42 – Exam Rank 04 Practice 🧪

Practice solutions for 42 Exam Rank 04 in C (ft_popen, picoshell, sandbox, argo, vbc). Personal study repo, not for cheating during the exam.

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⚠️ Disclaimer

This repository is only for personal study and revision:

• It is not an official 42 resource.
• It is not meant to be used during the actual exam.
• Please respect your campus rules and the spirit of the project.

Use it to understand concepts, re-implement exercises on your own, and build your muscle memory in C.

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📂 Repository Structure

The repository is organized by exam level and assignment:

exam-rank-04/
├── level-1
│   ├── ft_popen/
│   ├── picoshell/
│   └── sandbox/
└── level-2
    ├── argo/
    └── vbc/

Each directory contains my practice implementation and simple test code.

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🧩 Exercises Overview

level-1 / ft_popen

A minimal version of popen:

• Spawns a child process with fork + execve / execvp.
• Connects the child’s stdin/stdout to a pipe.
• Returns a file descriptor to read from or write to.
• Teaches pipes, file descriptors, and basic process control.

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level-1 / picoshell

A tiny shell pipeline executor:

• Executes a sequence of commands connected by pipes.
• Uses pipe, fork, dup2, execvp, wait.
• Goal: reproduce cmd1 | cmd2 | ... | cmdN behaviour in a minimal way.

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level-1 / sandbox

A small “sandbox” runner:

• Runs a user function / command with a time limit.
• Handles signals and timeouts.
• Practice for fork, alarm / timers, waitpid, and exit statuses.

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level-2 / argo

A lightweight JSON parser into a custom structure:

• Parses a limited subset of JSON (objects, arrays, strings, numbers, etc.).
• Builds a simple in-memory representation (AST / tree).
• Focuses on parsing, validation, and error handling.

⚠️ IMPORTANT: argo implementation is NOT included in this repository.

🚫 Reason: reports indicate this exercise is no longer present in recent exams and the author hasn't encountered students who received it. The subject.txt is kept for reference.

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level-2 / vbc

A minimal expression evaluator:

• Parses and evaluates arithmetic expressions like: 1 + 2 * (3 + 4)
• Handles operator precedence and parentheses.
• Good exercise for recursive descent parsing and integer arithmetic.

⚠️ NOTE: vbc workflow

🔧 The exercise is to fix the provided given_code.c (found in level-2/vbc/) — implement missing parts or correct bugs so the program works as intended.

🔍 To clearly see what changed between the broken "given" version and your fixed implementation, use an online diff tool such as Diffchecker: https://www.diffchecker.com/text-compare/ — it highlights line-by-line differences and makes reviewing fixes much easier.

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🛠️ Build & Run

All projects are built and run via the root Makefile.

From the repository root:

# Build all binaries (ft_popen, picoshell, sandbox, argo, vbc)
make

# Build a single project
make ft_popen
make picoshell
make sandbox
make argo
make vbc
make ft_popen_short
make picoshell_short

# Build and run a single project
make run_ft_popen
make run_picoshell
make run_sandbox
make run_argo
make run_vbc
make run_ft_popen_short
make run_picoshell_short

# Clean object files and binaries
make clean   # remove all .o files
make fclean  # remove .o files and all binaries
make re      # full rebuild (fclean + all)

All commands above must be run from the root directory of the repository.

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📖 How I Use This Repo

• Re-implement functions from scratch without copy-paste.
• Add small test mains for each exercise.
• Try to solve with limited functions, just like in the exam.
• Refactor until the code is clean, readable and robust.

If you are a 42 student: Treat this repo as a reference and practice ground, not as something to memorize. The real skill for the exam is being able to write these functions again under pressure.

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