04-20-2011
This doesn't work because bash doesn't substitute twice. If you have a string with "$varname" in it, it won't go back and start over and realize you also wanted $varname to be evaluated, too!
To do that kind of doublethink, you have to stuff it into an eval.
ARGS="$(eval $stringwithvarinit)"
Beware that you can do anything in an eval. Someone could stuff an `rm -rf ~/` in your config file and it could run it.
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LEARN ABOUT OSX
universal::require
UNIVERSAL::require(3) User Contributed Perl Documentation UNIVERSAL::require(3)
NAME
UNIVERSAL::require - require() modules from a variable
SYNOPSIS
# This only needs to be said once in your program.
require UNIVERSAL::require;
# Same as "require Some::Module"
my $module = 'Some::Module';
$module->require or die $@;
# Same as "use Some::Module"
BEGIN { $module->use or die $@ }
DESCRIPTION
If you've ever had to do this...
eval "require $module";
to get around the bareword caveats on require(), this module is for you. It creates a universal require() class method that will work with
every Perl module and its secure. So instead of doing some arcane eval() work, you can do this:
$module->require;
It doesn't save you much typing, but it'll make alot more sense to someone who's not a ninth level Perl acolyte.
Methods
require
my $return_val = $module->require or die $@;
my $return_val = $module->require($version) or die $@;
This works exactly like Perl's require, except without the bareword restriction, and it doesn't die. Since require() is placed in the
UNIVERSAL namespace, it will work on any module. You just have to use UNIVERSAL::require somewhere in your code.
Should the module require fail, or not be a high enough $version, it will simply return false and not die. The error will be in $@ as well
as $UNIVERSAL::require::ERROR.
$module->require or die $@;
use
my $require_return = $module->use or die $@;
my $require_return = $module->use(@imports) or die $@;
Like "UNIVERSAL::require", this allows you to "use" a $module without having to eval to work around the bareword requirement. It returns
the same as require.
Should either the require or the import fail it will return false. The error will be in $@.
If possible, call this inside a BEGIN block to emulate a normal "use" as closely as possible.
BEGIN { $module->use }
SECURITY NOTES
UNIVERSAL::require makes use of "eval STRING". In previous versions of UNIVERSAL::require it was discovered that one could craft a class
name which would result in code being executed. This hole has been closed. The only variables now exposed to "eval STRING" are the
caller's package, filename and line which are not tainted.
UNIVERSAL::require is taint clean.
COPYRIGHT
Copyright 2001, 2005 by Michael G Schwern <schwern@pobox.com>.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html
AUTHOR
Michael G Schwern <schwern@pobox.com>
SEE ALSO
Module::Load, "require" in perlfunc, <http://dev.perl.org/rfc/253.pod>
perl v5.16.2 2009-03-30 UNIVERSAL::require(3)