Using jq with bash to run command for each object in array

Question

How can I run a Bash command for every JSON object in a JSON array using jq? So far I have this:

cat credentials.json | jq -r \'.[] | .user, .date, .         


        

Answer 1

Your best bet is probably to output each record in something like TSV format, then read that from a shell loop.

jq -r '.[]|[.user, .date, .email] | @tsv' |
  while IFS=$'\t' read -r user date email; do
    mycommand -u "$user" -d "$date" -e "$email"
  done

jq itself doesn't have anything like a system call to run an external command from within a filter, although it seems that they are working on it.

Answer 2

You could have jq output the commands to execute, something like

.[] | "mycommand \(.user|@sh) \(.date|@sh) \(.email|@sh)"

Then execute it. Something like

bash <(jq -r '.[] | "mycommand \(.user|@sh) \(.date|@sh) \(.email|@sh)"' foo)

Answer 3

With xargs:

curl localhost:8082/connectors | jq .[] | xargs -L1 -I'{}' curl -XDELETE 'localhost:8082/connectors/{}' 

Or equivalently, to show the output of that first curl:

echo '["quickstart-file-sink4","quickstart-file-source","quickstart-file-sink","quickstart-file-sink2","quickstart-file-sink3","quickstart-file-source2"]' | jq .[] | xargs -L1 -I'{}' curl -XDELETE 'localhost:8082/connectors/{}' 

jq .[] strips off one level of containment, so that a list becomes output as one line per item.

xargs -L1 processes one line at a time

xargs -I'{}' specifies that the string {} be replaced with the input line when invoking the following command.

xargs is essentially a map operator for the shell.

Answer 4

Here is another variation which I based on the answer from @chepner.

echo "$config" | jq -c '.[]' |
while IFS=$"\n" read -r c; do
    echo "start"
    host=$(echo "$c" | jq -r '.host')
    echo $host
    echo "end"
done

I used jq's -c option to output "compact" jsons, so they are all on one line.

In combination with IFS=$"\n", I was able to loop over each item in the input json's array and do what I wanted to do.

So, with an input of

[
 {
  "host": "host1",
  "settings": {}
 },
 {
  "host": "host1",
  "settings": {}
 }
]

the output is

start
host1
end
start
host2
end

Answer 5

I came across the same problem recently where xargs doesn't help that much due to the relatively complicated set of arguments I wanted to pass around. Thus I implemented an sh filter (and its friends) to jq. I haven't yet had enough time to write documentation and tests for it so not creating a PR for it to become a part of the official codebase yet. So now it's only for the ones who are willing to compile this version themselves:

https://github.com/haochenx/jq/tree/sh-support