Display, set, or remove CMD environment variables. Changes made with SET will remain only for the duration of the current CMD session.
Syntax
SET variable
SET variable=string
SET /A variable=expression
SET "variable="
SET /P variable=[promptString]
SET "
Key
variable : A new or existing environment variable name
string : A text string to assign to the variable.
expression: : Arithmetic Sum
Arithmetic expressions (SET /a)
The expression to be evaluated can include the following operators:
Multiply * Divide / Add + Subtract - Modulus % AND & OR | XOR ^ LSH << RSH >> Multiply Variable *= Divide Variable /= Add Variable += Subtract Variable -= AND Variable &= OR Variable |= XOR Variable ^= LSH Variable <<= RSH Variable >>=
Also see SetX, VarSearch and VarSubstring for more advanced variable manipulation.
Variable names are not case sensitive but the contents can be.
The number one problem people run into with SET is having extra spaces around either the variable name or the string, SET is not forgiving of extra spaces like many other scripting languages.
Variables can contain spaces, variable names can also contain spaces, but this is not recommended.
Type SET without parameters to display all the current environment variables.
Type SET with a variable name to display that variable
SET _department
or use ECHO:
ECHO [%_department%]
The SET command invoked with a string (and no equal sign) will display a wildcard list of all matching variables
Display variables that begin with 'P':
SET p
Display variables that begin with an underscore
SET _
Example of storing a text string:
C:\> SET _dept=Sales and Marketing
C:\> set _
_dept=Sales and Marketing
One variable can be based on another, but this is not dynamic
E.g.
C:\> set xx=fish
C:\> set msg=%xx% chips
C:\> set msg
msg=fish chips
C:\> set xx=sausage
C:\> set msg
msg=fish chips
C:\> set msg=%xx% chips
C:\> set msg
msg=sausage chips
Avoid starting variable names with a number, this will avoid the variable being mis-interpreted as a parameter
%123_myvar% < > %1 23_myvar
To display undocumented system variables:
SET "
The /P switch allows you to set a variable equal to a line of input entered by the user.
The Prompt string is displayed before the user input is read.
@echo off
Set /P _dept=Please enter Department:
If "%_dept%"=="" goto :sub_error
If /i "%_dept%"=="finance" goto sub_finance
If /i "%_dept%"=="hr" goto sub_hr goto:eof :sub_finance echo You chose the finance dept goto:eof :sub_hr echo You chose the hr dept
The Prompt string can be empty.
The CHOICE command is an alternative to SET /P
To place the first line of a file into a variable:
Set /P _MyVar=<MyFilename.txt
A variable can contain spaces and also the variable name itself may contain spaces,
therefore the following assignment:
SET _var =MyText
will create a variable called "_var " - note the trailing space
To avoid problems with extra spaces, issue SET statements
in parentheses, like this:
(SET _department=Some Text)
Alternatively:
SET "_department=Some Text"
Note: To actually include a bracket in the variable, use an escape character.
The SET command will set ERRORLEVEL to 1 if the variable name is not found in the current environment.
This can be detected using the IF ERRORLEVEL command
Type SET with just the variable name and an equals sign:
SET _department=
Better still, to be sure there is no trailing space after the = use:
(SET _department=)
or
SET "_department="
Enclose any logical expressions in "quotes"
Several calculations can be put on one line if separated with commas.
Warning: any SET /A calculation that returns a fractional result will be rounded down to the nearest whole integer.
Examples:
SET /A _result=2+4
(=6)
SET /A _result=5
(=5)
SET /A _result+=5
(=10)
SET /A _result="2<<3"
(=16) { 2 Lsh 3 = binary 10 Lsh 3 = binary 10000 = decimal 16 }
SET /A _result="5%%2"
(=1) { 5/2 = 2 + 2 remainder 1 = 1 }
In a batch script, the Modulus operator (%) must be doubled up to (%%).
SET /A will treat any character string in the expression as an environment variable name. This allows you to do arithmetic with environment variables without having to type any % signs to get the values. SET /A _result=5 + _MyVar
Numeric values are decimal numbers, unless prefixed by
0x for hexadecimal numbers,
0 for octal numbers.
So 0x12 = 022 = 18 decimal
The octal notation can be confusing - all numeric values that start with zeros are treated as octal but 08 and 09 are not valid numbers because 8 and 9 are not valid octal digits.
This is often a cause of error when performing date arithmetic. For example SET /a _day=07 will return the value 7, but SET /a _day=09 will return an error.
Changes made using the SET command are NOT permanent, they apply to the current CMD prompt only and remain only until the CMD window is closed.
To permanently change a variable at the command line use SetX
or with the GUI - Control Panel | System | Environment | System/User Variables
Changing a variable permanently with SetX will not affect any CMD prompt that is already open.
Only new CMD prompts will get the new setting.
You can of course use SetX in conjunction with SET to change both at the same time:
Set _Library=T:\Library\
SetX _Library T:\Library\ /m
Neither SET nor SetX will affect other CMD sessions that are already running on the machine . This as a good thing, particularly on multi-user machines, your scripts won't have to contend with a dynamically changing environment while they are running.
It is possible to add permanent environment variables to the registry (HKCU\Environment), but this is an undocumented (and likely unsupported) technique and still it will not take effect until the users next login.
System environment variables can be found in the registry here:
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
The CALL SET syntax allows a variable substring to be evaluated, read the CALL page for more detail on this technique:
SET start=10 SET length=9 SET string=The quick brown fox jumps over the lazy dog CALL SET substring=%%string:~%start%,%length%%% ECHO (%substring%)
Any SET statement in c:\autoexec.bat may be parsed at boot time
Variables set in this way are not available to 32 bit gui programs - they won't appear in the control panel.
They will appear at the CMD prompt.
If autoexec.bat CALLS any secondary batch files, the additional batch files will NOT be parsed at boot.
This behaviour can be useful on a dual boot PC.
If Command Extensions are disabled all SET commands are disabled other than simple assignments like:
_variable=MyText
The CMD shell will fail to read an environment variable if it contains more than 8,191 characters.
# I got my mind set on you
# I got my mind set on you... - George Harrison
Related:
Syntax - Environment Variables - List of default variables
CALL - Evaluate environment variables
SETX - Set an environment variable permanently.
SETLOCAL - Begin localisation of environment variable
changes
ENDLOCAL - End localisation of environment changes, use to return values
EXIT - Set a specific ERRORLEVEL
Parameters - get a full or partial
pathname from a command line variable.
PATH - Change the %PATH% environment variable.
PATHMAN - Resource Kit utility for modification of both the system
and user paths. Pathman can resolve many problems
and can improve performance by removing duplicate paths. For details see Pathman.wri
REG - Read or Set Registry values
REGEDIT - Import or export registry settings
WMIC ENVIRONMENT - Set environment vars through WMI
StackOverflow - Storing a Newline in a variable
Powershell: Set-Variable - Set a variable and a value (set/sv)
Powershell: Read-Host - Prompt for user input
Equivalent bash command (Linux): env - Display, set, or remove environment variables
