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Revision as of 19:09, 21 April 2009
 | This article needs additional citations for verification. (July 2007) |
Template:Infobox Windows component
cmd.exe is the command line interpreter on OS/2, Windows CE and on Windows NT-based operating systems (including Windows 2000, XP, Vista, Server 2003 and Server 2008). It is the analog of COMMAND.COM in MS-DOS and Windows 9x systems, or of the Unix shells used on Unix-like systems.
Versions
Therese Stowell developed the initial version of cmd.exe for Windows NT.[1] Although some old DOS commands are not supported or have been changed (e.g. the functionality of deltree was rolled into rd in the form of the /s parameter), cmd.exe still has a greater number of built-in commands.
Both the OS/2 and the Windows NT versions of cmd.exe have more detailed error messages than the blanket "Bad command or file name" (in the case of malformed commands) of command.com. In the OS/2 version of cmd.exe, errors are reported in the current 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.
cmd.exe, which remains part of Windows Vista and Windows Server 2008 for backward compatibility, will be supplemented with Windows PowerShell, Microsoft's new extensible command line shell and task-based scripting technology.
Technical information
Unlike COMMAND.COM, which is a DOS program, cmd.exe is a native program for the platform. This allows it to take advantage of features available to native programs on the platform and not available to DOS programs. For example, since cmd.exe is a native text-mode application on OS/2, 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 in cmd.exe, unlike COMMAND.COM. (COMMAND.COM uses temporary files, and runs the two sides serially, one after the other.)
Technically, cmd.exe is a Windows program that acts as a DOS-like command line interpreter. It is generally compatible, but provides extensions which address the limitations of COMMAND.COM:
SETLOCAL/ENDLOCALcommands limit the scope of changes to the environment- internal
CALLandGOTOlabels lessen the need for individual batch files to perform parts of a task. - filename-parsing extensions to the
SETcommand are comparable to C shell. - an expression-evaluation extensions is also provided in the
SETcommand. - an expansion of the
FORcommand to support parsing files and arbitrary sets in addition to filenames. - use of arrow keys to scroll through command history (provided by
DOSKeyinCOMMAND.COM) - off-by-default path completion capabilities similar to
bashtab completion - a directory stack accessible with the
PUSHDandPOPDcommands IFcan perform case-insensitive comparisons and numeric equality and inequality comparisons in addition to case-sensitive string comparisons
The extensions can be disabled, providing a stricter compatibility mode.
See also
- Batch file Description of writing scripts in the shell
- Comparison of computer shells
- List of DOS commands
References
- ^ Zachary, G. Pascal (1994). Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft. Warner Books. ISBN 0-02-935671-7.
