cmd.exe

Command Prompt (cmd.exe)
Other names	Windows Command Processor
Developer(s)	Microsoft, IBM, ReactOS contributors
Initial release	December 1987; 37 years ago
Operating system	Windows NT family; Windows CE family; OS/2; eComStation; ArcaOS; ReactOS;
Platform	IA-32, x86-64, ARM (and historically DEC Alpha, MIPS, PowerPC, and Itanium)
Predecessor	COMMAND.COM
Type	Command-line interpreter

cmd.exe, a.k.a. Command Prompt, is a shell program on later versions of Windows (NT and CE families), OS/2,^[1], eComStation, ArcaOS, and ReactOS^[2]. In some versions of Windows (CE .NET 4.2,^[3] CE 5.0^[4] and Embedded CE 6.0^[5]) 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 COMMAND.COM as the shell. cmd.exe replaced COMMAND.COM 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 cmd.exe.

The initial version of cmd.exe for Windows NT was developed by Therese Stowell.^[6] Windows CE 2.11 was the first embedded Windows release to support a console and a Windows CE version of cmd.exe.^[7] The ReactOS implementation of cmd.exe is derived from FreeCOM, the FreeDOS command line interpreter.^[2]

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, COMMAND.COM 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 separator & or &&.^[8]

With the & separator, a subsequent command is executed even if the previous command indicates an error.^[9] In the following example, each of the three commands is executed, one after the other, and regardless of their result code.

>CommandA & CommandB & CommandC

With the && separator, a command must complete successfully for the subsequent command to execute. In the following example, CommandB only executes if CommandA completes successfully, and CommandC only executes if CommandB also completes successfully.

>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^[10] 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:^[8] &<>[]{}^=;!'+,`~ 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 & you
me
'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:^[11]

Windows NT family

Internal commands in Windows NT and later:^[12]

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,^[13] Windows CE 5.0^[14] and Windows Embedded CE 6.0:^[15]

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 net command is available as an external command.

ReactOS

Internal commands in ReactOS:^[2]

?
alias
assoc
beep
call
cd
chdir
choice
cls
color
copy
ctty
date
del
delete
delay
dir
dirs
echo
echos
echoerr
echoserr
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, cmd.exe provides various user experience enhancments as compared to COMMAND.COM, including:

More detailed error reporting for malformed commands than the generic COMMAND.COM "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 can then be issued with the error message number to obtain further information.
Supports using of arrow keys to scroll through command history. With COMMAND.COM, this functionality was only available in DR DOS; via HISTORY) and later via an external component called DOSKEY.
Adds rotating command-line completion for file and folder paths, where the user can cycle through results for the prefix using the Tab ↹, and ⇧ Shift+Tab ↹ 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 cmd.exe and COMMAND.COM 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 SETLOCAL EnableDelayedExpansion, 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.^[16] The extensions can be disabled, providing a stricter compatibility mode.
The COMMAND.COM DELTREE command was merged into the rd command via the /S switch.
SetLocal and EndLocal commands limit the scope of changes to the environment. Changes made to the command line environment after SetLocal are local to the batch file. EndLocal restores the previous settings.^[17]
The call command allows subroutines within batch file. The COMMAND.COM CALL command only supports calling external batch files.
File name parser extensions to the set command are comparable with C shell.^{[further explanation needed]}
The set command can perform expression evaluation.
An expansion of the for command supports parsing files and arbitrary sets in addition to file names.
The new pushd and popd commands provide access past navigated paths similar to forward and back buttons in a web browser or File Explorer.
The conditional if 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.

