根據BASH中可能的另一個變量的內容調用變量？

Question

比方說，我有3個變量，A=1,B=2,C=3和最後一個變量，其中包含任何一個的名稱（VAR=A）。根據VAR的內容而不是是否可以撥打A，B，C'if if？

贊echo "${$VAR}"？

Answer 1

是的。

eval echo \$$VAR 

還有這樣做的唯一的bash路，使用間接參考：

echo ${!VAR} 

Answer 2

A=1 
B=2 
C=3 
VAR=B 
echo ${!VAR} 

輸出：

文檔（男人bash）：

If the first character of parameter is an exclamation point (!), a level of variable indirection is introduced. Bash uses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself. This is known as indirect expansion. The exceptions to this are the expansions of ${!prefix*} and ${!name[@]} described below. The exclamation point must immediately follow the left brace in order to introduce indirection.