# Manpage: cmd.exe

Starts a new instance of the Windows XP command interpreter

CMD [/A | /U] [/Q] [/D] [/E:ON | /E:OFF] [/F:ON | /F:OFF] [/V:ON | /V:OFF]
[[/S] [/C | /K] string]

/C      Carries out the command specified by string and then terminates
/K      Carries out the command specified by string but remains
/S      Modifies the treatment of string after /C or /K (see below)
/Q      Turns echo off
/D      Disable execution of AutoRun commands from registry (see below)
/A      Causes the output of internal commands to a pipe or file to be ANSI
/U      Causes the output of internal commands to a pipe or file to be
Unicode
/E:ON   Enable command extensions (see below)
/E:OFF  Disable command extensions (see below)
/F:ON   Enable file and directory name completion characters (see below)
/F:OFF  Disable file and directory name completion characters (see below)
/V:ON   Enable delayed environment variable expansion using ! as the
delimiter. For example, /V:ON would allow !var! to expand the
variable var at execution time.  The var syntax expands variables
at input time, which is quite a different thing when inside of a FOR
loop.
/V:OFF  Disable delayed environment expansion.

Note that multiple commands separated by the command separator '&&'
are accepted for string if surrounded by quotes.  Also, for compatibility
reasons, /X is the same as /E:ON, /Y is the same as /E:OFF and /R is the
same as /C.  Any other switches are ignored.

If /C or /K is specified, then the remainder of the command line after
the switch is processed as a command line, where the following logic is
used to process quote (") characters:

1.  If all of the following conditions are met, then quote characters
on the command line are preserved:

- no /S switch
- exactly two quote characters
- no special characters between the two quote characters,
where special is one of: &<>()@^|
- there are one or more whitespace characters between the
the two quote characters
- the string between the two quote characters is the name
of an executable file.

2.  Otherwise, old behavior is to see if the first character is
a quote character and if so, strip the leading character and
remove the last quote character on the command line, preserving
any text after the last quote character.

If /D was NOT specified on the command line, then when CMD.EXE starts, it
looks for the following REG_SZ/REG_EXPAND_SZ registry variables, and if
either or both are present, they are executed first.

HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\AutoRun

and/or

HKEY_CURRENT_USER\Software\Microsoft\Command Processor\AutoRun

Command Extensions are enabled by default.  You may also disable
extensions for a particular invocation by using the /E:OFF switch.  You
can enable or disable extensions for all invocations of CMD.EXE on a
machine and/or user logon session by setting either or both of the
following REG_DWORD values in the registry using REGEDT32.EXE:

HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\EnableExtensions

and/or

HKEY_CURRENT_USER\Software\Microsoft\Command Processor\EnableExtensions

to either 0x1 or 0x0.  The user specific setting takes precedence over
the machine setting.  The command line switches take precedence over the
registry settings.

The command extensions involve changes and/or additions to the following
commands:

DEL or ERASE
COLOR
CD or CHDIR
MD or MKDIR
PROMPT
PUSHD
POPD
SET
SETLOCAL
ENDLOCAL
IF
FOR
CALL
SHIFT
GOTO
START (also includes changes to external command invocation)
ASSOC
FTYPE

To get specific details, type commandname /? to view the specifics.

Delayed environment variable expansion is NOT enabled by default.  You
can enable or disable delayed environment variable expansion for a
particular invocation of CMD.EXE with the /V:ON or /V:OFF switch.  You
can enable or disable completion for all invocations of CMD.EXE on a
machine and/or user logon session by setting either or both of the
following REG_DWORD values in the registry using REGEDT32.EXE:

HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\DelayedExpansion

and/or

HKEY_CURRENT_USER\Software\Microsoft\Command Processor\DelayedExpansion

to either 0x1 or 0x0.  The user specific setting takes precedence over
the machine setting.  The command line switches take precedence over the
registry settings.

If delayed environment variable expansion is enabled, then the exclamation
character can be used to substitute the value of an environment variable
at execution time.

File and Directory name completion is NOT enabled by default.  You can
enable or disable file name completion for a particular invocation of
CMD.EXE with the /F:ON or /F:OFF switch.  You can enable or disable
completion for all invocations of CMD.EXE on a machine and/or user logon
session by setting either or both of the following REG_DWORD values in
the registry using REGEDT32.EXE:

HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\CompletionChar
HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\PathCompletionChar

and/or

HKEY_CURRENT_USER\Software\Microsoft\Command Processor\CompletionChar
HKEY_CURRENT_USER\Software\Microsoft\Command Processor\PathCompletionChar

with the hex value of a control character to use for a particular
function (e.g.  0x4 is Ctrl-D and 0x6 is Ctrl-F).  The user specific
settings take precedence over the machine settings.  The command line
switches take precedence over the registry settings.

If completion is enabled with the /F:ON switch, the two control
characters used are Ctrl-D for directory name completion and Ctrl-F for
file name completion.  To disable a particular completion character in
the registry, use the value for space (0x20) as it is not a valid
control character.

Completion is invoked when you type either of the two control
characters.  The completion function takes the path string to the left
of the cursor appends a wild card character to it if none is already
present and builds up a list of paths that match.  It then displays the
first matching path.  If no paths match, it just beeps and leaves the
display alone.  Thereafter, repeated pressing of the same control
character will cycle through the list of matching paths.  Pressing the
Shift key with the control character will move through the list
backwards.  If you edit the line in any way and press the control
character again, the saved list of matching paths is discarded and a new
one generated.  The same occurs if you switch between file and directory
name completion.  The only difference between the two control characters
is the file completion character matches both file and directory names,
while the directory completion character only matches directory names.
If file completion is used on any of the built in directory commands
(CD, MD or RD) then directory completion is assumed.

The completion code deals correctly with file names that contain spaces
or other special characters by placing quotes around the matching path.
Also, if you back up, then invoke completion from within a line, the
text to the right of the cursor at the point completion was invoked is
&()[]{}^=;!'+,~
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