To retrieve a list of all the indices in an Elasticsearch cluster using the Elasticsearch API, you can use the GET _cat/indices API. This API returns a list of all the indices in the cluster along with their metadata, such as the index name, number of shards and replicas, and the status of the index.
Here is an example of using the GET _cat/indices API:
curl -X GET "localhost:9200/_cat/indices?v"
This will return a list of all the indices in the cluster, with each index listed on a separate line. The '?v' parameter is optional and can be used to include additional information in the output, such as the index mapping and settings.
You can also use the GET _cat/indices/<index_name> API to get information about a specific index. For example:
curl -X GET "localhost:9200/_cat/indices/my_index?v"
This will return metadata and status information for the index named "my_index".