Delete a file in ASM?

How is this done? I saw very little documentation on it and I think it went something like,

Code:

---

lea dx, ptrtofilename;
mov ah, 41h;

---

but I wasn't entirely sure.. can anyone clarify?

It depends. What instruction set are you using? Is it going to be 32-bit or 16-bit? If its 32-bit (well, MASM), it wouldn't be too hard.

chem

INT 21H Function 41H : Delete File
This function deletes a file (but not read-only) from within a program. Load the address in the DX of an ASCII string containing the device path and filename, with no wild-card references:

Code:

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ASCstrng DB 'd:\pathname', 00H ; ASCII string
...
MOV AH,41H
LEA DX, ASCstrng
INT 21H

---

A valid operation clears the carry flag, marks the filename in the directory as deleted, and releases the file's allocated disk space in the FAT. An error sets the carry flag and returns code 02, 03, or 05 in the AX.

you should get yourself Ralf-Brown's Interrupt List
http://www.cs.cmu.edu/afs/cs/user/ra...WWW/files.html

Thats compiler specific isn't it? I mean, the interrupts wouldn't work in 32-bit assembly?

Which is why I asked what he was using..

chem

compiler specific?
that is MS DOS (operating system) interrupt to delete a file, of course, you must using FAT filesystem.

whether the interrupt would works in 32-bit windows... em.. could create a com file to try. i am not so sure, but i guess it should work.

I'll give it a test when I get my new PC.

chem

k, just confirm, you can use the DOS interrupt to delete file, create directory and much more.

Code:

---

ORG 100h

jmp start

aa db 'c:\apple.txt',00h

start:
mov ah,41h
mov dx,aa
int 21h
mov ax,4ch
int 21h

---

create a file in c:\apple.txt or wat sover place u want to put and (if change then modify the aa variable)
i use fasm assembler (free and open source) http://flatassembler.net

Code:

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fasm myfile.txt myfile.com

---

Nice. That will become very useful. I've always had to resort to calling API's. No doubt this would be alot faster aswell (without having to go through all the windows crap beforehand).

Ta.

chem

Uh, in Windows, you should be calling the APIs, not using DOS interrupts. It's always better to do it the supported way.

ya, so that the code works in FAT, NTFS or watever new FS microsoft introduce ;-p

Quote:

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Originally Posted by penagate

Uh, in Windows, you should be calling the APIs, not using DOS interrupts. It's always better to do it the supported way.

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True, but it's always good to experiment (if you've got the money, and decide to ruin your PC :D).

PS: How often do you change your avatar penagate? My god, its like you change it after every meal :p

chem

Change is healthy (or whatever). I refocused it again after twice being accused by RobDog of not seeing things properly :)

Congrats on 2K posts BTW.

lol. RobDog is wise.

Ta :)

chem