a）您提供的数据应该是表单编码的，而不是以JSON对象的形式呈现; b）您还应该在“code”参数中提供授权代码值。例如：

curl -d "client_id=MY_CLIENT_ID&\
  client_secret=MY_SECRET_KEY&\
  redirect_uri=http://localhost/etc&\
  grant_type=authorization_code&\
  code=CODE" https://oauth2.googleapis.com/token

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虽然不直接使用CURL，但您也可以使用Google OAuth Playground获取和测试OAuth令牌：https://developers.google.com/oauthplayground/

create and execute a python script file to obtain JWT assertion key which will be further used in curl command :

python script for generating jwt assertion key :
import jwt
import os
import json
import sys

# Load the service account key JSON
service_account_key = json.loads(open("name of your service account key file").read())

# Extract necessary information from the service account key JSON
client_email = service_account_key["client_email"]


# Create the payload with necessary claims
payload = {
    "iss": client_email,
    "sub": client_email,
    "aud": "https://oauth2.googleapis.com/token",
    "exp": expired timestamp,  # Replace with the expiration timestamp
    "iat": current timestamp,  # Replace with the issuance timestamp
    "scope": "https://www.googleapis.com/auth/cloud-platform"
}

# Sign the payload with the service account's private key
#with open(os.path.join(sys.path[0], 'privatekey.pem'), "r") as private_key_file:
#    private_key = private_key_file.read()

private_key = "mention your private key present in service account key file"

jwt_assertion = jwt.encode(payload, private_key, algorithm="RS256")

print(jwt_assertion)

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assertion key will be obtained after executing the above python script , paste that in below curl command ,

Now, curl -X POST "https://oauth2.googleapis.com/token" \
     -d "scope=read&grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer" \
     -d "assertion=(your jwt_assertion key)"

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