Ravi Malghan am Donnerstag, 27. April 2006 19.52:
Hello Ravi
(please start a new thread for a new question)
> Hi: I am extracting some value from $complete_event as
> follows. What can I check to see if the extraction
> returned a valid value? "if($_)" seems to be giving
> incorrect values.
look at perldoc perlvar for the meaning of the $_ var.
It's not what you want in your case below.
You're more interested in the question "What can I check to see if the
extraction succeeded?";
if the extracted value is valid or not is a secondary problem and is
implementation specific.
> In the following statement, $srcIp
> is being set to an old extracted value if there is no
> valid value following srcIP in my $complete_string
> instead of 0.
True; from perldoc perlre:
"NOTE: failed matches in Perl do not reset the match variables, which makes it
easier to write code that tests for a series of more specific cases and
remembers the best match."
> $complete_event =~ /srcIp=(.+) srcPort=/;
> if($_) {$srcIp = $1;}
> else {$srcIp = 0;}
Only use $1 etc. if the match succeeded:
if ($complete_event =~ /srcIp=(.+) srcPort=/) {
if($1) {$srcIp = $1;}
else {$srcIp = 0;}
}
or shorter
my $srcIp=$1 ? $1 : 0
if $complete_event =~ /srcIp=(.+) srcPort=/;
Eventually you also want to be more specific in what is a valid value to
extract, at least ([\d.]+) instead of (.+) .
hope this helps
Dani
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