Getting and setting environment variables<\/p>\n
The variables can be used both in scripts and on the command line<\/a>. They are usually referenced by putting special symbols in front of or around the variable name. For instance, to display the user home directory, in most scripting environments, the user has to type:<\/p>\n On DOS<\/a>, OS\/2 or Windows<\/a> systems, the user has to type this:<\/p>\n In Windows PowerShell<\/a>, the user has to type this:<\/p>\n In DOS, OS\/2 and Windows, the To set a variable to a particular value, use:<\/p>\n However, this is temporary. Permanent change to the environment variable can be achieved through editing the registry (not recommended for novices) and using the Windows Resource Kit<\/a> application Users of the Windows GUI can manipulate variables via <Control Panel:System:Advanced:Environment Variables>; through the Windows Registry<\/a> this is done changing the values under HKCU\\Environment (for user specific variables) and HKLM\\SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Environment (for System variables).<\/p>\n To set a variable whose name is in another variable:<\/p>\n This feature allows certain interesting applications. For example, a uni-dimensional array of elements (vector) may be generated this way:<\/p>\n To see the current value of a particular variable, use:<\/p>\n or<\/p>\n Note: Please take note that doing so will print out all variables beginning with ‘VARIABLE’. Another example is:<\/p>\n To see the value of an array element a double expansion is required: one for the subscript value and an additional expansion for the array element. This may be achieved via Delayed\u00a0!VARIABLE! Expansion this way:<\/p>\n To delete a variable, the following command is used:<\/p>\n To set a system variable:<\/p>\n This variable contains the full path to the command processor<\/a>, command.com<\/a>.<\/p>\n This variable contains a semicolon-delimited list of directories in which the command interpreter<\/a> will search for executable files<\/a>. Equivalent to the Unix $PATH variable (although note that PATH on Windows additionally performs the same task as LD_LIBRARY_PATH on Unix-like systems). Note that\u00a0%PATH% can also be set like this PATH=c:\\dos; where SET isn’t required.<\/p>\n These variables contain the path to the directory where temporary files<\/a> should be stored.<\/p>\n These variables generally expand to discrete values, such as the current working directory<\/a>, the current date, or a random number. Some of these are true environment variables and will be expanded by all functions that handle environment variables. Others, like\u00a0%CD% simply look like environment variables and will only be expanded by some functions and shells. They are not case sensitive.<\/p>\n This variable points to the current directory. Equivalent to the output of the command cd<\/tt> when called without arguments.<\/p>\n This variable expands to the current date. The date is displayed according to the current user’s date format<\/a> preferences.<\/p>\n The following is a way of reformatting the date and time for use in file copies. The example assumes UK format of day month year and the time is set for a 24 hour clock.<\/p>\n This variable points to the current error level. If there was an error in the previous command, it is checked against this.<\/p>\n This variable returns a random number between 0 and 32767.