From c9376a4700ca71605c27fa84e0ad49d043846158 Mon Sep 17 00:00:00 2001
From: Kristian Evers <kristianevers@gmail.com>
Date: Wed, 27 Sep 2017 23:13:16 +0200
Subject: Add section PROJ.4 environment variables.

---
 docs/source/usage/environmentvars.rst | 43 +++++++++++++++++++++++++++++++++++
 docs/source/usage/index.rst           |  1 +
 2 files changed, 44 insertions(+)
 create mode 100644 docs/source/usage/environmentvars.rst

(limited to 'docs/source/usage')

diff --git a/docs/source/usage/environmentvars.rst b/docs/source/usage/environmentvars.rst
new file mode 100644
index 00000000..38cb46de
--- /dev/null
+++ b/docs/source/usage/environmentvars.rst
@@ -0,0 +1,43 @@
+.. _environmentvars:
+
+================================================================================
+Environment variables
+================================================================================
+
+PROJ.4 can be crontrolled by setting environment variables. Most users will
+have a use for the :envvar:`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=
+
+.. envvar:: PROJ_LIB
+
+    The location of PROJ.4 :doc:`resource files<resource_files>`.
+    It is only possible to specify a single library in :envvar:`PROJ_LIB`; e.g. it
+    does not behave like PATH. PROJ.4 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.
+
+.. envvar:: PROJ_DEBUG
+
+    Set the debug level of PROJ.4. The default debug level is zero, which results
+    in no debug output when using PROJ.4. A number from 1-3, whit 3 being the most
+    verbose setting.
diff --git a/docs/source/usage/index.rst b/docs/source/usage/index.rst
index 5979426a..81ea4b6b 100644
--- a/docs/source/usage/index.rst
+++ b/docs/source/usage/index.rst
@@ -17,5 +17,6 @@ command line applications or the C API that is a part of the software package.
    projections
    transformation
    resource_files
+   environmentvars
    operations/index
 
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