How do I conditionally send a body param in my curl request-CodePudding

I am creating a simple bash script. I have this curl request, and I only want to send objects_count in my raw data body if it is non empty.

I know that this line of code works: '[ ! -z "$objects_count" ] && echo "not empty"'

However when I implement it in my curl request, I get an error

    objects='[]'
    objects_count=''

    curl --location --request POST 'http://0.0.0.0:5000' \
    --header 'Content-Type: application/json' \
    --data-raw '{
        "objects":'$objects',
        '[ ! -z "$objects_count" ] && "objects_count":$objects_count'
    }'

curl: (3) URL using bad/illegal format or missing URL
curl: (3) unmatched close brace/bracket in URL position 1:
]
 ^

CodePudding user response：

Bash doesn't have a conditional operator that can be used in expressions. Use a simple if statement to set a variable to the data you want to send.

if [ -z "$objects_count" ]
then
    data='{"objects":'$objects'}'
else
    data='{"objects":'$objects', "objects_count":'$objects_count'}'
fi

curl --location --request POST 'http://0.0.0.0:5000' \
    --header 'Content-Type: application/json' \
    --data-raw "$data"

CodePudding user response：

You cannot use expressions like that in the middle of an expression. If you really want an expression you need a subshell, and inside the subshell echo the string you want:

curl --location --request POST 'http://0.0.0.0:5000' \
--header 'Content-Type: application/json' \
--data-raw '{
    "objects":'$objects',
    '$([ ! -z "$objects_count" ] && echo '"objects_count":'$objects_count)'
}'

However, there's a trick using parameter substitution where you can expand a string only of a variable isn't null (or unset):

echo ${objects_count: non empty}

Then you don't need an expression:

curl --location --request POST 'http://0.0.0.0:5000' \
--header 'Content-Type: application/json' \
--data-raw '{
    "objects":'$objects',
    '${objects_count: '"objects_count":'$objects_count}'
}'

I don't see why you would need to selectively output this element though, in JSON you can typically just do "object_counts": null or something like that.

BTW, instead of doing [ ! -z "$foo" ] you can just do [ -n $foo ].