Commands and Batch Files
Some obvious questions:
- What are commands?
- What are batch files?
- Why do we need them?
- How useful are they?
- In this age of bash,
perl, python and other more powerful tools, are they worth learning?
Windows traditionally came with a very rudimentary way to automate some tasks. The technique is batch file programming. Newer version of Windows
are beginning to include more advanced tools such as power shell.
In its most simplest
form, a batch file is simply a text file that contains a bunch of commands to run. Hence the term "batch".
For example, the following shows the contents of a very trivial batch file that:
- compiles/links some .c files,
- runs the resulting executable redirecting its output to a file,
- then diffs that file with another text file.
Batch file with three commands:
:: Builds, runs, and diffs the test program
gcc -o program.exe driver.c file.c
program.exe > output.txt
diff output.txt output-master.txt
If the name of this batch file is build.bat, then you simply type that filename on the command line:
C:\> build.bat
Like executables, supplying the extension is optional (and rarely needed):
C:\> build
Essentially, if you can type it on the command line, you can put it in a batch file.
- Internal (built-in) commands like dir, cls, copy, del, type
- External commands like attrib.exe, xcopy.exe, notepad.exe, explorer.exe, and other batch files
The command interpreter on Windows is cmd.exe. (Older versions used command.exe.) When you type a command in the command window, the system is
searched in the order listed below. As soon as a matching command is found, the search ends.
- Internal commands are looked at first
- External commands are searched:
- The current directory
- Directories listed in the PATH environment variable are searched in the order listed
If no extension is provided, the search appends these extensions in order:
- .com
- .exe
- .bat
- .cmd
So, if you have a file named go.exe and go.bat and you type just go at the command
line, then go.exe will run. If you want to run the batch file, you must type go.bat to override
the default behavior.
All commands have the same structure and syntax. Once you understand this simple syntax, the commands won't appear so cryptic and arbitrary.
The structure of a command is:
COMMAND [/option1 /option2 /option3 ...] [arg1 arg2 arg3 ...]
Some Windows commands will accept the minus sign - as well as the forward slash / (Linux and Mac OS X don't use the forward slash):
COMMAND [-option1 -option2 -option3 ...] [arg1 arg2 arg3 ...]
Also, some options can take arguments themselves:
COMMAND [-option1 optarg1 -option2 -option3 optarg3 ...] [arg1 arg2 arg3 ...]
Notes: (These apply to commands on most operating systems, including Windows, Linux, and Mac OS X)
- The very first item on the command line MUST be a command (internal or external).
- Some commands can have their behavior altered by various options.
- Some options require arguments and some options have optional arguments.
- Many commands require arguments and options to be supplied.
- Many commands will perform their default behavior in the absence of options or arguments.
- One or more spaces separate options and arguments. (That's why having filenames and folder names with spaces is a bad idea.)
- If you must deal with a file or folder with a space in the name, enclose it in "double-quotes".
- Some commands allow you to mix the options with the arguments. (Some commands require all options before or after all of the arguments to the command.)
Examples: Try all of these on a Windows computer. (You may have to modify the directory names)
- cls - Clears the screen (internal).
- dir - Lists the contents of a directory (internal).
C:\> dir
C:\> dir c:\windows
C:\> dir /w c:\windows
C:\> dir "C:\Program Files"
- copy - Makes a copy of a file or multiple files (internal, assumes that a file named a.txt already exists).
C:\> copy a.txt b.txt
C:\> copy a.txt b.txt c:\sandbox
C:\> copy /Y a.txt b.txt c:\sandbox
C:\> copy a.txt + b.txt + c.txt d.txt
C:\> copy /B a.mp3 + b.mp3 + c.mp3 d.mp3
- xcopy - More powerful command to copy multiple files (external).
xcopy /C /D /E /F /H /I /Y C:\windows\*.exe C:\sandbox
- g++ - GNU C++ compiler (from Cygwin, not part of Windows)
g++ -Wall -Wextra -ansi -pedantic -o program.exe main.cpp file1.cpp file2.cpp
Redirection and Piping
This is where the real power of the command line lies. It is simply impossible (or, at the very least, tremendously difficult) to do these things using a graphical user interface (GUI). There is a wealth of information about this on the Internet.
You can start
here and
here to learn more about this for Windows.
Fortunately, Windows does have the ability to do redirection and piping, but, unfortunately, Windows does not provide most of the necessary commands/programs to make use of these techniques. The easiest way
to get these missing commands/programs is to install Cygwin on Windows. That will give you 95% of what you will need to be productive from the command line in Windows. For Linux and Mac OS X, all of the necessary
commands/programs are already present.
