You can ask ES to sort the results via the s (sort) searchParameter using s=i or s=index
curl "localhost:9200/_cat/indices?pretty&s=i"
curl "localhost:9200/_cat/aliases?pretty&s=index"
To see the column’s headers, add “&v” :
curl "localhost:9200/_cat/indices?pretty&v&s=index"`.
You can find some explanations in the cat/indices documentation