Systems Programming Assignment 6: Python Scripting Solution

For this assignment, you will use Python3 to create an alternative to the rm command. This program, rm.py, will take an arbitrary number of paths as arguments and, for each argument, move them to ∼/rm_trash . If ∼/rm_trash does not already exist, it should be created.




Hint: The shutil module may prove useful.







Duplicate Files




If a file with the same name already exists in ∼/rm_trash , you should append -1 to the end of the filename before any extension(s) if they exist so that both files are preserved. If a file with the same name in ∼/rm_trash already has -1, the new file should be appended with -2 and automatically incremented for subsequent copies.




For example, if a file named file.txt is removed 4 times, ∼/rm_trash should contain the following four files: file.txt, file-1.txt, file-2.txt, and file-3.txt.




Note: It is possible that a file being removed will already have a dash and a number at the end of the name. If this is true, you should be sure not modify the original name and only append the counter. For example, if a file named newfile-1.txt is deleted twice, ∼/rm_trash should contain newfile-1.txt and newfile-1-1.txt. You may assume that there will be no conflicts in file




names (e.g., rm.py file-1.txt; rm.py file.txt)







Recursion




Your program should recursively delete files if any argument is -r. If -r is not set, directories should be ignored and your program should print




rm.py: cannot remove ’DIR ’: Is a directory




to STDERR once for each directory encountered where DIR is the name of the directory.




When deleting recursively, simply move the directory to ∼/rm_trash using the duplicate naming rules as described above and leave the contents alone. You do not need to modify the names of the files within the removed directory.




Paths




If an argument does not point to a file, your program should print




rm.py: cannot remove ’FILE ’: No such file or directory




to STDERR once for each invalid argument where FILE is the path given.




When moving a file into ∼/rm_trash you should always place it at the root of the directory. For example, if /path/to/a/file.txt is passed as an argument, file.txt should be moved to




∼/rm_trash/file.txt and not ∼/rm_trash/path/to/a/file.txt.













Assignment 6: Python Scripting Page 1 of 2
Program Execution




Your program should be invoked as a single Python file (see below) with an arbitrary number of arguments representing paths to files (including directories). The -r option may be passed as any argument. Some examples are listed below.




$ rm.py /path/to/some/file ./somefile someotherfile




rm.py /path/to/some/file ./somefile someotherfile -r



rm.py -r /path/to/some/file ./somefile someotherfile



rm.py *.java






Extra Credit (10 points)




For extra credit, create a separate program called restore.py which, given a path to where a file used to be before it was removed with rm.py, will restore the most recent version.




Hint: Consider keeping track of the original and new locations of removed files to handle situations where removed files from different paths have the same name. Note that if you use this strategy, the information will need to persist between executions of rm.py and restore.py.




Attempts at extra credit will not be considered if rm.py does not work correctly.







Assignment Data




No sample data is included with this assignment as it should work for all files. As always, you should test your program with your own data as well to be sure that it works correctly.




Program Files




Your submission will consist of one or two files depending on if you attempt the extra credit:




rm.py - implementation of rm



restore.py - extra credit






Submission




Turn your assignment in via Blackboard. Your zip file, named LastnameFirstname.zip should contain only your rm.py and optionally restore.py.




If you attempt the extra credit, name your file LastnameFirstname_EC.zip. Without the _EC, your submission will be graded as normal.


































Assignment 6: Python Scripting Page 2 of 2