In a nutshell:
- To redirect input from a file to a program using the < operator. (Example: prog < input.txt)
- To redirect output from a program to a file, use the > operator. (Example: prog > output.txt)
- To append output to a file (instead of overwrite the file) use the >> operator. (Example: prog >> output.txt)
- To connect stdout of a one program to stdin of another program, use the | operator. (Example: prog1 | prog2)
Examples showing commands, redirection, piping, switches, arguments: (sort, cut, and uniq are part of Cygwin, not Windows)
C:\> ipconfig | grep "IP Address" | cut -c 45- | grep "192.168" | sort
C:\> ipconfig | grep "IP Address" | cut -c 45- | grep "192.168" | cut -b9- | sort
C:\> ipconfig | grep "IP Address" | cut -c 45- | cut -d. -f1,2 | sort | uniq
C:\> ipconfig > ip.txt
C:\> grep "IP Address" < ip.txt | cut -c 45- | cut -d. -f1,2 | sort | uniq > results.txt
C:\> type results.txt
Here is ip.txt from a Windows XP computer. You'll have to modify the command above for Windows 7 because the format
of the output has changed.
More info.
Detailed info on the Windows NT command shell.
By the way, Windows NTWindows NT
is the basis for all NT operating systems (2000, Vista, 7, etc.) Previous versions of Windows (Windows 3.0, Windows 95, 98) were different (internally).
And, yes, Windows NT really did start at version 3.1!
| Marketing Name | Internal Name | Date Released | Build No. |
|---|
| Windows NT 3.1 | NT 3.1 | July 1993 | 528 |
| Windows NT 3.5 | NT 3.5 | September 1994 | 807 |
| Windows NT 3.51 | NT 3.51 | May 1995 | 1057 |
| Windows NT 4 | NT 4.0 | July 1996 | 1381 |
| Windows 2000 | NT 5.0 | December 1999 | 2195 |
| Windows XP | NT 5.1 | August 2001 | 2600 |
| Windows Server 2003 | NT 5.2 | March 2003 | 3790 |
| Windows Vista | NT 6.0 | January 2007 | 6000 |
| Windows Server 2008 | NT 6.0 | March 2008 | 6001 |
| Windows 7 | NT 6.1 | October 2009 | 7600 |
| Windows Server 2008 R2 | NT 6.1 | October 2009 | 7600 |
| Windows 8 | NT 6.2 | October 2012 | 9200 |
| Windows Server 2012 | NT 6.2 | September 2012 | 9200 |
| | |
| | |
| | |
There are many commands used in batch file programming, and like most programming, they follow the 80/20 rule (or even 90/10) rule:
"80% of the time you will use 20% of the commands"
The fastest way to find out how a command works is to get help from the command line. Windows doesn't have a facility like the
man pages on Linux and with Cygwin. Instead, to get help on a command type:
C:> command /?
or
C:> help command
where command is an internal or external command (e.g. dir, copy, attrib, etc.)
In my opinion, these are the commands you'll use most of the time. Consider them the "core" commands. Well, some aren't really core,
but are simple and you may find them useful on their own or within batch files.
Some core batch file techniques
One of the most important aspects of working at the command prompt is to customize it so you can be productive. This includes things like:
- Changing the size and fonts of the command window
- Changing the colors of the text and background (COLOR)
- Enabling Quick Edit mode and buffer sizes
- Modifying what is displayed at the prompt. (PROMPT)
By the way, the bulk of this reference was created with a batch file called makehelp.bat. Modifying it
so that there are hyperlinks and matches the output below is an exercise for the student. The resulting HTML output will look like this:
winhelp.html.
Hints:
- Special characters need to be escaped with the carat (^) character. Special characters are:
& | ( ) < > ^
- Accessing variables in batch files require two percent signs:
set name=Fred
echo %Fred%
- Printing a percent sign (%) requires two of them:
echo "We're having a 25%% off sale today!"
- UPPERCASE and lowercase are different in URLs. (Index.html is not the same as index.html, even if you think it works.)
- To print a blank line, use echo with a period (no space between echo and the period):
echo.
- Use variables where you can. You are programmers, so I shouldn't have to say that. If I told you I want the file named doshelp.html instead
of winhelp.html, or the base URL change, if you need to change more than one line, you've done it wrong.
ATTRIB
Displays or changes file attributes.
ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [drive:][path][filename]
[/S [/D]]
+ Sets an attribute.
- Clears an attribute.
R Read-only file attribute.
A Archive file attribute.
S System file attribute.
H Hidden file attribute.
[drive:][path][filename]
Specifies a file or files for attrib to process.
/S Processes matching files in the current folder
and all subfolders.
/D Processes folders as well.
Back to table
CALL
Calls one batch program from another.
CALL [drive:][path]filename [batch-parameters]
batch-parameters Specifies any command-line information required by the
batch program.
If Command Extensions are enabled CALL changes as follows:
CALL command now accepts labels as the target of the CALL. The syntax
is:
CALL :label arguments
A new batch file context is created with the specified arguments and
control is passed to the statement after the label specified. You must
"exit" twice by reaching the end of the batch script file twice. The
first time you read the end, control will return to just after the CALL
statement. The second time will exit the batch script. Type GOTO /?
for a description of the GOTO :EOF extension that will allow you to
"return" from a batch script.
In addition, expansion of batch script argument references (%0, %1,
etc.) have been changed as follows:
%* in a batch script refers to all the arguments (e.g. %1 %2 %3
%4 %5 ...)
