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bufsize in subprocess

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  bufsize in subprocess yves@zioup.com - 2012-01-21 22:45 -0700
    Re: bufsize in subprocess Chris Rebert <clp2@rebertia.com> - 2012-01-21 23:27 -0800
      Re: bufsize in subprocess yves@zioup.com - 2012-01-22 09:43 -0700
        Re: bufsize in subprocess yves@zioup.com - 2012-01-22 10:05 -0700

#19205 — bufsize in subprocess

Is this the expected behaviour?
When I run this script, it reads only once, but I expected once per line with 
bufsize=1.

What I am trying to do is display the output of a slow process in a tkinter 
window as it runs. Right now, the process runs to completion, then display the 
result.

     import subprocess

     com = ['/bin/ls', '-l', '/usr/bin']
     with subprocess.Popen(com, bufsize=1, stdout=subprocess.PIPE, 
stderr=subprocess.STDOUT) as proc:
         print('out: ' + str(proc.stdout.read(), 'utf8'))


Thanks.

-- 
Yves.                                                  http://www.SollerS.ca/
                                                        http://ipv6.SollerS.ca
                                                        http://blog.zioup.org/

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#19207

On Sat, Jan 21, 2012 at 9:45 PM,  <yves@zioup.com> wrote:
> Is this the expected behavior?

Yes. `.read()` [with no argument] on a file-like object reads until
EOF. See http://docs.python.org/library/stdtypes.html#file.read

> When I run this script, it reads only once, but I expected once per line
> with bufsize=1.

You want proc.stdout.readline().
http://docs.python.org/library/stdtypes.html#file.readline

> What I am trying to do is display the output of a slow process in a tkinter
> window as it runs. Right now, the process runs to completion, then display
> the result.
>
>    import subprocess
>
>    com = ['/bin/ls', '-l', '/usr/bin']
>    with subprocess.Popen(com, bufsize=1, stdout=subprocess.PIPE,
> stderr=subprocess.STDOUT) as proc:
>        print('out: ' + str(proc.stdout.read(), 'utf8'))

Cheers,
Chris

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#19221

On 2012-01-22 00:27, Chris Rebert wrote:
> On Sat, Jan 21, 2012 at 9:45 PM,<yves@zioup.com>  wrote:
>> Is this the expected behavior?
>
> Yes. `.read()` [with no argument] on a file-like object reads until
> EOF. See http://docs.python.org/library/stdtypes.html#file.read

Right, got it now.

> You want proc.stdout.readline().

Yes, or a for loop, this works for me now:


      import subprocess

      com = ['/bin/ls', '-l', '/usr/bin']
      with subprocess.Popen(com, stdout=subprocess.PIPE, 
stderr=subprocess.STDOUT) as proc:
          for line in proc:
            print('out: ' + str(line, 'utf8'))



-- 
Yves.                                                  http://www.SollerS.ca/
                                                        http://ipv6.SollerS.ca
                                                        http://blog.zioup.org/

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#19224

  import subprocess

  com = ['/bin/ls', '-l', '/usr/bin']
  with subprocess.Popen(com, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) 
as proc:
    for line in proc.stdout:
      print('out: ' + str(line, 'utf8'))

-- 
Yves.                                                  http://www.SollerS.ca/
                                                        http://ipv6.SollerS.ca
                                                        http://blog.zioup.org/

[toc] | [prev] | [standalone]

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