A feature-rich Unix shell implementation in C with support for job control, piping, I/O redirection, and signal handling.

• Built-in Commands: cd, pwd, echo, ls, pinfo, history, jobs, fg, bg, sig, repeat
• Process Management: Run commands in foreground or background (append &)
• I/O Redirection: Input (<), output (>), and append (>>)
• Piping: Chain commands with |
• Job Control: Manage background processes with jobs, fg, bg
• Signal Handling: Ctrl-Z (SIGTSTP) and Ctrl-C (SIGINT) for process control
• Command History: Access last 20 commands with history

# Build the shell
make

# Run the shell
./shell

# Run command in background
sleep 10 &

# I/O redirection
cat < input.txt > output.txt
echo "append" >> file.txt

# Piping
ls -l | grep ".c" | wc -l

# Job control
jobs                    # List background processes
fg 1                    # Bring job 1 to foreground
bg 2                    # Resume job 2 in background
sig 9 1234              # Send signal 9 to PID 1234

# Built-in commands
cd ~                    # Change to shell's root directory
cd -                    # Return to previous directory
pinfo 1234              # Show process info for PID 1234
repeat 3 echo hello     # Execute command 3 times

The project is organized into feature-based modules:

• core/ - Core shell logic (execute, parse, prompt)
• builtins/ - Built-in commands (cd, pwd, echo, ls, pinfo, history, repeat, jobs, fg, bg, sig)
• io/ - I/O operations (redirect, piped_command)
• process/ - Process management (list for background jobs)
• signals/ - Signal handlers (handler1, handler2, handler3)
• utils/ - Utility functions (read_details, pinfo2)

The Makefile automatically compiles all files across these directories.

• Root directory: The shell uses its execution directory as the root (~). All relative paths resolve against this directory.
• Signal handling: Ctrl-Z (SIGTSTP) and Ctrl-C (SIGINT) affect foreground processes only; the shell itself is protected.
• Command history: History is maintained for the current session only (last 20 commands). It does not persist across shell restarts.
• Background processes: Each background process gets its own process group and is tracked until completion.