Substitution of batch parameters (%n) has been enhanced. You can
now use the following optional syntax:
%~1 - expands %1 removing any surrounding quotes (")
%~f1 - expands %1 to a fully qualified path name
%~d1 - expands %1 to a drive letter only
%~p1 - expands %1 to a path only
%~n1 - expands %1 to a file name only
%~x1 - expands %1 to a file extension only
%~s1 - expanded path contains short names only
%~a1 - expands %1 to file attributes
%~t1 - expands %1 to date/time of file
%~z1 - expands %1 to size of file
%~$PATH:1 - searches the directories listed in the PATH
environment variable and expands %1 to the fully
qualified name of the first one found. If the
environment variable name is not defined or the
file is not found by the search, then this
modifier expands to the empty string
The modifiers can be combined to get compound results:
%~dp1 - expands %1 to a drive letter and path only
%~nx1 - expands %1 to a file name and extension only
%~dp$PATH:1 - searches the directories listed in the PATH
environment variable for %1 and expands to the
drive letter and path of the first one found.
%~ftza1 - expands %1 to a DIR like output line
In the above examples %1 and PATH can be replaced by other
valid values. The %~ syntax is terminated by a valid argument
number. The %~ modifiers may not be used with %*
Back to table
CHDIR
Displays the name of or changes the current directory.
CHDIR [/D] [drive:][path]
CHDIR [..]
CD [/D] [drive:][path]
CD [..]
.. Specifies that you want to change to the parent directory.
Type CD drive: to display the current directory in the specified drive.
Type CD without parameters to display the current drive and directory.
Use the /D switch to change current drive in addition to changing current
directory for a drive.
If Command Extensions are enabled CHDIR changes as follows:
The current directory string is converted to use the same case as
the on disk names. So CD C:\TEMP would actually set the current
directory to C:\Temp if that is the case on disk.
CHDIR command does not treat spaces as delimiters, so it is possible to
CD into a subdirectory name that contains a space without surrounding
the name with quotes. For example:
cd \winnt\profiles\username\programs\start menu
is the same as:
cd "\winnt\profiles\username\programs\start menu"
which is what you would have to type if extensions were disabled.
Back to table
CLS
Clears the screen.
CLS
Back to table
COLOR
Sets the default console foreground and background colors.
COLOR [attr]
attr Specifies color attribute of console output
Color attributes are specified by TWO hex digits -- the first
corresponds to the background; the second the foreground. Each digit
can be any of the following values:
0 = Black 8 = Gray
1 = Blue 9 = Light Blue
2 = Green A = Light Green
3 = Aqua B = Light Aqua
4 = Red C = Light Red
5 = Purple D = Light Purple
6 = Yellow E = Light Yellow
7 = White F = Bright White
If no argument is given, this command restores the color to what it was
when CMD.EXE started. This value either comes from the current console
window, the /T command line switch or from the DefaultColor registry
value.
The COLOR command sets ERRORLEVEL to 1 if an attempt is made to execute
the COLOR command with a foreground and background color that are the
same.
Example: "COLOR fc" produces light red on bright white
Back to table
COPY
Copies one or more files to another location.
COPY [/D] [/V] [/N] [/Y | /-Y] [/Z] [/A | /B ] source [/A | /B]
[+ source [/A | /B] [+ ...]] [destination [/A | /B]]
source Specifies the file or files to be copied.
/A Indicates an ASCII text file.
/B Indicates a binary file.
/D Allow the destination file to be created decrypted
destination Specifies the directory and/or filename for the new file(s).
/V Verifies that new files are written correctly.
/N Uses short filename, if available, when copying a file with a
non-8dot3 name.
/Y Suppresses prompting to confirm you want to overwrite an
existing destination file.
/-Y Causes prompting to confirm you want to overwrite an
existing destination file.
/Z Copies networked files in restartable mode.
The switch /Y may be preset in the COPYCMD environment variable.
This may be overridden with /-Y on the command line. Default is
to prompt on overwrites unless COPY command is being executed from
within a batch script.
To append files, specify a single file for destination, but multiple files
for source (using wildcards or file1+file2+file3 format).
Back to table
DATE
Displays or sets the date.
DATE [/T | date]
Type DATE without parameters to display the current date setting and
a prompt for a new one. Press ENTER to keep the same date.
If Command Extensions are enabled the DATE command supports
the /T switch which tells the command to just output the
current date, without prompting for a new date.
Back to table
DEL
Deletes one or more files.
DEL [/P] [/F] [/S] [/Q] [/A[[:]attributes]] names
ERASE [/P] [/F] [/S] [/Q] [/A[[:]attributes]] names
names Specifies a list of one or more files or directories.
Wildcards may be used to delete multiple files. If a
directory is specified, all files within the directory
will be deleted.
/P Prompts for confirmation before deleting each file.
/F Force deleting of read-only files.
/S Delete specified files from all subdirectories.
/Q Quiet mode, do not ask if ok to delete on global wildcard
/A Selects files to delete based on attributes
attributes R Read-only files S System files
H Hidden files A Files ready for archiving
- Prefix meaning not
If Command Extensions are enabled DEL and ERASE change as follows:
The display semantics of the /S switch are reversed in that it shows
you only the files that are deleted, not the ones it could not find.
Back to table
DIR
Displays a list of files and subdirectories in a directory.
