declare command, export command

declare command
declare[+/-][options] variable name 
option 
-: Set the type attribute for the variable 
+: Cancel the type attribute of the variable 
-a: Declare the variable as an array type 
-i: Declare the variable as an integer type (integer) 
- x: Declare the variable as an environment variable 
-r: Declare the variable as a read-only variable 
-p: Display the declared type of the specified variable

export command (declare environment variables)
export is equivalent to declare -x
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Author: Code Hammer 
Source: CSDN 
Original text: https://blog .csdn.net/forcezs/article/details/80511828 
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