os.system question

[Kevin Walzer]

>>import os

>>foo = os.system('whoa mi')

kevin

>>print foo

0

>>>

The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the
value of 'kevin' associated with foo?

--
Kevin Walzer
Code by Kevin

http://www.codebykevin.com

[Steven D'Aprano]

Re: os.system question

On Wed, 06 Aug 2008 21:07:40 -0400, Kevin Walzer wrote:

>>>import os
>>foo = os.system('whoa mi')

kevin

>>print foo

0

>>>
>>>

The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the
value of 'kevin' associated with foo?

That's because os.system captures the return code of the system call,
which is 0 in this case because whoami succeeded. Meanwhile whoami
printed its result to standard output, as normal.

What you want is os.popen('whoam i', 'r').read()

Also look at the popen2 module.



--
Steven

[Larry Wang]

Re: os.system question

os.system() simply executes the command in a subshell, and returns the
command's exit status which in your case is '0'. If you need to capture the
stdout, stderr, etc. stuff, subprocess module is preferred which offers more
powerful functionalities over os.system().

Nessus

"Kevin Walzer" <kw@codebykevin .comwrote in message
news:1c5bf$489a 4add$4275d90a$1 5022@FUSE.NET.. .

>import os
>foo = os.system('whoa mi')

kevin

>print foo

0

>>

>
The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the value
of 'kevin' associated with foo?
>
--
Kevin Walzer
Code by Kevin
http://www.codebykevin.com

[SamG]

Re: os.system question

On Aug 7, 6:07 am, Kevin Walzer <k...@codebykev in.comwrote:

 >>import os
 >>foo = os.system('whoa mi')
kevin
 >>print foo
0
 >>>
>
The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the
value of 'kevin' associated with foo?
>
--
Kevin Walzer
Code by Kevinhttp://www.codebykevin .com

Why dont you try commands module instead....

In [28]: import commands

In [29]: dir(commands)
Out[29]:
['__all__',
'__builtins__',
'__doc__',
'__file__',
'__name__',
'getoutput',
'getstatus',
'getstatusoutpu t',
'mk2arg',
'mkarg']

In [30]: (a,b) = commands.getsta tusoutput('whoa mi')

In [31]: print a
0

In [32]: print b
luma35

[Kevin Walzer]

Re: os.system question

SamG wrote:

>
Why dont you try commands module instead....
>

Thank you! That was just what I needed.



--
Kevin Walzer
Code by Kevin

http://www.codebykevin.com

[Eric Wertman]

Re: os.system question

In your case you could also use the os.environ dictionary:

import os
print os.environ['USER']

[Mike Driscoll]

Re: os.system question

On Aug 6, 8:07 pm, Kevin Walzer <k...@codebykev in.comwrote:

 >>import os
 >>foo = os.system('whoa mi')
kevin
 >>print foo
0
 >>>
>
The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the
value of 'kevin' associated with foo?
>
--
Kevin Walzer
Code by Kevinhttp://www.codebykevin .com

Just an FYI, the os.system, commands, and os.popen* stuff is
deprecated in Python 2.4+. The subprocess module is supposed to
replace them all.

See the docs for more info: http://docs.python.org/lib/module-subprocess.html

I think the equivalent is subprocess.Pope n with the communicate()
method:

http://docs.python.org/lib/node532.html

HTH

Mike

[Brad]

Re: os.system question

Kevin Walzer wrote:

>>import os
>>foo = os.system('whoa mi')

kevin

>>print foo

0

>>>

>
The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the
value of 'kevin' associated with foo?
>

Hi Kevin, check out popen. It should let you do what you want.

import os
name=os.popen(' whoami').read()

[Asun Friere]

Re: os.system question

On Aug 8, 6:07 am, Mike Driscoll <kyoso...@gmail .comwrote:

On Aug 6, 8:07 pm, Kevin Walzer <k...@codebykev in.comwrote:
>

>>import os
>>foo = os.system('whoa mi')

kevin

>>print foo

0

>>>

>

The standard output of the system command 'whoami' is my login name. Yet
the value of the 'foo' object is '0,' not 'kevin.' How can I get the
value of 'kevin' associated with foo?

