Cmd.exe explained

Cmd.exe should not be confused with COMMAND.COM.

, also known as Command Prompt, is a shell program on later versions of Windows (NT and CE families), OS/2,^[1] eComStation, ArcaOS, and ReactOS. In some versions of Windows (CE .NET 4.2,^[2] CE 5.0^[3] and Embedded CE 6.0^[4]) it is referred to as the Command Processor Shell. Implementation differs between operating systems, but with significant consistency of behavior and available commands.

Older, related operating systems, DOS and Windows 9x, provided as the shell. replaced in the Windows product line with the introduction of NT. Current versions of Windows include PowerShell as an alternative shell that runs side-by-side with .

The initial version of for Windows NT was developed by Therese Stowell.^[5] Windows CE 2.11 was the first embedded Windows release to support a console and a Windows CE version of .^[6] The ReactOS implementation of is derived from FreeCOM, the FreeDOS command line interpreter.

Use

Desktop integration

In Windows, the shell is presented in the desktop via Windows Terminal or on older versions via Windows Console.

Concurrent piping

In OS/2 and Windows, the shell supports pipes to allow both sides of a pipeline to run concurrently. As a result, it is possible to redirect the standard error stream. In contrast, uses temporary files, and runs the two sides serially, one after the other.

Command separator

Multiple commands can be included in a single line using the command separators, or ||.^[7]

With the separator, a subsequent command is executed even if the previous command indicates an error.^[8] In the following example, each of the three commands is executed, one after the other, and regardless of their exit code.

>CommandA & CommandB & CommandC

With the separator, a command must succeed, i.e. yield the exit code 0, for the subsequent command to execute. In the following example, only executes if completes successfully, and only executes if also completes successfully.

>CommandA && CommandB && CommandC

With the || separator, a command must fail, i.e. yield an exit code not equal 0, for the subsequent command to execute. In the following example, executes if fails, and executes if succeeds.

>CommandA || CommandB && CommandC

Command line limit

The shell limits the length of a command line which includes entered text, individual environment variables that are inherited by other processes, and all environment variable expansions^[9] On Windows XP and later, the maximum length is 8191 (2¹³-1) characters. On earlier versions, such as Windows 2000 or Windows NT 4.0, the maximum length is 2047 (2¹¹-1) characters.

Escaping special characters

The shell reserves the following characters as special:^[7] &<>[]{}^=;!'+,`~ and whitespace. In some cases, an argument that contains such characters must be enclosed in double quotes to escape from the special character handling. For example:

>echo me & youme'you' is not recognized as an internal or external command,operable program or batch file.

>echo "me & you""me & you"

Internal commands

The following sections list internal commands for implementations of the shell on various operating systems.

OS/2

Internal commands in OS/2:^[10]

• break
• chcp
• cd
• chdir
• cls
• copy
• date
• del
• detach
• dir
• dpath
• echo
• erase
• exit
• for
• goto
• if
• md
• mkdir
• path
• pause
• prompt
• rd
• rem
• ren
• rename
• rmdir
• set
• shift
• start
• time
• type
• ver
• verify
• vol

Windows NT family

Internal commands in Windows NT and later:^[11]

• assoc
• break
• call
• cd
• chdir
• cls
• color
• copy
• date
• del
• dir
• dpath
• echo
• endlocal
• erase
• exit
• for
• ftype
• goto
• help
• if
• keys
• md
• mkdir
• mklink
• move
• path
• pause
• popd
• prompt
• pushd
• rd
• rem
• ren
• rename
• rmdir
• set
• setlocal
• shift
• start
• time
• title
• type
• ver
• verify
• vol

Windows CE

Internal commands in Windows CE .NET 4.2,^[12] Windows CE 5.0^[13] and Windows Embedded CE 6.0:^[14]

• attrib
• call
• cd
• chdir
• cls
• copy
• date
• del
• dir
• echo
• erase
• exit
• goto
• help
• if
• md
• mkdir
• move
• path
• pause
• prompt
• pwd
• rd
• rem
• ren
• rename
• rmdir
• set
• shift
• start
• time
• title
• type

The command is available as an external command.

ReactOS

Internal commands in ReactOS:^[15]

• ?
• alias
• assoc
• beep
• call
• cd
• chdir
• choice
• cls
• color
• copy
• ctty
• date
• del
• delete
• delay
• dir
• dirs
• echo
• echos
  • • endlocal
• erase
• exit
• for
• free
• goto
• history
• if
• memory
• md
• mkdir
• mklink
• move
• path
• pause
• popd
• prompt
• pushd
• rd
• rmdir
• rem
• ren
• rename
• replace
• screen
• set
• setlocal
• shift
• start
• time
• timer
• title
• type
• ver
• verify
• vol

Comparison with COMMAND.COM

On Windows, provides various user experience enhancments as compared to, including:

