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os.system() with imbeded quotes on centos

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  os.system() with imbeded quotes on centos cevyne@gmail.com - 2013-04-01 12:22 -0700
    Re: os.system() with imbeded quotes on centos Chris Angelico <rosuav@gmail.com> - 2013-04-02 06:33 +1100
    Re: os.system() with imbeded quotes on centos John Gordon <gordon@panix.com> - 2013-04-01 20:26 +0000
      Re: os.system() with imbeded quotes on centos Cameron Simpson <cs@zip.com.au> - 2013-04-06 09:00 +1100
      Re: os.system() with imbeded quotes on centos Chris Rebert <clp2@rebertia.com> - 2013-04-05 16:36 -0700

#42486 — os.system() with imbeded quotes on centos

I get the example os.system('ls -al')     no problem.

i'm trying to create a variable with my command built in it but needs to include quotes.
Portion of code is as follows:
someip = '192.168.01.01'

var1 = 'lynx -dump http://' + someip + '/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk' 

print  var1

os.system(var1)


If I print var1 it looks right .  If I use the os.system(var1) as above it seems to have a problem near the end of the string with msg 
sh: .submit=+++Go%21+++: command not found

clearly there is some escape sequence that I don't understand .

I tried combinations of single and double quotes and mixed around var1 in os.system(), but that generates command not found.  

I need it to look like how I enter it manually and works
lynx -dump 'http://192.168.01.01/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk' 

Probably obvious to many but i'm spinning my wheels.  many thanks for help .

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#42490

On Tue, Apr 2, 2013 at 6:22 AM,  <cevyne@gmail.com> wrote:
> var1 = 'lynx -dump http://' + someip + '/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk'
> lynx -dump 'http://192.168.01.01/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk'


The problem is the &, which splits the command. Note how your manual
execution puts single quotes around just the URL; in the other
version, you're not doing that. (Though I'm not entirely sure why your
> junk is inside the quotes - is that an error?) Try this:

var1 = 'lynx -dump "http://' + someip +
'/cgi-bin/xxxx.log&.submit=+++Go%21+++"  > junk'

ChrisA

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#42496

In <0c9717ca-52dd-49ce-8102-e1432883858a@googlegroups.com> cevyne@gmail.com writes:

> someip = '192.168.01.01'
> var1 = 'lynx -dump http://' + someip + '/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk' 

'&' is a special character in shell commands.  You'll need to quote or
escape it.

Try this:

    someip = '192.168.01.01'
    var1 = 'lynx -dump "http://' + someip + '/cgi-bin/xxxx.log&.submit=+++Go%21+++"  > junk' 

Note the extra pair of double-quotes around the http:// part.

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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#42856

On 01Apr2013 20:26, John Gordon <gordon@panix.com> wrote:
| In <0c9717ca-52dd-49ce-8102-e1432883858a@googlegroups.com> cevyne@gmail.com writes:
| > someip = '192.168.01.01'
| > var1 = 'lynx -dump http://' + someip + '/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk' 
| 
| '&' is a special character in shell commands.  You'll need to quote or
| escape it.

Or better still, use the subprocess module and avoid going via the
os.system() altogether:

  http://docs.python.org/2/library/subprocess.html#popen-constructor

If you must go via the os.system(), write yourself a generic function
to quote a string for the shell, and to quote a bunch of strings
(essentially " ".join( quoted-individual-strings )). And use it
rigorously.

Anything else is asking for shell injection attacks/errors, just
as bad as hand constructing SQL statements.

For example, if I must construct a shell command from arbitrary
strings (like your URL) I use quote() from this:

  https://bitbucket.org/cameron_simpson/css/src/tip/lib/python/cs/sh.py

That code's nothing special, just what I rolled some years ago for
exactly this purpose.

The core lesson is: never waste time figuring out _whether_ you
need to treat shell strings specially. Just treat them specially
and consistently and be safe.

Cheers,
-- 
Cameron Simpson <cs@zip.com.au>
-- 
cat: /Users/cameron/rc/mail/signature.: No such file or directory

The Design View editor of Visual InterDev 6.0 is currently incompatible
with Compatibility Mode, and may not function correctly.
- George Politis <george@research.canon.com.au>, 22apr1999,
  quoting http://msdn.microsoft.com/vstudio/technical/ie5.asp

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#42863

On Fri, Apr 5, 2013 at 3:00 PM, Cameron Simpson <cs@zip.com.au> wrote:
> On 01Apr2013 20:26, John Gordon <gordon@panix.com> wrote:
> | In <0c9717ca-52dd-49ce-8102-e1432883858a@googlegroups.com> cevyne@gmail.com writes:
> | > someip = '192.168.01.01'
> | > var1 = 'lynx -dump http://' + someip + '/cgi-bin/xxxx.log&.submit=+++Go%21+++  > junk'
> |
> | '&' is a special character in shell commands.  You'll need to quote or
> | escape it.
>
> Or better still, use the subprocess module and avoid going via the
> os.system() altogether:
>
>   http://docs.python.org/2/library/subprocess.html#popen-constructor
>
> If you must go via the os.system(), write yourself a generic function
> to quote a string for the shell, and to quote a bunch of strings
> (essentially " ".join( quoted-individual-strings )). And use it
> rigorously.
>
> Anything else is asking for shell injection attacks/errors, just
> as bad as hand constructing SQL statements.
>
> For example, if I must construct a shell command from arbitrary
> strings (like your URL) I use quote() from this:
>
>   https://bitbucket.org/cameron_simpson/css/src/tip/lib/python/cs/sh.py
>
> That code's nothing special, just what I rolled some years ago for
> exactly this purpose.

No need for third-party code, just use the std lib:
http://docs.python.org/2/library/pipes.html#pipes.quote
http://docs.python.org/3/library/shlex.html#shlex.quote

(But yeah, best of all is to just use `subprocess` with shell=False.)

Cheers,
Chris

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