File deletion

File deletion is a way of removing a file from a computer's file system.

Examples of reasons for deleting files are:

All operating systems include commands for deleting files (rm on Unix, era in CP/M and DR-DOS, del/erase in MS-DOS/PC DOS, DR-DOS, Microsoft Windows etc.). File managers also provide a convenient way of deleting files. Files may be deleted one-by-one, or a whole directory tree may be deleted.

The common problem with deleting files is accidental removal of information that later proves to be important. One way to deal with this is to back up files regularly. Erroneously deleted files may then be found in archives.

Another technique often used is not to delete files instantly, but to move them to a temporary directory whose contents can then be deleted at will. This is how the "recycle bin" or "trash can" works. Microsoft Windows and Apple's Mac OS X, as well as some Linux distributions, all employ this strategy.

In MS-DOS, one can use the undelete command. In MS-DOS the "deleted" files are not really deleted, but only marked as deleted—so they could be undeleted during some time, until the disk blocks they used are eventually taken up by other files. This is how data recovery programs work, by scanning for files that have been marked as deleted. As the space is freed up per byte, rather than per file, this can sometimes cause data to be recovered incompletely. Defragging a drive may prevent undeletion, as the blocks used by deleted file might be overwritten since they are marked as "empty".

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