| # XMLmind XML Editor - Online Help |

## 3. Environment variables

The following environment variables are convenient to use while customizing or extending XXE. However, these variables are not really meant to be used in production.

Notes:

- All the scripts used to start XXE (that is, `xxe`, `xxe.bat` and `xxe.jstart`, `convertdoc`, `convertdoc.bat`) automatically define system properties corresponding to the following environment variables.

- You cannot use the following environment variables on the Mac[39] due to limitations in Apple's Java™ launcher.

Variable name | Value | Description
--- | --- | ---
`XXE_ADDON_PATH` | List of directory filenames separated by semi-colons ('`;`'). | ### Important Do not forget to clear, or even disable, the Quick Start cache before using `XXE_ADDON_PATH`. All the directories referenced in this list are recursively scanned by XXE during its startup to dynamically discover add-ons. Linux example:
    ~$ XXE_ADDON_PATH="my_docbook;+" convertdoc \
        docb.toHTML doc.xml -u out
More info in chapter "The lookup phase during XXE startup" of Section 1, “Dynamic discovery of add-ons” in XMLmind XML Editor - Configuration and Deployment.
`XXE_GUI` | Relative or absolute filename or URL of an XXE GUI specification (`.xxe_gui`) file. A relative filename is relative to the current working directory. | Specifies which GUI to use for the newly started XXE. Linux example:
    ~$ XXE_GUI=my_gui.xxe_gui xxe &
More info in XMLmind XML Editor - Customizing the User Interface.
`XXE_PREFS_DIR` | Relative or absolute filename of a directory. A relative filename is relative to the current working directory. | Specifies a custom user preferences directory. This directory is created if it does not already exist. Linux example:
    ~$ XXE_PREFS_DIR=test xxe &

[39] This is the case only with `XMLEditor.app`, the application bundle contained in the `.dmg` distribution. If you are a local guru or a consultant you may prefer to download and install the `xxe-*.zip` or `xxe-*.tar.gz` distribution rather than the `xxe-*.dmg` distribution.

After unzipping this archive in a directory of your choice, XMLmind XML Editor may be started using the ``XXE_install_dir`/bin/xxe` shell script. Unlike `XMLEditor.app` which leverages Apple's Java™ launcher, the `xxe` shell script makes it easy working with environment variables such as `XXE_GUI`, `XXE_ADDON_PATH`, etc.