mtiman / rustybox

Rust implementation of GNU Utils

Rustybox

Rustybox is a copy of BusyBox written in Rust. In the following paragraphs I will describe my approach for each implemented function.

For parsing the input I decided to match the first argument with the commands and send the other CLI arguments as parameters.

pwd

Fetched the current dir with env::current_dir() and displayed it. The homework didn't mention an Error code in case of a pwd fail, so I used -2.

echo

Checked the first parameters for flags and printed the rest. I don't think echo can fail.

cat

Opens each given file and prints the contents. (Using fs::File::open() and read_to_string().)

mkdir

Creates every given directory using fs::create_dir.

mv

Because mv either moves or renames files, I had to break it into some cases: 1 - moving a file to a directory 2 - renaming a file 3 - renaming a directory.

ln

Symlink and hard_link are the functions I used to create the links, according to the flags.

rmdir

remove_dir for each given directory name. If the given argument isn't a directory, it fails and an error code is returned.

rm

Used remove_file and my rmdir for removing files, also remove_dir_all for removing recursively.

ls

I used contains() for looking up the flags and filter() for skipping them while iterating. My approach involved using fs::read_dir and printing the entries. I had to sort the entries so that the ls -l cases didn't differ from the ref. I decided to make an additional function for the recursive ls because the format differs from the normal one.

ls -l was by far the most complex assignment of this homework. I needed many helper functions for computing the information displayed by it. Firstly, I got the permissions using .permissions().mode() and matched them with the display type. Then, I got the owner and group by parsing /etc/passwd and /etc/group. The size of the file is stored in metadata, so it was easy to fetch. In the end I made a function for formatting the last modify time using chrono. All this information was formatted in another function which was called for every file.

cp

I used fs::copy for copying the files. In the case of copying into a directory, I had to format the name of the file so that the new file was inside the directory.

For cp -r I called my function recursively, each time creating a Vec<String> to be passed as argument, containing the source and destination of the copy, along with the recursive flag.

touch

I initially looked for functions that would modify the file's times but they were part of the nightly build, so I decided to read from file to modify the access time and write a null byte for updating the modify time. I am looking forward to improving this function.

chmod

Similarly to ls -l I parsed the permissions and used set_permissions() to update the files. I also had to converse the permissions to base 8 for easier understanding.

grep

I used the regex crate for checking weather each line from the given file was a match. Also implemented the -i.(the homework mentions -i to be inverting the result, corresponding to -v for the Linux grep.)

Notes

I learned a lot about Rust by doing this homework. I tried refactoring some bits of code after learning about new functions but the code might still seem a bit inconsistent. https://doc.rust-lang.org was extremely useful for researching modules and reading about the methods. Chat-GPT was also very useful for better understanding the syntax and quickly finding methods, although not always coming up with good answers.

I am looking forward to feedback and ways I could improve my Rust knowledge.

Verify

Run the following commands to test your homework:

You will have to install NodeJS (it is installed in the codespace)

# Clone tests repository
git submodule update --init 

# Update tests repository to the lastest version
cd tests
git pull 
cd ..

# Install loadash
npm install lodash

Install rustybox

cargo install --path .

If the rustybox command can't be found, be sure to add the default cargo installation folder into the PATH environment variable

export PATH=/home/<your username here>/.cargo/bin:$PATH

Run tests

cd tests
# Run all tests 
./run_all.sh

# Run single test
./run_all.sh pwd/pwd.sh