=================
Awk-Like Examples
=================

This page contains common examples of common awk_-like operations (taken from `Awk One-Liners Explained`_) not covered
in :doc:`sed` and :doc:`perl`.

.. _awk: www.gnu.org/s/gawk/
.. _`Awk One-Liners Explained`: http://www.catonmat.net/series/awk-one-liners-explained

.. figure:: awk-programming-one-liners-explained.jpg
  :alt: awk

  
--------------------------
Numbering and Calculations
--------------------------  
  
15. Find the line containing the largest (numeric) first field.  
    ::
    
        >>> print stream_vals('foo.csv', cols = 0) | enumerate()_ | filt(lambda (i, v): (v, i)) | (min_() | select_inds(1))

    .. Note::    
        
        The first two stages,
        ::
        
            >>> stream_vals('foo.csv', cols = 0) | enumerate()_
            
        enumerates the first fields of the lines.
        
        The next stage,
        ::
        
            filt(lambda (i, v): (v, i))
            
        reverses the tuples. Using Python's lexicographic ordering, 
        ::
        
            min_() 
            
        extracts the tuple with the smallest value. The enumeration is retrieved using 
        ::
        
            select_inds(1)
            
        (note the use of :ref:`sink chaining <sink_chaining>`).

17. Print the last field of each line.
    ::
    
        >>> print stream_vals('foo.csv') | select_inds(-1) | to_stream(sys.stdout)

18. Print the last field of the last line.
    ::
    
        >>> print stream_vals('foo.csv') | select_inds(-1) | nth(-1)


--------------------------------
Text Conversion and Substitution
--------------------------------

38. Print the first two fields in reverse order on each line.
    ::
    
        >>> print stream_vals('foo.csv') | select_inds((1, 0)) | to_stream(sys.stdout)

39. Swap first field with second on every line.
    ::
    
        >>> print stream_vals('foo.csv') | \
        ...     filt(lambda l: '%s,%s,%s' % (l[1], l[0], ','.join(l[2: ]))) | \
        ...     to_stream(sys.stdout)

40. Delete the second field on each line.
        >>> print stream_vals('foo.csv') | \
        ...     filt(lambda l: '%s,%s' % (l[0], ','.join(l[2: ]))) | \
        ...     to_stream(sys.stdout)

41. Print the fields in reverse order on every line.
        >>> print stream_vals('foo.csv') | filt(lambda l: lle(reversed(l))) | to_stream(sys.stdout)