Basic Environment Variable knowledge

Article Title: Basic knowledge about environment variables. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

1. View All environment variables: env

2. view a variable value: echo $ variable name

3. Set a new variable: export variable name = variable value

4. Set a variable value if it already exists.

Export classpath = $ classpath:/path/to/program

Note: different variables in unix are separated by colons (:).

5. Use unset to clear Environment Variables

Set can set the value of an environment variable. Clear the unset.

If not specified, the variable is null.

Eg: $ export TEST = "test" // Add a variable

$ Env | grep TEST // This command has output to prove that the variable TEST already exists.

The output result is as follows: TEST = test

$ Unset TEST // Delete

$ Env | grep TEST // This command is not output, proving that the variable TEST does not exist

6. Set the java class path

There are three methods:

1> permanent, implemented by setting the classpath environment variable at the system level.

Reload the profile environment # source/etc/profile

2> temporarily, you can set the classpath environment variable in the Command window or shell.

3> at runtime, the class path must be specified each time the java application and JVM are started.

This article from the CSDN blog, reproduced please indicate the source: http://blog.csdn.net/blueyaya/archive/2005/09/29/491800.aspx