How to include JSON string in cURL command when curl command itself is a string

Question

I have the following string:

barrelRepDoc='{"'"_id"'":"'"push_$systemName"'","'"source"'":"'"$systemName"'","'"target"'":"'"platform2ReplicationTargetBaseURL/$systemName"'","'"create_target"'":true,"'"continuous"'":true,"'"user_ctx"'":{"'"name"'":"'"admin"'","'"roles"'":["'"_admin"'"]},"'"owner"'":"'"admin"'"}'

And I'm passing that string as the -d parameter into a cURL string such as this:

barrelRepcURL="curl -u $username:$password -X POST couchURL/db -H 'Content-Type:application/json' -d '$barrelRepDoc'"

And I'm then executing the command on this line:

barrelRepcURLresponse=$($barrelRepcURL)

And I'm getting invalid JSON. However, if I print out $barrelRepcURL, I get a string that executes as it is supposed to when pasted into the terminal.

I would like feedback on the cURL command, which is why I'm using a string. (echo $barrelRepcURLresponse)

How can I include the barrelRepDoc within the cURL command string and keep valid JSON?

Use a tool like jq to generate the JSON: barrelRepDoc=$(jq -n --arg systemName foo '{_id: ("push_" + $systemName), source: $systemName, target: ("platform2ReplicationTargetBaseURL/" + $systemName), create_target: true, continuous: true, user_ctxa: { name: "admin", roles: ["_admin"]}, owner: "admin"}') (It looks much better with some whitespace in your script.) — chepner
– chepner, Commented Mar 14, 2016 at 14:44

Tom Fenech · Accepted Answer · 2016-03-15 00:33:54Z

5

Is there any reason you're trying to use a string instead of a function?

This would work:

barrelRepcURL() {
    local username=$1
    local password=$2
    local barrelRepDoc=$3
    curl -u "$username":"$password" -X POST couchURL/db -H 'Content-Type:application/json' -d "$barrelRepDoc"
}

Then just call it like barrelRepcURL user pass "$barrelRepDoc". Obviously you could skip the creation of local variables and just use the positional parameters directly if you wanted.

The response of the curl command will already be printed to the screen so there's no need to store it to a variable just for that. However, it's still possible to use response=$(barrelRepcURL ...) if you want.

You might want to consider using printf to build your JSON variable by the way:

printf -v barrelRepDoc '{"_id":"push_%s","source":"%s","target":"platform2ReplicationTargetBaseURL/%s","create_target":true,"continuous":true,"user_ctx":{"name":"admin","roles":["_admin"]},"owner":"admin"}' "$systemName" "$systemName" "$systemName"

The -v switch can be used to write to a variable. It's still a long line but means that you don't have to bother with as many quotes.

Alternatively, as suggested by chepner in the comments (thanks) you could use a tool such as jq to produce the JSON:

barrelRepDoc=$(jq -n --arg systemName foo '{
    _id: ("push_" + $systemName), 
    source: $systemName, 
    target: ("platform2ReplicationTargetBaseURL/" + $systemName),
    create_target: true, 
    continuous: true, 
    user_ctxa: { name: "admin", roles: ["_admin"] },
    owner: "admin"
}')

In this example, you would replace foo with the value that would be used as $systemName.

edited Mar 15, 2016 at 0:33

answered Mar 14, 2016 at 11:34

Tom Fenech

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1 Comment

chepner Over a year ago

Rather than printf, use something like jq to generate the JSON, which will take care of all the quoting (including escaping quotes that occur in interpolated values.)

glenn jackman · Accepted Answer · 2016-03-14 13:46:37Z

2

This is BashFaq50 -- the short answer is to use an array to hold the curl command:

barrelRepDoc='{"_id":"push_'"$systemName"'","source":"'"$systemName"'","target":"platform2ReplicationTargetBaseURL/'"$systemName"'","create_target":true,"continuous":true,"user_ctx":{"name":"admin","roles":["_admin"]},"owner":"admin"}'

barrelRepcURL=( 
    curl -u "$username:$password"
         -X POST
         -H 'Content-Type:application/json' 
         -d "$barrelRepDoc"
            couchURL/db 
)

barrelRepcURLresponse=$( "${barrelRepcURL[@]}" )

Tom has a great answer though. Seriously consider his advice.

answered Mar 14, 2016 at 13:46

glenn jackman

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