Get Next Line

Description

A C implementation of the get_next_line function that reads a line from a file descriptor. This project handles efficient line-by-line reading from files, with support for multiple open file descriptors simultaneously. The implementation manages dynamic memory allocation to accumulate and return complete lines, regardless of buffer size.

Technologies & Concepts

• File descriptor handling in C
• Static variable usage for state persistence across function calls
• Dynamic memory allocation and management
• Efficient buffer handling for incremental reading
• Boundary case handling (empty files, no newline, multiple consecutive newlines)

Installation

git clone https://github.com/fabbbiodc/get_next_line.git
cd get_next_line

Usage

make        # Compile mandatory version
make bonus  # Compile bonus version (multiple fd support)

Include the header and call the function:

#include "get_next_line.h"

char *line = get_next_line(fd);
while (line != NULL)
{
    printf("%s", line);
    free(line);
    line = get_next_line(fd);
}

Testing

The project includes built-in test targets:

make test   # Run mandatory tests
make test_b # Run bonus tests (multiple fd)

Compilation

Command	Description
make	Compile mandatory version
make bonus	Compile bonus version (multiple fd)
make clean	Remove object files
make fclean	Remove all build artifacts
make re	Full rebuild

How It Works

The get_next_line function reads from a file descriptor one line at a time:

1. Reading - Uses read() with a configurable BUFFER_SIZE to fetch data incrementally
2. Accumulating - Stores residual data in a static variable to preserve state between calls
3. Extracting - Identifies newline boundaries and returns complete lines
4. Cleanup - Returns NULL when EOF is reached and frees remaining memory

The bonus version extends this to handle multiple file descriptors simultaneously by maintaining a separate static buffer for each fd.

Key Features

• Configurable Buffer Size - Compile with -D BUFFER_SIZE=<value> to tune read performance
• Multiple File Descriptor Support - Bonus implementation reads from several open files concurrently
• Memory Safe - Properly handles allocation, reallocation, and cleanup of line buffers
• Edge Case Handling - Handles empty files, files without trailing newlines, and consecutive newlines

Project Structure

get_next_line/
├── get_next_line.c             # Main implementation
├── get_next_line.h             # Header file with prototype and BUFFER_SIZE
├── get_next_line_utils.c       # Utility functions (strchr, strdup, join)
├── get_next_line_bonus.c       # Bonus implementation (multiple fd support)
├── get_next_line_bonus.h       # Bonus header
├── get_next_line_utils_bonus.c # Bonus utilities
├── test_mandatory.c            # Mandatory tests
├── test_bonus.c                # Bonus tests
├── test1.txt                   # Test file 1
├── test2.txt                   # Test file 2
└── Makefile                    # Build & test automation

Tech Stack

• Language: C
• System Calls: read(), malloc(), free()
• Build: Makefile with configurable BUFFER_SIZE

Resources

• The read() System Call - Core system call used for reading
• Static Variables in C - Key concept for state persistence
• Dynamic Memory Management - malloc, realloc, and free reference