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Top Forums Shell Programming and Scripting Usage of '-' in eval command. Post 302878528 by Don Cragun on Friday 6th of December 2013 01:56:28 PM
Old 12-06-2013
Quote:
Originally Posted by Kuldip
Hi Bakunin,


The value of HAPROXY_LISTENER_NAME is "search-engine" and just search-engine doesnt makes any sense it gets combined with HAPROXY_LISTENER
& PORT to form a variable HAPROXY_LISTENER_search-engine_PORT.This variable is exported and has a value so that it could be fetched.
No it cannot. The command:
Code:
export HAPROXY_LISTENER_search-engine_PORT

is used to export variables, but the above command returns the following diagnostic:
Code:
export: HAPROXY_LISTENER_search-engine_PORT: is not an identifier

In the shell command language, in the C programming language, in the FORTRAN programming language, in the awk programming language, and in hundreds of other languages, "-" is not a valid character in a variable name.

If you are using a language where HAPROXY_LISTENER_search-engine_PORT is a valid variable name and you want to write a shell script to create names like this to be included in source code for that language, we can write shell scripts to do that. We cannot write a shell script that can use HAPROXY_LISTENER_search-engine_PORT as a shell variable name.
 

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Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEUser3Contributed Perl DocumePerl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval(3)

NAME
Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval - Write "eval { my $foo; bar($foo) }" instead of "eval "my $foo; bar($foo);"". AFFILIATION
This Policy is part of the core Perl::Critic distribution. DESCRIPTION
The string form of "eval" is recompiled every time it is executed, whereas the block form is only compiled once. Also, the string form doesn't give compile-time warnings. eval "print $foo"; # not ok eval {print $foo}; # ok CONFIGURATION
There is an "allow_includes" boolean option for this Policy. If set, then strings that look like they only include a single "use" or "require" statement (with the possible following statement that consists of a single number) are allowed. With this option set, the following are flagged as indicated: eval 'use Foo'; # ok eval 'require Foo'; # ok eval "use $thingy;"; # ok eval "require $thingy;"; # ok eval "use $thingy; 1;"; # ok eval "require $thingy; 1;"; # ok eval 'use Foo; blah;'; # still not ok eval 'require Foo; 2; 1;'; # still not ok eval 'use $thingy;'; # still not ok eval 'no Foo'; # still not ok If you don't understand why the number is allowed, see Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval. This option inspired by Ricardo SIGNES' Perl::Critic::Policy::Lax::ProhibitStringyEval::ExceptForRequire. SEE ALSO
Perl::Critic::Policy::ControlStrucutres::RequireBlockGrep Perl::Critic::Policy::ControlStrucutres::RequireBlockMap AUTHOR
Jeffrey Ryan Thalhammer <jeff@imaginative-software.com> COPYRIGHT
Copyright (c) 2005-2011 Imaginative Software Systems. All rights reserved. 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::Policy::BuiltinFunctions::ProhibitStringyEval(3)
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