MySQL Cookbook, 2nd Edition

Setting Environment Variables

An environment variable has a value that can be accessed by programs that you run. By setting environment variables, you modify your operating environment. One such variable is PATH, which is used by your command interpreter to determine which directories to search when it looks for programs such as mysql that you tell it to execute. If your PATH is set correctly, you can invoke programs easily no matter what your current directory is. If PATH is not set correctly, your command interpreter will not find them. For example, if the PATH value does not include the directory where mysql is installed, a “command not found” error may occur if you attempt to run mysql by entering its name. You must run it either by specifying its full pathname, or by changing location into the directory where it is installed. Both strategies are unpleasant, and more so with repetition. It’s much better to set your PATH value to name the directories containing the programs you want to use.

Other environment variables are important in other contexts. For example, if you run Perl or Ruby scripts that use module files that you’ve installed, you may need to set the PERL5LIB or RUBYLIB variable to tell Perl or Ruby where to find those modules. For Java, the JAVA_HOME variable should be set to indicate the location of your Java installation, and CLASSPATH should be set to the list of libraries and class files that your Java programs need.

The following discussion describes how to set ...