DIR [drive:][path][filename] [/A[[:]attributes]] [/B] [/C] [/D] [/L] [/N]
[/O[[:]sortorder]] [/P] [/Q] [/S] [/T[[:]timefield]] [/W] [/X] [/4]
[drive:][path][filename]
Specifies drive, directory, and/or files to list.
/A Displays files with specified attributes.
attributes D Directories R Read-only files
H Hidden files A Files ready for archiving
S System files - Prefix meaning not
/B Uses bare format (no heading information or summary).
/C Display the thousand separator in file sizes. This is the
default. Use /-C to disable display of separator.
/D Same as wide but files are list sorted by column.
/L Uses lowercase.
/N New long list format where filenames are on the far right.
/O List by files in sorted order.
sortorder N By name (alphabetic) S By size (smallest first)
E By extension (alphabetic) D By date/time (oldest first)
G Group directories first - Prefix to reverse order
/P Pauses after each screenful of information.
/Q Display the owner of the file.
/S Displays files in specified directory and all subdirectories.
/T Controls which time field displayed or used for sorting
timefield C Creation
A Last Access
W Last Written
/W Uses wide list format.
/X This displays the short names generated for non-8dot3 file
names. The format is that of /N with the short name inserted
before the long name. If no short name is present, blanks are
displayed in its place.
/4 Displays four-digit years
Switches may be preset in the DIRCMD environment variable. Override
preset switches by prefixing any switch with - (hyphen)--for example, /-W.
Back to table
ECHO
Displays messages, or turns command-echoing on or off.
ECHO [ON | OFF]
ECHO [message]
Type ECHO without parameters to display the current echo setting.
Back to table
FOR
Runs a specified command for each file in a set of files.
FOR %variable IN (set) DO command [command-parameters]
%variable Specifies a single letter replaceable parameter.
(set) Specifies a set of one or more files. Wildcards may be used.
command Specifies the command to carry out for each file.
command-parameters
Specifies parameters or switches for the specified command.
To use the FOR command in a batch program, specify %%variable instead
of %variable. Variable names are case sensitive, so %i is different
from %I.
If Command Extensions are enabled, the following additional
forms of the FOR command are supported:
FOR /D %variable IN (set) DO command [command-parameters]
If set contains wildcards, then specifies to match against directory
names instead of file names.
FOR /R [[drive:]path] %variable IN (set) DO command [command-parameters]
Walks the directory tree rooted at [drive:]path, executing the FOR
statement in each directory of the tree. If no directory
specification is specified after /R then the current directory is
assumed. If set is just a single period (.) character then it
will just enumerate the directory tree.
FOR /L %variable IN (start,step,end) DO command [command-parameters]
The set is a sequence of numbers from start to end, by step amount.
So (1,1,5) would generate the sequence 1 2 3 4 5 and (5,-1,1) would
generate the sequence (5 4 3 2 1)
FOR /F ["options"] %variable IN (file-set) DO command [command-parameters]
FOR /F ["options"] %variable IN ("string") DO command [command-parameters]
FOR /F ["options"] %variable IN ('command') DO command [command-parameters]
or, if usebackq option present:
FOR /F ["options"] %variable IN (file-set) DO command [command-parameters]
FOR /F ["options"] %variable IN ('string') DO command [command-parameters]
FOR /F ["options"] %variable IN (`command`) DO command [command-parameters]
filenameset is one or more file names. Each file is opened, read
and processed before going on to the next file in filenameset.
Processing consists of reading in the file, breaking it up into
individual lines of text and then parsing each line into zero or
more tokens. The body of the for loop is then called with the
variable value(s) set to the found token string(s). By default, /F
passes the first blank separated token from each line of each file.
Blank lines are skipped. You can override the default parsing
behavior by specifying the optional "options" parameter. This
is a quoted string which contains one or more keywords to specify
different parsing options. The keywords are:
eol=c - specifies an end of line comment character
(just one)
skip=n - specifies the number of lines to skip at the
beginning of the file.
delims=xxx - specifies a delimiter set. This replaces the
default delimiter set of space and tab.
tokens=x,y,m-n - specifies which tokens from each line are to
be passed to the for body for each iteration.
This will cause additional variable names to
be allocated. The m-n form is a range,
specifying the mth through the nth tokens. If
the last character in the tokens= string is an
asterisk, then an additional variable is
allocated and receives the remaining text on
the line after the last token parsed.
usebackq - specifies that the new semantics are in force,
where a back quoted string is executed as a
command and a single quoted string is a
literal string command and allows the use of
double quotes to quote file names in
filenameset.
Some examples might help:
FOR /F "eol=; tokens=2,3* delims=, " %i in (myfile.txt) do @echo %i %j %k
would parse each line in myfile.txt, ignoring lines that begin with
a semicolon, passing the 2nd and 3rd token from each line to the for
body, with tokens delimited by commas and/or spaces. Notice the for
body statements reference %i to get the 2nd token, %j to get the
3rd token, and %k to get all remaining tokens after the 3rd. For
file names that contain spaces, you need to quote the filenames with
double quotes. In order to use double quotes in this manner, you also
need to use the usebackq option, otherwise the double quotes will be
interpreted as defining a literal string to parse.
