How can I find the value of a shell variable whose name is the value of another shell variable?

How can I find the value of a shell variable whose name is the value of another shell variable? 


Versions of Bash newer than Bash-2.0 support this directly.  You can use 



	${!var}



For example, the following sequence of commands will echo `z':



	var1=var2

	var2=z

	echo ${!var1}



For sh compatibility, use the `eval' builtin.  The important

thing to remember is that `eval' expands the arguments you give

it again, so you need to quote the parts of the arguments that

you want `eval' to act on. 



For example, this expression prints the value of the last positional

parameter:



	eval echo \"\$\{$#\}\"



The expansion of the quoted portions of this expression will be

deferred until `eval' runs, while the `$#' will be expanded

before `eval' is executed.  In versions of bash later than bash-2.0,



	echo ${!#}



does the same thing.



This is not the same thing as ksh93 `nameref' variables, though the syntax

is similar.  I may add namerefs in a future bash version.

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