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POPython Process hangs until child process terminate using tee scheme
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  1. POPython Process hangs until child process terminate using tee scheme
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    copied!<p>I have a following problem related to process synchronization.</p> <p>There is a python script startup.py, an executable maestro, and an executable tee. My python script startup.py starts maestro program and pipes the stderr/stdout of maestro into the log file using tee as well write into the console.</p> <p>I achieved this using following code:</p> <pre><code>cmd = "maestro" mae_err_log = "output.txt" maestro = subprocess.Popen(cmd, stderr = subprocess.STDOUT, stdout=subprocess.PIPE) tee = subprocess.Popen(['tee', mae_err_log], stdin = maestro.stdout) maestro.stdout.close() tee.communicate() maestro_status = maestro.returncode sys.exit(maestro_status) </code></pre> <p>My maestro program is a gui program when I exit from the maestro program, it internally call posix system("maestro_cleanup &amp;") api and immediately exit. I noticed that my maestro program does not release the console until maestro_cleanup program terminate although I am running maestro_cleanup in the background. I need to run maestro_cleanup in the background as it takes time and I do not want to hold the console for the period until maestro_cleanup finishes. Using above code, maestro program does not terminate until maestro_cleanup finishes.</p> <p>I see "ps -elf" shows following:</p> <pre><code>0 S j 16876 6678 0 75 0 - 65307 wait 18:56 pts/53 00:00:00 python startup.py 0 Z j 17230 16876 4 76 0 - 0 exit 18:56 pts/53 00:00:04 [maestro] &lt;defunct&gt; 0 S j 17231 16876 0 77 0 - 948 pipe_w 18:56 pts/53 00:00:00 /usr/bin/tee output.txt 0 S j 17424 1 0 77 0 - 948 - 18:57 pts/53 00:00:00 maestro_cleanup </code></pre> <p>You can see the maestro_cleanup parent process is session process id instead maestro because I started maestro_cleanup using system api in background.</p> <p>Any idea why maestro does not terminate until maestro_cleanup finishes?</p> <p>Any help would be appreciated.</p> <p>-Vipin</p>
 

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