1/18/2013

Setting PATH & CLASSPATH in Windows, Solaris, and Linux

How to set the PATH and CLASSPATH environment variables on Microsoft Windows, Solaris, and Linux:
For Windows 7:
a) Setting PATH:
In Environment Variables --> System Variables --> Create New Variable with name PATH, if not exists.
Edit path as shown below:
Example:
Path:  C:\Program Files\Java\jdk1.7.0\bin; 
Check Sample Images:
b) Setting CLASSPATH:

In Environment Variables --> System Variables --> Create New Variable with name CLASSPATH, if not exists.
Edit CLASSPATH as shown below:
Example:
CLASSPATH:  C:\Program Files\Java\jdk1.7.0\lib;
Check Sample Images:



Windows XP
  1. Select Start, select Control Panel. double click System, and select the Advanced tab.
  2. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New.
  3. In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
Windows Vista:
  1. From the desktop, right click the My Computer icon.
  2. Choose Properties from the context menu.
  3. Click the Advanced tab (Advanced system settings link in Vista).
  4. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New.
  5. In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
Windows 7:
  1. From the desktop, right click the Computer icon.
  2. Choose Properties from the context menu.
  3. Click the Advanced system settings link.
  4. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New.
  5. In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.

PATH Variable (Solaris and Linux):

You can run the JDK just fine without setting the PATH variable, or you can optionally set it as a convenience. However, you should set the path variable if you want to be able to run the executables (javac, java, javadoc, and so on) from any directory without having to type the full path of the command. If you do not set the PATH variable, you need to specify the full path to the executable every time you run it, such as:
% /usr/local/jdk1.7.0/bin/javac ClassName.java
To find out if the path is properly set, execute:
% java -version




This will print the version of the java tool, if it can find it. If the version is old or you get the error java: Command not found, then the path is not properly set.



To set the path permanently, set the path in your startup file.

For C shell (csh), edit the startup file (~/.cshrc):




set path=(/usr/local/jdk1.7.0/bin )




For bash, edit the startup file (~/.bashrc):




PATH=/usr/local/jdk1.7.0/bin:
export PATH




For ksh, the startup file is named by the environment variable, ENV. To set the path:




PATH=/usr/local/jdk1.7.0/bin:
export PATH






For sh, edit the profile file (~/.profile):




PATH=/usr/local/jdk1.7.0/bin:
export PATH






Then load the startup file and verify that the path is set by repeating the java command:

For C shell (csh):




% source ~/.cshrc
% java -version




For ksh, bash, or sh:




% . /.profile
% java -version














CLASSPATH variable (All platforms)

               The CLASSPATH variable is one way to tell applications, including the JDK tools, where to look for user classes. (Classes that are part of the JRE, JDK platform, and extensions should be defined through other means, such as the bootstrap class path or the extensions directory.)



               The preferred way to specify the class path is by using the -cp command line switch. This allows the CLASSPATH to be set individually for each application without affecting other applications. Setting the CLASSPATH can be tricky and should be performed with care.



                The default value of the class path is ".", meaning that only the current directory is searched. Specifying either the CLASSPATH variable or the -cp command line switch overrides this value.

To check whether CLASSPATH is set on Microsoft Windows NT/2000/XP, execute the following:




C:> echo %CLASSPATH%




On Solaris or Linux, execute the following:




% echo $CLASSPATH






                  If CLASSPATH is not set you will get a CLASSPATH: Undefined variable error (Solaris or Linux) or simply %CLASSPATH% (Microsoft Windows NT/2000/XP).

To modify the CLASSPATH, use the same procedure you used for the PATH variable.

Class path wildcards allow you to include an entire directory of .jar files in the class path without explicitly naming them individually. For more information, including an explanation of class path wildcards, and a detailed description on how to clean up the CLASSPATH environment variable.












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