Bash how to parse asscoiative array from argument?

Question

I am trying to read a string into an associative array.

The string is being properly escaped and read into .sh file:

./myScript.sh "[\"el1\"]=\"val1\" [\"el2\"]=\"val2\""

within the script

#!/bin/bash -e
declare -A myArr=( "${1}" ) #it doesn't work either with or without quotes

All I get is:

line 2: myArr: "${1}": must use subscript when assigning associative array

Googling the error only results in "your array is not properly formatted" results.

Like using eval this is likely to produce code injection or other bugs when dealing with complex inputs. — l0b0
– l0b0, Commented Mar 9, 2021 at 1:09
Would you be OK with something like ./myScript.sh el1 val1 el2 val2? — l0b0
– l0b0, Commented Mar 9, 2021 at 1:10

l0b0 · Accepted Answer · 2021-03-09 01:16:32Z

3

You could read key/value pairs from variable inputs in series:

$ cat > example.bash <<'EOF'
#!/usr/bin/env bash

declare -A key_values
while true
do
    key_values+=(["$1"]="$2")
    shift 2
    if [[ $# -eq 0 ]]
    then
        break
    fi
done

for key in "${!key_values[@]}"
do
    echo "${key} = ${key_values[$key]}"
done
EOF
$ chmod u+x example.bash
$ ./example.bash el1 val1 el2 val2
el2 = val2
el1 = val1

This should be safe no matter what the keys and values are.

answered Mar 9, 2021 at 1:16

l0b0

59.6k32 gold badges155 silver badges247 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

KamilCuk · Accepted Answer · 2021-03-09 11:02:52Z

1

Instead of caring about proper double escaping, set the variables on caller side, and use bash declare -p. That way you will always get properly escaped string.

declare -A temp=([el1]=val1 [el2]=val2)
./script.sh "$(declare -p temp)"

Then do:

# ./script.sh
# a safer version of `eval "$1"`
declare -A myarr="${1#*=}"

answered Mar 9, 2021 at 11:02

KamilCuk

146k8 gold badges84 silver badges154 bronze badges

Comments

Theo · Accepted Answer · 2021-03-10 09:57:35Z

0

solution:

./test.sh "( [\"el1\"]=\"val1\" [\"el2\"]=\"val2\" )"

and within the script:

#!/bin/bash -e

declare -A myArr="${1}"
declare -p myArr

for i in "${!myArr[@]}"
do
  echo "key  : $i"
  echo "value: ${myArr[$i]}"
done

Returns:

> ./test.sh "( [\"el1\"]=\"val1\" [\"el2\"]=\"val2\" )"
declare -A myArr=([el2]="val2" [el1]="val1" )
key  : el2
value: val2
key  : el1
value: val1

I can't explain why this works, or why the order changes though.

Test it yourself here

edited Mar 10, 2021 at 9:57

answered Mar 8, 2021 at 23:12

Theo

2,9705 gold badges29 silver badges59 bronze badges

3 Comments

Gordon Davisson Over a year ago

This doesn't work in my testing; it creates a single array element (indexed by "0") containing the entire argument as a literal string. Add declare -p myArr at the end to see what's actually happening.

Theo Over a year ago

@GordonDavisson it works for me perfectly - what is your issue? also improved on answer, you can see the output of declare -p myArr

Gordon Davisson Over a year ago

Ah, I see, I was testing it without supplying the outer parentheses in the argument (I just copied the argument format from the original question). With parens, it works for me too.

Collectives™ on Stack Overflow

Bash how to parse asscoiative array from argument?

3 Answers 3

Comments

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related