# Packages

> In computer programming, a package is a collection of modules or programs that are often published as tools for a range of common use cases, such as text processing and doing math. Programmers can install these packages and take advantage of their functionality within their own code. 

This page provides instructions for installing, using, and troubleshooting packages in Julia.

## Installing Packages <a href="#installing_packages" id="installing_packages"></a>

* Start Julia REPL by typing the following in Terminal or PowerShell (Note: do not need to type $ - this is to indicate the shell prompt)

```
$ julia
```

* Go into REPL mode for Pkg, Julia’s built in package manager, by pressing `]`

```
$ julia ]
```

```
$ (@v1.4) pkg>
```

* Update package repository in Pkg REPL

```
$ (@v1.4) pkg> update
```

* Add packages in Pkg REPL

```
$ (@v1.4) pkg> add CSV
```

```
$ (@v1.4) pkg> add DataFrames
```

* Check installation

```
(@v1.4) pkg> status
            Status `~/.julia/environments/v1.0/Project.toml`
                [336ed68f] CSV v0.4.3
                [a93c6f00] DataFrames v0.17.1
                ...
```

* Get back to the Julia REPL and exit by pressing backspace or ^C.

```
(@v1.4) pkg>

julia>
```

* To see REPL history

```
$ more ~/.julia/logs/repl_history.jl
```

## Using Packages <a href="#using_packages" id="using_packages"></a>

```julia
julia> using CSV
julia> using DataFrames

julia> exit()
```

## Troubleshooting <a href="#troubleshooting" id="troubleshooting"></a>

* If you get an error like: `ERROR: SystemError: opening file "C:\\Users\\User\\.julia\\registries\\General\\Registry.toml"`: No such file or directory
  * Delete `C:\\Users\\User\\.julia\\registries` where User is your computer’s username and try again
  * <https://discourse.julialang.org/t/registry-toml-missing/24152>

## Resources <a href="#documentation" id="documentation"></a>

* [Julia Pkg](https://docs.julialang.org/en/v1/stdlib/Pkg/index.html)
* [Julia Package Registries](https://julialang.org/packages/)
* [JuliaHealth](https://juliahealth.org/) and [BioJulia](https://github.com/BioJulia) organizations (focused on Julia packages for health and life sciences)
* Julia Package: [CSV.jl](https://juliadata.github.io/CSV.jl/stable/)
* Julia Package: [DataFrames.jl](https://juliadata.github.io/DataFrames.jl/stable/)