.

Specifying project on startup

Instead of using activate from within Julia you can specify the project on startup using the --project=<path> flag. For example, to run a script from the command line using the environment in the current directory you can run

\$ julia --project=. myscript.jl