Custom Shell Implementation

This project is a custom shell implementation designed to replicate basic shell functionality while supporting additional features like command execution, built-in commands, and autocompletion.

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🖥 Running the Shell

To start the shell locally, use the provided script:

./your_program.sh

🔧 How It Works

• The script sets up the execution environment using pipenv.
• It ensures proper error handling (set -e).
• The program is executed via Python using:

pipenv run python3 -u -m app.main "$@"

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🛠 Example Usage

$ echo "Hello, world!"
Hello, world!

$ pwd
/home/user

$ cd /tmp
$ pwd
/tmp

$ type ls
ls is /bin/ls

$ exit 0

🔹 Output Redirection Example

$ ls /tmp > /tmp/listing.txt
$ cat /tmp/listing.txt
file1.txt  file2.txt

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🚀 Features Implemented

✅ Command Execution

• Executes system commands by searching for executables in $PATH.
• Supports both built-in commands and external programs.

✅ Built-in Commands

• echo <args> → Prints arguments to stdout.
• exit <code> → Exits the shell with the given status code.
• pwd → Prints the current working directory.
• cd <dir> → Changes the working directory (supports ~ for home).
• type <cmd> → Identifies whether a command is a built-in or an external executable.

✅ Input Parsing

• Tokenizes user input while handling special cases like quotes and escape sequences.
• Supports redirection (>, 1>, >>, 2> for stdout and stderr).

✅ Output Redirection

• Redirects output to specified files using >, 1>, >> (append mode).
• Redirects error output using 2>.

✅ Autocompletion

• Pressing <TAB> autocompletes commands from:
  • Built-in commands.
  • Executables found in $PATH.
• Displays multiple matches when ambiguous, restoring the original prompt afterward.

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🏗 Project Structure

/app
├── constants.py    # Defines command constants
├── main.py         # Entry point of the shell
├── processor.py    # Handles command execution and parsing
├── utils.py        # Helper functions

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