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how to change os.popen4 to subprocess

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  how to change os.popen4 to subprocess skyworld <chenyong20000@gmail.com> - 2012-10-26 19:28 -0700
    Re: how to change os.popen4 to subprocess MRAB <python@mrabarnett.plus.com> - 2012-10-27 04:02 +0100
      Re: how to change os.popen4 to subprocess skyworld <chenyong20000@gmail.com> - 2012-10-26 23:30 -0700
        RE: how to change os.popen4 to subprocess "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-10-30 14:47 +0000
    Re: how to change os.popen4 to subprocess Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-27 04:10 +0100

#32260 — how to change os.popen4 to subprocess

Hi,

I'm new to python and I'm trying to porting some scripts from v0.96 to
v2.0.1. A piece of code is like this:

cmd_h = os.popen4(env['SYSCMDLINE'])[1]

the system indicates the popen4 is deprecated and suggest to use
subprocess. Can anybody tell me how to use subprocess in this case?
and what does "[1]" here means?

thanks.

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#32262

On 2012-10-27 03:28, skyworld wrote:
> Hi,
>
> I'm new to python and I'm trying to porting some scripts from v0.96 to
> v2.0.1. A piece of code is like this:
>
> cmd_h = os.popen4(env['SYSCMDLINE'])[1]
>
> the system indicates the popen4 is deprecated and suggest to use
> subprocess. Can anybody tell me how to use subprocess in this case?
> and what does "[1]" here means?
>
os.popen4 returns a tuple of (child_stdin, child_stdout_and_stderr).
The [1] gets the child_stdout_and_stderr member.

Using the subprocess module:

# Untested!
cmd_h = subprocess.Popen(env['SYSCMDLINE'], stdout=subprocess.PIPE, 
stderr=subprocess.STDOUT, shell=True).stdout

Explanation:

The command line: env['SYSCMDLINE']

Return stdout: stdout=subprocess.PIPE

stderr should be combined with stdout: stderr=subprocess.STDOUT

Let the shell parse the command line: shell=True

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#32267

On Oct 27, 11:02 am, MRAB <pyt...@mrabarnett.plus.com> wrote:
> On 2012-10-27 03:28, skyworld wrote:> Hi,
>
> > I'm new to python and I'm trying to porting some scripts from v0.96 to
> > v2.0.1. A piece of code is like this:
>
> > cmd_h = os.popen4(env['SYSCMDLINE'])[1]
>
> > the system indicates the popen4 is deprecated and suggest to use
> > subprocess. Can anybody tell me how to use subprocess in this case?
> > and what does "[1]" here means?
>
> os.popen4 returns a tuple of (child_stdin, child_stdout_and_stderr).
> The [1] gets the child_stdout_and_stderr member.
>
> Using the subprocess module:
>
> # Untested!
> cmd_h = subprocess.Popen(env['SYSCMDLINE'], stdout=subprocess.PIPE,
> stderr=subprocess.STDOUT, shell=True).stdout
>
> Explanation:
>
> The command line: env['SYSCMDLINE']
>
> Return stdout: stdout=subprocess.PIPE
>
> stderr should be combined with stdout: stderr=subprocess.STDOUT
>
> Let the shell parse the command line: shell=True

thanks

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#32494

Replying to skyworld because I could not find the original message
from MRAB.

skyworld wrote:
> On Oct 27, 11:02 am, MRAB <pyt...@mrabarnett.plus.com> wrote:
> > On 2012-10-27 03:28, skyworld wrote:> Hi,
> >
> > > I'm new to python and I'm trying to porting some scripts from v0.96 to
> > > v2.0.1. A piece of code is like this:
> >
> > > cmd_h = os.popen4(env['SYSCMDLINE'])[1]
> >
> > > the system indicates the popen4 is deprecated and suggest to use
> > > subprocess. Can anybody tell me how to use subprocess in this case?
> > > and what does "[1]" here means?
> >
> > os.popen4 returns a tuple of (child_stdin, child_stdout_and_stderr).
> > The [1] gets the child_stdout_and_stderr member.
> >
> > Using the subprocess module:
> >
> > # Untested!
> > cmd_h = subprocess.Popen(env['SYSCMDLINE'], stdout=subprocess.PIPE,
> > stderr=subprocess.STDOUT, shell=True).stdout
> >
> > Explanation:
> >
> > The command line: env['SYSCMDLINE']
> >
> > Return stdout: stdout=subprocess.PIPE
> >
> > stderr should be combined with stdout: stderr=subprocess.STDOUT
> >
> > Let the shell parse the command line: shell=True
> 
> thanks
> --

I thought the usage of shell=True is usually discouraged? The 
subprocess documentation[0] should be helpful to figure it out.
"""
Warning: Invoking the system shell with shell=True can be a security 
hazard if combined with untrusted input. See the warning under 
Frequently Used Arguments for details.
"""

[0] http://docs.python.org/2/library/subprocess.html 


Ramit


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#32263

On 27/10/2012 03:28, skyworld wrote:
> Hi,
>
> I'm new to python and I'm trying to porting some scripts from v0.96 to
> v2.0.1. A piece of code is like this:

What software are you talking about here, it's certainly not Python 
versions as the most up to date are 2.7.3 and 3.3.0?

>
> cmd_h = os.popen4(env['SYSCMDLINE'])[1]
>
> the system indicates the popen4 is deprecated and suggest to use
> subprocess. Can anybody tell me how to use subprocess in this case?
> and what does "[1]" here means?

If you don't know what the [1] means you've got problems :)  I suggest 
you read the tutorial here first 
http://docs.python.org/tutorial/index.html then the subprocess module 
here http://docs.python.org/library/subprocess.html#module-subprocess, 
specifically 
http://docs.python.org/library/subprocess.html#subprocess-replacements

>
> thanks.
>

No problem.

-- 
Cheers.

Mark Lawrence.

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