Pipeline of 3 or more commands leaks Unix sockets

[ezamriy]

I've noticed that a pipeline of 3 or more commands leaks Unix sockets until a process is crashed with "Too many open files" error.

Steps to reproduce:

1. Run the following code:

   import plumbum
   cat = plumbum.local['cat']
   grep = plumbum.local['grep']
   while True:
       print (cat['/etc/passwd'] | grep['root'] | cat)()

2. See the number of opened descriptors increasing:

   ls -la /proc/${PID}/fd | wc -l

3. After some time (dependent on system limits) the process will crash.

Both 1.6.6 and 1.6.7 versions are affected.

The issue is not reproducible with 2-command pipelines.

[ChrisGute]

+1 same here

[deniswvieira]

+1. plumbum==1.6.8

A workaround can be: local['bash']['-c', 'cat /etc/passwd | grep "root" | cat']()