Python: NullPointerException for os.system() and os.popen()

Question

I am getting a NullPointerException for os.system() and os.popen() on python 2.2.1. The weird thing is that i have two servers and this same code works fine on one but not on the other. What could be missing in the second server?

Below is the code snippet

import sys
import os

print (sys.version)   #This line works on both servers and gives 2.2.1 os output 
os.system('pwd')
os.popen('hostname -f').read().rstrip('\n')

I get the following error in the second server:

*File "/u01/oracle/mwhome/wlserver_10.3/common/wlst/modules/jython-modules.jar/Lib/javaos$py.class", line 333, in system
File "/u01/oracle/mwhome/wlserver_10.3/common/wlst/modules/jython-modules.jar/Lib/popen2.py", line 31, in ?
File "/u01/oracle/mwhome/wlserver_10.3/common/wlst/modules/jython-modules.jar/Lib/javashell.py", line 17, in ?
File "/u01/oracle/mwhome/wlserver_10.3/common/wlst/modules/jython-modules.jar/Lib/string$py.class", line 434, in ?
    at java.io.File.<init>(File.java:222)
    at java.lang.Package$1.run(Package.java:527)
    at java.lang.Package.defineSystemPackage(Package.java:520)
    at java.lang.Package.getSystemPackages(Package.java:511)
    at java.lang.ClassLoader.getPackages(ClassLoader.java:1513)
    at java.lang.ClassLoader.getPackages(ClassLoader.java:1511)
    at java.lang.Package.getPackages(Package.java:281)
    at org.python.core.JavaImportHelper.buildLoadedPackages(Unknown Source)
    at org.python.core.JavaImportHelper.tryAddPackage(Unknown Source)
    at org.python.core.imp.import_next(Unknown Source)
    at org.python.core.imp.import_name(Unknown Source)
    at org.python.core.imp.importName(Unknown Source)
    at org.python.core.ImportFunction.load(Unknown Source)
    at org.python.core.ImportFunction.__call__(Unknown Source)
    at org.python.core.PyObject.__call__(Unknown Source)
    at org.python.core.__builtin__.__import__(Unknown Source)
    at org.python.core.imp.importFromAs(Unknown Source)
    at org.python.core.imp.importFrom(Unknown Source)
    at string$py.f$0(C:\wlst\jython_2.2.1\Lib\string.py:434)
    at string$py.call_function(C:\wlst\jython_2.2.1\Lib\string.py)
    at org.python.core.PyTableCode.call(Unknown Source)
    at org.python.core.PyCode.call(Unknown Source)
    at org.python.core.imp.createFromCode(Unknown Source)
    at org.python.core.imp.createFromPyClass(Unknown Source)
    at org.python.core.ZipFileImporter$ZipFileLoader.load_module(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
java.lang.NullPointerException: java.lang.NullPointerException*

Answer 1

I could be wrong here but I noticed that there is 'C:\' in the stacktrace. If this is running on a windows system 'pwd' and 'hostname' likely wont work if os.system / popen are executing exactly what you put in the argument which is likely why you are getting the error.

I am not a windows guru by any means but I dont think those commands exist outside of *nix based OS's.