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I have some (256) files that I want to edit, modifying certain bytes of them. One-by-one method is out of the question since it would take hours, but I also can't seem to find a method of editing the file in hex. I know the command hexdump, but it doesn't really help, or at least I didn't find out how yet.
Someone advised me to use vi and its command :%!xxd to edit in hex, but then again this method would require me to modify each and every file one by one. Maybe if I could use vi in a script it would work, but I didn't find any useful information about that either.
Interesting, but I'm wondering if you could do this with some set space between offsets, and if it can only change the first instance. I needed to do this at one point and ended up writing a C program to do it. For example say you need to match 0x49 then X bytes later you need to match 0x44 and Y bytes later you need to match 0x33, and if all these 3 match then you change each of them to something else. Can that be done or is it too complicated.
Either way, I was just looking for a simpler solution, but I still have the code I wrote for that program, so if you need it say so.
Last edited by H_TeXMeX_H; 02-28-2009 at 04:32 AM.
Well maybe you could "jump through" the file's bytes using two cycles for the rows and columns and maybe "cut" or something with a similar effect, setting X and Y as a parameter, and if the bytes are found in the places needed, it could change them.
I didn't have this problem because the filetype is very simple and can be edited using an external program. I set all of the desired bytes to a basically unused number, then just looked for it and changed all of them using the command aforementioned.
(Although I had some problems with the naming because for some reason the script added a ^M non-printable character to the end of the file extensions, probably due to my lazyness at 2am to write a proper cycle and not just use excel's CONCATENATE to generate the needed commands line by line, heh)
While this code works, I've managed to find a weakness of its: in this specific example, it will change every instance of 0x49, 0x44 and 0x33 into 0x2d, whether or not they are together. But what if, lets say, I only want to change the 0x44 bytes IF they are preceeded by 0x49 and followed by 0x33?
The server I'm contacting to be able to use linux lags like hell, so I can't really try out my ideas, but am I right if I think that a regular expression should do the job?
it checks the current index for x62, then the next byte for x02, then 4729 bytes back for x01, so change this statement as you see fit. I'm not a professional programmer and wrote this up in about 1 hour some time ago. I also hardcoded the file name as game.exe, this was done for safety reasons, because it is a dangerous program.
Forgot to mention that the bytes are changed here: