JAVA

pytho count avro file

Get the latest released version or build it from source.
https://github.com/jwoschitz/avrocount/releases/latest

Then simply invoke the tool via

java -jar avrocount.jar /path/to/myfile.avro

And it will print the amount of records found within the file to stdout.
  
Folders containing avro files

java -jar avrocount.jar /path/to/folder