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POGetting realtime output using subprocess
 

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    <p>I am trying to write a wrapper script for a command line program (svnadmin verify) that will display a nice progress indicator for the operation. This requires me to be able to see each line of output from the wrapped program as soon as it is output.</p> <p>I figured that I'd just execute the program using <code>subprocess.Popen</code>, use <code>stdout=PIPE</code>, then read each line as it came in and act on it accordingly. However, when I ran the following code, the output appeared to be buffered somewhere, causing it to appear in two chunks, lines 1 through 332, then 333 through 439 (the last line of output)</p> <pre><code>from subprocess import Popen, PIPE, STDOUT p = Popen('svnadmin verify /var/svn/repos/config', stdout = PIPE, stderr = STDOUT, shell = True) for line in p.stdout: print line.replace('\n', '') </code></pre> <p>After looking at the documentation on subprocess a little, I discovered the <code>bufsize</code> parameter to <code>Popen</code>, so I tried setting bufsize to 1 (buffer each line) and 0 (no buffer), but neither value seemed to change the way the lines were being delivered.</p> <p>At this point I was starting to grasp for straws, so I wrote the following output loop:</p> <pre><code>while True: try: print p.stdout.next().replace('\n', '') except StopIteration: break </code></pre> <p>but got the same result.</p> <p>Is it possible to get 'realtime' program output of a program executed using subprocess? Is there some other option in Python that is forward-compatible (not <code>exec*</code>)?</p>
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    1. COHave you tried omitting the `sydout=PIPE` so the subprocess writes directly to your console, bypassing the parent process?
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      1. USS.Lott
    2. COThe thing is that I want to read the output. If it is output directly to the console, how could I do that? Also, I don't want the user to see the output from the wrapped program, just my output.
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      1. USChris Lieb
    3. COThen why a "real-time" display? I don't get the use case.
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