How to request the schema from a GraphQL service using curl?

The body you need is pretty involved for an introspection query, but I think you’re looking for something like this

introspection_query.json:

{ 
  "query": "query IntrospectionQuery {
      __schema {
        queryType { name }
        mutationType { name }
        subscriptionType { name }
        types {
          ...FullType
        }
        directives {
          name
          description
          locations
          args {
            ...InputValue
          }
        }
      }
    }

    fragment FullType on __Type {
      kind
      name
      description
      fields(includeDeprecated: true) {
        name
        description
        args {
          ...InputValue
        }
        type {
          ...TypeRef
        }
        isDeprecated
        deprecationReason
      }
      inputFields {
        ...InputValue
      }
      interfaces {
        ...TypeRef
      }
      enumValues(includeDeprecated: true) {
        name
        description
        isDeprecated
        deprecationReason
      }
      possibleTypes {
        ...TypeRef
      }
    }

    fragment InputValue on __InputValue {
      name
      description
      type { ...TypeRef }
      defaultValue
    }

    fragment TypeRef on __Type {
      kind
      name
      ofType {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
                ofType {
                  kind
                  name
                  ofType {
                    kind
                    name
                  }
                }
              }
            }
          }
        }
      }
    }"
}

and then you can do

curl -i -X POST http://localhost:8080/graphql -H "Content-Type: application/json" -d @introspection_query.json

Shamefully stolen from
gist.github.com/martinheld/9fe32b7e2c8fd932599d36e921a2a825