Basic DOS commands

Overview

Occasionally, on your Windows computer, you may need to perform a procedure by typing in commands at the Command Prompt. Entering commands in this way allows you to bypass the Windows graphical user interface and communicate directly with the operating system. You are most likely to need to work in this way if you get an infection and have to disinfect your computer from the command line, for example, using SAV32CLI, the command line version of Sophos Anti-Virus on Windows.

To communicate through the Windows command line, you will need to use MS-DOS commands. This article lists some basic DOS commands that you are likely to find useful when working from the command line, but there are many more available. To find out more about MS-DOS, consult a book, online dictionary or encyclopedia, or other specialist publication.

The following sections are covered:

• DOS commands
• Accessing the command prompt from Windows
• Accessing the command prompt in safe mode
• Feedback and contact

DOS commands

Command and Usage	Examples
ATTRIB Change file attributes. + adds an attribute, - removes it. Attributes are: A=archive; R=read only; S=system; H=hidden.	ATTRIB -R -A -S -H <VIRUS.EXE> All these attributes will be removed from virus.exe.
C: Go to the C: drive. Similarly A: and D: etc.	C:
CD Change directory. When you change directory, the prompt changes, showing the path of the directory you are currently in. Note, directory is the term used by DOS for what Windows calls a folder.	CD\ takes you to the top of the directory tree (typically to C:) . CD.. moves you one level up the directory tree (i.e. up towards the root directory). CD <DIRECTORYNAME> takes you to that directory. You can use one or more subdirectory names, separated by \ e.g.  CD WINNT\Media takes you to the directory C:\WINNT\Media To change to another path, type the full path with slashes. e.g.  CD \WINDOWS\SYSTEM
CLS Clear the screen.	CLS
DEL Delete one or more files in the current directory. Can be used with the * and the ? wildcards. DEL *.* will delete ALL files in the current directory, USE WITH CAUTION. (Note: DEL cannot be used to delete directories. Use RD to remove a directory.)	DEL <VIRUS.EXE> deletes virus.exe DEL *.JPG will delete all files with the extension JPG. DEL MY*.* will delete all files beginning with MY and with any extension. DEL MY??.* will delete files that are 4 characters long and begin with MY and with any extension.
DIR Displays the contents of a directory (folder). Note, directory is the term used by DOS for what Windows calls a folder. These switches can be combined, so DIR /W /P will return multiple rows listing a page at a time. You can use the * and the ? wildcards to search for a particular file. The ? character represents ONE character, and the * character represents multiple characters. DIR *.* lists all the files in a directory.	DIR displays all files and folders in the current directory. Folders are indicated in the list by <DIR>. Files are usually listed by name. DIR /P displays the contents a page at a time, i.e. as many as will fit in your command line window. Press any key to display the next page. DIR /W displays the files/folders in multiple rows. This view gives less information per file. DIR *.JPG displays all files with the extension JPG in the current directory and all subdirectories. DIR MY??.* displays all files beginning with MY, exactly 4 characters long, and with any extension. DIR /S lists the contents of all subdirectories. DIR /AH displays all hidden files.
EDIT Runs DOS EDIT (a simple text editor). Useful for editing batch files and viewing logs. This command requires QBASIC.EXE to be present.	EDIT <VIRUSLOG.TXT> opens the file viruslog.txt and allows you to edit it. EDIT <NEWFILE.TXT> creates a new file called newfile.txt and opens it up for you to edit.
HELP Displays DOS Help. For help on an individual command, type HELP then the command for which you want more information.	HELP DIR displays information on the DIR command.
MD Make Directory creates a new directory below the current one. (The command can also be written as MKDIR.)	MD <NEWDIR> creates a new directory called Newdir.
PRINT Prints the specified file (if the printer is supported in DOS - many are not).	PRINT <LOGFILE.TXT> Prints LOGFILE.TXT
RD Remove directory. Removes a sub-directory of the current directory. The directory you want to remove must be empty of all files. (The command can also be written as RMDIR)	RD <DIRECTORYNAME>
RENAME Rename a file. You must use the full file name including the suffix.	RENAME <OLDNAME.EXE> <NEWNAME.EXE>
TYPE Displays the contents of a file on the screen. If you use this command on a file which is not a text file, the display will be unintelligible. Use with |MORE to display the text on a page by page basis, and prevent it scrolling off the screen. | is a pipe character.	TYPE C:\README.TXT|MORE
> When you run a DOS command, output is usually sent to the screen. Use > to redirect output from the screen to a file. It runs the command preceding the >, creates a file in the current directory with the name you specify, and sends the information/output returned by the command, to that file.	COMMAND > FILENAME.TXT e.g. SWEEP > REPORT.TXT The details of any infected files reported by SWEEP are sent to a file called REPORT.TXT.

Accessing the command prompt from Windows

To access the command prompt from Windows (a DOS box), do as follows:

1. At the task bar, select Start|Run.
2. Type
   CMD
   or on some versions of Windows
   COMMAND
3. Click OK.

A command prompt will open.

Accessing the command prompt in safe mode

• For Windows NT/2000/XP/2003, see How to remove malicious files with SAV32CLI.
• For Windows 95/98/Me you can boot from a startup disk, or use MS DOS mode
  1. At the task bar, select Start|Shut down.
  2. Select Restart in MS-DOS mode.
  3. Click OK.