DOS-COMMANDS

What if a Windows system file is damaged? What if a virus damaged such a file? You can rescue your PC, in DOS. Here we go...for a general explanation of Dos-commands. You'll notice that some commands are quite powerful, and can delete data on your HDD. Don't just type every command you see here, if you don't know what you're doing.

General rule:

1. Everything you do has a result in the *current* directory (the one you are in at the moment you type the command). Some commands may execute on the whole disk (debug, deltree, scandisk, defrag, format, and fdisk).

2. To start an executable file from the DOS command-line (executable = everything with extention ".bat" ; ".com" ; ".exe"), just type the name you see before the extention. To start up the file "setup.exe" from floppy drive a:, you can type "a:\setup (Enter)" or first “a: (Enter)” and then “setup (Enter)”.

Basics:

• a: - go to drive a: (floppy).
• c: - go to drive c: (hard drive).
• cd\ - go to the root-direcory (Change Directory).
• dir - show files and subdirectories (of course: in the current directory).
• cd windows - go to the directory, named "windows".
• dir /p - show files / subdirs, but screen after screen.
• dir *.dll - show all files with extention ".dll".
• dir *.dll |more - same, but screen by screen.
• cd.. - one step back in de directory structure (from c:\windows to c:\).
• md test - make a directory, named "test". Make Directory (name).
• cd test - go in this directory (Change Directory).
• copy c:\*.* - copy everything from c:\(root) over here (here is now "c:\test" - assuming you type the commands in the sequence of this text).
• copy a:\setup.exe c:\test - copy the file "setup.exe" from floppy to HDD, directory c:\test.
• ren one.bat two.bat - rename the file "one.bat" to "two.bat" (if "one.bat" exists).
• del *.bat - delete all files with ext. ".bat" (only do this in c:\test - don’t do this in "c:\"!).
• del config.* - delete all files with name config (any ext.) (only in "c:\test"!).
• del msdos.sys - delete the file msdos.sys (! only do this in c:\test!).
• del *.* - delete everything (only in c:\test, don’t do this in c:\!).
• cd.. - back to c:\ (root) - in fact, one step back in the directory structure.
• rd test - remove the directory "test" (there still can be hidden files in it, so this may not work - see the attrib options further on).
• dir /? - show help and command line options for the command "dir".
• prompt /? - same for the prompt-command (try this on all commands - " /?" right behind it).

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Advanced...

• attrib *.* -h-r-s-a - change all file attributes - so that you can see / remove / change them all (hidden, read-only, system, archive).
• attrib *.* +h+r - hide all files, and set them all "read-only".
• attrib io.sys -h-r-s-a - allows us to see and change "io.sys" <note: don’t change it, unless you have a good boot disk ;-) >.
• time - show system clock, possibly change the time.
• date - same for the date.
• find /n "CTTY" c:\command.com - find the word CTTY in the file "command.com".
• prompt $p$g - show current drive and directory.
• prompt $p$g Type Exit to quit. . . - same, but with this text...
• path - show in which directorys the system looks for a file if it can’t be found in the current directory.
• path=c:\tools;%path% - add the directory ‘c:\tools’ to the path.
• deltree *.* - delete all files, including all subdirectories and files in the subdirectories (Don’t do this in c:\).
• deltree /y *.* - same, but without asking comfirmation for each file.
• deltree /y *.* >nul - same, but the user can’t see that files are being deleted.
• label - see/change the name of the drive..
• fdisk - show partitions of a drive (Don’t change partitions if you still need files on that drive!).
• format a: - format a floppy for Dos.
• format c: - format HDD (or partition) for Dos. (!Don't do this if you need data on that disk!)

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Work with files (overwrite, create, input, and output redirection....

• dir >a:\test.txt - show files and subdirectories, and redirect the output to a file "test.txt" on floppy. The screen output has been redirected to the file by the ">" sign - the ‘>‘- sign means: "redirect output to").
• dir >prn - send the list of files and subdirectories to the printer.
• type test.txt - show the file "test.txt" on the screen. This command has the same result as
  "copy test.txt con" (copy <filename> to console).
• notepad test.txt - in windows this also works - "start test.txt with notepad.exe".
• echo whatever >>test.txt - add the word "whatever" in the file "test.txt" (append).
• echo Killroy was here >test.txt - The words "Killroy was here" are written to test.txt, but the previous contents of the file is overwritten because we only used one ">"- sign.
• type test.txt - show again.
• echo bigdisk >a.txt - make a file "a.txt" with only the word "bigdisk" in it.
• label <a.txt - rename the disk to the word in "a.txt" (< : get input from).
• echo bigdisk |label - the current disk will be renamed in one command to "bigdisk" (the | - sign (or ‘pipe’) gives the output of a program (or command) to another program).
• echo y |format c: - the HDD will be formatted unconditionally (no confirmation (Y/N) is asked because the "Y" is given to the format command by the | - sign. Don't test this on your PC if you need data on it - it *does* work. Of course, for a German or Dutch Dos-version you need to type "echo j |format c:" or if the OS language is French: "echo o |format c:" (Oui, oui, c'est ça).
• echo y |format c: >nul - the same but the user doesn’t see what’s happening.
• time >>test.txt - hit the ‘Enter’ key twice in order not to change the time, or,
• echo. |time >>test.txt - in this case, just hit ‘enter’ once. ("echo." - notice the ‘.’ - gives the ‘Enter’).
• type test.txt - *sigh* do I still have to explain this? ....
  > redirects output to (file or device after the ‘>‘- sign) Any already existing file with the same name is overwritten.
  >> appends to a file, if the file doesn’t exist, it is created.
  < gets input from (file or device). Devices are nul, clock$, aux, con, prn, com1 - com4, lpt1...
• copy clock$ test.txt - If you leave this command running in the background (interrupt with Ctrl + C) you’ll fill up the HDD. Clocktics are written to file, 1 Mbyte / minute on a P75. Useless command otherwise, but hey, we're just testing...
• netstat -an 30 >>log.txt - log all network addresses and ports, on my PC and on the remote PC, do this every 30 seconds -in a file "log.txt". Try to get on my HDD via the internet or network without me seeing you (in the log file). Interrupt with Ctrl + C.
• copy test.txt lpt1 - send the file ‘test.txt’ to the printer (if the printer is connected to LPT1).
• echo g=ffff:0 |debug - cold reboot your PC. Start debug, and execute the instructions. It's a zero after ffff: , not the letter "o". Also:
• echo o 64,fe |debug (O - out, not 0 (zero)). Confusing, huh?
• choice /cy /n /ty,9 >nul - Wait 9 seconds. Start the program "choice", don’t show output on the screen, choose ‘y’ after 9 seconds, continue.
• echo rem you don’t see this on your screen >nul >>c:\autoexec.bat - append the line ‘rem etc. ...’ to c:\autoexec.bat, don’t show execution on the screen.
• ctty nul - If you execute this command in a complete dos-exit, the PC will freeze. Input and output aren’t from the keyboard and to the screen, but from and to the ‘nul’ device.
• ctty con - In and output normal again (can only be given from within a ‘bat’ file, if after ctty nul).

knip@bigfoot.com

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