WitsShell - Unix-like Command Line Interpreter

University of the Witwatersrand · School of Computer Science & Applied Mathematics
Course: COMS3010A Shell Project

A simple Unix-like command line interpreter that supports interactive and batch modes, I/O redirection, parallel command execution, and essential built-in commands.

Features

• Interactive & Batch Modes - Run commands interactively or from script files
• Process Management - Uses fork(), execv(), and wait() for command execution
• I/O Redirection - Output redirection with > operator
• Parallel Commands - Execute multiple commands simultaneously with &
• Built-in Commands - exit, cd, and path commands
• Path Resolution - Configurable search paths for executable resolution

Building and Running

Build the Project

make

Run the Shell

# Interactive mode
make run

# Or run directly after building
./witsshell

# Batch mode (run with a script file)
./witsshell <batchfile>

Clean Build Files

make clean

Usage Examples

# Basic command execution
witsshell> ls -la

# Change directory
witsshell> cd /home/user

# Output redirection
witsshell> ls -la /tmp > output.txt

# Parallel command execution
witsshell> ls & echo "hello" & pwd

# Set search path
witsshell> path /bin /usr/bin /usr/local/bin

# Exit shell
witsshell> exit

Built-in Commands

Command	Description	Arguments
exit	Terminates the shell	None
cd <dir>	Changes current directory	Exactly one directory path
path [dir1 dir2 ...]	Sets executable search paths	Zero or more directory paths

Project Structure

The shell implements core Unix shell functionality:

• Command Parsing - Tokenizes input and handles whitespace
• Process Creation - Forks child processes for command execution
• Path Resolution - Searches configured directories for executables
• I/O Redirection - Redirects stdout and stderr to files using >
• Parallel Execution - Runs multiple commands concurrently with &
• Error Handling - Standardized error reporting for all failure cases

License

This project is for educational purposes as part of COMS3010A coursework at the University of the Witwatersrand.