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Full Discussion: Safe way to eval variable declarations?
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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LEARN ABOUT CENTOS

expand

EXPAND(1)							   User Commands							 EXPAND(1)

NAME

       expand - convert tabs to spaces

SYNOPSIS

       expand [OPTION]... [FILE]...

DESCRIPTION

       Convert tabs in each FILE to spaces, writing to standard output.  With no FILE, or when FILE is -, read standard input.

       Mandatory arguments to long options are mandatory for short options too.

       -i, --initial
	      do not convert tabs after non blanks

       -t, --tabs=NUMBER
	      have tabs NUMBER characters apart, not 8

       -t, --tabs=LIST
	      use comma separated list of explicit tab positions

       --help display this help and exit

       --version
	      output version information and exit

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report expand translation bugs to <http://translationproject.org/team/>

AUTHOR

       Written by David MacKenzie.

COPYRIGHT

       Copyright (C) 2013 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       unexpand(1)

       The  full documentation for expand is maintained as a Texinfo manual.  If the info and expand programs are properly installed at your site,
       the command

	      info coreutils 'expand invocation'

       should give you access to the complete manual.

GNU coreutils 8.22						     June 2014								 EXPAND(1)
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