get_next_line

Implementation of a function that reads a file descriptor line by line, returning each line on successive calls. This project is part of the 42 curriculum and focuses on static variables, memory management, buffers, and efficient file reading.

Developed at 42 Telefónica by Diego Valladares Ortega.

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🧩 Overview

The goal of this project is to implement the function:

char *get_next_line(int fd);

This function returns the next line read from a file descriptor, including the newline
character \n if present. It must work with:

- Regular files

- Standard input

- Pipes

- Multiple file descriptors at the same time

- Bonus version with independent buffers per fd

The function must be memory safe, handle partial reads, and avoid leaks, double frees, and undefined behavior.

🚀 Features ✔️ Mandatory

Reads one line at a time efficiently

Returns NULL on EOF or error

Preserves leftover buffer between calls

Works with any valid file descriptor

Handles incomplete buffers and lines of any length

✔️ Bonus

Supports multiple fds at once

Each fd keeps its own internal buffer

Works with parallel reads like:

get_next_line(fd1);
get_next_line(fd2);
get_next_line(fd1);

📁 Project Structure

src/
  get_next_line.c
  get_next_line_utils.c
  get_next_line_bonus.c
  get_next_line_utils_bonus.c

include/
  get_next_line.h
  get_next_line_bonus.h

tests/
  main.c
  test1.txt
  test2.txt
  test3.txt
  prueba.txt

Makefile
LICENSE
.gitignore
README.md

🔧 How to Compile Build mandatory version

cc -Wall -Werror -Wextra -Iinclude src/get_next_line.c src/get_next_line_utils.c -c
ar rcs libgnl.a get_next_line.o get_next_line_utils.o

Build mandatory + bonus

make bonus

🧪 Example Test Program

You can test your function using the file in tests/main.c:

cc tests/main.c -L. -lgnl -Iinclude -o test_gnl
./test_gnl

Or test individual files:

./test_gnl tests/test1.txt
./test_gnl tests/test2.txt

You can also test it with standard input:

./test_gnl
<write something>
<press CTRL + D>

📚 What I Learned

File descriptor operations (read)

Handling dynamic buffers and partial reads

Managing static variables in C

String and memory manipulation

Avoiding memory leaks and dangling pointers

Developing scalable logic for multiple file descriptors

Defensive programming and edge-case handling

📄 License

This project is licensed under the MIT License. See the LICENSE file for more details.