I've been using this method since i first learned about raw disk access (dev files) and grep.
I think it should be mentioned that this will work properly only if the file was not fragmented - Which will usually be the case in EXT3 unless you are using almost all of the space in the drive, but may happen frequently if you are using a FAT file system (which is used a lot in USB disks).
Also, If you just deleted a binary file this method will be problematic as well, and in that case you can use a tool like photorec to scan the disk and even limit it only to the free space on the drive - which reduce the time it takes to go over a disk and can detect all kinds of binary file types (uses the magic number of the file to detect the type).
Like other people mentioned here before, you should recover all the data to a different partition/disk than the one you are trying to recover a file from.
With that said - recovering data is a tedious and error prone process, so if the data is worth enough(and for some silly reason you don't have a backup) you should:
A. turn off the computer immediately after you've discovered the loss of data (to reduce the chances of overwriting anything important)
B.Give the computer/disk to a professional to recover (because you obviously aren't one since you don't keep backups)
I think it should be mentioned that this will work properly only if the file was not fragmented - Which will usually be the case in EXT3 unless you are using almost all of the space in the drive, but may happen frequently if you are using a FAT file system (which is used a lot in USB disks).
Also, If you just deleted a binary file this method will be problematic as well, and in that case you can use a tool like photorec to scan the disk and even limit it only to the free space on the drive - which reduce the time it takes to go over a disk and can detect all kinds of binary file types (uses the magic number of the file to detect the type).
Like other people mentioned here before, you should recover all the data to a different partition/disk than the one you are trying to recover a file from.
With that said - recovering data is a tedious and error prone process, so if the data is worth enough(and for some silly reason you don't have a backup) you should:
A. turn off the computer immediately after you've discovered the loss of data (to reduce the chances of overwriting anything important)
B.Give the computer/disk to a professional to recover (because you obviously aren't one since you don't keep backups)