# Environment variables

Assuming you are in a {{root}} enabled system, your shell environment probably defines `ROOTSYS`, 
`PATH` and `LD_LIBRARY_PATH` variables (unless they are installed in standard location). In order to 
use {{uranie}}, assuming it is not installed in standard or {{root}} location, the environment 
variable `LD_LIBRARY_PATH` needs to be completed and must contain the sub directory `lib` of the 
{{uranie}} installation.

To achieve this, one can set the environment variable `URANIESYS` to {{uranie}}'s installation 
directory. Then, depending on the shell family used, the variable `LD_LIBRARY_PATH` can be updated 
as follows:

````{admonition} **C Shell** Family (csh, tcsh, etc.)
```csh
##------ Uranie ------
setenv URANIESYS MyUranieInstallDirectory

setenv LD_LIBRARY_PATH ${URANIESYS}/lib:$LD_LIBRARY_PATH
```
````

````{admonition} **Bourne Shell** Family (sh, bash, etc.)
```bash
##------ Uranie ------
export URANIESYS=MyUranieInstallDirectory

export LD_LIBRARY_PATH=${URANIESYS}/lib:$LD_LIBRARY_PATH
```
````

{{uranie}} may need some external libraries that must be reachable via the `LD_LIBRARY_PATH`. You 
can adapt the former script to take it into account. {{uranie}} installation procedure provides a 
configuration script that tries to create a safe environment.