Where is environment variables?

Every process has an environment block that contains a set of environment variables and their values. There are two types of environment variables: user environment variables (set for each user) and system environment variables (set for everyone). An environment variable is a dynamic-named value that can affect the way running processes will behave on a computer.

By default, a child process inherits the environment variables of its parent process. Programs started by the command processor inherit the command processor’s environment variables.

How to set or change the Environment Variables?

Windows

Environment Variables

Windows 10 and Windows 8
  1. In Search, search for and then select: System (Control Panel)
  2. Click the Advanced system settings link.
  3. 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.
  4. In the Edit System Variable (or New System Variable) window, specify the value of the PATHenvironment variable. Click OK. Close all remaining windows by clicking OK.
  5. Reopen Command prompt window, and run your java code.
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 PATHenvironment variable. Click OK. Close all remaining windows by clicking OK.
  6. Reopen Command prompt window, and run your java code.
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 PATHenvironment variable. Click OK. Close all remaining windows by clicking OK.
  6. Reopen Command prompt window, and run your java code.
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 PATHenvironment variable. Click OK. Close all remaining windows by clicking OK.
  4. Reopen Command prompt window, and run your java code.

Mac OS X

To run a different version of Java, either specify the full path, or use the java_home tool:

% /usr/libexec/java_home -v 1.8.0_73 --exec javac -version

Solaris and Linux

  1. To find out if the path is properly set:
    In a terminal windows, enter:
    % 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.
  2. Determine which java executable is the first one found in your PATH
    In a terminal window, enter:
    % which java
Set the PATH permanently

To set the path permanently, set the path in your startup file.
Note: Instructions for two most popular Shells on Linux and Solaris are listed.

Bash Shell

Edit the startup file (~/.bashrc)

  1. Modify PATH variable
    PATH=/usr/local/jdk1.8.0/bin:$PATH
    export PATH
  2. Save and close the file
  3. Load the startup file
    % . /.profile
  4. Verify that the path is set by repeating the java command
    % java -version
C Shell (csh)

Edit the startup file (~/.cshrc)

  1. Set Path
    set path=(/usr/local/jdk1.8.0/bin $path)
  2. Save and close the file
  3. Load the startup file
    % source ~/.cshrc
  4. Verify that the path is set by repeating the java command
    % java -version

 

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External command

An external command is an MS-DOS command that is not included in command.com. External commands are commonly external either because they require large requirements or are not commonly used commands. The illustration shows each of the external commands are separate files. However, the internal commands are all included in the command.com file.

external command, internal command

Listing of external commands

Below are examples of MS-DOS and Windows command line external commands currently listed on Computer Hope.

  • Append
  • Arp
  • Assign
  • At
  • Attrib
  • Backup
  • Bcdedit
  • Bootsect
  • Cacls
  • Chcp
  • Chkdsk
  • Chkntfs
  • Choice
  • Cipher
  • Clip
  • Comp
  • Compact
  • Convert
  • Debug
  • Defrag
  • Delpart
  • Deltree
  • Diskcomp
  • Diskcopy
  • Doskey
  • Dosshell
  • Driverquery
  • Dumpchk
  • Edit
  • Edlin
  • Expand
  • Extract
  • Fasthelp
  • Fc
  • Fciv
  • Fdisk
  • Find
  • Forfiles
  • Format
  • FTP
  • Gpupdate
  • Graftabl
  • Help
  • Hostname
  • ICacls
  • Ipconfig
  • Label
  • Loadfix
  • logoff
  • Mem
  • Mode
  • More
  • Move
  • Msav
  • Msbackup
  • Mscdex
  • Mscdexnt
  • Mwbackup
  • Msd
  • Msg
  • Nbtstat
  • Net
  • Netsh
  • Netstat
  • Nlsfunc
  • Nslookup
  • Pathping
  • Ping
  • Power
  • Print
  • Reg
  • Robocopy
  • Route
  • Runas
  • Sc
  • Scandisk
  • Scanreg
  • Schtasks
  • Setver
  • Sfc
  • Share
  • Shutdown
  • Smartdrv
  • Sort
  • Subst
  • Sys
  • Systeminfo
  • Taskkill
  • Tasklist
  • Telnet
  • Tracert
  • Tree
  • Tskill
  • Undelete
  • Unformat
  • Wmic
  • Xcopy

Where are the external command files stored?

Many of the external commands are located in the Windows\system32 or Winnt\system32 directories. If you need to locate the external file to delete it, rename it or replace it, you can also find the file through MS-DOS.

How do you run an external command?

As long as the file exists and you have the proper paths, an external command runs just like an internal command by typing the command name at the prompt. However, if the paths are not set properly or they are missing because the command line would not know where to look for the external command, you would get an error. Unless of course you were in the same directory as the command.

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