import pyparsing, sys, doctest

integer_pattern = pyparsing.Optional(pyparsing.Word(pyparsing.nums))
terminators = [pyparsing.Literal(';') + integer_pattern,
               pyparsing.Literal('\\t') + integer_pattern]
complete_pattern = reduce(lambda x, y: x ^ y, terminators)
redirect_pattern = pyparsing.oneOf('< >') + pyparsing.restOfLine
pipe_pattern = pyparsing.Literal('|') + pyparsing.restOfLine

for pattern in (complete_pattern, redirect_pattern, pipe_pattern):
    pattern.ignore(pyparsing.sglQuotedString)
    pattern.ignore(pyparsing.dblQuotedString)

def parse(txt):
    """
    >>> sorted(parse('select * from dual;').items())
    [('inputFrom', None), ('outputTo', None), ('pipeTo', None), ('terminator', [';'])]
    >>> sorted(parse('select * from dual E').items())
    [('inputFrom', None), ('outputTo', None), ('pipeTo', None), ('terminator', None)]
    >>> sorted(parse('select * from').items())
    [('inputFrom', None), ('outputTo', None), ('pipeTo', None), ('terminator', None)]
    >>> sorted(parse('select * from dual; > result.txt').items())
    [('inputFrom', None), ('outputTo', 'result.txt'), ('pipeTo', None), ('terminator', [';'])]
    >>> sorted(parse("select * from dual where val = 'x > y'").items())
    [('inputFrom', None), ('outputTo', None), ('pipeTo', None), ('terminator', None)]
    >>> sorted(parse('select * from dual; | wc -c').items())
    [('inputFrom', None), ('outputTo', None), ('pipeTo', 'wc -c'), ('terminator', [';'])]
    >>> sorted(parse('select * from dual; | sort > sorted.txt').items())
    [('inputFrom', None), ('outputTo', None), ('pipeTo', 'sort > sorted.txt'), ('terminator', [';'])]
    """
    result = {'inputFrom': None, 'outputTo': None, 'pipeTo': None, 'terminator': None}
    found = complete_pattern.searchString(txt)
    if found:
        result['terminator'] = found[0][:]
    found = pipe_pattern.searchString(txt)
    if found:
        result['pipeTo'] = found[0][1].strip()
    else:  # pipe overrides redirects
        found = redirect_pattern.searchString(txt)
        if found:
            if found[0][0] == '>':
                result['outputTo'] = found[0][1].strip()
            else:
                result['inputFrom'] = found[0][1].strip()

    return result
    
if __name__ == '__main__':
    doctest.testmod()