environment : Java Glossary

Overview

• W95/W98/Me control the environment with SET PATH= in autoexec.bat.
• Linux controls the environment with export PATH= in your .bashrc file. You might want to set up environment variables to control your locale, e.g.
  export LC_ALL=fr_FR
  export LANG=fr_FR
  export LANGUAGE=fr_FR
• For NT/W2K/XP/W2K3/Vista/W7, since there is no autoexec.bat, you have to preload the environment strings into the environment with Start ⇒ Settings Control Panel ⇒ system ⇒ environment. You can use traditional BAT files to create them, then echo, copy and paste them into the permanent environment. Remember to click set before you click OK or your new settings will be discarded. Also remember to enclose any filenames containing blanks in quotes e.g. "E:\Program Files\gnu\wincvs 1.1". Alternatively always install your apps in directories without embedded spaces. The Control Panel uses a microscopic unreadable font. To proofread, copy/paste to an editor. Beware of spurious spaces introduced by copy/pasting.
• For the Mac, I am told you use JBindery pre Mac OS X use use a magic file described below.

W95/W98/Me Environment

If you find it, make it look exactly like that. If don’t see it, add it. You will need to use a text editor such as NOTEPAD to make the change. The /e:17374 specifies the desired size of the set environment in bytes. Make sure there exists a file called: C:\windows\command.com. If not look for one in C:\ and copy it over.

Here is how to set up your config.sys if you use 4DOS.

NT/W2K/XP/W2K3/Vista/W7 Environment

You can export the NT/W2K/XP/W2K3/Vista/W7 set parameters from the registry two ways that don’t require JNI:

Restart any command prompt boxes after making changes to the environment. Reboot if your changes would affect any programs started with the task manager.

Environment Accessing Kludges

• Use JNI JNI to poke or peek at the environment in a platform specific way.
• exec set xxx and echo %xxx% commands. Beware, all changes to the SET environment are lost as soon as your child task exits.
• Use JConfig.
• Use properties.
• use the java.exe -d%flavour% gambit to transfer data from the set environment to a Java property.
• System.getenv is not considered 100% kosher, but it will get you the environment. It was deprecated in some JDKs, then later resurrected. On windows is it key names are case-insenstive, on other platforms they are case-sensitive. The is no corresponding System. setEnv, but you can set up the environment for an execed process. getenv was deprecated for a while then reinstated.
• Echo the results of set to a env.txt file before your program starts, or in an exec.

Key Environment Variables

Macintosh

The desktop picks up its environment from a property list file in ~/.MacOSX/environment.plist. Both the directory and the file must be created; neither exists by default. The file can be created with the Property List Editor utility included in the developer tools; you can also create a property list with any text editor. Each property in the root dictionary defines one environment variable.

Here is a minimal *.plist file:

This file is loaded at login time; changes to the file only take effect when you log out and back in. Shell-style expansion of variables in values is not applied to environment variables defined here.

OS X also ships with bash, which launches whenever you run Terminal; it respects the ~/.bash_profile. Environment variables defined in ~/.bash_profile only affect bash, e.g., the terminal. Most of the environment variables Java cares about (PATH, ANT_HOME, etc) should be set this way, as they only make sense in the context of the terminal anyway. Locale and language settings are better left to the OS X localization code (which sets appropriate environment variables for you).

For people doing server development, a sensible value of JAVA_HOME is /Library/Java/Home. Owen Jacobson tells me he has never had to set it, even for JBoss or Maven.

In general OS X discourages using the environment in the way most UNICES and Windows do. In general, only UNIX-heritage applications use it at all; native programs tend to prefer the Preferences API and the associated glue in the AppKit framework.

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