Styjun

I'm trying to run a command which would print the output in console and send some output to serial port (USB0).

Based on the output from both the places, I need to decide on which path to take and continue the program. I would like to achieve this with pexpect as I need to add a timeout and look for a list of strings.

My intention is to run pexpect.expect commands for different pexpect instances in parallel.

I tried to create a minified test-case for this scenario.

Ex-1: This is what I'm expecting to do.

def run_cmd(a, host, rt):
 b = a.expect([pexpect.EOF, pexpect.TIMEOUT, host])
 rt[host] = b

if __name__ == '__main__':
 jobs = []
 rt = multiprocessing.Manager().dict()
 host = 'a.b.c.d'
 a = pexpect.spawn("ssh %s" % host)
 p = multiprocessing.Process(target=run_cmd, args=(a, host, rt))
 jobs.append(p)
 p.start()

 for proc in jobs:
 proc.join()

 pprint(rt.values())

Ex-2: This is working and I cannot launch a spawn for every call.

def run_cmd(host, rt):
 a = pexpect.spawn("ssh %s" % host)
 b = a.expect([pexpect.EOF, pexpect.TIMEOUT, host])
 rt[host] = b

if __name__ == '__main__':
 jobs = []
 rt = multiprocessing.Manager().dict()
 p = multiprocessing.Process(target=run_cmd, args=('a.b.c.d', rt))
 jobs.append(p)
 p.start()

 for proc in jobs:
 proc.join()

 pprint(rt.values())

Ex-1 given above is resulting in the following error.

Process Process-2: 
Traceback (most recent call last): 
 File "/proj/sival2/ctallapa/tools/apps/Anaconda3/5.3.0/lib/python3.7/site-packages/ptyprocess/ptyprocess.py", line 705, in isalive 
 pid, status = os.waitpid(self.pid, waitpid_options) 
ChildProcessError: [Errno 10] No child processes 

During handling of the above exception, another exception occurred: 

Traceback (most recent call last): 
 File "/proj/sival2/ctallapa/tools/apps/Anaconda3/5.3.0/lib/python3.7/site-packages/pexpect/pty_spawn.py", line 23, in _wrap_ptyprocess_err 
 yield 
 File "/proj/sival2/ctallapa/tools/apps/Anaconda3/5.3.0/lib/python3.7/site-packages/pexpect/pty_spawn.py", line 682, in isalive 
 alive = ptyproc.isalive() 
 File "/proj/sival2/ctallapa/tools/apps/Anaconda3/5.3.0/lib/python3.7/site-packages/ptyprocess/ptyprocess.py", line 711, in isalive 
 'process. Did someone else call waitpid() ' + 
ptyprocess.util.PtyProcessError: isalive() encountered condition where "terminated" is 0, but there was no child process. Did someone else call waitpid() on our process?