bash associative arrays--variable containing value pair

Question

I have a file that looks like this:

stringtests (6 tests)
alphatests (1 tests)
arraytests (100 tests)

I can extract and translate into:

["stringtests"]="6"
["alphatests"]="1"
["arraytests"]="100"

I place these in a variable ("tests"):

~> tests="[\"stringtests\"]=\"6\" [\"alphatests\"]=\"1\" [\"arraytests\"]=\"100\""

Then I try to put them in an associative array using the variable I get an error:

~> declare -A arr=( $tests )
-bash: arr: ["stringtests"]="6": must use subscript when assigning associative array
-bash: arr: ["alphatests"]="1": must use subscript when assigning associative array
-bash: arr: ["arraytests"]="100": must use subscript when assigning associative array

"eval" doesn't work either:

declare -A arr=( $(eval echo $tests) )
-bash: arr: [stringtests]=6: must use subscript when assigning associative array
-bash: arr: [alphatests]=1: must use subscript when assigning associative array
-bash: arr: [arraytests]=100: must use subscript when assigning associative array

But, if I put the values directly it works:

~> declare -A arr=( ["stringtests"]="6" ["alphatests"]="1" ["arraytests"]="100" )
~> echo ${arr[@]}
1 100 6
~> echo ${!arr[@]}
alphatests arraytests stringtests

Is it even possible to do this?

Need eval before declare not in the subshell.eval declare -A arr=( $tests ). Fails because = is evaluated before variable expansion so array sees ["stringtests"]="6" as a single string. — 123
– 123, Commented Oct 31, 2017 at 16:34
@123, eh? eval can be avoided entirely here, and when it can be avoided it should. — Charles Duffy
– Charles Duffy, Commented Oct 31, 2017 at 17:26
@CharlesDuffy Just pointing out the issue with their command, not suggesting it was the best option. — 123
– 123, Commented Oct 31, 2017 at 17:37

Cyrus · Accepted Answer · 2017-10-31 16:58:50Z

4

Replace

declare -A arr=( $tests )

with

declare -A arr='('$tests')'

tests="[\"stringtests\"]=\"6\" [\"alphatests\"]=\"1\" [\"arraytests\"]=\"100\""
declare -A arr='('$tests')'
declare -p arr

Output:

declare -A arr='([alphatests]="1" [arraytests]="100" [stringtests]="6" )'

edited Oct 31, 2017 at 16:58

answered Oct 31, 2017 at 16:41

Cyrus

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6 Comments

glenn jackman Over a year ago

probably safer to write declare -A arr="($tests)" so that the variable is quoted.

123 Over a year ago

@Cyrus How does escaping/quoting the parenths make it interpret the contents differently? Is there any documentation or am I missing something obvious?

Cyrus Over a year ago

@123: There are no details known to me.

123 Over a year ago

@Cyrus Did you just stumble upon it then? I can't see why it would make any difference. Why would the = be interpreted only if () are escaped?

Cyrus Over a year ago

@123: I stumbled upon it when I was looking at the output of: declare -p arr.

|

glenn jackman · Accepted Answer · 2017-10-31 17:23:47Z

1

I would avoid the temp variable altogether, and populate the array while you're parsing the file

declare -A arr
while IFS= read -r line; do 
    # bash regex: the literal bits are quoted
    if [[ $line =~ (.+)" ("([0-9]+) ]]; then 
        arr["${BASH_REMATCH[1]}"]="${BASH_REMATCH[2]}"
    fi
done < file
declare -p arr

declare -A arr='([alphatests]="1" [arraytests]="100" [stringtests]="6" )'

answered Oct 31, 2017 at 17:23

glenn jackman

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