EE209 Assignment 5: A Unix Shell (ish)

Name

• Kwon Larry

Partner

• Worked individually (eligible for Extra Credit 2)

Score

• 110 out of 100 (With Extra credit)

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Description

This project is a minimal but functional Unix shell called ish, developed for KAIST EE209: Programming Structures for EE. It supports interactive command parsing and execution, including:

• Lexical analysis of user input
• Parsing and execution of built-in commands: cd, exit, setenv, unsetenv
• Execution of external commands using fork and execvp
• Pipe (|) support to chain multiple commands
• Signal handling for SIGINT and SIGQUIT
• Initialization with .ishrc file from $HOME
• Error handling with informative messages

Extra Credit

• ✅ Input/output redirection using < and > (Extra Credit 1)
• ✅ Worked individually (Extra Credit 2)

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File Structure

.
├── ish.c                 # Main shell logic
├── lexer.c/.h           # Tokenizer module
├── parser.c/.h          # Command parser
├── executor.c/.h        # Process and execution logic
├── builtin.c/.h         # Built-in command handlers
├── redirection.c/.h     # I/O redirection handling
├── signal.c/.h          # Signal handling (SIGINT, SIGQUIT)
├── dynarray.c/.h        # Dynamic array (from course materials)
├── Makefile             # Build automation script
└── README.md            # Project information

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Build Instructions

To compile the project, run:

make

To clean up build artifacts:

make clean

This will generate the ish executable using gcc209.

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Usage

Start the shell with:

./ish

If a readable .ishrc file exists in $HOME, ish will execute its contents at launch.

After that, you can interactively type commands at the % prompt.

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Features Implemented

Feature	Implemented
Built-in commands	✅
Command execution via execvp	✅
Pipe (`	`) support
Redirection <, >	✅ (Extra Credit 1)
.ishrc parsing	✅
Signal Handling (SIGINT, SIGQUIT)	✅
Memory management (no leaks)	✅
Worked alone (Extra Credit 2)	✅