>

--
Kevin Walzer
Code by Kevinhttp://www.codebykevin .com

>
Just an FYI, the os.system, commands, and os.popen* stuff is
deprecated in Python 2.4+. The subprocess module is supposed to
replace them all.
>
See the docs for more info:http://docs.python.org/lib/module-subprocess.html
>
I think the equivalent is subprocess.Pope n with the communicate()
method:
>

http://docs.python.org/lib/node532.html

>
HTH
>
Mike

Something like this should work,

>>from subprocess import Popen, PIPE
>>me = Popen('whoami', stdout=PIPE, shell=True).std out.read()

but if I was in a hurry to find out who I was I would be tempted still
to use the deprecated "os.popen('whoa mi').read()".

[norseman]

Re: os.system question

Asun Friere wrote:

On Aug 8, 6:07 am, Mike Driscoll <kyoso...@gmail .comwrote:

>On Aug 6, 8:07 pm, Kevin Walzer <k...@codebykev in.comwrote:
>>

>> >>import os
>> >>foo = os.system('whoa mi')
>>kevin
>> >>print foo
>>0
>> >>>
>>The standard output of the system command 'whoami' is my login name. Yet
>>the value of the 'foo' object is '0,' not 'kevin.' How can I get the
>>value of 'kevin' associated with foo?
>>--
>>Kevin Walzer
>>Code by Kevinhttp://www.codebykevin .com

>Just an FYI, the os.system, commands, and os.popen* stuff is
>deprecated in Python 2.4+. The subprocess module is supposed to
>replace them all.
>>
>See the docs for more info:http://docs.python.org/lib/module-subprocess.html
>>
>I think the equivalent is subprocess.Pope n with the communicate()
>method:
>>
>http://docs.python.org/lib/node532.html
>>
>HTH
>>
>Mike

>
Something like this should work,
>

>>>from subprocess import Popen, PIPE
>>>me = Popen('whoami', stdout=PIPE, shell=True).std out.read()

>
but if I was in a hurry to find out who I was I would be tempted still
to use the deprecated "os.popen('whoa mi').read()".

I assume Asun added the above line. I agree with whoever wrote it. SLT

--

http://mail.python.org/mailman/listinfo/python-list

>

=============== ===========

Can we take a moment and look at what is happening here?

Python developers are creating an unwanted item!

Let's take a good look:

1) import os 9
2) name=os.popen(' whoami').read() 30

3) from subprocess import Popen, PIPE 34
4) me = Popen('whoami', stdout=PIPE, shell=True).std out.read() 59

While lines 1 and 3 are typically done once per module, line 3 would
seem to imply the need for making specific requests for sub-process and
associated and (required) other pieces. Lots of combinations to
remember, fumble, and have to re-research to do the simple.

Stats point up something too:
30/9 = 3.333...
59/30 = 1.966...

without any other factors such as normally additional lines of code for
the more verbose 'better' package it still will take at least twice as
long to code the same thing. Add Murphy's Law and the typos go through
the roof. Expect (after all is said and done) for the same process to
take 3 times as much clock time to complete the same project using the
padded up new and improved vs the concise.

This is not intuitive and it is not necessary and it most certainly is
not wanted. Not by the programmer, not by the client and not by the one
paying the paycheck. If 1&2 have a security hole - address it directly.
Do not add more confusion to help cover greater holes. Or to pad your
pockets because you are bored.

Somebody had to say it. Besides, as a trouble shooter I used to get
paid to locate and fire people that padded it up to their employers. The
things of which individuals can justify to themselves is truly amazing.

I still prefer assembly. It's all right there, right up front. No
compiler anomalies (accidental or intentional) to deal with.


Man the shelters Honey; major incoming expected momentarily. :)



Steve
norseman@hughes .net

[Steven D'Aprano]

Re: os.system question

On Tue, 12 Aug 2008 14:42:28 -0700, norseman wrote:

Can we take a moment and look at what is happening here?
>
Python developers are creating an unwanted item!
>
Let's take a good look:
>
1) import os 9
2) name=os.popen(' whoami').read() 30
>
3) from subprocess import Popen, PIPE 34
4) me = Popen('whoami', stdout=PIPE, shell=True).std out.read() 59

....

I still prefer assembly. It's all right there, right up front. No
compiler anomalies (accidental or intentional) to deal with.

Please tell me more, I am very interested in this assembly of which you
speak. How would you write a program in assembly that does the same as
the above code, and will run on any major platform? I would love to see
the code. I expect it will be much shorter and more intuitive than the
Python code you dislike, leading to fewer errors and less padding of the
programmer's pockets at the expense of their employers.



