= Referencias indirectas
== indirection, indirect references
usar el valor de una variable para acceder al contenido de otra
<code bash>
# declaramos 2 variables
export xyzzy=plugh ; export plugh=cave

echo ${xyzzy}  # normal, xyzzy to plugh -> plugh

echo ${!xyzzy} # indirection, xyzzy to plugh to cave -> cave
</code>

existen 2 casos en el que este comportamiento se ve modificado:
  * ''${!N*}'' : muestra las variables que empiecen por N
  * ''${!name[@]}''

<code bash>
export myVar="hi"
echo ${!my*} # myVar

export ${!my*}="bye"
echo $myVar # bye
</code>

/vía: [[https://stackoverflow.com/questions/8515411/what-is-indirect-expansion-what-does-var-mean]]

== asignación a variable referenciada indirectamente
<code bash>
#!/bin/bash

AQUI_VALOR="GHJGHJGHJ"
VARIABLE=AQUI_VALOR

read -p "Valor: " VALOR
echo ${VALOR}

declare "${VARIABLE}=$VALOR"
# typeset equivalente a declare, soportado por otros shells (zsh)
# printf -v "${VARIABLE} '%s' "${VALOR}"

echo $AQUI_VALOR        # $VALOR
echo "=="
echo $VARIABLE          # $VARIABLE
</code>

/via: [[https://stackoverflow.com/questions/9938649/indirect-variable-assignment-in-bash]]
== + info
  * [[http://tldp.org/LDP/abs/html/ivr.html]]
  * [[https://stackoverflow.com/questions/8515411/what-is-indirect-expansion-what-does-var-mean]]
  * en arrays: [[https://stackoverflow.com/questions/11180714/how-to-iterate-over-an-array-using-indirect-reference]]