.. _workshop-single-point:

Printing the first point
================================================================================

.. include:: ../../includes/substitutions.rst

.. index:: info command, Start Here, installation

Exercise
--------------------------------------------------------------------------------

This exercise uses PDAL to print information from the first point. Issue the
following command in your `OSGeo4W Shell`.

.. literalinclude:: ./single-point-command.txt
    :linenos:

Here's a summary of what's going on with that command invocation

1. ``pdal``: The ``pdal`` application :)

2. ``info``: We want to run :ref:`info_command` on the data. All commands
   are run by the ``pdal`` application.

3. ``c:/Users/hobu/PDAL/exercises/info/interesting.las``: The file we
   are running the command on. PDAL will be able to identify this file
   is an |ASPRSLAS| file from the extension, ``.las``, but not every
   file type is easily identified. You can use a :ref:`pipeline <pipeline_command>`
   to override which :ref:`reader <readers>` PDAL will use to
   open the file.

4. ``-p 0``: ``-p`` corresponds to "print a point", and ``0`` means to print
   the first one (computer people count from 0).


.. image:: ../../images/info-interesting-single-point.png
    :target: ../../../_images/info-interesting-single-point.png

Notes
--------------------------------------------------------------------------------

.. index:: JSON, CSV

1. PDAL uses |JSON| as the exchange format when printing information from :ref:`info_command`.
   JSON is a structured, human-readable format that is much simpler than its |XML| cousin.

2. You can use the :ref:`writers.text` writer to output point attributes to |CSV| format for
   other processing.

3. Output help information on the command line by issuing the ``--help`` option

4. A common query with ``pdal info`` is ``--all``, which will print all header,
   metadata, and statistics about a file.

