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Undelete utility

Posted on 1998-04-27
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Last Modified: 2010-04-15
i have to design a graphical user interface for the following:
a)Allow a user to unerase a deleted file/directory
b)Allow a user to recover(as much as possible)deleted files which have been partially overwritten(automatic)
c)Allow a user to recover(as much as possible)deleted files which have been partially overwritten(Manual unerase)
I am allowed use a mix of C and assembly
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Question by:GILLY
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22 Comments
 

Author Comment

by:GILLY
ID: 1256111
i would really appreciate it if anyone could help out i realise a knowledge beyond C is really neede but i am really stuck
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Author Comment

by:GILLY
ID: 1256112
Adjusted points to 150
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LVL 84

Expert Comment

by:ozo
ID: 1256113
Files in what operating system?
Allowed by whom?
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Expert Comment

by:bing031398
ID: 1256114
Some operating systems do not have a facility for undeleting. I mean there is no way to undelete a file.
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LVL 1

Expert Comment

by:Nexial
ID: 1256115
Are you designing just the user interface to functions already in existence or are you also having to code the underlying functionality?   Your question sort of suggests that all you are interested in is the UI.

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LVL 11

Expert Comment

by:alexo
ID: 1256116
Using assembly for UI is bad for your mental health.
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LVL 3

Expert Comment

by:braveheart
ID: 1256117
You have not mentioned which operating system you are using. If you are using DOS or Windoze you could write an interface to the existing undelete facility. However, if you are using UNIX, you will need to write your own utility which copies files to be deleted to some trash area, copies them back again to undelete, and some function to really delete the file or empty the trash area. So long as your trash area never fills up you will never overwrite files which have been deleted - but what are you going to do if you DO fill the disk.

You will only want to use an assembly language if you are having to interface with the guts of your machine - hey, maybe you are writing a File Management System?

For the UI I doubt if you will want to use assembly but maybe you should think about using or porting some existing toolkit.
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Author Comment

by:GILLY
ID: 1256118
i am using the DOS operating system, i have to code my own functions to access the FAT and the sectors in the disk, i am not allowed use dos commands such as "undelete". Basically i have to write a program that finds for the user all the files that have been deleted you know this by the funny symbol at the start of the file name instead fo the first letter of the filename.  this is done by accesing the FAT on a disk, i only have to work on floppy's.  Does that make my question any easier to understand
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LVL 3

Expert Comment

by:rmichels
ID: 1256119
Actually you need to access the directory entries NOT the fat to check for undeleted file. The directory is stored separately from the fat.  And..once you find a deleted file..you need to check to see if the FAT(s) it previously occupied, is once again in use.  Undelete utilities make some large assumptions in that they usually assume contiguous clusters.
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LVL 3

Expert Comment

by:braveheart
ID: 1256120
So really, your question has very little to do with C and lots to do with DOS. Have you considered that your program may have to take into account different versions of DOS too.

I would have thought that, unless you are using a really old version of DOS that you could code everything in C using SVC calls rather than having to resort to assembler.
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LVL 1

Expert Comment

by:cph
ID: 1256121
Have a look at saferv20.zip on any virtual software library (VSL) on the net.
ftp://garbo.uwasa.fi/pc/diskutil/saferv20.zip
or
ftp://sunsite.doc.ic.ac.uk/packages/simtelnet/msdos/diskutil/safera16.zip
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LVL 11

Expert Comment

by:alexo
ID: 1256122
Gilly, read a bit about FAT12, FAT16 and FAT32 structures.
Get DiskEdit from Norton Utils (or something similar) and spellunk the FAT of your disk.

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Author Comment

by:GILLY
ID: 1256123
Thanks a million to everyone who tried to help me out, i realise it wasn't exactly a question about C but i will check out the web pages that you given me.
Thanks again, i will probably talk to you soon again!!!
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LVL 11

Expert Comment

by:alexo
ID: 1256124
It is customary to allow one of the participants (say the one who contributed most) to get the points.
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Expert Comment

by:bing031398
ID: 1256125
You got your help. Maybe its time to reward the person. THERE IS NO FREE LUNCH.
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LVL 11

Expert Comment

by:alexo
ID: 1256126
I think he does...  I'll ask Linda to drop him an email.
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LVL 7

Expert Comment

by:linda101698
ID: 1256127
Please post a comment asking the person who helped you the most (you choose) to post an answer so you can grade this question.

Linda Gardner
Customer Service @ Experts Exchange
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Author Comment

by:GILLY
ID: 1256128
I am really sorry , i didn't realise the procedure, please forgive me
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Author Comment

by:GILLY
ID: 1256129
I give the points to braveheart, i don't know actually how i am supposed to give them, if you don't get them, please tell me how.
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LVL 3

Accepted Solution

by:
braveheart earned 150 total points
ID: 1256130
Since you rejected my answer it would be difficult to give me the points. However, you could always accept this one insted.
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LVL 7

Expert Comment

by:linda101698
ID: 1256131
Gilly,

Since braveheart now has the posted answer, all you need to do is choose the grade you want to award him to close this question and move it to the previously answered questions.  Thanks for reponding.

Linda
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Author Comment

by:GILLY
ID: 1256132
tHANKS TO EVERYONE WHO HELPED ME OUT IF I COULD SPLIT THE POINTS I WOULD, HOPE I CAN RETURN THE FAVOUR, EXCEPT TO BING WHO I THINK IS A BIT IGNORANT FOR BEING SO RUDE TO ME WHEN IT WAS JUST BECAUSE I AM NEW AND DIDN'T KNOW THE PROCEDURE
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