New subject: Changing UIDs on LOTS of files

7 Jun 2001


      Someone (sorry, deleted message) pointed out that perl's chown() call
probably follows symlinks, and that is indeed the case.  However, there is
a very simple workaround for that:
find dir ! -type l -print | mychown.c
Also, as someone pointed out, if you use chown -R you also want to use
-h (if your unix flavor supports that option) to change the owner of the
symlink itself rather than what the symlink points to.
...
If you run a separate chown process for each file, yes, that will be
very slow.  However, if these files are all in a small number of directory
trees, then just use the recursive option of chown.
chown -R newuser:newgrp dir
This chowns the entire tree and I can't think of anything on the client
side that would be faster.  I don't think ONTAP has anything on the
server side to do this operation.
Of course this assumes that you want the entire directory tree chown-ed
to the same user and group.  If you need to pick and choose based on
the existing uid (probably what you want) then I suggest doing something
like this:
find dir -print | mychown.pl
And write a mychown.pl perl script like this:
===========
%uidmap = (              # in %uidmap each line is olduid => newuid
  120 => 507,
  153 => 515,
  ...
);
$defaultuid = 507;       # for when the old uid is not in %uidmap
%gidmap = (              # in %gidmap each line is oldgid => newgid
  200 => 217,
  201 => 234,
  ...
);
$defaultgid = 212;       # for when the old gid is not in %gidmap
while(<>) {
    chop;
    @stat = stat($_);
    next if @stat == 0;  # stat call failed, move on
    $olduid = $stat[4];
    $oldgid = $stat[5];
    $newuid = exists($uidmap{$olduid}) ? $uidmap{$olduid} : $defaultuid;
    $newgid = exists($gidmap{$oldgid}) ? $gidmap{$oldgid} : $defaultgid;
    chown($newuid, $newgid, $_);
}
===========
Steve Losen   scl@virginia.edu    phone: 804-924-0640
University of Virginia               ITC Unix Support

Re: Changing UIDs on LOTS of files