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ls-to-xml-exercise.md

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Text file processing

Part 1

Write a program to display a structure of files and folders in a hierarchical format.

For example, say we have some structure of files and folders on disk. We list all the files contained in the current folder by running the following command:

find . -type f > output.txt

Now output.txt has a list of all the files (including those in subfolders). For example:

./file1.txt
./file2.mp3
./folder1/hello.py
./folder1/nested_folder/file3.txt
./folder1/nested_folder/file4.txt

Your program will read the contents of output.txt and write the following text to the terminal:

file1.txt
file2.mp3
folder1/
    hello.py
    nested_folder/
        file3.txt
        file4.txt

(Your program shouldn't actually scan the contents of the file system, it should only read output.txt.)

Hint: use open to read a file. You can iterate over a file in a for loop to read it line by line. You can split a string using str.split.

Part 2

Unfortunately, your program from Part 1 doesn't work for empty directories, because find . -type f lists only files. Change your program so that it reads the output of the ls -R1 command instead. Here's what the output of ls -R1 looks like for the file structure above:

file1.txt
file2.mp3
folder1

./folder1:
hello.py
nested_folder

./folder1/nested_folder:
file3.txt
file4.txt

Part 3

Instead of writing to the terminal, your program should write an XML file. For the same file structure above, the program would write an XML file with the following contents:

<tree>
 <file name="file1.txt" />
 <file name="file2.mp3" />
 <folder name="folder1">
   <file name="hello.py" />
   <folder name="nested_folder">
     <file name="file3.txt" />
     <file name="file4.txt" />
   </folder>
 </folder>
</tree>

Hint: use xml.etree to work with XML. The XML output doesn't have to be nicely formatted (xml.etree outputs everything on one line).

Part 4

Adjust your program so that it accepts a directory path as a command line argument, runs ls -R1 on that path, and then generates the XML output as before.

Hint: use sys.argv for reading command line args and subprocess.run to run a process.

Part 5

Add information about file owner and modification time to the XML file. Instead of ls -R1, run ls -Rhl to get this additional info. Its output looks like this:

total 8200
-rw-r--r--  1 matan  staff   509B  2 May 23:26 file1.txt
-rw-r--r--  1 matan  staff   3.5M  2 May 23:27 file2.mp3
drwxr-xr-x  4 matan  staff   128B  2 May 23:10 folder1

./folder1:
total 8192
-rw-r--r--  1 matan  staff   3.7M  2 May 23:27 hello.py
drwxr-xr-x  4 matan  staff   128B  2 May 23:10 nested_folder

./folder1/nested_folder:
total 24
-rw-r--r--  1 matan  staff   8.0K  2 May 23:29 file3.txt
-rw-r--r--  1 matan  staff   521B  2 May 23:10 file4.txt

The resulting XML file elements should now include additional attributes: owner, size (in bytes), and modified (formatted like 2019-05-02T23:29:00).

Hint: use the time module.