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Re: Parsing Question
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From:
Jim Gibson
Date:
February 1, 2012 13:05
Subject:
Re: Parsing Question
Message ID:
CB4EE910.17CC6%JimSGibson@gmail.com
On 2/1/12 Wed Feb 1, 2012 11:24 AM, "jbiskofski" <jbiskofski@gmail.com>
scribbled:
> Your comment about the open statement is OK. I guess it really comes down
> to style. I was trying to write something clear that Brandon could improve
> upon.
It is not simply a matter of style. Because of operator precedence, the
statement
open my $RR, '<', 'nagios.dat' || die 'unable to open nagios.dat :(';
will be parsed as
open my $RR, '<', ('nagios.dat' || die 'unable to open nagios.dat :(');
because the precedence of '||' is higher than that of ','. Because the
scalar value 'nagios.dat' is always true, the above statement is equivalent
to the following:
open my $RR, '<', 'nagios.dat';
In other words, the die will never get executed, regardless of the success
or failure of the open. So you either need to place parentheses around the
open arguments:
open( my $RR, '<', 'nagios.dat') || die 'unable to open nagios.dat :(';
or use the lower-precedent 'or' operator:
open my $RR, '<', 'nagios.dat' or die 'unable to open nagios.dat :(';
as Timothy has suggested.
For operator precedence, see 'perldoc perlop'.
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