Curl with multiline of JSON

Question

I remembered another way to do this with a "Here Document" as described in the Bash man page and detailed here. The @- means to read the body from STDIN, while << EOF means to pipe the script content until "EOF" as STDIN to curl. This layout may be easier to read than using separate files or the "echo a variable" approach.

curl -0 -v -X POST http://www.example.com/api/users \
-H "Expect:" \
-H 'Content-Type: application/json; charset=utf-8' \
--data-binary @- << EOF
{
    "field1": "test",
    "field2": {
        "foo": "bar"
    }
}
EOF

NOTE: Use the --trace <outfile> curl option to record exactly what goes over the wire. For some reason, this Here Document approach strips newlines. (Update: Newlines were stripped by curl -d option. Corrected!)

Along the lines of Martin's suggestion of putting the JSON in a variable, you could also put the JSON in a separate file, and then supply the filename to -d using curl's @ syntax:

curl -0 -v -X POST http://www.example.com/api/users \
  -H "Expect:" \
  -H 'Content-Type: text/json; charset=utf-8' \
  -d @myfile.json

The disadvantage is obvious (2 or more files where you used to have one.) But on the plus side, your script could accept a filename or directory argument and you'd never need to edit it, just run it on different JSON files. Whether that's useful depends on what you are trying to accomplish.

For some reason, this Here Document approach strips newlines

@eric-bolinger the reason the Heredoc strips newlines is because you need to tell your Heredoc to preserve newlines by quoting the EOF:

curl -0 -v -X POST http://www.example.com/api/users \
-H "Expect:" \
-H 'Content-Type: text/json; charset=utf-8' \
-d @- <<'EOF'

{
    "field1": "test",
    "field2": {
        "foo": "bar"
    }
}
EOF

Notice the single-ticks surrounding EOF the first time it's defined, but not the second.

You should use outer double quotes, and the escape all inner quotes like this:

curl -0 -v -X POST http://www.example.com/api/users \
-H "Expect:" \
-H 'Content-Type: text/json; charset=utf-8' \
-d \
"
{
    \"field1\": \"test\",
    \"field2\": {
        \"foo\": \"bar\"
    }
}"

You could assign your json to a var:

json='
{
    "field1": "test",
    "field2": {
        "foo": "bar"
    }
}'

Now you can forward this to curl using stdin:

echo $json | curl -0 -v -X POST http://www.example.com/api/users \
-H "Expect:" \
-H 'Content-Type: text/json; charset=utf-8' \
-d @-