How to evaluate the value of a variable ?

Shell Programming and Scripting
1

How to evaluate the value of a variable ?
For example:

a=var
$a=value !!!error happens!!!

I want to evaluate var=value, how to realize it?
Thanks!

---------- Post updated at 03:37 AM ---------- Previous update was at 02:22 AM ----------

I am using linux bash.

a=var
$a=value !!!error happens!!!

I want the following result:

$echo $a
var
$echo $var
value

So I want the value of $a to be a variable, and it can be valued.

2

Do you mean this?

$ a=var
$ var=value
$ eval echo \$$a
value
$
3

Sorry,

[river@localhost ~]$ a=var
[river@localhost ~]$ echo $a
var
[river@localhost ~]$ $a=value
bash: var=value: command not found...

May be a=var1 , or a=var2
I just want evaluate the content of $a, not evaluate directly, but through $a.
For example:

a=var1
$a=value      ** assume it is a right command**

so I want

echo $var1
value

But

$a=value

is not a right command.:wall:

4 
$ a=var1
$ eval $(echo $a=value)
$ echo $var1
value
5

Solved!!
Thanks for your help!