%i is explicitly declared in the for statement and the %j and %k
are implicitly declared via the tokens= option. You can specify up
to 26 tokens via the tokens= line, provided it does not cause an
attempt to declare a variable higher than the letter 'z' or 'Z'.
Remember, FOR variables are single-letter, case sensitive, global,
and you can't have more than 52 total active at any one time.
You can also use the FOR /F parsing logic on an immediate string, by
making the filenameset between the parenthesis a quoted string,
using single quote characters. It will be treated as a single line
of input from a file and parsed.
Finally, you can use the FOR /F command to parse the output of a
command. You do this by making the filenameset between the
parenthesis a back quoted string. It will be treated as a command
line, which is passed to a child CMD.EXE and the output is captured
into memory and parsed as if it was a file. So the following
example:
FOR /F "usebackq delims==" %i IN (`set`) DO @echo %i
would enumerate the environment variable names in the current
environment.
In addition, substitution of FOR variable references has been enhanced.
You can now use the following optional syntax:
%~I - expands %I removing any surrounding quotes (")
%~fI - expands %I to a fully qualified path name
%~dI - expands %I to a drive letter only
%~pI - expands %I to a path only
%~nI - expands %I to a file name only
%~xI - expands %I to a file extension only
%~sI - expanded path contains short names only
%~aI - expands %I to file attributes of file
%~tI - expands %I to date/time of file
%~zI - expands %I to size of file
%~$PATH:I - searches the directories listed in the PATH
environment variable and expands %I to the
fully qualified name of the first one found.
If the environment variable name is not
defined or the file is not found by the
search, then this modifier expands to the
empty string
The modifiers can be combined to get compound results:
%~dpI - expands %I to a drive letter and path only
%~nxI - expands %I to a file name and extension only
%~fsI - expands %I to a full path name with short names only
%~dp$PATH:I - searches the directories listed in the PATH
environment variable for %I and expands to the
drive letter and path of the first one found.
%~ftzaI - expands %I to a DIR like output line
In the above examples %I and PATH can be replaced by other valid
values. The %~ syntax is terminated by a valid FOR variable name.
Picking upper case variable names like %I makes it more readable and
avoids confusion with the modifiers, which are not case sensitive.
Back to table
GOTO
Directs cmd.exe to a labeled line in a batch program.
GOTO label
label Specifies a text string used in the batch program as a label.
You type a label on a line by itself, beginning with a colon.
If Command Extensions are enabled GOTO changes as follows:
GOTO command now accepts a target label of :EOF which transfers control
to the end of the current batch script file. This is an easy way to
exit a batch script file without defining a label. Type CALL /? for a
description of extensions to the CALL command that make this feature
useful.
Back to table
IF
Performs conditional processing in batch programs.
IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command
NOT Specifies that Windows should carry out
the command only if the condition is false.
ERRORLEVEL number Specifies a true condition if the last program run
returned an exit code equal to or greater than the number
specified.
string1==string2 Specifies a true condition if the specified text strings
match.
EXIST filename Specifies a true condition if the specified filename
exists.
command Specifies the command to carry out if the condition is
met. Command can be followed by ELSE command which
will execute the command after the ELSE keyword if the
specified condition is FALSE
The ELSE clause must occur on the same line as the command after the IF. For
example:
IF EXIST filename. (
del filename.
) ELSE (
echo filename. missing.
)
The following would NOT work because the del command needs to be terminated
by a newline:
IF EXIST filename. del filename. ELSE echo filename. missing
Nor would the following work, since the ELSE command must be on the same line
as the end of the IF command:
IF EXIST filename. del filename.
ELSE echo filename. missing
The following would work if you want it all on one line:
IF EXIST filename. (del filename.) ELSE echo filename. missing
If Command Extensions are enabled IF changes as follows:
IF [/I] string1 compare-op string2 command
IF CMDEXTVERSION number command
IF DEFINED variable command
where compare-op may be one of:
EQU - equal
NEQ - not equal
LSS - less than
LEQ - less than or equal
GTR - greater than
GEQ - greater than or equal
and the /I switch, if specified, says to do case insensitive string
compares. The /I switch can also be used on the string1==string2 form
of IF. These comparisons are generic, in that if both string1 and
string2 are both comprised of all numeric digits, then the strings are
converted to numbers and a numeric comparison is performed.
The CMDEXTVERSION conditional works just like ERRORLEVEL, except it is
comparing against an internal version number associated with the Command
Extensions. The first version is 1. It will be incremented by one when
significant enhancements are added to the Command Extensions.
CMDEXTVERSION conditional is never true when Command Extensions are
disabled.
The DEFINED conditional works just like EXISTS except it takes an
environment variable name and returns true if the environment variable
is defined.
%ERRORLEVEL% will expand into a string representation of
the current value of ERRORLEVEL, provided that there is not already
an environment variable with the name ERRORLEVEL, in which case you
will get its value instead. After running a program, the following
illustrates ERRORLEVEL use:
goto answer%ERRORLEVEL%
:answer0
echo Program had return code 0
:answer1
echo Program had return code 1
You can also using the numerical comparisons above:
IF %ERRORLEVEL% LEQ 1 goto okay
%CMDCMDLINE% will expand into the original command line passed to
CMD.EXE prior to any processing by CMD.EXE, provided that there is not
already an environment variable with the name CMDCMDLINE, in which case
you will get its value instead.
