Dynamic variable references

Question

I want to define a variable my_stacklist with the value for {mypc}_stacklist so if mypc=kast I get to access the content of kast_stacklist via my_stacklist.

I thougt this was the same as my earlier questions about dynamic variables , but cant fix it with declare or eval.

I use bash on a RPi 4 with the latest OS.

# want to have a my_stacklist for the current mypc and associating stacklist {mypc}_stacklist
mypc=kast
kast_stacklist=( stack1 stack2 stack3 stack4 )
screen_stacklist=( stack1 stack2 stack3 )

# First attempt
xxxx=$(eval "echo ${mypc}_stacklist") 
my_stacklist=$(eval "echo \$$xxxx")
printf "my_stacklist=${my_stacklist[@]}"

# Second attempt
#declare -n my_stacklist2=${xxxx[@]}        
declare -n my_stacklist2=${xxxx}        
printf "my_stacklist=${my_stacklist[@]}"
# i only get the first item instead of all items

I am a lithe further, but my script stills does not work #stacklist=( stack1 stack2 stack3 stack4 ) #kast_stacklist=( stack1 stack2 stack3 stack4 ) #screen_stacklist=( stack1 stack2 stack3 ) my_stacklist=(${mypc}_stacklist[@]) echo ${!my_stacklist} looks like my_stacklist is not the same format as stacklist that is currently used.. i want to make more stacklist, for each server on, so thats why i made kast_stacklist and screen_stacklist. Idea is to make a fixed variable that picks the right one based on $mypc — pvk
– pvk, Commented Feb 15, 2023 at 13:46
Does this answer your question? Shell variables in a for loop — AdminBee
– AdminBee, Commented Feb 15, 2023 at 14:58

glenn jackman · Accepted Answer · 2023-02-15 14:22:51Z

1

Use a nameref:

mypc=kast
kast_stacklist=(k1 k2 k3)
other_stacklist=(o1 o2 o3)

declare -n mystacklist="${mypc}_stacklist"

for i in "${!mystacklist[@]}"; do
  printf '%d\t%s\n' $i "${mystacklist[i]}"
done

0   k1
1   k2
2   k3

answered Feb 15, 2023 at 14:22

glenn jackman

88.5k16 gold badges124 silver badges179 bronze badges

that one is better then the trial i did last hours i=1 foo_kast=(fff ddd) ; foo_screen=(ggg ccc) ; kast_foo=(fff ddd) ; screen_foo=(ggg ccc) ; eval my_stacklist1=( \${foo_$mypc[@]} ) ; eval my_stacklist2=( \${${mypc}_foo[@]} ) ; echo ${my_stacklist1[$i]}; echo ${my_stacklist2[$i]}; echo ${my_stacklist1[@]}; echo ${my_stacklist2[@]};

pvk
– pvk

2023-02-15 14:58:21 +00:00
Commented Feb 15, 2023 at 14:58

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