Can read() be non-blocking?
thomasc at thomaschristensen.org
Thu Nov 6 23:54:23 CET 2008
This issue has been raised a couple of times I am sure. But I have yet
to find a satisfying answer.
I am reading from a subprocess and this subprocess sometimes hang, in
which case a call to read() call will block indefinite, keeping me from
The folloing sample code illustrates the problem:
proc = subprocess.Popen(['/usr/bin/foo', '/path/to/some/file'],
output = StringIO.StringIO()
r = select.select([proc.stdout.fileno()], , , 5)
# NOTE: This will block since it reads until EOF
data = proc.stdout.read()
if not data:
break # EOF from process has been reached
<Process the output...>
As the NOTE: comment above suggests the call to read() will block here.
I see two solutions:
1. Read one byte at a time, meaning call read(1).
2. Read non-blocking.
I think reading one byte at a time is a waste of CPU, but I cannot find
a way to read non-blocking.
Is there a way to read non-blocking? Or maybe event a better way in
generel to handle this situation?
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