%CMDEXTVERSION% will expand into a string representation of the
current value of CMDEXTVERSION, provided that there is not already
an environment variable with the name CMDEXTVERSION, in which case you
will get its value instead.
MKDIR
Creates a directory.
MKDIR [drive:]path
MD [drive:]path
If Command Extensions are enabled MKDIR changes as follows:
MKDIR creates any intermediate directories in the path, if needed.
For example, assume \a does not exist then:
mkdir \a\b\c\d
is the same as:
mkdir \a
chdir \a
mkdir b
chdir b
mkdir c
chdir c
mkdir d
which is what you would have to type if extensions were disabled.
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MOVE
Moves files and renames files and directories.
To move one or more files:
MOVE [/Y | /-Y] [drive:][path]filename1[,...] destination
To rename a directory:
MOVE [/Y | /-Y] [drive:][path]dirname1 dirname2
[drive:][path]filename1 Specifies the location and name of the file
or files you want to move.
destination Specifies the new location of the file. Destination
can consist of a drive letter and colon, a
directory name, or a combination. If you are moving
only one file, you can also include a filename if
you want to rename the file when you move it.
[drive:][path]dirname1 Specifies the directory you want to rename.
dirname2 Specifies the new name of the directory.
/Y Suppresses prompting to confirm you want to
overwrite an existing destination file.
/-Y Causes prompting to confirm you want to overwrite
an existing destination file.
The switch /Y may be present in the COPYCMD environment variable.
This may be overridden with /-Y on the command line. Default is
to prompt on overwrites unless MOVE command is being executed from
within a batch script.
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This command is not supported by the help utility. Try "now /?".
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PATH
Displays or sets a search path for executable files.
PATH [[drive:]path[;...][;%PATH%]
PATH ;
Type PATH ; to clear all search-path settings and direct cmd.exe to search
only in the current directory.
Type PATH without parameters to display the current path.
Including %PATH% in the new path setting causes the old path to be
appended to the new setting.
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PAUSE
Suspends processing of a batch program and displays the message
Press any key to continue . . .
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PROMPT
Changes the cmd.exe command prompt.
PROMPT [text]
text Specifies a new command prompt.
Prompt can be made up of normal characters and the following special codes:
$A & (Ampersand)
$B | (pipe)
$C ( (Left parenthesis)
$D Current date
$E Escape code (ASCII code 27)
$F ) (Right parenthesis)
$G > (greater-than sign)
$H Backspace (erases previous character)
$L < (less-than sign)
$N Current drive
$P Current drive and path
$Q = (equal sign)
$S (space)
$T Current time
$V Windows version number
$_ Carriage return and linefeed
$$ $ (dollar sign)
If Command Extensions are enabled the PROMPT command supports
the following additional formatting characters:
$+ zero or more plus sign (+) characters depending upon the
depth of the PUSHD directory stack, one character for each
level pushed.
$M Displays the remote name associated with the current drive
letter or the empty string if current drive is not a network
drive.
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POPD
Changes to the directory stored by the PUSHD command.
POPD
If Command Extensions are enabled the POPD command will delete
any temporary drive letter created by PUSHD when you POPD that
drive off the pushed directory stack.
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PUSHD
Stores the current directory for use by the POPD command, then
changes to the specified directory.
PUSHD [path | ..]
path Specifies the directory to make the current directory.
If Command Extensions are enabled the PUSHD command accepts
network paths in addition to the normal drive letter and path.
If a network path is specified, PUSHD will create a temporary
drive letter that points to that specified network resource and
then change the current drive and directory, using the newly
defined drive letter. Temporary drive letters are allocated from
Z: on down, using the first unused drive letter found.
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RMDIR
Removes (deletes) a directory.
RMDIR [/S] [/Q] [drive:]path
RD [/S] [/Q] [drive:]path
/S Removes all directories and files in the specified directory
in addition to the directory itself. Used to remove a directory
tree.
/Q Quiet mode, do not ask if ok to remove a directory tree with /S
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REM
Records comments (remarks) in a batch file or CONFIG.SYS.
REM [comment]
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RENAME
Renames a file or files.
RENAME [drive:][path]filename1 filename2.
REN [drive:][path]filename1 filename2.
Note that you cannot specify a new drive or path for your destination file.
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SET
Displays, sets, or removes cmd.exe environment variables.
SET [variable=[string]]
variable Specifies the environment-variable name.
string Specifies a series of characters to assign to the variable.
Type SET without parameters to display the current environment variables.
If Command Extensions are enabled SET changes as follows:
SET command invoked with just a variable name, no equal sign or value
will display the value of all variables whose prefix matches the name
given to the SET command. For example:
SET P
would display all variables that begin with the letter 'P'
SET command will set the ERRORLEVEL to 1 if the variable name is not
found in the current environment.
SET command will not allow an equal sign to be part of the name of
a variable.
