Atom – terminal text editor

Atom is a hobby text editor implemented in C for Unix-like terminals. It draws inspiration from modal editors such as Vim and focuses on providing a compact codebase that can be compiled with nothing more than a C compiler and the standard POSIX library.

This project is an exercise in building a terminal application from scratch, handling raw terminal I/O, managing file buffers, and implementing a modal user interface without external dependencies.

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Project Structure

.
├── LICENSE
├── Makefile        # Build instructions for the editor
├── README.md       # Project overview and documentation
├── include/        # Header files and additional source modules
│   ├── file_browser.c
│   ├── menu.c
│   └── syntax_highlight.c
└── main.c          # Core editor implementation and terminal helpers

The editor keeps its state in a central Buffer structure that holds the document, cursor position and active mode. Terminal interaction relies on raw-mode configuration via termios and a small set of ANSI escape sequences.

Getting Started

Prerequisites

• A C11-compatible compiler (GCC or Clang)
• A POSIX-compliant environment (Linux, macOS, etc)
• make for building the project

Build

To compile the editor, run the following command in the project root:

make

his will produce an executable file named atom.

Run

To edit an existing file, provide its name as a command-line argument:

./atom test.txt

If you run the editor without any arguments, it will start with an empty buffer and display the main menu.

./atom

Controls

Key(s)	Mode	Action
h,j,k,l	Viewing	Move cursor
i	Viewing	Switch to Insert Mode
Esc	Insert	Return to Viewing Mode
:	Viewing	Switch to Command Mode
Enter	Command	Execute the command
Esc	Command	Return to Viewing Mode
:w + Enter	Command	Save the file
:q + Enter	Command	Quit the editor
:wq + Enter	Command	Save and quit the editor