# Environment variables¶

PROJ can be controlled by setting environment variables. Most users will have a use for the PROJ_LIB.

On UNIX systems environment variables can be set for a shell-session with:

$export VAR="some variable" or it can be set for just one command line call:$ VAR="some variable" ./cmd

Environment variables on UNIX are usually removed with the unset command:

\$ unset VAR

On windows systems environment variables can be set in the command line with:

> set VAR="some variable"

`VAR will be available for the entire session, unless it is unset. This is done by setting the variable with no content:

> set VAR=
PROJ_LIB

The location of PROJ resource files. It is only possible to specify a single library in PROJ_LIB; e.g. it does not behave like PATH. PROJ is hardcoded to look for resource files in other locations as well, amongst those are the users home directory, /usr/share/proj and the current folder.

PROJ_DEBUG

Set the debug level of PROJ. The default debug level is zero, which results in no debug output when using PROJ. A number from 1-3, whit 3 being the most verbose setting.