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Sometimes we need to use the value of a variable to refer to the demand value as the value of the variable, ie A = "B", then there is one variable B = "value", the need to obtain access to "value" this value by A ;
There are two ways
#准备
v1="v2"
v2="hellow"
A value = $ {! Varname} manner, i.e., $ {!}
v3=${!v1}
Two expr value = $$ varname way that is expr \ $$
eval v4=\$$v1
Example:
