Spaces in Associative Array Keys while looping through multiple arrays in Bash

Question

I am having a bit of trouble while looping through multiple associative arrays in bash.

Here is the code I'm running: (stripped of the actual information)

arrays=("arrayone" "arraytwo")
declare -A arrayone=(["one"]=1 ["two"]=2)
declare -A arraytwo=(["text with spaces"]=value ["more text with spaces"]=differentvalue)
for array in ${arrays[*]} 
 do 
 for key in $(eval echo $\{'!'$array[@]\})   
       do 
       echo "$key"
       done
 done

This works perfectly fine until I run into a key value that has spaces in it. No matter what I do, I cannot get items with spaces to be treated correctly.

I would appreciate any ideas you have on how to get this working. If there is, a better way to do this, I'd be happy to hear it. I don't mind scratching this and starting over. It's just the best I've been able to come up with so far.

Thanks!

I'm aware of that, but I can't figure out how to do it in this particular instance. (It messes with my eval command) I've tried various combinations of double and single-quotes with backslashes, etc. and googled this to death already. Two hours later, I'm here. — contributor1
– contributor1, Commented Mar 16, 2015 at 18:58
Hm... true, $() is going to throw that away even if you get the internal expansion right. I don't think you can do it this way. You probably need to write a function for the inner loop and pass it $array[@] and do the indirect expansion in the function. Like isSubset from here. — Etan Reisner
– Etan Reisner, Commented Mar 16, 2015 at 19:07
Typically, to iterate over the values of an array where the name is dynamic, you'd need a placeholder var for the indirect expansion: tmp="${array}[@]"; for elem in "${!tmp}"; ... -- however, using that idiom, you can't iterate over the keys: this does not work: tmp='!'"${array}[@]"; for key in "${!tmp}"; ... -- this ${!tmp} expands to nothing. You may be reduced to parsing the output of declare -p "$array" — glenn jackman
– glenn jackman, Commented Mar 16, 2015 at 20:12

kojiro · Accepted Answer · 2015-03-17 12:34:35Z

4

Bash added the nameref attribute in 4.3. It allows you to make a name specifically a reference to another. In your case, you would do

declare -A assoc_one=(["one"]=1 ["two"]=2)
declare -A assoc_two=(["text with spaces"]=value ["more text with spaces"]=differentvalue)
declare -n array # Make it a nameref
for array in "${!assoc_@}"; do 
    for key in "${!array[@]}"; do
        echo "'$key'"
    done
done

and you get

'one'
'two'
'text with spaces'
'more text with spaces'

Names were changed to protect the idioms. I mean, I changed the array names so I could do "${!assoc_@}" without making array a special case.

edited Mar 17, 2015 at 12:34

answered Mar 17, 2015 at 2:55

kojiro

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4 Comments

mklement0 Over a year ago

"Names were changed to protect the idioms" was worth an up-vote in its own right. Good to know that you can defer binding a nameref, and even rebind iteratively when using a declare -n variable as a for control variable.

kojiro Over a year ago

@mklement0 what's more interesting is that I can't seem to rebind manually inside a while loop. This could lead to a followup SO question if I have time to do some research.

mklement0 Over a year ago

Yes, the for behavior is special (mentioned in the man page). To do it in a while loop, move the declare -n statement inside the loop; note that you must bind as part of the declare -n statement for this to work; e.g., while ...; do declare -n nameref=...; done.

contributor1 Over a year ago

Thanks! I knew there had to be a way to do this, but I wasn't getting anywhere. This was what I needed.

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