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docs: More on dereferencing variables

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Also that unclosed quote was driving me up the wall
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Fabian Boehm 2023-02-15 18:29:14 +01:00
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doc_src/language.rst
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@ -693,10 +693,29 @@ The ``$`` symbol can also be used multiple times, as a kind of "dereference" ope
# 20
# 30
``$$foo[$i]`` is "the value of the variable named by ``$foo[$i]``.
``$$foo[$i]`` is "the value of the variable named by ``$foo[$i]``".
When using this feature together with list brackets, the brackets will be used from the inside out. ``$$foo[5]`` will use the fifth element of ``$foo`` as a variable name, instead of giving the fifth element of all the variables $foo refers to. That would instead be expressed as ``$$foo[1..-1][5]`` (take all elements of ``$foo``, use them as variable names, then give the fifth element of those).
Some more examples::
set listone 1 2 3
set listtwo 4 5 6
set var listone listtwo
echo $$var
# Output is 1 2 3 4 5 6
echo $$var[1]
# Output is 1 2 3
echo $$var[2][3]
# $var[1] is listtwo, third element of that is 6, output is 6
echo $$var[..][2]
# The second element of every variable, so output is
# 2 5
.. _expand-command-substitution:
Command substitution