[TUHS] There is turmoil in Linux-land - When did rm first avoid going upwards?

Noel Chiappa jnc at mercury.lcs.mit.edu
Tue Apr 25 11:34:03 AEST 2017


    > From: Kurt H Maier

    > /etc/glob, which appears to report no-match if the first character is .

So I couldn't be bothered to work out how 'glob' worked exactly, so I just did
an experiment: I created a hacked version of 'rm' that had the directory
handling call to glob call 'echo' instead of 'rm'; it also printed 'tried'
instead of the actual unlink call, and printed 'cd' when it changed
directories.

I then set up two subsidiary directors, foo and .bar, with one containing
'.foo0 foo1' and the other '.bar0 bar1'.

Saying 'xrm -r -f .*' produced this:

  cd: .
  -r -f foo xrm xrm.c
  cd: ..
  -r -f foo xrm xrm.c
  cd: .bar
  -r -f bar1 

(This system has /tmp on a mounted file system, which is why the 'cd ..' was a
NOP. And a very good thing, too; at one point the phone rang, and it
distracted me, and I automatically typed 'rm', not 'xrm'... see below for what
happened. No biggie, there were only my test files there.  The output lines
are "-r -f foo xrm xrm.c" because that's what 'glob' passed to 'echo'.)

Saying 'xrm -r -f *' produced this:

  cd: foo
  -r -f foo1
  xrm: tried
  xrm.c: tried     

So apparently 'glob', when presented with '*' , ignores entries starting with
'.', but '.*' does not.


When I stupidly typed 'rm -r -f .*', it did more or les what I originally
thought it would: deleted all the files in all the directories (but only on
the /tmp device, because .. linked to the itself in /tmp, so it didn't escape
from that volume); leaving all the directories, but empty, except for the
files .foo0 and .bar0. So files and inferior directories with names starting
with '.' would have escaped, but nothing else.

	Noel


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