CS 100 Programming Project

Introduction

This is the RShell project for CS 100 Winter 2020.

It is a simple shell program which will convert the command from user input to native linux command.

Prototype and Research

The shell program is based on some linux system calls, such as fork(), waitpid() and execvp().

The fork() function creates a new process by duplicating the calling process. The new process is the child process, which is an almost duplicate of the calling process. The waitpid() function is used to wait for state changes in a child of the calling process, and obtain information about the child whose state has changed. The execvp() function provides an array of pointers to null-terminated string which contains the argument list for the new program.

Class Descriptions

There's a fundamental class for all the other classes. And all the other classes is derived from the fundamental class. It's name is the Base class. Another important class is Connector class, which will be used as the parent class for different concrete classes. These concrete classes include the OrConnecter class, the AndConnector class and SeparatorConnetor class.

Classes

• CBase

  The common class for all classes. It has a virtual function of execute(), which should be implemented by the derived classes.

• CConnector

  The parent class of other concrete connectors class. It inherits from the base class and will be inherited by other connector classes. Its data memebers are the two sides of objects, which will will implement the theirs functions on runtime. And the other utility functions will be declared in the funtions part, such as the setter and getter funtions, etc.

• CRedirConnector

  The redirection connector class. It will redirect the input and output according to the specific operators.

• CPipeConnector

  The piple connector class. It will implement the pipe function between system calls.

• CSpeparatorConnector

  The semicolon connector class. It will implement the function of the semicolon connector in the input string.

• COrConnector

  The "OR" connector class. It will implment the function of logic disconjunction.

• CAndConnector

  The "AND" connector class. It will implement the function of logic conjuntion.

• CCommand

  The acutal command executor class. It will receive and parse the command and execute the system call.

UML Diagram

Roadmap and Issues

The development of the project is from the bottom to the top. First step is try to parse the single command and then use the connector to operate the final results from individual command.

Contributors

• Shiyou Wang
• Biqian Cheng