how to check if a file exists in hdfs or not?
['Syntax: hdfs dfs -test -d hdfs_path.', 'Example: hdfs dfs -test -d /revisit/content/files.', 'echo $? —> to validate the previous command return code.', 'Syntax : hdfs dfs -test -e hdfs_path/filename.', 'Example: hdfs dfs -test -e /revisit/content/files/schema.xml.', 'echo $?']