cmd

Starts a new instance of the command interpreter, cmd.exe. If used without parameters, cmd displays the version and copyright information of the operating system.

Syntax

cmd [/c|/k] [/s] [/q] [/d] [/a|/u] [/t:{<b><f> | <f>}] [/e:{on | off}] [/f:{on | off}] [/v:{on | off}] [<string>]

Parameters

The following table lists valid hexadecimal digits that you can use as the values for <b> and <f>:

Remarks

• To redirect command output to the input of another command, use the pipe (|) operator. For example:

  <command1> | <command2>
  

• The double pipe (||) operator is used to execute the next command only if the previous command fails. In the given scenario, command2 is executed only if command1 fails. For example:

  <command1> || <command2>
  

• To redirect command output to a file, use the greater-than angle bracket > character. For example:

  <command1> > <file1.txt>
  

• To group or nest multiple commands together, use &. For example:

  <command1> & <command2>
  

• To use multiple commands for <string>, separate them by the command separator &&. For example:

  <command1> && <command2> && <command3>
  

  Note

  When you use &&, the command following && runs only if the preceding command completes successfully. Cmd executes the first command, and proceeds to the next only if the previous command was successful. Otherwise, if the previous command fails, the subsequent commands won't be executed.

• The ampersand &, pipe |, and parentheses ( ) are special characters that must be preceded by the escape character ^ or quotation marks when you pass them as arguments.

• If a command completes an operation successfully, it returns an exit code of zero (0) or no exit code.

• If the directory path, files, or any information you supply contains spaces, you must use double quotation marks (" ") around the text, such as "Computer Name". For example:

  mkdir Test && mkdir "Test 2" && move "Test 2" Test
  

• You must use quotation marks around the following special characters: & < > [ ] | { } ^ = ; ! ' + , ` ~ [white space].

• If you specify /c or /k, the cmd processes, the remainder of <string>, and the quotation marks are preserved only if all of the following conditions are met:

  • You don't also use /s.
  • You use exactly one set of quotation marks.
  • You don't use any special characters within the quotation marks, for example: & < > ( ) @ ^ |.
  • You use one or more white-space characters within the quotation marks.
  • The <string> within quotation marks is the name of an executable file.

  If the previous conditions aren't met, <string> is processed by examining the first character to verify whether it's an opening quotation mark. If the first character is an opening quotation mark, it's stripped along with the closing quotation mark. Any text following the closing quotation marks is preserved.

• If you don't specify /d, cmd looks for the following registry subkeys:

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\AutoRun\REG_SZ

  • HKEY_CURRENT_USER\Software\Microsoft\Command Processor\AutoRun\REG_EXPAND_SZ

  If one or both registry subkeys are present, they're executed before all other variables.

• You can disable command extensions for a particular process by using /e:off. You can enable or disable extensions for all cmd command-line options on a computer or user session by setting the following REG_DWORD values:

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\EnableExtensions\REG_DWORD

  • HKEY_CURRENT_USER\Software\Microsoft\Command Processor\EnableExtensions\REG_DWORD

  Set the REG_DWORD value to either 0×1 (enabled) or 0×0 (disabled) in the registry by using Regedit.exe. User-specified settings take precedence over computer settings, and command-line options take precedence over registry settings.

  Caution

  Incorrectly editing the registry might severely damage your system. Before making changes to the registry, you should back up any valued data on the computer.

• When you enable command extensions, the following commands are affected:

  • assoc
  • call
  • chdir (cd)
  • color
  • del (erase)
  • endlocal
  • for
  • ftype
  • goto
  • if
  • mkdir (md)
  • popd
  • prompt
  • pushd
  • set
  • setlocal
  • shift
  • start (also includes changes to external command processes)

• If you enable delayed environment variable expansion, you can use the exclamation point character (!) to substitute the value of an environment variable at run time.

• File and directory name completion isn't enabled by default. You can enable or disable file name completion for a particular process of the cmd command with /f:{on | off}.

