Simulate `bash` behaviour using Python and named pipes.

[Paul Wiseman]

On 5 August 2013 14:09, Luca Cerone <luca.cerone at gmail.com> wrote:

> Hi everybody,
> I am trying to understand how to use named pipes in python to launch
> external processes (in a Linux environment).
>
> As an example I am trying to "imitate" the behaviour of the following sets
> of commands is bash:
>
> > mkfifo named_pipe
> > ls -lah > named_pipe &
> > cat < named_pipe
>
> In Python I have tried the following commands:
>
> import os
> import subprocess as sp
>
> os.mkfifo("named_pipe",0777) #equivalent to mkfifo in bash..
> fw = open("named_pipe",'w')
> #at this point the system hangs...
>
> My idea it was to use subprocess.Popen and redirect stdout to fw...
> next open named_pipe for reading and giving it as input to cat (still
> using Popen).
>
> I know it is a simple (and rather stupid) example, but I can't manage to
> make it work..
>
>
> How would you implement such simple scenario?
>
> Thanks a lot in advance for the help!!!
>
>
You can pipe using subprocess

p1 = subprocess.Popen(["ls", "-lah"], stdout=subprocess.PIPE)
p2 = subprocess.Popen(["cat"], stdin=p1.stdout)
p1.wait()
p2.wait()

You can also pass a file object to p1's stdout and p2's stdin if you want
to pipe via a file.

with open("named_pipe", "rw") as named_pipe:
    p1 = subprocess.Popen(["ls", "-lah"], stdout=named_pipe)
    p2 = subprocess.Popen(["cat"], stdin=named_pipe)
    p1.wait()
    p2.wait()


> Luca
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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