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POHow to check if serial port is already open (by another process) in Linux, using Python 2.7 (and possibly pyserial)?
 

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  1. POHow to check if serial port is already open (by another process) in Linux, using Python 2.7 (and possibly pyserial)?
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    <p>I know there are other questions quite similar to mine, but none of them address the issue I'm having. </p> <p>I'd like to use <code>pyserial</code> to access a serial port (<code>/dev/tty...</code>), but only on the condition that another process hasn't already opened it.</p> <p>The following snippet returns four available ports on my Ubuntu 12.04 machine, when run once. If I run it a second time I would expect no ports to be available. Sadly, the same list of ports are returned. It seems <code>pyserial</code> cannot identify that another process has already opened the port.</p> <p>I'd expect a <code>SerialException</code> to be thrown, or the <code>isOpen()</code> method to return False, but <code>pyserial</code> happily opens the multiple times.</p> <pre><code>import serial from serial import tools from serial.tools import list_ports def available_ttys(): for tty in serial.tools.list_ports.comports(): try: port = serial.Serial(port=tty[0]) if port.isOpen(): yield port except serial.SerialException as ex: print 'Port {0} is unavailable: {1}'.format(tty, ex) def main(): ttys = [] for tty in available_ttys(): ttys.append(tty) print tty input('waiting ...') if __name__ == '__main__': main() </code></pre> <p>This is the output regardless of how many times I run it in parallel:</p> <pre><code>Port ('/dev/ttyS31', 'ttyS31', 'n/a') is unavailable: Could not configure port: (5, 'Input/output error') ... Port ('/dev/ttyS0', 'ttyS0', 'n/a') is unavailable: Could not configure port: (5, 'Input/output error') Serial&lt;id=0x7fca9d9f1c90, open=True&gt;(port='/dev/ttyUSB1', baudrate=9600, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=False, rtscts=False, dsrdtr=False) Serial&lt;id=0x7fca9d9f1cd0, open=True&gt;(port='/dev/ttyACM2', baudrate=9600, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=False, rtscts=False, dsrdtr=False) Serial&lt;id=0x7fca9d9f1e50, open=True&gt;(port='/dev/ttyACM1', baudrate=9600, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=False, rtscts=False, dsrdtr=False) Serial&lt;id=0x7fca9d9f1ed0, open=True&gt;(port='/dev/ttyACM0', baudrate=9600, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=False, rtscts=False, dsrdtr=False) waiting ... </code></pre>
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