<\/p>\n This variable points to the current time. The time is displayed according to the current user’s time format preferences.<\/p>\n These variables refer to locations of critical operating system resources, and as such generally are not user-dependent.<\/p>\n Contains the full path to the Application Data<\/a> directory of the logged-in user. Does not work on Windows NT 4.0 SP6 UK.<\/p>\n This variable is the temporary files of Applications. Its uses include storing of Desktop Themes<\/a>, Windows Error Reporting<\/a>, Caching and profiles of web browsers.<\/p>\n This variable contains the full path to the command processor; on Windows NT based operating systems this is cmd.exe<\/tt>, while on Windows 9x and ME it is the DOS command processor, COMMAND.COM<\/tt>.<\/p>\n This variable contains a semicolon-delimited (do not put spaces in between) list of directories in which the command interpreter will search for an executable file that matches the given command. Equivalent to the Unix<\/a> $PATH<\/tt> variable.<\/p>\n This variable points to Program Files directory, which stores all the installed program of Windows and others. The default on English-language systems is C:\\Program Files<\/tt>. In 64-bit editions of Windows (XP, 2003, Vista), there are also %ProgramFiles(x86)%<\/b> which defaults to C:\\Program Files (x86)<\/tt> and %ProgramW6432%<\/b> which defaults to C:\\Program Files<\/tt>. The\u00a0%ProgramFiles% itself depends on whether the process requesting the environment variable is itself 32-bit or 64-bit (this is caused by Windows-on-Windows 64-bit<\/a> redirection).<\/p>\n This variable points to Common Files directory. The default is C:\\Program Files\\Common Files<\/tt>.<\/p>\n The\u00a0%SystemDrive% variable is a special system-wide environment variable found on Microsoft<\/a> Windows NT<\/a> and its derivatives. Its value is the drive upon which the system directory was placed. Also see next item.<\/p>\n The value of\u00a0%SystemDrive% is in most cases C:<\/tt>.<\/p>\n The\u00a0%SystemRoot% variable is a special system-wide environment variable found on Microsoft Windows NT and its derivatives. Its value is the location of the system directory, including the drive and path.<\/p>\n The drive is the same as\u00a0%SystemDrive% and the default path on a clean installation depends upon the version of the operating system. By default, on a clean installation:<\/p>\n This variable points to the Windows directory (on Windows NT-based operating systems it is identical to the\u00a0%SystemRoot% variable, above). If the System is on drive C: then the default values are:<\/p>\n Note that Windows NT 4 Terminal Server Edition by default installs to C:\\WTSRV<\/tt>.<\/p>\n These variables store information related to resources and settings owned by various user profiles<\/a> within the system. As a general rule, these variables do not refer to critical system resources or locations that are necessary for the OS to run.<\/p>\n The\u00a0%AllUsersProfile%(%PROGRAMDATA%) variable expands to the full path to the All Users profile directory. This profile contains resources and settings that are used by all system accounts. Shortcut<\/a> links copied to the All Users’ Start menu or Desktop directories will appear in every user’s Start menu or Desktop<\/a>, respectively.