Project 3: Advanced Shell Commands Using Rust

Implement the following shell commands as Rust programs:

• findtext: Output every line that contains a specified pattern. The first command-line argument is the fixed-string pattern. Remaining arguments are the names of the files to inspect.
• order: Works like cat, except the output lines must be sorted before being output. All lines from all files will be mixed together and then sorted. If the “-r” command-line argument is provided, they should be sorted in reverse order.

Implement the following shell command-line interpreter:

• vssh1, the Very Simple SHell, version 1:
  • Displays the current working directory while awaiting user input.
  • If the user types exit, the program ends.
  • If the user types cd [dir], change current working directory accordingly.
  • If the user types a blank line, ignore it and display the prompt once again.
  • Execute any other command the user types by spawning a new process:
    • Be sure to include the nix crate in Cargo.toml using the following line under [dependencies]:
      • nix = {version = "0.26.2", features = ["process"]}
    • Use fork to create the child process.
    • Within the child process, use execvp to execute the command.
    • Within the parent process, use waitpid to wait for the child process to complete.
  • vssh1 should not panic. Be sure to explicitly handle every possible error.
  • There is no need to implement pipes (|) or input/output redirection (< and >). That is a topic for the next project.
• The vssh1 assignment was adapted from materials developed by David Evans at the University of Virginia.

Here is an example execution of vssh1:

gjf2a@20003LPUX:~/solutions320$ cargo run --bin vssh1
   Compiling solutions320 v0.1.0 (/home/gjf2a/solutions320)
    Finished dev [unoptimized + debuginfo] target(s) in 1.75s
     Running `target/debug/vssh1`
/home/gjf2a/solutions320$ cd src/bin
/home/gjf2a/solutions320/src/bin$ grep fn vssh1.rs
fn main() {
fn process_next_line() -> anyhow::Result<Status> {
fn run_command(command: &str) -> anyhow::Result<()> {
fn externalize(command: &str) -> Vec<CString> {
/home/gjf2a/solutions320/src/bin$ cd ..
/home/gjf2a/solutions320/src$ cd ..
/home/gjf2a/solutions320$ ls
Cargo.lock  Cargo.toml  grep_test.out  src  target  toml.out
/home/gjf2a/solutions320$ exit

The execvp system call requires the command to be formatted as a fixed-size array of c-style strings. The function below will perform this conversion for you:

fn externalize(command: &str) -> Vec<CString> {
    command.split_whitespace()
        .map(|s| CString::new(s).unwrap())
        .collect()
}

If the compiler requests a parameterized type for execvp, use CString.

Submissions

• You may place your files in the GitHub repository you used for the previous project, or you can create a new one for this project. Make sure your repository is private, and that you add the instructor as a collaborator.
• Post the GitHub URL you would like me to examine in your private channel of the CSCI 320 Team.

Assessment

• Partial: Correctly complete either vssh1 or both of findtext and order.
• Complete: All three programs correctly completed.