Bài viết

cmd.exe – Wikipedia

32
Command prompt program
Not to be confused with COMMAND.COMFor other uses, see CMD

“Command Prompt” redirects here. For the concept, see Command prompt

Bạn đang đọc: cmd.exe – Wikipedia

Command Prompt, commonly known as cmd.exe or cmd, is the default command-line interpreter for the OS/2,[1] eComStation, ArcaOS, Microsoft Windows (Windows NT family and Windows CE family), and ReactOS[2] operating systems. On Windows CE .NET 4.2,[3] Windows CE 5.0[4] and Windows Embedded CE 6.0[5] it is referred to as the Command Processor Shell. Its implementations differ between operating systems, but the behavior and basic set of commands are consistent. cmd.exe is the counterpart of COMMAND.COM in DOS and Windows 9x systems, and analogous to the Unix shells used on Unix-like systems. 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]

Operation[edit]

cmd.exe interacts with the user through a command-line interface. On Windows, this interface is implemented through the Win32 console. cmd.exe may take advantage of features available to native programs of its own platform. For example, on OS / 2 and Windows, it can use real pipes in command pipelines, allowing both sides of the pipeline to run concurrently. As a result, it is possible to redirect the standard error stream. ( COMMAND.COM uses temporary files, and runs the two sides serially, one after the other. )Multiple commands can be processed in a single command line using the command separator và và. [ 8 ]When using this separator in the Windows cmd.exe, each command must complete successfully for the following commands to execute. For example :

C:\> CommandA và và CommandB và và CommandC

In the above example, Command B will only execute if Command A completes successfully, and the execution of Command C depends on the successful completion of Command B. To process subsequent commands even if the previous command produces an error, the command separator và should be used. [ 9 ] For example :

C:\> CommandA và CommandB và CommandC

On Windows XP or later, the maximum length of the string that can be used at the command prompt is 8191 characters. On earlier versions, such as Windows 2000 or Windows NT 4.0, the maximum length of the string is 2047 characters. This limit includes the command line, individual environment variables that are inherited by other processes, and all environment variable expansions. [ 10 ]

Quotation marks are required for the following special characters:[8]

& < > [ ] { } ^ = ; ! ' +, ` ~ [white space]

Internal commands[edit]

The following is a list of the Microsoft OS / 2 internal cmd.exe commands : [ 11 ]

Windows NT family[edit]

The following list of internal commands is supported by cmd.exe on Windows NT and later : [ 12 ]

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

Windows CE[edit]

The following list of commands is supported by cmd.exe on 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

In addition, the net command is available as an external command stored in \ Windows \ net.exe .

ReactOS[edit]

The ReactOS implementation includes the following internal commands : [ 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[edit]

On Windows, cmd.exe is mostly compatible with COMMAND.COM but provides the following extensions over it :

  • More detailed error messages than the blanket “Bad command or file name” (in the case of malformed commands) of COMMAND.COM. In OS/2, errors are reported in the chosen language of the system, their text being taken from the system message files. The HELP
  • Supports using of arrow keys to scroll through command history. (Under DOS this function was only available under DR DOS (through 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 key (↹), 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 (e.g. “<", ">” 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 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.

Internal commands have also been improved :

See also[edit]

References[edit]

Further reading[edit]

0 ( 0 bình chọn )

Cây tri thức

https://caytrithuc.net
Nền tảng tri thức Việt

Ý kiến bạn đọc (0)

Trả lời

Email của bạn sẽ không được hiển thị công khai. Các trường bắt buộc được đánh dấu *

Bài viết liên quan

Bài viết mới