Two new switches have been added to the SET command:
SET /A expression
SET /P variable=[promptString]
The /A switch specifies that the string to the right of the equal sign
is a numerical expression that is evaluated. The expression evaluator
is pretty simple and supports the following operations, in decreasing
order of precedence:
() - grouping
! ~ - - unary operators
* / % - arithmetic operators
+ - - arithmetic operators
<< >> - logical shift
& - bitwise and
^ - bitwise exclusive or
| - bitwise or
= *= /= %= += -= - assignment
&= ^= |= <<= >>=
, - expression separator
If you use any of the logical or modulus operators, you will need to
enclose the expression string in quotes. Any non-numeric strings in the
expression are treated as environment variable names whose values are
converted to numbers before using them. If an environment variable name
is specified but is not defined in the current environment, then a value
of zero is used. This allows you to do arithmetic with environment
variable values without having to type all those % signs to get their
values. If SET /A is executed from the command line outside of a
command script, then it displays the final value of the expression. The
assignment operator requires an environment variable name to the left of
the assignment operator. Numeric values are decimal numbers, unless
prefixed by 0x for hexadecimal numbers, and 0 for octal numbers.
So 0x12 is the same as 18 is the same as 022. Please note that the octal
notation can be confusing: 08 and 09 are not valid numbers because 8 and
9 are not valid octal digits.
The /P switch allows you to set the value of a variable to a line of input
entered by the user. Displays the specified promptString before reading
the line of input. The promptString can be empty.
Environment variable substitution has been enhanced as follows:
%PATH:str1=str2%
would expand the PATH environment variable, substituting each occurrence
of "str1" in the expanded result with "str2". "str2" can be the empty
string to effectively delete all occurrences of "str1" from the expanded
output. "str1" can begin with an asterisk, in which case it will match
everything from the beginning of the expanded output to the first
occurrence of the remaining portion of str1.
May also specify substrings for an expansion.
%PATH:~10,5%
would expand the PATH environment variable, and then use only the 5
characters that begin at the 11th (offset 10) character of the expanded
result. If the length is not specified, then it defaults to the
remainder of the variable value. If either number (offset or length) is
negative, then the number used is the length of the environment variable
value added to the offset or length specified.
%PATH:~-10%
would extract the last 10 characters of the PATH variable.
%PATH:~0,-2%
would extract all but the last 2 characters of the PATH variable.
Finally, support for delayed environment variable expansion has been
added. This support is always disabled by default, but may be
enabled/disabled via the /V command line switch to CMD.EXE. See CMD /?
Delayed environment variable expansion is useful for getting around
the limitations of the current expansion which happens when a line
of text is read, not when it is executed. The following example
demonstrates the problem with immediate variable expansion:
set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "%VAR%" == "after" @echo If you see this, it worked
)
would never display the message, since the %VAR% in BOTH IF statements
is substituted when the first IF statement is read, since it logically
includes the body of the IF, which is a compound statement. So the
IF inside the compound statement is really comparing "before" with
"after" which will never be equal. Similarly, the following example
will not work as expected:
set LIST=
for %i in (*) do set LIST=%LIST% %i
echo %LIST%
in that it will NOT build up a list of files in the current directory,
but instead will just set the LIST variable to the last file found.
Again, this is because the %LIST% is expanded just once when the
FOR statement is read, and at that time the LIST variable is empty.
So the actual FOR loop we are executing is:
for %i in (*) do set LIST= %i
which just keeps setting LIST to the last file found.
Delayed environment variable expansion allows you to use a different
character (the exclamation mark) to expand environment variables at
execution time. If delayed variable expansion is enabled, the above
examples could be written as follows to work as intended:
set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "!VAR!" == "after" @echo If you see this, it worked
)
set LIST=
for %i in (*) do set LIST=!LIST! %i
echo %LIST%
If Command Extensions are enabled, then there are several dynamic
environment variables that can be expanded but which don't show up in
the list of variables displayed by SET. These variable values are
computed dynamically each time the value of the variable is expanded.
If the user explicitly defines a variable with one of these names, then
that definition will override the dynamic one described below:
%CD% - expands to the current directory string.
%DATE% - expands to current date using same format as DATE command.
%TIME% - expands to current time using same format as TIME command.
%RANDOM% - expands to a random decimal number between 0 and 32767.
%ERRORLEVEL% - expands to the current ERRORLEVEL value
%CMDEXTVERSION% - expands to the current Command Processor Extensions
version number.
%CMDCMDLINE% - expands to the original command line that invoked the
Command Processor.
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SHIFT
Changes the position of replaceable parameters in a batch file.
SHIFT [/n]
If Command Extensions are enabled the SHIFT command supports
the /n switch which tells the command to start shifting at the
nth argument, where n may be between zero and eight. For example:
SHIFT /2
would shift %3 to %2, %4 to %3, etc. and leave %0 and %1 unaffected.
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START
Starts a separate window to run a specified program or command.
