Bash pass argument for array selection - bash

Question

I'm trying to pass the second argument to get an array and loop trough but im getting this error: ${$2[#]}: bad substitution
my code is:
/etc/init.d/displaycameras start c1
#!/bin/bash
dis1cam1="screen -dmS dis1cam1 sh -c 'omxplayer --avdict rtsp_transport:tcp --win \"0 0 640 428\" rtsp://myvideo --live -n -1'";
camera_feeds=('c1=(dis1cam1 dis1cam2 dis1cam3 dis1cam4 dis1cam5 dis1cam6 dis1cam8 dis1cam9)' 'c2=(dis2cam1 dis2cam2 dis2cam3 dis2cam4)')
for elt in "${camera_feeds[#]}";do eval $elt;done
# Start displaying camera feeds
case "$1" in
start)
for i in "${$2[#]}"
do
eval eval '$'$i
done
echo "Camera Display 1 Started"
;;
Is there a way to pass the 2nd argument to call the c2 set ?
in this way is working perfect:
#!/bin/bash
dis1cam1="screen -dmS dis1cam1 sh -c 'omxplayer --avdict rtsp_transport:tcp --win \"0 0 640 428\" rtsp://myvideo --live -n -1'";
camera_feeds=('c1=(dis1cam1 dis1cam2 dis1cam3 dis1cam4 dis1cam5 dis1cam6 dis1cam8 dis1cam9)' 'c2=(dis2cam1 dis2cam2 dis2cam3 dis2cam4)')
for elt in "${camera_feeds[#]}";do eval $elt;done
# Start displaying camera feeds
case "$1" in
start)
for i in "${c1[#]}"
do
eval eval '$'$i
done
echo "Camera Display 1 Started"
;;

Answer 1

I would strongly advise implementing this differently.
#!/usr/bin/env bash
die() { echo "$*" >&2; exit 1; }
[[ $BASH_VERSION = [0-3]* ]] && die "Bash 4.3 or newer needed"
[[ $BASH_VERSION = 4.[0-2].* ]] && die "Bash 4.3 or newer needed"
dis1cam1() { : "code to start camera dis1cam1 here"; )
dis1cam2() { : "code to start camera dis1cam2 here"; )
# ...etc...
camera_feeds__c1=(dis1cam1 dis1cam2 dis1cam3 dis1cam4 dis1cam5 dis1cam6 dis1cam8 dis1cam9)
camera_feeds__c2=(dis2cam1 dis2cam2 dis2cam3 dis2cam4)
# here, we're showing the iterate-over-all-feeds case
# you can just set var=camera_feeds__c1 yourself if you prefer
for var in "${!camera_feeds__#}"; do # var will be camera_feeds__c1 or camera_feeds__c2
feed_name=${var#camera_feeds__} # feed_name will be "c1" or "c2"
declare -n camera_feeds=$var
for i in "${camera_feeds[#]}"; do
echo "Starting $i in feed $feed_name" >&2
"$i" # look up and run code in variable named in $i
done
unset -n camera_feeds
done
"${camera_feeds__#}" expands to the list of shell variables whose names start with camera_feeds__; this is thus the name of our two arrays.
declare -n camera_feeds=$var then makes camera_feeds an alias for the array presently being iterated over, such that for i in "${camera_feeds[#]}" iterates over that array.
unset -n camera_feeds clears this association.