How to dynamically find a value of a key-value in json in bash script

Question

I'm new to bash scripting. I am iterating over a list and want to get the value from a JSON object. I've tried all 3 of these and am getting a jq: 1 compile error

What is the proper syntax?

for key in $KEYS
  echo "ALIASES:" $ALIASES
  # ALIASES: {'a': 'apple', 'b': 'bananna'}

FRUIT=$(echo $ALIASES | jq ."$key" -r)
FRUIT=$(echo $ALIASES | jq .'$key' -r)
FRUIT=$(echo $ALIASES | jq .$key -r)

Answer 1

The main problem seems to be in your json data because you have:

{'a': 'apple', 'b', 'bananna'}

As far as I know using single quotes is not valid (use double quotes): json format.
The another problem I see is that you have a comma , between 'b' and 'bannana' (I assume you didn't notice that and you typed , instead of :)

So Your json data should be like this:

{"a": "apple", "b": "bananna"}

What is the proper syntax to get a key?

I usually see that the syntax '.key' is more used. However I think you should use any which works. For example, I see in your case that you are using a variable $key to get specific value from a json key. So, you should use something like ".$key" or maybe ."$key", .$key (I'm not sure if these are recommended):

Solution 1

FRUIT=$(echo $ALIASES | jq ".$key" -r)
#or
FRUIT=$(echo $ALIASES | jq ."$key" -r)
#or
FRUIT=$(echo $ALIASES | jq .$key -r)

If you use or want to use single quotes then you will not be able to pass any variable value to jq command. According to man bash:

Enclosing characters in single quotes (') preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash

Therefore If you want to use single quotes to a json value by specifying some key you should use:

FRUIT=$(echo $ALIASES | jq '.somekey' -r)
#e.g.
FRUIT=$(echo $ALIASES | jq '.a' -r)
echo $FRUIT
#Output:
apple

You can check these answers for a better understanding about single quotes and double quotes

Solution 2 (using jq --arg)
I'm not sure why the code above doesn't work for you (using the double quotes). However there is another possible solution to pass variables to jq, you can try:

val="a"
echo $ALIASES | jq --arg key "$val" '.[$key]' -r

---

As you are using python to get the json then you should use the method json.dumps(your_json), for example:

python3 -c 'import json;aliases = json.load(open("file"));print(json.dumps(aliases))'