Microsoft DOS set command

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About set
Availability
Syntax
Examples
Secret Commands

About set

Allows you to change one variable or string to another.

Availability

The set command is an internal command that is available in the below Microsoft operating systems.

All Versions of MS-DOS
Windows 95
Windows 98
Windows ME
Windows NT
Windows 2000
Windows XP
Windows 7

Syntax

MS-DOS, Windows 95, Windows 98, Windows ME Syntax

Displays, sets, or removes Windows environment variables.

SET [variable=[string]]

Type SET without parameters to display the current environment variables.

Windows 2000, Windows XP Syntax

Displays, sets, or removes cmd.exe environment variables.

SET [variable=[string]]

Type SET without parameters to display the current environment variables.

If Command Extensions are enabled SET changes as follows:

SET command invoked with just a variable name, no equal sign or value will display the value of all variables whose prefix matches the name given to the SET command. For example:

SET P

would display all variables that begin with the letter 'P'

SET command will set the ERRORLEVEL to 1 if the variable name is not found in the current environment.

SET command will not allow an equal sign to be part of the name of a variable.

Two new switches have been added to the SET command:

SET /A expression
SET /P variable=[promptString]

The /A switch specifies that the string to the right of the equal sign is a numerical expression that is evaluated. The expression evaluator is pretty simple and supports the following operations, in decreasing order of precedence:

If you use any of the logical or modulus operators, you will need to enclose the expression string in quotes. Any non-numeric strings in the expression are treated as environment variable names whose values are converted to numbers before using them. If an environment variable name is specified but is not defined in the current environment, then a value of zero is used. This allows you to do arithmetic with environment variable values without having to type all those % signs to get their values. If SET /A is executed from the command line outside of a command script, then it displays the final value of the expression. The assignment operator requires an environment variable name to the left of the assignment operator. Numeric values are decimal numbers, unless prefixed by 0x for hexadecimal numbers, and 0 for octal numbers. So 0x12 is the same as 18 is the same as 022. Note: the octal notation can be confusing: 08 and 09 are not valid numbers because 8 and 9 are not valid octal digits.

The /P switch allows you to set the value of a variable to a line of input entered by the user. Displays the specified promptString before reading the line of input. The promptString can be empty.

Environment variable substitution has been enhanced as follows:

%PATH:str1=str2%

would expand the PATH environment variable, substituting each occurrence of str1 in the expanded result with str2. str2 can be the empty string to effectively delete all occurrences of str1 from the expanded output. str1 can begin with an asterisk, which matches everything from the beginning of the expanded output to the first occurrence of the remaining portion of str1.

May also specify substrings for an expansion.

%PATH:~10,5%

would expand the PATH environment variable, and then use only the 5 characters that begin at the 11th (offset 10) character of the expanded result. If the length is not specified, then it defaults to the remainder of the variable value. If either number (offset or length) is negative, then the number used is the length of the environment variable value added to the offset or length specified.

%PATH:~-10%

would extract the last 10 characters of the PATH variable.

%PATH:~0,-2%

would extract all but the last 2 characters of the PATH variable.

Finally, support for delayed environment variable expansion has been added. This support is always disabled by default, but may be enabled/disabled via the /V command line switch to CMD.EXE. See CMD /?

Delayed environment variable expansion is useful for getting around the limitations of the current expansion that happens when a line of text is read, not when it is executed. The following example demonstrates the problem with immediate variable expansion:

set VAR=before
if "%VAR%" == "before" (
set VAR=after;
if "%VAR%" == "after" @echo If you see this, it worked
)

would never display the message, since the %VAR% in BOTH IF statements is substituted when the first IF statement is read, since it logically includes the body of the IF, which is a compound statement. So the IF inside the compound statement is really comparing "before" with "after" which will never be equal. Similarly, the following example will not work as expected:

set LIST=
for %i in (*) do set LIST=%LIST% %i
echo %LIST%

in that it will NOT build up a list of files in the current directory, but instead will just set the LIST variable to the last file found. Again, this is because the %LIST% is expanded just once when the FOR statement is read, and at that time the LIST variable is empty. So the actual FOR loop we are executing is:

for %i in (*) do set LIST= %i

which just keeps setting LIST to the last file found.

Delayed environment variable expansion allows you to use a different character (the exclamation mark) to expand environment variables at execution time. If delayed variable expansion is enabled, the above examples could be written as follows to work as intended:

set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "!VAR!" == "after" @echo If you see this, it worked
)

set LIST=
for %i in (*) do set LIST=!LIST! %i
echo %LIST%

If Command Extensions are enabled, then there are several dynamic environment variables that can be expanded, which don't show up.
the list of variables displayed by SET. These variable values are computed dynamically each time the value of the variable is expanded. If the user explicitly defines a variable with one of these names, then that definition will override the dynamic one described below:

%CD% - expands to the current directory string.

%DATE% - expands to current date using same format as DATE command.

%TIME% - expands to current time using same format as TIME command.

%RANDOM% - expands to a random decimal number between 0 and 32767.

%ERRORLEVEL% - expands to the current ERRORLEVEL value

%CMDEXTVERSION% - expands to the current Command Processor Extensions version number.

%CMDCMDLINE% - expands to the original command line that invoked the Command Processor.

Windows 2000 and Windows XP recovery console syntax

set [enviroment_variable]=[True/False]

Examples

set path=c:\windows\command

Set the path to c:\windows\command.

Notice: Users in Microsoft Windows 2000 and Windows XP may have difficulty defining the set values through the MS-DOS prompt. Additional information on how to set the path and other values in Windows 2000 and Windows XP through Microsoft Windows can be found on document CH000549.

set

Display the set values that are currently defined.

How to use the set command as a substitute for the choice command in Windows 2000 and Windows XP

In the below example a user would be prompted to enter an option of 1,2, or 3 to print hello, bye, or test.

@ECHO off
cls
:start
ECHO.
ECHO 1. Print Hello
ECHO 2. Print Bye
ECHO 3. Print Test
set choice=
set /p choice=Type the number to print text.
if not '%choice%'=='' set choice=%choice:~0,1%
if '%choice%'=='1' goto hello
if '%choice%'=='2' goto bye
if '%choice%'=='3' goto test
ECHO "%choice%" is not valid, try again
ECHO.
goto start
:hello
ECHO HELLO
goto end
:bye
ECHO BYE
goto end
:test
ECHO TEST
goto end
:end

Secret commands

If you wanted to hide all your directories from users you can use:

SET DIRCMD=0

This will prevent anyone from seeing the directories; however, they still can be accessed. To allow the directories to be visible again, type:

SET DIRCMD=