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Postings from January 2002
On Tue, Jan 08, 2002 at 08:06:14PM +0530, Prahlad Vaidyanathan wrote:
> <script>
> open(FD,'sudo grep -h "Connect time" /var/log/message* | grep -v COMMAND |') or die $! ;
> # Do some stuff ...
> while ( <FD> ) {
> # do more stuff
> }
> </script>
>
> In the above script (an attempt to check my ppp usage), the script
> actually runs 'sudo' only when reading from the file (line #3) and not
> when open() is run (line #1).
How did you go about determining this? As far as I know, this is not the
case; the command is run immediately upon open. It can be proven with:
perl -wle 'open(F, q{perl -wle "print STDERR q{test}" |") || die; sleep;'
If the command was only executed when F is read from you'd never see "test".
However, when I run the above, I see "test". The sleep is in there to prove
it's not being run due to the implicit close at the end of the script.
> ps. Is it inadvisable to open the said file like this (see the script
> above) ? If so, why ?
Opening it like this is fine, but I would use Perl to do the grepping, not
several invocations of grep.
Michael
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