How to append json array using jq shell in a loop?-CodePudding

I can create a json object with an array using jq like this

echo '{"input":{"names":[]}}' | jq --arg val "alice" '.input.names[0] = $val'| jq --arg val "bob" '.input.names[1] = $val'

which gives

{
  "input": {
    "names": [
      "alice",
      "bob"
    ]
  }
}

Now I want to recreate this in a shell script where "names" come from a shell array

#!/bin/sh

names=( alice bob )
                 
ITER=0
for i in "${names[@]}"
do                  
    echo '{"input":{"names":[]}}' |  jq --arg val "$i" '.input.names[$ITER]  = $val'
    echo ${I} ${ITER}                                                               
    ITER=$(expr $ITER   1)                                                          
done

but I run into

jq: error: $ITER is not defined at <top-level>, line 1:
.input.names[$ITER]  = $val             
jq: 1 compile error
0
jq: error: $ITER is not defined at <top-level>, line 1:
.input.names[$ITER]  = $val             
jq: 1 compile error
1

CodePudding user response：

You could get rid of the shell and use one jq call:

names=( alice bob )
jq -n --arg names "${names[*]}" '{"input": {"names": ($names / " ") } }'

name=( alice bob )
printf '%s\0' "${names[@]}" |
jq -sR '(. / "\u0000") as $names | { "input": { "names": $names } }'

CodePudding user response：

You don't capture the output of an iteration step, so you lose the output from the jq call and start all over again in the next iteration step.

Here's a bash solution which captures the output using $(...) and provides it for the next using <<<. (Note that there are better ways to solve this problem, e.g. without looping but by proving jq all elements to be added at once.)

json='{"input":{"names":[]}}'

for i in alice bob
do json="$(jq --arg val "$i" '.input.names  = [$val]' <<< "$json")"
done

echo "$json"

{
  "input": {
    "names": [
      "alice",
      "bob"
    ]
  }
}