References

^ "Notes on using the default OS/2 command processor (CMD.EXE)". www.tavi.co.uk.
^ ^a ^b ^c "reactos/reactos". GitHub. December 4, 2021.
^ "Command Processor Shell (Windows CE .NET 4.2)". Microsoft Docs. June 30, 2006. Archived from the original on August 31, 2022.
^ "Command Processor Shell (Windows CE 5.0)". Microsoft Docs. September 14, 2012. Archived from the original on August 28, 2022.
^ "Command Processor Shell (Windows Embedded CE 6.0)". Microsoft Docs. 2012. Archived from the original on September 5, 2022.
^ Zachary, G. Pascal (1994). Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft. The Free Press. ISBN 0-02-935671-7.
^ Douglas McConnaughey Boling (2001). Programming Microsoft Windows CE (2nd ed.). Microsoft Press. ISBN 978-0735614437.
^ ^a ^b "cmd". Microsoft Learn. September 12, 2023. Archived from the original on November 21, 2023.
^ "Command Redirection, Pipes - Windows CMD - SS64.com". ss64.com. Retrieved September 23, 2021.
^ Command prompt (Cmd.exe) command-line string limitation
^ Microsoft Operating System/2 User's Reference (PDF). Microsoft. 1987.
^ Hill, Tim (1998). Windows NT Shell Scripting. Macmillan Technical Publishing. ISBN 978-1578700479.
^ "Command Processor Commands (Windows CE .NET 4.2)". Microsoft Docs. June 30, 2006. Archived from the original on August 31, 2022.
^ "Command Processor Commands (Windows CE 5.0)". Microsoft Docs. September 14, 2012. Archived from the original on August 31, 2022.
^ "Command Processor Commands (Windows Embedded CE 6.0)". Microsoft Docs. January 5, 2012. Archived from the original on September 6, 2022.
^ "Windows 2000 delayed environment variable expansion". Windows IT Pro. Archived from the original on July 13, 2015. Retrieved July 13, 2015.
^ "Setlocal". TechNet. Microsoft. September 11, 2009. Retrieved January 13, 2015.

External links

"Command-line reference A-Z". Microsoft. April 26, 2023.
"Cmd". Microsoft Windows XP Product Documentation. Microsoft. Archived from the original on September 2, 2011. Retrieved May 24, 2006.
"Command Prompt: frequently asked questions". windows Help. Microsoft. Archived from the original on April 22, 2015. Retrieved April 20, 2015.
"An A–Z Index of the Windows CMD command line". SS64.com.
"Windows CMD.com – Hub of Windows Commands". windowscmd.com. Archived from the original on January 11, 2022. Retrieved January 4, 2022.
Most important CMD commands in Windows - colorconsole.de

[1] "Notes on using the default OS/2 command processor (CMD.EXE)". www.tavi.co.uk.

[ReactOS-2] "reactos/reactos". GitHub. December 4, 2021.

[3] "Command Processor Shell (Windows CE .NET 4.2)". Microsoft Docs. June 30, 2006. Archived from the original on August 31, 2022.

[4] "Command Processor Shell (Windows CE 5.0)". Microsoft Docs. September 14, 2012. Archived from the original on August 28, 2022.

[5] "Command Processor Shell (Windows Embedded CE 6.0)". Microsoft Docs. 2012. Archived from the original on September 5, 2022.

[Zachary_1994-6] Zachary, G. Pascal (1994). Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft. The Free Press. ISBN 0-02-935671-7.

[7] Douglas McConnaughey Boling (2001). Programming Microsoft Windows CE (2nd ed.). Microsoft Press. ISBN 978-0735614437.

[docs.microsoft.com-8] "cmd". Microsoft Learn. September 12, 2023. Archived from the original on November 21, 2023.

[9] "Command Redirection, Pipes - Windows CMD - SS64.com". ss64.com. Retrieved September 23, 2021.

[10] Command prompt (Cmd.exe) command-line string limitation

[11] Microsoft Operating System/2 User's Reference (PDF). Microsoft. 1987.

[12] Hill, Tim (1998). Windows NT Shell Scripting. Macmillan Technical Publishing. ISBN 978-1578700479.

[13] "Command Processor Commands (Windows CE .NET 4.2)". Microsoft Docs. June 30, 2006. Archived from the original on August 31, 2022.

[14] "Command Processor Commands (Windows CE 5.0)". Microsoft Docs. September 14, 2012. Archived from the original on August 31, 2022.

[15] "Command Processor Commands (Windows Embedded CE 6.0)". Microsoft Docs. January 5, 2012. Archived from the original on September 6, 2022.

[Delay-16] "Windows 2000 delayed environment variable expansion". Windows IT Pro. Archived from the original on July 13, 2015. Retrieved July 13, 2015.

[SetLocal-17] "Setlocal". TechNet. Microsoft. September 11, 2009. Retrieved January 13, 2015.

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