CSCI 420 - Operating Systems & Concurrency

Spring 2017

Rush - the Rust Shell, part 2

Assignment

In this assignment, we continue implementing an interactive Unix shell using the Rust language. Implement your shell according to the following steps:

If the line ends with the & symbol, it should run in the background. That is, your shell should not wait for it to terminate; the command line should immediately return. Your shell should print the PID of the process, so that the user may later manage it as needed.
The line may contain two or more commands connected with the pipe symbol (|). If this happens, start a process for each command, setting up pipes to send the output of each left-hand command to the input of the following right-hand command.
If the line contains a < symbol, the immediately following string is the input source for the command. If it contains a >, the command's output goes to the targeted file.
The * pattern-matching symbol should work with arbitrary paths.

Grading

Completing each step is worth 10 points. Full credit will be received for completing any three of the steps, so the assignment is worth 30 points. If an additional step is completed, it will be worth 10 points of extra credit. Furthermore, if the first three steps are completed and they will all work together properly on a single command line, that is also worth 10 points of extra credit. No credit will be given for code that fails to compile. Partial credit may be given for incomplete or flawed versions of a given step.

Tips

The most straightforward implementation of pipes is to use the Rust std::process library. This is a very high-level API, and so it will be necessary to run each process to completion (saving its output) before starting the next process in the pipe (sending the old output as its input).
A lower-level approach can use nix, which is a Rust binding to the basic Unix system calls. Each system call has a corresponding (safe) Rust wrapper. In this case, one can create a pipeline using file descriptors. This creates true parallelism between the processes, but it arguably takes a bit more effort. A successful implementation of this approach will be worth 5 points of extra credit. This program might be a helpful model for creating your solution.

Acknowledgement

This assignment was adapted from materials developed by David Evans at the University of Virginia.