Command Prompt, also known as cmd.exeorcmd, 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.COMinDOS 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]
 | |
| Other names | Windows Command Processor |
|---|---|
| Developer(s) | Microsoft, IBM, ReactOS contributors |
| Initial release | December 1987; 36 years ago (1987-12) |
| Operating system |
|
| Platform | IA-32, x86-64, ARM (and historically DEC Alpha, MIPS, PowerPC, and Itanium) |
| Predecessor | COMMAND.COM |
| Type | Command-line interpreter |
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 &&.[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 && CommandB && CommandC
In the above example, CommandB will only execute if CommandA completes successfully, and the execution of CommandC depends on the successful completion of CommandB. To process subsequent commands even if the previous command produces an error, the command separator & should be used.[9] For example:
C:\>CommandA & CommandB & CommandC
OnWindows XP or later, the maximum length of the string that can be used at the command prompt is 8191 (213-1) characters. On earlier versions, such as Windows 2000orWindows NT 4.0, the maximum length of the string is 2047 (211-1) 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]
& < > [ ] { } ^ = ; ! ' + , ` ~
and white space.
The following is a list of the Microsoft OS/2 internal cmd.exe commands:[11]
The following list of internal commands is supported by cmd.exeonWindows NT and later:[12]
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]
In addition, the net command is available as an external command stored in \Windows\net.exe.
The ReactOS implementation includes the following internal commands:[2]
On Windows, cmd.exe is mostly compatible with COMMAND.COM but provides the following extensions over it:
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:
