[Gllug] 'safe' deletion of files

[t.clarke]

David Damerell <damerell at chiark.greenend.org.uk> wrote:-

>The real answer to this one is that by all means one should have a
>non-permanent deletion command, but it absolutely should not be called
>"rm". Then when users get used to it, it will just not work on other
>systems.

As a matter of interest, I knocked-up something to use on our Unix system,
specifically to deal with the problem of files being deleted and then
the user (sometimes me!) discovering later that the file might be useful after
all !
It isn't perfect, but seems to do the job reasonably efficiently.
An extract from the source is appended below. It should compile on linux - if
anyone might find it useful just email me.
Tim





--
/*
'Remove Safely' program.
Instead of simply deleting the file(s), the program attempts to rename them
into a '.trash' directory on the same filesystem, or failing that attempts
to copy them to a default /var/.trash' directory and then delete.
Ideally, there needs to be a .trash directory on each mounted filesystem,
to avoid unecessary copying. However, if disc space is at a premium,
the lack of a .trash directory on that filesystem will cause immediate
copying and deleting, thus freeing space on that filesystem.
The program determines the filesystem .trash directory to use simply by
attempting rename operations at the root level and 'working down', up to
a level of 4 directories.   If you have filesystems mounted at a lower level,
then simply increase the defined value DIRLIMIT appropriately.
If a file being 'deleted' already has a copy of an earlier version within
the destination .trash directory, it is appended with ~A and the rename
operation tried again, up to '~Z'.  Thus up to 26 versions of the saved file
may exist within the .trash directory before 'deletion' will fail.
It is probably a good strategy to periodically irrevocably delete (using rm)
the files building up within the .trash directories, or move them to a 'master
archive' fiesystem !
The files contained within the .trash directories are given filenames
equivalent to their original full pathnames, but with '/' replaced by '\'.
Thus file '/usr/tmp/abc' would (assuming directory /.trash exists) be renamed
as '/.trash/usr\tmp\abc'.
The /var/.trash directory can of course be a symbolic link to another
directory on another filesystem, since it is only copied-to.

NOTE:  if symbolic links are specified, it is the link that is renamed, not the
the underlying file. However, if the link cannot be renamed (across filesystems)
it is simply deleted as the underlying file still exists and there is no point
in copying the data.

Multiple files can be 'deleted', eg:  rms  a b c   or  rms * .
Directories CANNOT be 'deleted'.
*/


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