"""Routines to help recognizing sound files.

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Function whathdr() recognizes various types of sound file headers.

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It understands almost all headers that SOX can decode.

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The return tuple contains the following items, in this order:

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- file type (as SOX understands it)

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- sampling rate (0 if unknown or hard to decode)

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- number of channels (0 if unknown or hard to decode)

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- number of frames in the file (-1 if unknown or hard to decode)

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- number of bits/sample, or 'U' for U-LAW, or 'A' for A-LAW

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If the file doesn't have a recognizable type, it returns None.

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If the file can't be opened, OSError is raised.

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To compute the total time, divide the number of frames by the

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sampling rate (a frame contains a sample for each channel).

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Function what() calls whathdr(). (It used to also use some

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heuristics for raw data, but this doesn't work very well.)

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Finally, the function test() is a simple main program that calls

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what() for all files mentioned on the argument list. For directory

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arguments it calls what() for all files in that directory. Default

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argument is "." (testing all files in the current directory). The

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option -r tells it to recurse down directories found inside

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explicitly given directories.

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"""

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# The file structure is top-down except that the test program and its

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# subroutine come last.

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__all__ = ['what', 'whathdr']

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from collections import namedtuple

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SndHeaders = namedtuple('SndHeaders',

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'filetype framerate nchannels nframes sampwidth')

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SndHeaders.filetype.__doc__ = ("""The value for type indicates the data type

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and will be one of the strings 'aifc', 'aiff', 'au','hcom',

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'sndr', 'sndt', 'voc', 'wav', '8svx', 'sb', 'ub', or 'ul'.""")

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SndHeaders.framerate.__doc__ = ("""The sampling_rate will be either the actual

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value or 0 if unknown or difficult to decode.""")

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SndHeaders.nchannels.__doc__ = ("""The number of channels or 0 if it cannot be

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determined or if the value is difficult to decode.""")

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SndHeaders.nframes.__doc__ = ("""The value for frames will be either the number

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of frames or -1.""")

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SndHeaders.sampwidth.__doc__ = ("""Either the sample size in bits or

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'A' for A-LAW or 'U' for u-LAW.""")

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def what(filename):

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"""Guess the type of a sound file."""

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res = whathdr(filename)

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return res

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def whathdr(filename):

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"""Recognize sound headers."""

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with open(filename, 'rb') as f:

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h = f.read(512)

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for tf in tests:

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res = tf(h, f)

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if res:

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return SndHeaders(*res)

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return None

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#-----------------------------------#

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# Subroutines per sound header type #

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#-----------------------------------#

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tests = []

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def test_aifc(h, f):

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import aifc

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if not h.startswith(b'FORM'):

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return None

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if h[8:12] == b'AIFC':

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fmt = 'aifc'

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elif h[8:12] == b'AIFF':

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fmt = 'aiff'

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else:

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return None

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f.seek(0)

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try:

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a = aifc.open(f, 'r')

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except (EOFError, aifc.Error):

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return None

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return (fmt, a.getframerate(), a.getnchannels(),

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a.getnframes(), 8 * a.getsampwidth())

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tests.append(test_aifc)

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def test_au(h, f):

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if h.startswith(b'.snd'):

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func = get_long_be

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elif h[:4] in (b'\0ds.', b'dns.'):

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func = get_long_le

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else:

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return None

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filetype = 'au'

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hdr_size = func(h[4:8])

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data_size = func(h[8:12])

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encoding = func(h[12:16])

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rate = func(h[16:20])

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nchannels = func(h[20:24])

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sample_size = 1 # default

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if encoding == 1:

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sample_bits = 'U'

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elif encoding == 2:

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sample_bits = 8

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elif encoding == 3:

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sample_bits = 16

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sample_size = 2

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else:

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sample_bits = '?'

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frame_size = sample_size * nchannels

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if frame_size:

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nframe = data_size / frame_size

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else:

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nframe = -1

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return filetype, rate, nchannels, nframe, sample_bits

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tests.append(test_au)

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def test_hcom(h, f):

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if h[65:69] != b'FSSD' or h[128:132] != b'HCOM':

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return None

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divisor = get_long_be(h[144:148])

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if divisor:

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rate = 22050 / divisor

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else:

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rate = 0

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return 'hcom', rate, 1, -1, 8

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tests.append(test_hcom)

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def test_voc(h, f):

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if not h.startswith(b'Creative Voice File\032'):

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return None

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sbseek = get_short_le(h[20:22])

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rate = 0

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if 0 <= sbseek < 500 and h[sbseek] == 1:

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ratecode = 256 - h[sbseek+4]

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if ratecode:

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rate = int(1000000.0 / ratecode)

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return 'voc', rate, 1, -1, 8

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tests.append(test_voc)

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def test_wav(h, f):

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import wave

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# 'RIFF' <len> 'WAVE' 'fmt ' <len>

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if not h.startswith(b'RIFF') or h[8:12] != b'WAVE' or h[12:16] != b'fmt ':

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return None

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f.seek(0)

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try:

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w = wave.openfp(f, 'r')

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except (EOFError, wave.Error):

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return None

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return ('wav', w.getframerate(), w.getnchannels(),

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w.getnframes(), 8*w.getsampwidth())

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tests.append(test_wav)

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def test_8svx(h, f):

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if not h.startswith(b'FORM') or h[8:12] != b'8SVX':

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return None

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# Should decode it to get #channels -- assume always 1

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return '8svx', 0, 1, 0, 8

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tests.append(test_8svx)

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def test_sndt(h, f):

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if h.startswith(b'SOUND'):

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nsamples = get_long_le(h[8:12])

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rate = get_short_le(h[20:22])

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return 'sndt', rate, 1, nsamples, 8

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tests.append(test_sndt)

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def test_sndr(h, f):

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if h.startswith(b'\0\0'):

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rate = get_short_le(h[2:4])

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if 4000 <= rate <= 25000:

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return 'sndr', rate, 1, -1, 8

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tests.append(test_sndr)

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#-------------------------------------------#

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# Subroutines to extract numbers from bytes #

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#-------------------------------------------#

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def get_long_be(b):

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return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3]

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def get_long_le(b):

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return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | b[0]

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def get_short_be(b):

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return (b[0] << 8) | b[1]

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def get_short_le(b):

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return (b[1] << 8) | b[0]

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#--------------------#

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# Small test program #

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#--------------------#

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def test():

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import sys

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recursive = 0

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if sys.argv[1:] and sys.argv[1] == '-r':

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del sys.argv[1:2]

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recursive = 1

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try:

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if sys.argv[1:]:

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testall(sys.argv[1:], recursive, 1)

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else:

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testall(['.'], recursive, 1)

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except KeyboardInterrupt:

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sys.stderr.write('\n[Interrupted]\n')

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sys.exit(1)

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def testall(list, recursive, toplevel):

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import sys

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import os

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for filename in list:

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if os.path.isdir(filename):

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print(filename + '/:', end=' ')

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if recursive or toplevel:

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print('recursing down:')

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import glob

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names = glob.glob(os.path.join(filename, '*'))

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testall(names, recursive, 0)

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else:

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print('*** directory (use -r) ***')

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else:

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print(filename + ':', end=' ')

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sys.stdout.flush()

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try:

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print(what(filename))

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except OSError:

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print('*** not found ***')

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if __name__ == '__main__':

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test()

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