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Top Forums UNIX for Dummies Questions & Answers Passing Shell Variables to an awk command Post 302549634 by Corona688 on Tuesday 23rd of August 2011 01:23:08 PM
Old 08-23-2011
Substitution doesn't happen in single-quotes, no, even if you surround it by double quotes. You have to end the single quotes in an ugly mess like

Code:
$2>="'"$i"'" && $2 <="'"$j"'"

This has an unfortunate side-effect: If any of the string contains valid (or worse, invalid) awk code, it will be considered part of the awk statement and executed. Meaning, someone could feed an " || system("rm -Rf ~/"); into it and get it executed...

It's far cleaner and better and safer to pass them explicitly with -v:

Code:
awk -v VAR1="$VAR1" -v VAR2="$VAR2" '$2>=VAR1 && $2 <=VAR2' ...

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Perl::Critic::Policy::ValuesAndExpressions::ProhibitQuPerl::Critic::Policy::ValuesAndExpressions::ProhibitQuotesAsQuotelikeOperatorDelimiters(3pm)

NAME
Perl::Critic::Policy::ValuesAndExpressions::ProhibitQuotesAsQuotelikeOperatorDelimiters - Don't use quotes ("'", """, "`") as delimiters for the quote-like operators. AFFILIATION
This Policy is part of the core Perl::Critic distribution. DESCRIPTION
With the obvious exception of using single-quotes to prevent interpolation, using quotes with the quote-like operators kind of defeats the purpose of them and produces obfuscated code, causing problems for future maintainers and their editors/IDEs. $x = q"q"; #not ok $x = q'q'; #not ok $x = q`q`; #not ok $x = qq"q"; #not ok $x = qr"r"; #not ok $x = qw"w"; #not ok $x = qx`date`; #not ok $x =~ m"m"; #not ok $x =~ s"s"x"; #not ok $x =~ tr"t"r"; #not ok $x =~ y"x"y"; #not ok $x =~ m'$x'; #ok $x =~ s'$x'y'; #ok $x = qr'$x'm; #ok $x = qx'finger foo@bar'; #ok CONFIGURATION
This policy has three options: "single_quote_allowed_operators", "double_quote_allowed_operators", and "back_quote_allowed_operators", which control which operators are allowed to use each of "'", """, "`" as delimiters, respectively. The values allowed for these options are a whitespace delimited selection of the "m", "q", "qq", "qr", "qw", "qx", "s", "tr", and "y" operators. By default, double quotes and back quotes (backticks) are not allowed as delimiters for any operators and single quotes are allowed as delimiters for the "m", "qr", "qx", and "s" operators. These defaults are equivalent to having the following in your .perlcriticrc: [ValuesAndExpressions::ProhibitQuotesAsQuotelikeOperatorDelimiters] single_quote_allowed_operators = m s qr qx double_quote_allowed_operators = back_quote_allowed_operators = SUGGESTED BY
Michael Schwern AUTHOR
Elliot Shank "<perl@galumph.com>" COPYRIGHT
Copyright (c) 2007-2011 Elliot Shank. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module. perl v5.14.2 Perl::Critic::Policy::ValuesAndExpressions::ProhibitQuotesAsQuotelikeOperatorDelimiters(3pm)
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