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Re: FYI: 1.6b snapshot


From: Ben Elliston
Subject: Re: FYI: 1.6b snapshot
Date: 23 Dec 2002 12:02:16 +1100
User-agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.4 (Honest Recruiter)

Hi Akim,

>>>>> "Akim" == Akim Demaille <address@hidden> writes:

  Akim> I'm afraid you're taking useless risks here, typically for 8+3

You always have such a way with words.  Alas:

  Akim> {
  Akim>   tmp=$TMPDIR/$1$$-$RANDOM
  Akim>   (umask 077 && mkdir $tmp)
  Akim> }

If $1 is two to four characters long, $$ is up to 5 characters long
for a 16-bit process ID and $RANDOM is a similarly large natural
number, then you've just blown 8.3 systems out of the water.

Furthermore, $RANDOM does not seem to be as portable as it ought to
be.  If it's unsupported by a shell it will, of course, expand to the
empty string giving:

        tmp=$TMPDIR/$1$$-

.. where $1 is known.  So this code can silently fail and generate a
temporary filename that has the equivalent strength as foo-$$.  May I
suggest the following alternative?

 {
   test -n "$RANDOM" && tmp=$TMPDIR/$1$$-$RANDOM && (umask 077 && mkdir $tmp)
 }

I am currently reviewing a config.guess patch that uses the guts of
your AS_TMPDIR macro to generate a secure tmp directory.  Thanks for
that.

Ben



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