<\/p>\n The variable holds the name of the Workgroup<\/a> or Windows Domain<\/a> to which the current user belongs. The related variable,\u00a0%LOGONSERVER%, holds the hostname<\/a> of the server that authenticated the current user’s logon credentials (name and password). For Home PCs, and PCs in a Workgroup, the authenticating server is usually the PC itself. For PCs in a Windows Domain, the authenticating server is a domain controller<\/a> (a primary domain controller, or PDC, in Windows NT 4-based domains).<\/p>\n The\u00a0%UserProfile% variable is a special system-wide environment variable found on Microsoft Windows NT and its derivatives. Its value is the location of the current user’s profile directory, in which is found that user’s HKCU registry hive (NTUSER<\/tt>).<\/p>\n Users can also use the %USERNAME%<\/b> variable to determine the active users login identification.<\/p>\n In certain cases it is not possible to create file paths containing environment variables using the Windows GUI, and it is necessary to fight with the user interface to make things work as intended.<\/p>\n Default Values on Microsoft Windows<\/p>\n In this list, there is no environment variable that refers to the location of the user’s My Documents directory, so there is no standard method for setting a program’s home directory to be the My Documents directory.<\/p>\n","protected":false},"excerpt":{"rendered":"echo $HOME<\/pre>\n<\/div>\n<\/div>\n
echo %HOME%<\/pre>\n<\/div>\n<\/div>\n
Write-Output $HOME<\/pre>\n<\/div>\n<\/div>\n
DOS, OS\/2 and Windows (Command Prompt)<\/h3>\n
set<\/code><\/b> command without any arguments displays all environment variables along with their values.<\/p>\nset VARIABLE=value<\/pre>\n<\/div>\n<\/div>\n
setx.exe<\/code>. With the introduction of Windows Vista<\/a>, the setx<\/code> command became part of Windows.<\/p>\nset %VARNAME%=value<\/pre>\n<\/div>\n<\/div>\n
set VECTOR[%I%]=value of element subscript %I%\n\n:MkVec\nset VECNAME=%1\nset i=0\n:loop\n shift\n if \"%1\" == \"\" goto exitloop\n set \/a i+=1\n set %VECNAME%[%i%]=%1\n goto loop\n:exitloop\nexit \/B %i%\n\ncall :MkVec DOWNAME=Monday Tuesday Wednesday Thursday Friday Saturday Sunday<\/pre>\n<\/div>\n<\/div>\n
echo %VARIABLE%<\/pre>\n<\/div>\n<\/div>\n
set VARIABLE<\/pre>\n<\/div>\n<\/div>\n
C:\\> set p\nPath=c:\\.. ..\nPATHEXT=.COM;.EXE;.BAT;\nPROCESSOR_ARCHITECTURE=.. ..\nPROCESSOR_IDENTIFIER=x8..\nPROCESSOR_LEVEL=6..\nPROCESSOR_REVISION=1706..\nProgramFiles=C:\\Program.. .\nPROMPT=$P$G<\/pre>\n<\/div>\n<\/div>\n
set DOW=value of Day of Week (1..7)\necho !DOWNAME[%DOW%]!<\/pre>\n
set VARIABLE=<\/pre>\n<\/div>\n<\/div>\n
Windows PowerShell<\/h3>\n
Set-Content -Path Env:VARIABLE -value value\n$Env:VARIABLE = value # alternate form<\/pre>\n<\/div>\n<\/div>\n
Examples of DOS environment variables<\/h4>\n
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Examples from Microsoft Windows<\/h3>\n
Discrete value variables<\/h4>\n
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@echo off\necho %DATE% %TIME%\nfor \/F \"tokens=1-3 delims=\/\" %%a in (\"%DATE%\") do set MTH=%%a& set DAY=%%b& set YR=%%c\nfor \/F \"tokens=1-3 delims=:.\" %%a in (\"%TIME%\") do set HR=%%a& set MIN=%%b& set SEC=%%c\nif \"%HR:~0,1%\"==\" \" set HR=0%HR:~1,1%\nset MYDATE=%YR%%MTH%%DAY%-%HR%%MIN%%SEC%\necho %MYDATE%<\/pre>\n<\/div>\n<\/div>\n
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System path variables<\/h4>\n
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User management variables<\/h4>\n
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Windows GUI forced variable expansion<\/h3>\n
