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Top Forums Shell Programming and Scripting Evaluate the value of a variable? Post 302282923 by Ilja on Monday 2nd of February 2009 07:07:24 AM
Old 02-02-2009
Evaluate the value of a variable?

I have variables:
FOO="Text"
BAR="FOO"

I'd like to be able to evaluate the variable named as the value of $BAR.
echo $FOO
Text

echo $BAR
FOO

This is what I'd like to do:
echo ${$BAR} (this won't work)
Text
 

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Perl::Critic::Utils::PPI(3)				User Contributed Perl Documentation			       Perl::Critic::Utils::PPI(3)

NAME
Perl::Critic::Utils::PPI - Utility functions for dealing with PPI objects. DESCRIPTION
Provides classification of PPI::Elements. INTERFACE SUPPORT
This is considered to be a public module. Any changes to its interface will go through a deprecation cycle. IMPORTABLE SUBS
"is_ppi_expression_or_generic_statement( $element )" Answers whether the parameter is an expression or an undifferentiated statement. I.e. the parameter either is a PPI::Statement::Expression or the class of the parameter is PPI::Statement and not one of its subclasses other than "Expression". "is_ppi_generic_statement( $element )" Answers whether the parameter is an undifferentiated statement, i.e. the parameter is a PPI::Statement but not one of its subclasses. "is_ppi_statement_subclass( $element )" Answers whether the parameter is a specialized statement, i.e. the parameter is a PPI::Statement but the class of the parameter is not PPI::Statement. "is_ppi_simple_statement( $element )" Answers whether the parameter represents a simple statement, i.e. whether the parameter is a PPI::Statement, PPI::Statement::Break, PPI::Statement::Include, PPI::Statement::Null, PPI::Statement::Package, or PPI::Statement::Variable. "is_ppi_constant_element( $element )" Answers whether the parameter represents a constant value, i.e. whether the parameter is a PPI::Token::Number, PPI::Token::Quote::Literal, PPI::Token::Quote::Single, or PPI::Token::QuoteLike::Words, or is a PPI::Token::Quote::Double or PPI::Token::Quote::Interpolate which does not in fact contain any interpolated variables. This subroutine does not interpret any form of here document as a constant value, and may not until PPI::Token::HereDoc acquires the relevant portions of the PPI::Token::Quote interface. This subroutine also does not interpret entities created by the Readonly module or the constant pragma as constants, because the infrastructure to detect these appears not to be present, and the author of this subroutine (not Mr. Shank or Mr. Thalhammer) lacks the knowledge/expertise/gumption to put it in place. "is_subroutine_declaration( $element )" Is the parameter a subroutine declaration, named or not? "is_in_subroutine( $element )" Is the parameter a subroutine or inside one? "get_constant_name_element_from_declaring_statement($statement)" This subroutine is deprecated. You should use "get_constant_name_elements_from_declaring_statement()" in PPIx::Utilities::Statement instead. Given a PPI::Statement, if the statement is a "use constant" or Readonly declaration statement, return the name of the thing being defined. Given use constant 1.16 FOO => 'bar'; this will return "FOO". Similarly, given Readonly::Hash my %FOO => ( bar => 'baz' ); this will return "%FOO". Caveat: in the case where multiple constants are declared using the same "use constant" statement (e.g. "use constant { FOO => 1, BAR => 2 };", this subroutine will return the declaring PPI::Structure::Constructor. In the case of "use constant 1.16 { FOO => 1, BAR => 2 };" it may return a PPI::Structure::Block instead of a PPI::Structure::Constructor, due to a parse error in PPI. "get_next_element_in_same_simple_statement( $element )" Given a PPI::Element, this subroutine returns the next element in the same simple statement as defined by is_ppi_simple_statement(). If no next element can be found, this subroutine simply returns. If the $element is undefined or unblessed, we simply return. If the $element satisfies "is_ppi_simple_statement()", we return, unless it has a parent which is a PPI::Structure::List. If the $element is the last significant element in its PPI::Node, we replace it with its parent and iterate again. Otherwise, we return "$element->snext_sibling()". "get_previous_module_used_on_same_line( $element )" Given a PPI::Element, returns the PPI::Element representing the name of the module included by the previous "use" or "require" on the same line as the $element. If none is found, simply returns. For example, with the line use version; our $VERSION = ...; given the PPI::Token::Symbol instance for $VERSION, this will return "version". If the given element is in a "use" or <require>, the return is from the previous "use" or "require" on the line, if any. 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 v5.16.3 2014-06-09 Perl::Critic::Utils::PPI(3)
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