🔥💾 INITIATING PROJECT 01_fd_dup_chain_bomb/
Let’s weaponize dup() — turn it into a system-filling, table-clogging, FD-exhausting monster.

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📂 01_fd_dup_chain_bomb

🧠 Purpose:

Explore file descriptor (FD) table duplication limits, FD exhaustion edge behavior, and how dup() can be turned into a chain reaction.

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🧪 What You’ll Learn:

• How dup() allocates the lowest available FD

• How to detect when the system runs out of FDs

• What errors you get from dup() when out of FDs

• How to simulate a controlled FD explosion

• How to recover and cleanup properly

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📄 File Structure:

01_fd_dup_chain_bomb/
├── main.c
├── dup_utils.c
├── dup_utils.h
├── Makefile
├── README.md
└── output.txt

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📄 main.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include "dup_utils.h"
 
#define MAX_FD 65536
 
int	main(void)
{
	int	*fd_list;
	int	i;
 
	fd_list = malloc(sizeof(int) * MAX_FD);
	if (!fd_list)
	{
		perror("malloc");
		return (1);
	}
 
	// Step 1: Open one file
	int fd = open("output.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (fd == -1)
	{
		perror("open");
		return (1);
	}
	dprintf(fd, "Starting FD bomb 💣\n");
 
	// Step 2: Start chaining
	i = 0;
	while (i < MAX_FD)
	{
		int newfd = dup(fd);
		if (newfd == -1)
		{
			perror("dup");
			break;
		}
		fd_list[i] = newfd;
		i++;
	}
	dprintf(fd, "Total dup'd: %d\n", i);
	close(fd);
	cleanup_fds(fd_list, i);
	free(fd_list);
	return (0);
}

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📄 dup_utils.c

#include <unistd.h>
#include "dup_utils.h"
 
void	cleanup_fds(int *fds, int count)
{
	while (--count >= 0)
		close(fds[count]);
}

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📄 dup_utils.h

#ifndef DUP_UTILS_H
# define DUP_UTILS_H
 
void	cleanup_fds(int *fds, int count);
 
#endif

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📄 Makefile

NAME = fd_dup_chain_bomb
 
SRC = main.c dup_utils.c
OBJ = $(SRC:.c=.o)
CC = gcc
CFLAGS = -Wall -Wextra -Werror
 
all: $(NAME)
 
$(NAME): $(OBJ)
	$(CC) $(CFLAGS) -o $@ $^
 
clean:
	rm -f $(OBJ)
 
fclean: clean
	rm -f $(NAME)
 
re: fclean all

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📄 README.md

# 💣 `01_fd_dup_chain_bomb`
 
## 🧠 Overview
This project tests how far you can `dup()` a single file descriptor before the system runs out of FD entries.
 
## ✅ Objectives
- Fill the FD table using chained `dup()`
- Understand `EMFILE` and `ENFILE` failure states
- Benchmark how many FDs your system can handle per process
- Clean up everything and close properly
 
## 📤 Output
Logs to `output.txt`:

Starting FD bomb 💣 Total dup’d: 1024 ← depends on system limits

## 🚨 Warnings
- May exhaust system resources if run with elevated limits
- Check your `ulimit -n` before running

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📄 output.txt

Starting FD bomb 💣
Total dup'd: 1024

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✅ Ready to Build?

cd asymmetric_c/01_fd_dup_chain_bomb
make
./fd_dup_chain_bomb

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Say the word and I’ll queue 02_fd_leak_visualizer/ next.
You’re now building the OS simulator layer by layer.
🔥 Keep going?