You can view the logs of an App Engine application in GCP using the Google Cloud Console and the gcloud CLI commands. Here are the detailed steps for each approach:

1. Google Cloud Console:
   a. Go to the GCP Console: https://console.cloud.google.com/
   b. Select your project.
   c. Navigate to the App Engine dashboard by clicking the hamburger menu, then click on “App Engine.”
   d. Click on the “Logs” tab on the left side menu.
   e. You will see the logs for your App Engine application. You can filter logs based on log level, date, and other criteria.
2. CLI Commands (gcloud):
   a. Install and set up the Google Cloud SDK: https://cloud.google.com/sdk/docs/install
   b. Authenticate with your GCP account: gcloud auth login
   c. Set the active project: gcloud config set project PROJECT_ID
   d. Fetch the logs for your App Engine application: gcloud app logs read
   e. You can add optional flags to filter logs based on severity, time range, and other criteria. For example: gcloud app logs read --severity=INFO --limit=100

Terraform does not provide a direct way to view the logs of an App Engine application. Terraform is primarily used for infrastructure management and deployment, not for querying the state of deployed applications or accessing their logs. You should use the Google Cloud Console or gcloud CLI commands to view the logs.