clp2 at rebertia.com
Wed Sep 16 01:30:03 CEST 2009
On Tue, Sep 15, 2009 at 12:26 PM, kj <no.email at please.post> wrote:
> I'm trying to write a function, sort_data, that takes as argument
> the path to a file, and sorts it in place, leaving the last "sentinel"
> line in its original position (i.e. at the end). Here's what I
> have (omitting most error-checking code):
> def sort_data(path, sentinel='.\n'):
> tmp_fd, tmp = tempfile.mkstemp()
> out = os.fdopen(tmp_fd, 'wb')
> cmd = ['/usr/local/bin/sort', '-t', '\t', '-k1,1', '-k2,2']
> p = Popen(cmd, stdin=PIPE, stdout=out)
> in_ = file(path, 'r')
> while True:
> line = in_.next()
> if line != sentinel:
> retcode = p.wait()
> if retcode != 0:
> raise CalledProcessError(retcode, cmd)
> shutil.move(tmp, path)
> This works OK, except that it does not catch the stderr from the
> called sort process. The problem is how to do this. I want to to
> avoid having to create a new file just to capture this stderr
> output. I would like instead to capture it to an in-memory buffer.
> Therefore I tried using a StringIO object as the stderr parameter
> to Popen, but this resulted in the error "StringIO instance has no
> attribute 'fileno'".
> How can I capture stderr in the scenario depicted above?
Use a pipe by setting stderr=PIPE?:
p = Popen(cmd, stdin=PIPE, stdout=out, stderr=PIPE)
error_output = p.stderr.read()
Or am I missing something?
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