--
Steven

[Steven D'Aprano]

Re: os.system question

On Mon, 11 Aug 2008 19:28:13 -0700, Asun Friere wrote:

Something like this should work,
>

>>>from subprocess import Popen, PIPE
>>>me = Popen('whoami', stdout=PIPE, shell=True).std out.read()

>
but if I was in a hurry to find out who I was I would be tempted still
to use the deprecated "os.popen('whoa mi').read()".

Is it really deprecated? Since when? I'm using Python 2.5 and it doesn't
raise any warnings or mention anything in the doc string.

The current documentation does say:

"The subprocess module provides more powerful facilities for spawning new
processes and retrieving their results; using that module is preferable
to using this function."

http://docs.python.org/lib/os-newstreams.html#os-newstreams

but that's not the same as deprecating os.popen.



--
Steven

[Wojtek Walczak]

Re: os.system question

Dnia 12 Aug 2008 22:58:22 GMT, Steven D'Aprano napisa³(a):

>but if I was in a hurry to find out who I was I would be tempted still
>to use the deprecated "os.popen('whoa mi').read()".

>
Is it really deprecated? Since when? I'm using Python 2.5 and it doesn't
raise any warnings or mention anything in the doc string.

I think that the deprecation warnings were added in Python 2.6.

--
Regards,
Wojtek Walczak,

http://www.stud.umk.pl/~wojtekwa/

[Asun Friere]

Re: os.system question

On Aug 13, 8:58 am, Steven D'Aprano <st...@REMOVE-THIS-
cybersource.com .auwrote:

On Mon, 11 Aug 2008 19:28:13 -0700, Asun Friere wrote:
>

but if I was in a hurry to find out who I was I would be tempted still
to use the deprecated "os.popen('whoa mi').read()".

>
Is it really deprecated? Since when? I'm using Python 2.5 and it doesn't
raise any warnings or mention anything in the doc string.
>

I should perhaps have put 'deprecated' in quotation marks? Note the
post I was responding to and my own stated preference. Though I
admit, I have been trying out Popen just recently.

The current documentation does say:
>
"The subprocess module provides more powerful facilities for spawning new
processes and retrieving their results; using that module is preferable
to using this function."
>

http://docs.python.org/lib/os-newstreams.html#os-newstreams

>
but that's not the same as deprecating os.popen.
>

Current documentation also states:

"[The subprocess] module intends to replace several other, older
modules and functions, such as: ... [inter alia] ... os.system,
os.popen*, commands.*"

http://docs.python.org/lib/module-subprocess.html

Which is also not exactly the same thing as deprecating os.popen, but
it does sound somehwat more ominous. One hopes the subprocess module
is not successful in realising its intentions.

I note 3.0 runs os.popen without complaint (and had thought to mention
that in my previous). Right now I'm wondering whether I should
install the beta 2.6 to see whether Wotjek is pulling our leg or
not. :)

[Wojtek Walczak]

Re: os.system question

Dnia Tue, 12 Aug 2008 23:38:56 -0700 (PDT), Asun Friere napisa³(a):

I note 3.0 runs os.popen without complaint (and had thought to mention
that in my previous). Right now I'm wondering whether I should
install the beta 2.6 to see whether Wotjek is pulling our leg or
not. :)

:) Checked it to make sure.

Python 2.6b2 (r26b2:65082, Aug 13 2008, 01:12:28)
[GCC 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.

>>import popen2

__main__:1: DeprecationWarn ing: The popen2 module is deprecated. Use the subprocess module.

>>import os
>>print os.popen('whoam i').read()

gminick

>>print os.popen2('whoa mi')[1].read()

gminick

>>print os.popen2('whoa mi')[0].read()

__main__:1: DeprecationWarn ing: os.popen2 is deprecated. Use the subprocess module.
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IOError: [Errno 9] Bad file descriptor

>>>

The strange thing is that os.popen2 prints the deprecation warning
only when it's called inappropriately . Got to investigate it further.

os.popen won't return any deprecation warning in Py2.6beta2 probably
because it is defined in Lib/platform.py and not in Lib/os.py and
I guess that somebody has forgotten to add the warnings in there.

--
Regards,
Wojtek Walczak,

http://www.stud.umk.pl/~wojtekwa/