• You can enable or disable file and directory name completion for all processes of the cmd command on a computer or for a user logon session by setting the following REG_DWORD values:

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\CompletionChar\REG_DWORD

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\PathCompletionChar\REG_DWORD

  • HKEY_CURRENT_USER\Software\Microsoft\Command Processor\CompletionChar\REG_DWORD

  • HKEY_CURRENT_USER\Software\Microsoft\Command Processor\PathCompletionChar\REG_DWORD

  To set the REG_DWORD value, run Regedit.exe and use the hexadecimal value of a control character for a particular function (for example, 0×9 is TAB and 0×08 is BACKSPACE). Use the [0×20] value for white space, because it isn't a valid control character. User-specified settings take precedence over computer settings, and command-line options take precedence over registry settings.

  Caution

  Incorrectly editing the registry might severely damage your system. Before making changes to the registry, you should back up any valued data on the computer.

• If you enable file and directory name completion by using /f:on, use CTRL+D for directory name completion and CTRL+F for file name completion. The only difference between the key combinations CTRL+D and CTRL+F is that CTRL+D only matches directory names and CTRL+F matches both file and directory names. If you use file and directory name completion on the built-in directory commands cd, md, or rd, directory completion is assumed.

• Pressing CTRL+D or CTRL+F processes the file and directory name completion. These key combination functions append a wildcard character to <string> if one isn't present, build a list of paths that match, and then display the first matching path. If none of the paths match, the file and directory name completion function beeps and doesn't change the display.

  • To move through the list of matching paths, press CTRL+D or CTRL+F repeatedly.
  • To move through the list backwards, press the SHIFT key and CTRL+D or CTRL+F simultaneously.
  • To discard the saved list of matching paths and generate a new list, edit <string> and press CTRL+D or CTRL+F.
  • If you switch between CTRL+D and CTRL+F, the saved list of matching paths is discarded, and a new list is generated.

• File and directory name completion correctly processes file names that contain white space or special characters if you place quotation marks around the matching path.

• If you process file and directory name completion from within <string>, at the point in <string> where the completion was processed, any part of the path to the right of the cursor is discarded.

Using environment variables

The cmd command-shell environment is defined by variables that determine the behavior of the command shell and the operating system. You can define the behavior of the command-shell environment or the entire operating system environment by using two types of environment variables, system and local. System environment variables define the behavior of the global operating system environment. Local environment variables define the behavior of the environment of the current instance of cmd.

Only users with administrative privileges can change system variables. These variables are most commonly used in logon scripts. Local environment variables are only available when the user for whom they were created is logged on to the computer. Local variables set in the HKEY_CURRENT_USER hive are valid only for the current user, but define the behavior of the global operating system environment.

The following list describes the various types of variables in descending order of precedence:

1. Built-in system variables.
2. System variables found in the HKEY_LOCAL_MACHINE hive.
3. Local variables found in the HKEY_CURRENT_USER hive.
4. All environment variables and paths set in the Autoexec.bat file.
5. All environment variables and paths set in a logon script (if present).
6. Variables used interactively in a script or batch file.

In the command shell, each instance of cmd inherits the environment of its parent application. Therefore, you can change the variables in the new cmd environment without affecting the environment of the parent application.

You can view the environment variables in your environment by running one of the following commands:

set

Get-ChildItem Env:

Setting environment variables

To view a variable, type:

set <VariableName>

To add a variable, type:

set <VariableName>=<value>

To delete a variable, type:

set <VariableName>=

You can use most characters as variable values, including white space. If you use the special characters <, >, |, &, or ^, you must precede them with the escape character ^ or double quotation marks. If you use double quotation marks, they're included as part of the value because everything following the equal sign is taken as the value. Consider the following examples:

To create the variable value New&Name, type:

set <VariableName>=New^&Name

To create the variable value "New&Name", type:

set <VariableName>="New&Name"

If you type set <VariableName>=New&Name (without the carat ^ or double quotes) at the command prompt, the following error message might display:

"'Name' is not recognized as an internal or external command, operable program or batch file."

Variable names aren't case-sensitive. However, set displays the variable exactly as you typed it. You can combine uppercase and lowercase letters in your variable names to make your code more readable, for example, UserName.

Substituting environment variable values

To substitute variable values in the command line or scripts, enclose the variable name in percent signs (%VariableName%). This allows cmd to reference the variable's value instead of treating it as literal text. When a script is run, cmd replaces instances of the variable with its value. For example, using %USERNAME% in a script automatically substitutes in the actual username. Variable substitution isn't recursive; cmd checks variables only once.

Related links

• Command-Line Syntax Key