James wrote:
> Hi,
>
> I have a snippet of code in a Python script I'm whipping up that's
> causing a not-so-pretty output. Here's the code:
>
> subprocess.call( "yes '' | make oldconfig" , shell=True )
>
> When I run this code, Python loyally executes the command, and then I
> see the following error on my console:
>
> -----
>
> yes: standard output: Broken pipe
> yes: write error
>
> Thoughts / ideas?
File this one under 'wicked scary hack', but my first thought would be
to redirect stderr of 'yes' to /dev/null, while preserving stderr of
'make oldconfig'. Something like this:
import subprocess as sp
sp.call("yes '' 2> /dev/null | make oldconfig", shell=True)
... or ...
import subprocess as sp
p1 = sp.Popen("yes ''", shell=True, stdout=sp.PIPE,
stderr=file('/dev/null', 'w'))
p2 = sp.Popen('make oldconfig', shell=True,
stdin=p1.stdout)
However, since the 'equivalent' shell command doesn't seem to result in
a broken pipe error there must be a better way. Upon further inspection:
$ strace yes 'Spam' | head -n 10
<...>
--- SIGPIPE (Broken pipe) @ 0 (0) ---
+++ killed by SIGPIPE +++
<...>
We may need to handle SIGPIPE. A quick search leads here:
http://article.gmane.org/gmane.comp.python.devel/88798/
... so, thanks to Mr. Woodcraft ...
import subprocess as sp
import signal
# warning: uses the system default action
# for SIGPIPE for all children, use subprocess
# preexec_fn arg if this is not desirable
signal.signal(signal.SIGPIPE, signal.SIG_DFL)
sp.call("yes 'Spam' | head -n 10", shell=True)
HTH,
Marty
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