START ["title"] [/D path] [/I] [/MIN] [/MAX] [/SEPARATE | /SHARED]
[/LOW | /NORMAL | /HIGH | /REALTIME | /ABOVENORMAL | /BELOWNORMAL]
[/AFFINITY ] [/WAIT] [/B] [command/program]
[parameters]
"title" Title to display in window title bar.
path Starting directory
B Start application without creating a new window. The
application has ^C handling ignored. Unless the application
enables ^C processing, ^Break is the only way to interrupt
the application
I The new environment will be the original environment passed
to the cmd.exe and not the current environment.
MIN Start window minimized
MAX Start window maximized
SEPARATE Start 16-bit Windows program in separate memory space
SHARED Start 16-bit Windows program in shared memory space
LOW Start application in the IDLE priority class
NORMAL Start application in the NORMAL priority class
HIGH Start application in the HIGH priority class
REALTIME Start application in the REALTIME priority class
ABOVENORMAL Start application in the ABOVENORMAL priority class
BELOWNORMAL Start application in the BELOWNORMAL priority class
AFFINITY The new application will have the specified processor
affinity mask, expressed as a hexadecimal number.
WAIT Start application and wait for it to terminate
command/program
If it is an internal cmd command or a batch file then
the command processor is run with the /K switch to cmd.exe.
This means that the window will remain after the command
has been run.
If it is not an internal cmd command or batch file then
it is a program and will run as either a windowed application
or a console application.
parameters These are the parameters passed to the command/program
If Command Extensions are enabled, external command invocation
through the command line or the START command changes as follows:
non-executable files may be invoked through their file association just
by typing the name of the file as a command. (e.g. WORD.DOC would
launch the application associated with the .DOC file extension).
See the ASSOC and FTYPE commands for how to create these
associations from within a command script.
When executing an application that is a 32-bit GUI application, CMD.EXE
does not wait for the application to terminate before returning to
the command prompt. This new behavior does NOT occur if executing
within a command script.
When executing a command line whose first token is the string "CMD "
without an extension or path qualifier, then "CMD" is replaced with
the value of the COMSPEC variable. This prevents picking up CMD.EXE
from the current directory.
When executing a command line whose first token does NOT contain an
extension, then CMD.EXE uses the value of the PATHEXT
environment variable to determine which extensions to look for
and in what order. The default value for the PATHEXT variable
is:
.COM;.EXE;.BAT;.CMD
Notice the syntax is the same as the PATH variable, with
semicolons separating the different elements.
When searching for an executable, if there is no match on any extension,
then looks to see if the name matches a directory name. If it does, the
START command launches the Explorer on that path. If done from the
command line, it is the equivalent to doing a CD /D to that path.
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TIME
Displays or sets the system time.
TIME [/T | time]
Type TIME with no parameters to display the current time setting and a prompt
for a new one. Press ENTER to keep the same time.
If Command Extensions are enabled the TIME command supports
the /T switch which tells the command to just output the
current time, without prompting for a new time.
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TYPE
Displays the contents of a text file or files.
TYPE [drive:][path]filename
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XCOPY
Copies files and directory trees.
XCOPY source [destination] [/A | /M] [/D[:date]] [/P] [/S [/E]] [/V] [/W]
[/C] [/I] [/Q] [/F] [/L] [/G] [/H] [/R] [/T] [/U]
[/K] [/N] [/O] [/X] [/Y] [/-Y] [/Z]
[/EXCLUDE:file1[+file2][+file3]...]
source Specifies the file(s) to copy.
destination Specifies the location and/or name of new files.
/A Copies only files with the archive attribute set,
doesn't change the attribute.
/M Copies only files with the archive attribute set,
turns off the archive attribute.
/D:m-d-y Copies files changed on or after the specified date.
If no date is given, copies only those files whose
source time is newer than the destination time.
/EXCLUDE:file1[+file2][+file3]...
Specifies a list of files containing strings. Each string
should be in a separate line in the files. When any of the
strings match any part of the absolute path of the file to be
copied, that file will be excluded from being copied. For
example, specifying a string like \obj\ or .obj will exclude
all files underneath the directory obj or all files with the
.obj extension respectively.
/P Prompts you before creating each destination file.
/S Copies directories and subdirectories except empty ones.
/E Copies directories and subdirectories, including empty ones.
Same as /S /E. May be used to modify /T.
/V Verifies each new file.
/W Prompts you to press a key before copying.
/C Continues copying even if errors occur.
/I If destination does not exist and copying more than one file,
assumes that destination must be a directory.
/Q Does not display file names while copying.
/F Displays full source and destination file names while copying.
/L Displays files that would be copied.
/G Allows the copying of encrypted files to destination that does
not support encryption.
/H Copies hidden and system files also.
/R Overwrites read-only files.
/T Creates directory structure, but does not copy files. Does not
include empty directories or subdirectories. /T /E includes
empty directories and subdirectories.
/U Copies only files that already exist in destination.
/K Copies attributes. Normal Xcopy will reset read-only attributes.
/N Copies using the generated short names.
/O Copies file ownership and ACL information.
/X Copies file audit settings (implies /O).
/Y Suppresses prompting to confirm you want to overwrite an
existing destination file.
/-Y Causes prompting to confirm you want to overwrite an
existing destination file.
/Z Copies networked files in restartable mode.
The switch /Y may be preset in the COPYCMD environment variable.
This may be overridden with /-Y on the command line.
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