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Top Forums Shell Programming and Scripting Safe way to eval variable declarations? Post 302911293 by Michael Stora on Thursday 31st of July 2014 02:42:08 AM
Old 07-31-2014
Quote:
Originally Posted by Chubler_XL
I'd suggest not using eval at all, just code your own allowed expansions e.g.:

Code:
expand='$RANDOM'
[ ${expand:0:1} = "$" ] && {
   expand=${expand:1}
   expand=${!expand}
}

So here we support $var and not $(command)
OK, so I understand what expand=${expand:1} is doing (cannot do anything but manipulate variable in variable substitution), but what does expand=${!expand} do?

Mike
 

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Text::Tabs(3pm) 					 Perl Programmers Reference Guide					   Text::Tabs(3pm)

NAME
Text::Tabs -- expand and unexpand tabs per the unix expand(1) and unexpand(1) SYNOPSIS
use Text::Tabs; $tabstop = 4; # default = 8 @lines_without_tabs = expand(@lines_with_tabs); @lines_with_tabs = unexpand(@lines_without_tabs); DESCRIPTION
Text::Tabs does about what the unix utilities expand(1) and unexpand(1) do. Given a line with tabs in it, expand will replace the tabs with the appropriate number of spaces. Given a line with or without tabs in it, unexpand will add tabs when it can save bytes by doing so (just like "unexpand -a"). Invisible compression with plain ASCII! EXAMPLE
#!perl # unexpand -a use Text::Tabs; while (<>) { print unexpand $_; } Instead of the "expand" comand, use: perl -MText::Tabs -n -e 'print expand $_' Instead of the "unexpand -a" command, use: perl -MText::Tabs -n -e 'print unexpand $_' LICENSE
Copyright (C) 1996-2002,2005,2006 David Muir Sharnoff. Copyright (C) 2005 Aristotle Pagaltzis This module may be modified, used, copied, and redistributed at your own risk. Publicly redistributed modified versions must use a different name. perl v5.12.1 2010-04-26 Text::Tabs(3pm)
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