Programming Pig

Chapter 3. Grunt

Grunt^[4] is Pig’s interactive shell. It enables users to enter Pig Latin interactively and provides a shell for users to interact with HDFS.

To enter Grunt, invoke Pig with no script or command to run. Typing:

pig -x local

will result in the prompt:

grunt>

This gives you a Grunt shell to interact with your local filesystem. If you omit the -x local and have a cluster configuration set in PIG_CLASSPATH, this will put you in a Grunt shell that will interact with HDFS on your cluster.

As you would expect with a shell, Grunt provides command-line history and editing, as well as Tab completion. It does not provide filename completion via the Tab key. That is, if you type kil and then press the Tab key, it will complete the command as kill. But if you have a file foo in your local directory and type ls fo, and then hit Tab, it will not complete it as ls foo. This is because the response time from HDFS to connect and find whether the file exists is too slow to be useful.

Although Grunt is a useful shell, remember that it is not a full-featured shell. It does not provide a number of commands found in standard Unix shells, such as pipes, redirection, and background execution.

To exit Grunt you can type quit or enter Ctrl-D.

Entering Pig Latin Scripts in Grunt

One of the main uses of Grunt is to enter Pig Latin in an interactive session. This can be particularly useful for quickly sampling your data and for prototyping new Pig Latin scripts.

You can enter Pig Latin directly into Grunt. ...