Simple Shell

Overview

This project is a Simple Shell implementation written in C, designed as part of CMPT 201 coursework. The shell provides basic functionality for executing commands, supports internal commands, handles background processes, manages a command history, and gracefully deals with signals like CTRL-C.

Code Structure

  a8
  |-- CMakeLists.txt
  |-- include
  |   \-- *.h
  |-- gtest
  |   \-- (test source)
  \-- src
      \-- *.c

Features

• External Command Execution
  • Executes standard Linux commands.
  • Supports both:
    • Foreground execution (waits for completion).
    • Background execution (with & at the end).
• Internal Commands The shell supports the following built-in commands:

Internal Commands

Command	Description
exit	Exits the shell (no arguments allowed).
pwd	Prints the current working directory.
cd	Changes directories with support for ~, -, and the home directory.
help	Provides information about internal commands.
history	Displays the last 10 commands executed.

History Feature

Feature	Description
Command Tracking	Keeps track of the last 10 commands (including background commands).
!!	Repeats the last command.
!n	Repeats the command with number n.

Signal Handling

Signal	Behavior
CTRL-C (SIGINT)	Prevents the shell from terminating and displays **hel

Error Handling

Standard error messages are handled using provided macros (msgs.h) to ensure proper output. Errors such as:

• Invalid command
• Forking issues
• Directory errors
• Invalid history requests ...are all covered.

Example Usage

/home/user$ ls -la
/home/user$ cd ~/projects
/home/user$ history
/home/user$ !!     # Repeats the last command
/home/user$ !5     # Repeats the command with history number 5
/home/user$ cat file.txt &

Acknowledgment

Created by Mohamed Hefeeda, modified by Brian Fraser, Keval Vora, Tianzheng Wang, and Steve Ko.