CODEWITHSUNDEEP
bashvariables
Bryce Thomas
Bryce Thomas

Reputation: 10799

Bash alias for string variable/copy by reference instead of value

Consider the following Bash script:

$ A=35
$ echo $A
35
$ B=$A
$ echo $B
35
$ B=43
$ echo $B
43
$ echo $A
35

I declared a variable A, assigned the value 35 to it, made B equal to A, and assigned the value 43 to B. It appears that A retains the value 35 after all this, so I'm guessing when you assign one variable in bash to another, it's copy by value, not copy by reference.

What I want to be able to do is change B's value and have it reflected in A (copy by reference). Or, in my real case, I simply don't want to incur the memory overhead of copy by value, as I know it's a large variable and don't want to store it twice in memory. Is there a way to do this in Bash?

Upvotes: 2

Views: 697

Answers (1)

Matteo
Matteo

Reputation: 14940

You can reference another variable with

$ a=42
$ reference=a
$ echo ${!reference}
42

To change the value of the referenced variable

$ eval ${reference}=4
$ echo ${!reference}
4
echo $a
4

Upvotes: 3

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