3.6) How do I "undelete" a file?
 Someday, you are going to accidentally type something like
 "rm * .foo", and find you just deleted "*" instead of "*.foo".
 Consider it a rite of passage.
 Of course, any decent systems administrator should be doing
 regular backups. Check with your sysadmin to see if a recent
 backup copy of your file is available. But if it isn't, read
 on.
 For all intents and purposes, when you delete a file with "rm" it
 is gone. Once you "rm" a file, the system totally forgets which
 blocks scattered around the disk were part of your file. Even
 worse, the blocks from the file you just deleted are going to be
 the first ones taken and scribbled upon when the system needs
 more disk space. However, never say never. It is theoretically
 possible *if* you shut down the system immediately after the "rm"
 to recover portions of the data. However, you had better have a
 very wizardly type person at hand with hours or days to spare to
 get it all back.
 Your first reaction when you "rm" a file by mistake is why not
 make a shell alias or procedure which changes "rm" to move files
 into a trash bin rather than delete them? That way you can
 recover them if you make a mistake, and periodically clean out
 your trash bin. Two points: first, this is generally accepted
 as a *bad* idea. You will become dependent upon this behaviour
 of "rm", and you will find yourself someday on a normal system
 where "rm" is really "rm", and you will get yourself in trouble.
 Second, you will eventually find that the hassle of dealing with
 the disk space and time involved in maintaining the trash bin, it
 might be easier just to be a bit more careful with "rm". For
 starters, you should look up the "-i" option to "rm" in your
 manual.
 If you are still undaunted, then here is a possible simple
 answer. You can create yourself a "can" command which moves
 files into a trashcan directory. In csh(1) you can place the
 following commands in the ".login" file in your home directory:
 alias can 'mv \!* ~/.trashcan' # junk file(s) to trashcan
 alias mtcan 'rm -f ~/.trashcan/*' # irretrievably empty trash
 if ( ! -d ~/.trashcan ) mkdir ~/.trashcan # ensure trashcan exists
 You might also want to put a:
 rm -f ~/.trashcan/*
 in the ".logout" file in your home directory to automatically
 empty the trash when you log out. (sh and ksh versions are left
 as an exercise for the reader.)
 MIT's Project Athena has produced a comprehensive
 delete/undelete/expunge/purge package, which can serve as a
 complete replacement for rm which allows file recovery. This
 package was posted to comp.sources.misc (volume 17, issue
 023-026)