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https://github.com/littlefs-project/littlefs.git
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c9a6e3a95b
This mostly involved futzing around with some of the less intuitive parts of Unix's named-pipes behavior. This is a bit important since the tests can quickly generate several gigabytes of trace output.
103 lines
2.7 KiB
Python
Executable File
103 lines
2.7 KiB
Python
Executable File
#!/usr/bin/env python3
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import os
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import sys
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import threading as th
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import time
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def openio(path, mode='r'):
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if path == '-':
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if 'r' in mode:
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return os.fdopen(os.dup(sys.stdin.fileno()), 'r')
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else:
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return os.fdopen(os.dup(sys.stdout.fileno()), 'w')
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else:
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return open(path, mode)
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def main(path, lines=1, keep_open=False):
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ring = [None] * lines
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i = 0
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count = 0
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lock = th.Lock()
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event = th.Event()
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done = False
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# do the actual reading in a background thread
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def read():
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nonlocal i
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nonlocal count
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nonlocal done
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while True:
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with openio(path, 'r') as f:
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for line in f:
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with lock:
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ring[i] = line
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i = (i + 1) % lines
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count = min(lines, count + 1)
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event.set()
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if not keep_open:
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break
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done = True
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th.Thread(target=read, daemon=True).start()
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try:
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last_count = 1
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while not done:
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time.sleep(0.01)
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event.wait()
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event.clear()
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# create a copy to avoid corrupt output
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with lock:
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ring_ = ring.copy()
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i_ = i
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count_ = count
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# first thing first, give ourself a canvas
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while last_count < count_:
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sys.stdout.write('\n')
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last_count += 1
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for j in range(count_):
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# move cursor, clear line, disable/reenable line wrapping
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sys.stdout.write('\r%s\x1b[K\x1b[?7l%s\x1b[?7h%s' % (
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'\x1b[%dA' % (count_-1-j) if count_-1-j > 0 else '',
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ring_[(i_-count+j) % lines][:-1],
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'\x1b[%dB' % (count_-1-j) if count_-1-j > 0 else ''))
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sys.stdout.flush()
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except KeyboardInterrupt:
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pass
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sys.stdout.write('\n')
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if __name__ == "__main__":
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import sys
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import argparse
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parser = argparse.ArgumentParser(
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description="Efficiently displays the last n lines of a file/pipe.")
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parser.add_argument(
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'path',
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nargs='?',
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default='-',
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help="Path to read from.")
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parser.add_argument(
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'-n',
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'--lines',
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type=lambda x: int(x, 0),
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default=1,
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help="Number of lines to show, defaults to 1.")
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parser.add_argument(
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'-k',
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'--keep-open',
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action='store_true',
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help="Reopen the pipe on EOF, useful when multiple "
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"processes are writing.")
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sys.exit(main(**{k: v
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for k, v in vars(parser.parse_args()).items()
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if v is not None}))
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