• More detailed error reporting for malformed commands than the generic "Bad command or file name". In OS/2, errors are reported in the chosen language of the system, their text being taken from the system message files. The [[help (command)|HELP]] command can then be issued with the error message number to obtain further information.
• Supports using of arrow keys to scroll through command history. With, this functionality was only available in DR DOS (via HISTORY) and later via an external component called .
• Adds rotating command-line completion for file and folder paths, where the user can cycle through results for the prefix using the, and for reverse direction.
• Treats the caret character as the escape character; the character following it is to be taken literally. There are special characters in and that are meant to alter the behavior of the command line processor. The caret character forces the command line processor to interpret them literally.
• Supports delayed variable expansion with, allowing values of variables to be calculated at runtime instead of during parsing of script before execution (Windows 2000 and later), fixing DOS idioms that made using control structures hard and complex. The extensions can be disabled, providing a stricter compatibility mode.
• The [[DELTREE]] command was merged into the [[RMDIR|rd]] command via the switch.
• and commands limit the scope of changes to the environment. Changes made to the command line environment after are local to the batch file. restores the previous settings.
• The command allows subroutines within batch file. The command only supports calling external batch files.
• File name parser extensions to the command are comparable with C shell.
• The command can perform expression evaluation.
• An expansion of the [[For loop|for]] command supports parsing files and arbitrary sets in addition to file names.
• The new [[PUSHD|pushd]] and [[POPD|popd]] commands provide access past navigated paths similar to forward and back buttons in a web browser or File Explorer.
• The conditional command can perform case-insensitive comparisons and numeric equality and inequality comparisons in addition to case-sensitive string comparisons. This was available in DR-DOS, but not in PC DOS or MS-DOS.

Further reading

• Book: David Moskowitz. David Kerr. 1994. OS/2 2.11 Unleashed. 2nd. Sams Publishing. 978-0672304453. none.
• Book: Stanek, William R.. 2008. Windows Command-Line Administrator's Pocket Consultant. 2nd. Microsoft Press. 978-0735622623. none.

External links

• Web site: Command-line reference A-Z. April 26, 2023 . Microsoft.
• Web site: Cmd . . Microsoft Windows XP Product Documentation . 2006-05-24 . https://web.archive.org/web/20110902070525/http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/cmd.mspx . 2011-09-02 . dead.
• Web site: Command Prompt: frequently asked questions . . windows Help . 2015-04-20 . https://web.archive.org/web/20150422041137/http://windows.microsoft.com/en-us/windows/command-prompt-faq#1TC=windows-7 . 2015-04-22 . dead.
• Web site: An A–Z Index of the Windows CMD command line . SS64.com.
• Web site: Windows CMD.com – Hub of Windows Commands . windowscmd.com . 2022-01-04 . 2022-01-11 . https://web.archive.org/web/20220111180551/https://windowscmd.com/ . dead .
• Most important CMD commands in Windows - colorconsole.de

Notes and References

1. Web site: Notes on using the default OS/2 command processor (CMD.EXE). www.tavi.co.uk.
2. Web site: Command Processor Shell (Windows CE .NET 4.2). Microsoft Docs . June 30, 2006 . live . https://web.archive.org/web/20220831154120/https://docs.microsoft.com/en-us/previous-versions/windows/embedded/ms879823(v%3dmsdn.10) . August 31, 2022.
3. Web site: Command Processor Shell (Windows CE 5.0). Microsoft Docs . September 14, 2012 . live . https://web.archive.org/web/20220828195757/https://docs.microsoft.com/en-us/previous-versions/windows/embedded/aa453925(v%3dmsdn.10) . August 28, 2022.
4. Web site: Command Processor Shell (Windows Embedded CE 6.0). Microsoft Docs . 2012 . live . https://web.archive.org/web/20220905191436/https://docs.microsoft.com/en-us/previous-versions/windows/embedded/ee499728(v%3dwinembedded.60) . September 5, 2022.
5. Book: Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft . G. Pascal . Zachary . 1994 . . 0-02-935671-7 . registration .
6. Book: Douglas McConnaughey Boling. 2001. Programming Microsoft Windows CE. 2nd. Microsoft Press. 978-0735614437.
7. Web site: cmd. Microsoft Learn . September 12, 2023 . live . https://web.archive.org/web/20231121065635/https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/cmd . November 21, 2023.
8. Web site: Command shell overview. 2026-02-22. Microsoft TechNet.
9. https://support.microsoft.com/en-us/help/830473/command-prompt-cmd-exe-command-line-string-limitation Command prompt (Cmd.exe) command-line string limitation
10. Book: Microsoft Operating System/2 User's Reference. 1987. Microsoft.
11. Book: Hill. Tim. Windows NT Shell Scripting. 1998. Macmillan Technical Publishing. 978-1578700479. registration.
12. Web site: Command Processor Commands (Windows CE .NET 4.2). Microsoft Docs . June 30, 2006 . live . https://web.archive.org/web/20220831154120/https://docs.microsoft.com/en-us/previous-versions/windows/embedded/ms879786(v=msdn.10) . August 31, 2022.
13. Web site: Command Processor Commands (Windows CE 5.0). Microsoft Docs . September 14, 2012 . live . https://web.archive.org/web/20220831150618/https://docs.microsoft.com/en-us/previous-versions/windows/embedded/ms907227(v=msdn.10) . August 31, 2022.
14. Web site: Command Processor Commands (Windows Embedded CE 6.0). Microsoft Docs . January 5, 2012 . live . https://web.archive.org/web/20220906020659/https://docs.microsoft.com/en-us/previous-versions/windows/embedded/ee505427(v=winembedded.60) . September 6, 2022.
15. Web site: reactos/reactos . GitHub . December 4, 2021.