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linuxbashlocal

in bash what does the -n parameter in "local -n" mean?

in bash what does the -n parameter in local -n var... mean? - how does it differ from local var...

I can't find a good example / explanation for it. There are no man pages for keywords (it seems?). The closest I have found is a comment here: local: -n: invalid option - which suggests something about not using ! param expansion

Solution

  • Parameters to local are unfortunately not documented in help local, but in help declare:

     `-n` make NAME a reference to the variable named by its value

    How does it work?

    #! /bin/bash
f () {
    local -n x=y
    y=12
    x=42
    echo $x $y  # 42 42
}
f

    You can achieve similar behaviour with the ! indirection (that's what the comment in the linked question means):

    #! /bin/bash
f () {
    x=y
    y=12
    echo ${!x}  # 12
}
f