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Top Forums Shell Programming and Scripting Usage of '-' in eval command. Post 302878493 by rbatte1 on Friday 6th of December 2013 10:40:03 AM
Old 12-06-2013
The hyphen can be used in CoBOL code, but it is considered as plain text for Unix shells. I've fallen across this the other way around when I wanted to set a variable to a value built from another variable like this:-
Code:
fileheader=myfile
rundate=`date +%Y%m%d`
filename=$fileheader_$rundate

I wanted to end up with myfile_20131206 as the filename format and I got very confused because it always evaluated to just 20131206 (or whatever the date was)

This was because the underscore is considered part of the variable name and the variable fileheader_ was undefined. This is not pretty, but I had to change the code to read:-
Code:
fileheader=myfile
rundate=`date +%Y%m%d`
filename=${fileheader}_$rundate

.... and learn from my error.

I too would like to know what you are actually trying to achieve. We might have a better way to do it, save you some hassle and provide something for others to read and learn from. Indeed, I'm quite happy to learn myself if there is a better way than I am currently using.



Robin
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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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