How to send nested object data as post data using curl command in shell script?

Question

I am trying to send a post request using curl command in shell script.

When i run this curl command in terminal, it is working fine.

curl -d '{"DataArr":[{"serialno":"ab1","filePath":"/home/name/notes1"}]}' -H 'Content-Type: application/json' -H 'Authorization: tasfdgfdhh...' http://localhost:8081/create 

The same I am trying to run this as shell script file, it is hitting the server but the data format is not expected. The array bracket is converting as :" or something like :{ . I tried so many times with different possibilities but i do not understand how to prepare correct request. Below is the code and the response at server side.

I am using looping statement to simulate multiple requests,

code:
#!/bin/bash
echo "hello welcome to testing";
token=asdghadjakalskl.....

requestNo=10
i=0
sNo=(ab1 ab2 ab3 ab4 ab5)
fn=(notes1 Pictures/crop.jpeg Pictures/cat.jpeg Pictures/mountain.jpg Pictures/magic.jpeg Pictures/tree.jpg)

echo $1

for (( i=0; i< $1;i++ ))
do
    # echo "welcome inside the loop $s"
    
    echo ${sNo[i%5]} ${fn[i%6]}
    f="/home/name/${fn[i%6]}"
    # echo $token
    echo file $f
    echo $i request sent
   
    curl -d '{"DataArr":[{"serialno":'${sNo[i%5]}',"filePath":'$f'}]}' -H "'Content-Type: application/json'" -H 'Authorization: '$token'' http://localhost:8080/create

    
done

At server side,

{"{\"qualityDataArr\":":{"{\"serialNumberCustomer\":ab1,\"filePath\":/home/name/notes1}":""}}

Please guide me. Thank you!

Answer 1

Try echo """'{\"DataArr\":[{\"serialno\":\"${sNo[i%5]}\",\"filePath\":\"$f\"}]}'""" and if it displays well, then use echo curl -d """'{\"DataArr\":[{\"serialno\":\"${sNo[i%5]}\",\"filePath\":\"$f\"}]}'""" -H "'Content-Type: application/json'" -H """'Authorization: $token'""" http://localhost:8080/create | bash

Answer 2

There are some issues with the curl command here that I would prefer to approach slightly differently.

The first issue is the preparation of the JSON.

With '{"DataArr":[{"serialno":'${sNo[i%5]}',"filePath":'$f'}]}', the resulting JSON has a problem. The values for serialno and filePath looks likely alphanumeric or may contain spaces, meaning the values would need to be double quoted, eg "filePath": "/path/to/some where/to/new note", and this is not handled.

I would suggest to prepare the JSON using jq and store in a shell variable for later use with curl -d. Example,

jq --null-input               \
   --arg serialno ${sNo[i%5]} \
   --arg filePath $f          \
   '{"DataArr": [{"serialno": $serialno,"filePath": $filePath}]}'

--null-input is used because we wants to construct JSON data from scratch

--arg name value allows us to pass a string value to jq as a predefined variable.

This will for example gives you the following well formed JSON:

{
  "dataarr": [
    {
      "serialno": "ab1",
      "filepath": "/home/name/notes1"
    }
  ]
}

And this well formed JSON can be stored in a shell variable for later use:

prepared_payload=$( jq --null-input               \
                       --arg serialno ${sNo[i%5]} \
                       --arg filePath $f          \
                       '{"DataArr": [{"serialno": $serialno,"filePath": $filePath}]}' )

Now we can use this prepared_payload, like curl -d "${prepared_payload}"

The next issue is the inappropriate usage of single and double quotes in curl header options -H "'Content-Type: application/json'" and -H 'Authorization: '$token''

There are related past questions/answers, that can be helpful to take a deeper look at,

Difference between single and double quotes in Bash https://www.gnu.org/software/bash/manual/html_node/Single-Quotes.html https://www.gnu.org/software/bash/manual/html_node/Double-Quotes.html

The preferred approach would be -H "Content-Type: application/json" and -H "Authorization: $token"

The end curl command would thus looks as follows:

prepared_payload=$( jq --null-input               \
                       --arg serialno ${sNo[i%5]} \
                       --arg filePath $f          \
                       '{"DataArr": [{"serialno": $serialno,"filePath": $filePath}]}' )

curl -d "${prepared_payload}" -H "Content-Type: application/json" \
                              -H "Authorization: $token"          \
                              http://localhost:8080/create