03-18-2003
PERL: how to tell if variable is NULL
How to I do a check on a variable to see if it's null-- I am using Perl.
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I have the necessity to use this command:
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never defined or set B
The above command send a cat error.
Any idea?
Thanks.
Giovanni (1 Reply)
Discussion started by: gio123bg
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Hello
I want to check for NULL variable..
but this is not working..please help
thanks in advance
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hi forum
i beginning with script and i want test un null variable in a schell
i just don t know the syntax here is a litle example
y=test
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unset y
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then
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exit
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Hi,
I have to check whether an argument say $ARGV is not null in an if operator. Please let me know the operator. It would be great if you write a psuedo code.
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korn shell
If
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sample.cfg
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DELETE=`cat $logfile1 | egrep -i "Delete" | sed 's/ */ /g' | cut -d" " -f2`
INSERT=`cat $logfile1 | egrep -i "Insert" | sed 's/ */ /g' | cut -d" " -f2`
UPDATE=`cat $logfile1 | egrep -i "Update" | sed 's/ */ /g' | cut -d" " -f2`
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LEARN ABOUT DEBIAN
perl::critic::policy::regularexpressions::prohibitcapturewithout
Perl::Critic::Policy::RegularExpressions::ProhibitCapturUserhContributed)Perl::Critic::Policy::RegularExpressions::ProhibitCaptureWithoutTest(3pm)
NAME
Perl::Critic::Policy::RegularExpressions::ProhibitCaptureWithoutTest - Capture variable used outside conditional.
AFFILIATION
This Policy is part of the core Perl::Critic distribution.
DESCRIPTION
If a regexp match fails, then any capture variables ($1, $2, ...) will be undefined. Therefore it's important to check the return value of
a match before using those variables.
This policy checks that the previous regexp for which the capture variable is in-scope is either in a conditional or causes an exception or
other control transfer (i.e. "next", "last", "redo", "return", or sometimes "goto") if the match fails.
A "goto" is only accepted by this policy if it is a co-routine call (i.e. "goto &foo") or a "goto LABEL" where the label does not fall
between the "goto" and the capture variable in the scope of the "goto". A computed "goto" (i.e. something like "goto (qw{foo bar
baz})[$i]") is not accepted by this policy because its target can not be statically determined.
This policy does not check whether that conditional is actually testing a regexp result, nor does it check whether a regexp actually has a
capture in it. Those checks are too hard.
This policy also does not check arbitrarily complex conditionals guarding regexp results, for pretty much the same reason. Simple things
like
m/(foo)/ or die "No foo!";
die "No foo!" unless m/(foo)/;
will be handled, but something like
m/(foo) or do {
... lots of complicated calculations here ...
die "No foo!";
};
are beyond its scope.
CONFIGURATION
By default, this policy considers "die", "croak", and "confess" to throw exceptions. If you have additional subroutines or methods that may
be used in lieu of one of these, you can configure them in your perlcriticrc as follows:
[RegularExpressions::ProhibitCaptureWithoutTest]
exception_source = my_exception_generator
BUGS
This policy does not recognize named capture variables. Yet.
AUTHOR
Chris Dolan <cdolan@cpan.org>
COPYRIGHT
Copyright (c) 2006-2011 Chris Dolan.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
perl v5.14.2 2012-Perl::Critic::Policy::RegularExpressions::ProhibitCaptureWithoutTest(3pm)