CODEWITHSUNDEEP
python
Abraxas
Abraxas

Reputation: 361

Python - Relative Paths in os.system calls

I am building a python utility which automates sysadmin type tasks. Part of the tool involves writing scripts and then calling them with powershell from the python interface. An example of such code is this:

def remote_ps_session():
  target = raw_input("Enter your target hostname: ")
  print "Creating target.ps1 file to establish connection"
  pstarget = open("pstarget.ps1", "w")
  pstarget.write("$target = New-Pssession " + target + "\n")
  pstarget.write("Enter-PSSession $target" + "\n")
  pstarget.close()
  print "File created. Initiating Connection to remote host..."
  os.system("powershell -noexit -ExecutionPolicy Unrestricted " + "C:\path\to\my\file\pstarget.ps1")

I would like to do two things which I think can be answered with the same method, I've just yet to find out what is best (importing vs variables vs initial setup definitions and so on)

For simplicity we'll say the utility is in C:\utility and the powershell functions are in a functions folder one level deeper: C:\utility\functions

I want to be able to specify a location for 1) where the script (the file that is written) is saved to and then 2) refer to that location when the os.system call is made. I want this to be able to run on most/any modern Windows system.

My thoughts on possibilities are:

  1. When the script launches get the current directory and save that as a variable, if I need to go back a directory take that variable and remove everything after the last \ and so on. Doesn't seem ideal.
  2. On the first launch of the file prompt for system locations to put in variables. For instance have it prompt 'where do you want your log files?' 'where do you want your output files?' 'where do you want your generated scripts?' These could then be referred to as variables but would break if they ever moved folders and may not be easy to 'fix' for a user.
  3. I imagine there is some way to refer to current directories and navigate to ..\parallel folder to where I am executing from. ....\2 folders up, but that also seems like it might be messy. I've yet to see what a standard/best practice for managing this is.

Edit: based on some comments I think __file__ might be the place to start looking. I'm going to dig in to this some but any examples (for example: __file__/subfoldernameor whatever the usage would be would be cool.

Upvotes: 1

Views: 1225

Answers (1)

Nikita
Nikita

Reputation: 6331

Python has a lib dedicated to path manipulation os.path, so anytime you need filesystem paths manipulation take a look at it.

As for your particular questions, run the following example, to see how you can use the functions from this lib:

test.py

import os
# These two should basicly be the same,
# but `realpath` resolves symlinks
this_file_absolute_path = os.path.abspath(__file__)
this_file_absolute_path1 = os.path.realpath(__file__)
print(this_file_absolute_path)
print(this_file_absolute_path1)
this_files_directory_absolute_path = os.path.dirname(this_file_absolute_path)
print(this_files_directory_absolute_path)
other_script_file_relative_path = "functions/some.ps"
print(other_script_file_relative_path)
other_script_file_absolute_path = os.path.join(this_files_directory_absolute_path,
                                               other_script_file_relative_path)
print(other_script_file_absolute_path)
print("powershell -noexit -ExecutionPolicy Unrestricted %s" %
      other_script_file_absolute_path)

You should get output similar to this:

/proj/test_folder/test.py
/home/user/projects/test_folder/test.py
/proj/test_folder
functions/some.ps
/proj/test_folder/functions/some.ps
powershell -noexit -ExecutionPolicy Unrestricted /proj/test_folder/functions/some.ps

Upvotes: 2

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