cmd.exe interacts with the user through acommand-line interface. On Windows, this interface is implemented through theWin32 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 realpipes in command pipelines, allowing both sides of the pipeline to run concurrently. As a result, it is possible to redirect thestandard 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 Windowscmd.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 ifCommandA completes successfully, and the execution ofCommandC depends on the successful completion ofCommandB. 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 asWindows 2000 orWindows NT 4.0, the maximum length of the string is 2047 (211-1) characters. This limit includes the command line, individualenvironment variables that are inherited by otherprocesses, and all environment variable expansions.[10]
On Windows,cmd.exe is mostly compatible withCOMMAND.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) ofCOMMAND.COM. In OS/2, errors are reported in the chosen language of the system, their text being taken from the system message files. TheHELP command can then be issued with the error message number to obtain further information.
Supports using of arrow keys to scroll through command history. (Under DOS this function was only available underDR DOS (throughHISTORY) and later via an external component calledDOSKEY.)
Addsrotating command-line completion for file and folder paths, where the user can cycle through results for the prefix using theTab ↹, and⇧Shift+Tab ↹ for reverse direction.
Treats thecaret character (^) as theescape character; the character following it is to be taken literally. There are special characters incmd.exe andCOMMAND.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 withSETLOCAL 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 usingcontrol structures hard and complex.[16] The extensions can be disabled, providing a stricter compatibility mode.
Internal commands have also been improved:
TheDELTREE command was merged into theRD command, as part of its/Sswitch.
SetLocal andEndLocal commands limit the scope of changes to the environment. Changes made to the command line environment afterSetLocal commands are local to thebatch file.EndLocal command restores the previous settings.[17]
TheCall command allows subroutines within batch file. TheCall command inCOMMAND.COM only supports calling external batch files.
An expansion of theFor command supports parsing files and arbitrary sets in addition to file names.
The newPushD andPopD commands provide access past navigated paths similar to "forward" and "back" buttons in a web browser orFile Explorer.
The conditionalIF command can performcase-insensitive comparisons and numeric equality and inequality comparisons in addition to case-sensitive string comparisons. (This was available in DR-DOS, but not inPC DOS orMS-DOS.)
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