[SOLVED] Help executing shell commands in a Python script

zippy4251 · 09-21-2012, 01:35 PM

I am trying to create a Python script that would search recursively for a specific file extension and run a command on each individual file that is found. I did this in bash using a for loop that looked like this:

Code:

for files in $(find -type f -name "*.001")
do
     ftkimager $files --verify >> images.txt
done

ftkimager is a command line program for imaging hard drives. The script looks for .001 files, verifies against a MD5 hash, and places the results into images.txt

I wanted to let the user input a starting directory, so I added that to my Python script and use the subprocess module to run shell commands and execute ftkimager. Here is what I have so far for the Python script:

Code:

import subprocess

source = raw_input ("Enter the Path \n")

for files in subprocess.call (['find '+source+' -type f -name "*.001"], shell=True)
subprocess.call (['ftkimager '+source' --verify'], shell=True)

When run, I get an invalid syntax error on the for loop. Since the other parts work when I comment out the for statement, I'm assuming I'm doing the for loop incorrectly but I don't know how to get the command to work properly. Does anyone know how to fix this, or (if possible) do what I want to do in a better way?

dugan · 09-21-2012, 01:38 PM

Code:

for files in subprocess.call (['find '+source+' -type f -name "*.001"]', shell=True):

You forgot a closing quote.

zippy4251 · 09-21-2012, 02:01 PM

That fixed that! One step closer to success. Now I get the error "TypeError: 'int' object is not iterable" during the for loop. Now from what I'm gathering this means that "files" is not an integer, which is true. I'm pretty new to this so my thought may be way off here, but do I need to make "image" a string somehow?

TobiSGD · 09-21-2012, 02:14 PM

subprocess.call() will not return the output of the shell-command, but the exit code of that command, usually 0 if no error occured. Therefore the error-message that you can't iterate an int, simply because files is an int. If you want the actuall output have a look at either the stdout and stderr options of subprocess.call() or the subprocess.check_output() function: http://docs.python.org/library/subprocess.html

dugan · 09-21-2012, 02:19 PM

You should also be using glob to generate a list of files to iterate over, not calling find.

audriusk · 09-21-2012, 04:12 PM

I feel that shell scripts are better suited for tasks like this:

Code:

read -p 'Enter the path: ' dir
find $dir -type f -name '*.001' -print0 \
  | xargs -0 -I{} ftkimager {} --verify >> images.txt

zippy4251 · 09-25-2012, 09:34 AM

Thanks for all the help!

Quote:

If you want the actuall output have a look at either the stdout and stderr options of subprocess.call() or the subprocess.check_output() function: http://docs.python.org/library/subprocess.html

I'm looking more into this now to make things work how I want.

Quote:

You should also be using glob to generate a list of files to iterate over, not calling find.

The problem with glob is it is not recursive. I did find there's a module called glob2 that is recursive however.

Quote:

I feel that shell scripts are better suited for tasks like this:

Yep, I had a shell script that I posted first as an example that does work. I think that shell scripts are better suited for simple tasks, but I wanted to use it as a way to start learning Python. Necessity is the mother of invention and programming in my mind

.

Since my original question was answered, I marked this as solved and will post any other questions in a new thread.

dugan · 09-25-2012, 11:20 AM

Quote:

Originally Posted by zippy4251

The problem with glob is it is not recursive. I did find there's a module called glob2 that is recursive however.

You could also combine fnmatch with os.walk. I would guess that this is how glob2 is implemented.