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\n Variable<\/th>\n Windows XP<\/th>\n Windows Vista\/7<\/th>\n<\/tr>\n \n \u00a0%ALLUSERSPROFILE%<\/td>\n C:\\Documents and Settings\\All Users<\/td>\n C:\\ProgramData<\/td>\n<\/tr>\n \n \u00a0%APPDATA%<\/td>\n C:\\Documents and Settings\\{username}\\Application Data<\/td>\n C:\\Users\\{username}\\AppData\\Roaming<\/td>\n<\/tr>\n \n \u00a0%COMPUTERNAME%<\/td>\n {computername}<\/td>\n {computername}<\/td>\n<\/tr>\n \n \u00a0%COMMONPROGRAMFILES%<\/td>\n C:\\Program Files\\Common Files<\/td>\n C:\\Program Files\\Common Files<\/td>\n<\/tr>\n \n \u00a0%COMMONPROGRAMFILES(x86)%<\/td>\n C:\\Program Files (x86)\\Common Files (only in 64-bit version)<\/i><\/td>\n C:\\Program Files (x86)\\Common Files (only in 64-bit version)<\/i><\/td>\n<\/tr>\n \n \u00a0%COMSPEC%<\/td>\n C:\\Windows\\System32\\cmd.exe<\/td>\n C:\\Windows\\System32\\cmd.exe<\/td>\n<\/tr>\n \n \u00a0%HOMEDRIVE%<\/td>\n C:<\/td>\n C:<\/td>\n<\/tr>\n \n \u00a0%HOMEPATH%<\/td>\n \\Documents and Settings\\{username}<\/td>\n \\Users\\{username}<\/td>\n<\/tr>\n \n \u00a0%LOCALAPPDATA%<\/td>\n <\/td>\n C:\\Users\\{username}\\AppData\\Local<\/td>\n<\/tr>\n \n \u00a0%LOGONSERVER%<\/td>\n \\\\{domain_logon_server}<\/td>\n \\\\{domain_logon_server}<\/td>\n<\/tr>\n \n \u00a0%PATH%<\/td>\n C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;{plus program paths}<\/td>\n C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;{plus program paths}<\/td>\n<\/tr>\n \n \u00a0%PATHEXT%<\/td>\n .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.WSF;.WSH<\/td>\n .com;.exe;.bat;.cmd;.vbs;.vbe;.js;.jse;.wsf;.wsh;.msc<\/td>\n<\/tr>\n \n \u00a0%PROGRAMDATA%<\/td>\n <\/td>\n \u00a0%SystemDrive%\\ProgramData<\/td>\n<\/tr>\n \n \u00a0%PROGRAMFILES%<\/td>\n \u00a0%SystemDrive%\\Program Files<\/td>\n \u00a0%SystemDrive%\\Program Files<\/td>\n<\/tr>\n \n \u00a0%PROGRAMFILES(X86)%<\/td>\n \u00a0%SystemDrive%\\Program Files (x86) (only in 64-bit version)<\/i><\/td>\n \u00a0%SystemDrive%\\Program Files (x86) (only in 64-bit version)<\/i><\/td>\n<\/tr>\n \n \u00a0%PROMPT%<\/td>\n Code for current command prompt format. Code is usually $P$G<\/td>\n Code for current command prompt format. Code is usually $P$G<\/td>\n<\/tr>\n \n \u00a0%PSModulePath%<\/td>\n <\/td>\n \u00a0%SystemRoot%\\system32\\WindowsPowerShell\\v1.0\\Modules\\<\/td>\n<\/tr>\n \n \u00a0%PUBLIC%<\/td>\n <\/td>\n \u00a0%SystemDrive%\\Users\\Public<\/td>\n<\/tr>\n \n {Drive}:\\$Recycle.Bin<\/td>\n C:\\Recycle.Bin<\/td>\n C:\\$Recycle.Bin<\/td>\n<\/tr>\n \n \u00a0%SystemDrive%<\/td>\n C:<\/td>\n C:<\/td>\n<\/tr>\n \n \u00a0%SystemRoot%<\/td>\n The Windows directory, usually C:\\Windows, formerly C:\\WINNT<\/td>\n \u00a0%SystemDrive%\\Windows<\/td>\n<\/tr>\n \n \u00a0%TEMP% and\u00a0%TMP%<\/td>\n \u00a0%SystemDrive%\\Documents and Settings\\{username}\\Local Settings\\Temp<\/td>\n \u00a0%SystemDrive%\\Users\\{username}\\AppData\\Local\\Temp<\/td>\n<\/tr>\n \n \u00a0%USERDOMAIN%<\/td>\n {userdomain}<\/td>\n {userdomain}<\/td>\n<\/tr>\n \n \u00a0%USERNAME%<\/td>\n {username}<\/td>\n {username}<\/td>\n<\/tr>\n \n \u00a0%USERPROFILE%<\/td>\n \u00a0%SystemDrive%\\Documents and Settings\\{username}<\/td>\n \u00a0%SystemDrive%\\Users\\{username}<\/td>\n<\/tr>\n \n \u00a0%WINDIR%<\/td>\n \u00a0%SystemDrive%\\Windows<\/td>\n \u00a0%SystemDrive%\\Windows<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n