Networking Environment variables
The command shell makes several environment variables available to commands. Environment variables all begin and end with percent signs. You can use an environment variable anywhere in a command. For example,
C:\>echo %OS% running on a %PROCESSOR_IDENTIFIER%
displays a line such as this:
Windows_NT running on an x86 Family 15 Model 2 Stepping 8,
GenuineIntel
Interestingly, Windows NT, Windows 2000 Server, Windows Server 2003, and Windows Server 2008 all display "Windows_NT" for the operating system name.
If the environment variable represents a path, you may need to enclose it in quotation marks, like this:
C:\>dir "%HOMEPATH%"
This command displays the contents of the user's home directory. The quotation marks are required here because the environme>nt variable expands to a pathname that may include spaces, and the command shell requires that long filenames that include spaces must be enclosed in quotation marks.
Table-1 lists the environment variables that are available to you and your commands.
| Variable | Description |
|---|---|
| %ALLUSERSPROFILE% | The location of the All Users profile |
| %APPDATA% | The path where applications store data by default |
| %CD% | The path to the current directory |
| %CMDCMDLINE% | The command line that was used to start the command shell |
| %CMDEXTVERSION% | The version number of the command shell |
| %COMPUTERNAME% | The computer's name |
| %COMSPEC% | The path to the command shell executable (cmd.exe) |
| %DATE% | The current date in the format generated by the date /t command |
| %ERRORLEVEL% | The error returned by the most recent command |
| %HOMEDRIVE% | The drive letter of the user's home directory |
| %HOMEPATH% | The path to the user's home directory |
| %HOMESHARE% | The network path to the user's shared home directory |
| %LOGONSERVER% | The name of the domain controller the user logged on to |
| %NUMBER_OF_PROCESSORS% | The number of processors on the computer |
| %OS% | The name of the operating system |
| %PATH% | The current search path |
| "%PATHEXT%" | A list of the extensions the operating system treats as executable files |
| %PROCESSOR_ARCHITECTURE% | The chip architecture of the processor |
| %PROCESSOR_IDENTIFIER% | A description of the processor |
| %PROCESSOR_REVISION% | The revision level of the processor |
| %PROMPT% | The current prompt string |
| %RANDOM% | A random number between 1 and 32,767 |
| %SYSTEMDRIVE% | The drive containing the operating system |
| %SYSTEMROOT% | The path to the operating system |
| %TEMP% | The path to a temporary folder for temporary files |
| %TMP% | Same as %TEMP% |
| %TIME% | The time in the format produced by the time /t command |
| %USERDOMAIN% | The name of the user's domain |
| %USERNAME% | The user's account name |
| %USERPROFILE% | The path to the user's profile |
| %WINDIR% | The path to the operating system directory |
Batch files
A batch file is simply a text file that contains one or more commands. Batch files are given the extension .bat and can be run from a command prompt as if they were commands or programs. You can also run a batch file from the Start menu by choosing Start → Run, typing the name of the batch file, and clicking OK.
As a network administrator, you'll find plenty of uses for batch files. Most of them won't be very complicated. For example, here are some examples of very simple batch files:
- Used a one-line file to copy the entire contents of an important shared network drive to a user's computer every night at 10 p.m. The user had just purchased a new Dell computer with a 100GB drive, and the server had only a 20GB drive. The user wanted a quick-and-dirty backup solution that would complement the regular tape backups that ran every night.
- Used a pair of short batch files to stop and then restart Exchange server before and after nightly backups for backup software that didn't have an Exchange plug-in that could back up the mail store while it was open.
- If frequently need to work with several related folders at once, create a short batch file that opens Explorer windows for each of the folders. (You can open an Explorer window from a batch file simply by typing the path to the folder that you want to open as a command.) Then, place the batch file on my desktop so I can get to it quickly.
You can also use batch files to create logon scripts that are executed whenever a user logs on. Microsoft keeps trying to get users to use profiles instead of logon scripts, but many networks still use logon scripts.