📜 get_next_line

get_next_line is a 42 project focused on implementing a function that reads a file (or input) one line at a time, regardless of line length or buffer size.
This project reinforces memory management, static variables, and low-level file reading.

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🧠 Goal

Implement the function:

char *get_next_line(int fd);

that returns the next line from a file descriptor:

• Includes the terminating \n (except at end-of-file)
• Uses dynamic memory allocation
• Maintains leftover data between calls using a static variable
• Works efficiently using a configurable BUFFER_SIZE

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📚 Description

✅ Mandatory part

The project must:

• Read text one line per call
• Use only the read() function for input
• Store unfinished data in a static variable
• Return NULL when nothing is left to read
• Handle arbitrarily long lines and any buffer size

🧩 Bonus part

Additionally, the bonus version must:

• Support multiple file descriptors simultaneously
• Keep a separate static buffer for each FD
• Ensure the function remains independent across calls

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⚙️ Compilation

Compile using:

cc -Wall -Wextra -Werror -D BUFFER_SIZE=42 *.c

Examples:

cc -Wall -Wextra -Werror -D BUFFER_SIZE=1 *.c
cc -Wall -Wextra -Werror -D BUFFER_SIZE=1000 *.c

Run:

./a.out file.txt

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🧱 Project Structure

get_next_line/
├── get_next_line.c
├── get_next_line.h
├── get_next_line_utils.c
├── get_next_line_bonus.c
├── get_next_line_bonus.h
├── get_next_line_utils_bonus.c
└── README.md

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🔍 How It Works

📌 Core logic

1. Use read() to fill a temporary buffer.
2. Append this buffer to leftover data stored in a static string.
3. Extract a full line (ending with \n if present).
4. Save the remaining data for the next call.
5. Return the extracted line.

📌 Important details

• The function returns NULL on error or when EOF is reached.
• No global variables allowed.
• Returned lines must be freed by the caller.
• Static variables preserve state between calls.

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⭐ Bonus: Multiple File Descriptors

The bonus version stores leftover data per FD, like:

buffer[3] → leftover from FD 3
buffer[4] → leftover for FD 4
buffer[5] → leftover for FD 5

This allows alternating between descriptors:

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

Each FD continues where it left off.

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🧪 Example Usage

int fd = open("file.txt", O_RDONLY);
char *line;

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

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🧾 Notes

• Must handle very long lines correctly.
• Must compile without memory leaks.
• Must work with files, stdin, and pipes.
• Implementation must follow the 42 Norm.

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📜 License

This project is part of the 42 curriculum and intended for educational use.
Feel free to explore the code, but try to understand it rather than copying it. ✨