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<h1 align="center">WalkDir Minimal - A lightweight, POSIX-only directory walker</h1>
<h3 align="center">A minimal, 100% safe Rust directory walker for POSIX systems that prioritizes determinism and zero dependencies.</h3>
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## 🔍 Overview
`walkdir_minimal` is a **lightweight, POSIX-only directory walker** written in
**100% safe Rust**, designed for **maximum portability**, **robust error handling**,
and **predictable iteration order** across UNIX-like systems.
Unlike the popular [`walkdir`](https://crates.io/crates/walkdir) crate, which
offers extensive configurability and Windows support, `walkdir_minimal` aims to
provide a **clean, dependency-free** and **fully deterministic** implementation
that follows the UNIX filesystem model precisely — no abstractions, no hidden
buffering, no non-POSIX extensions.
## ✨ Key Features
* 🧱 **POSIX-only**: Works on Linux, FreeBSD, OpenBSD, NetBSD, and Solaris.
* ⚙️ **No dependencies**: Implemented using only `std::fs`, `std::path`, and
minimal data structures.
* 🦦 **Lightweight and predictable**: The walker uses a manual stack (no recursion),
allowing predictable memory and performance behavior.
* 🦉 **Configurable options** via `WalkOptions`:
* `follow_links`: whether to follow symbolic links to directories.
* `max_depth`: optional limit on traversal depth.
* 🧠 **Cycle detection**: Detects and prevents infinite loops caused by symbolic
links that form cycles.
* 🚫 **Graceful handling of I/O errors**: Broken symlinks, permission-denied
directories, and other errors are returned as `Err(WalkError::Io)`.
* 🦦 **Filtering**: Supports entry-level filtering with a user-provided closure.
* 🧫 **Deterministic**: The order of traversal follows the order provided by the
filesystem’s `readdir(3)` implementation — consistent across runs on the same system.
* 🧪 **Minimal yet robust**: Designed for projects that require reliable,
low-level control rather than high-level abstraction.
## 🪶 Design Philosophy
`walkdir_minimal` is built under the following principles:
1. **POSIX compliance first** — all filesystem operations map directly to their POSIX
equivalents (`lstat`, `stat`, `opendir`, `readdir`, etc., via Rust’s `std::fs`).
2. **Deterministic behavior** — the iterator never hides errors, skips entries
silently, or spawns threads.
3. **No allocations beyond what’s necessary** — uses `Vec` for the manual stack
and `HashSet` for visited inode/device pairs (loop detection).
4. **No recursion** — prevents stack overflows and maintains stable memory usage
even for deeply nested trees.
5. **Minimalism** — the crate is intentionally limited to features that can be
reasoned about and verified easily.
6. **Transparency** — the API surfaces raw I/O results instead of silently
ignoring or swallowing them.
`walkdir_minimal` embodies **clarity over complexity**. Its goal is not to compete
with feature-rich crates, but to provide a **clean reference implementation**
of a POSIX-only directory walker.
## ⚖️ Comparison with `walkdir`
| Cross-platform | ✅ (Windows, macOS, Linux) | ❌ POSIX only |
| Dependencies | Many (e.g., same-file, winapi) | ❌ None |
| Error handling | Complex iterator states | Simple `Result<Entry, WalkError>` |
| Loop detection | Optional, platform-specific | Deterministic `(dev, ino)` hashing |
| Symbolic links | Optional follow | Optional follow |
| Custom sorting | Supported | Not supported (filesystem order only) |
| Performance | Optimized for general use | Optimized for predictability |
| Safety | 100% safe Rust | 100% safe Rust |
| Recursion | Implicit | Manual stack |
| Binary size | Larger | Tiny |
| Filter API | Supported (`filter_entry`) | Supported |
| Error type | `walkdir::Error` | `WalkError` |
| Metadata caching | Yes | No (on-demand) |
| Thread safety | Yes | No (intentionally minimal) |
## 🦉 Example Usage
```rust
use walkdir_minimal::{WalkDir, WalkError};
fn main() -> Result<(), WalkError> {
for entry in WalkDir::new(".")?.follow_links(false) {
match entry {
Ok(e) => println!("{}", e.path().display()),
Err(err) => eprintln!("Error: {}", err),
}
}
Ok(())
}
```
Output example:
```
.
./src
./src/lib.rs
./src/entry.rs
./src/error.rs
./src/walkdir.rs
```
## 📦 WalkOptions
```rust
#[derive(Clone, Debug)]
pub struct WalkOptions {
pub follow_links: bool,
pub max_depth: usize,
}
```
* **`follow_links`** — When `true`, symbolic links to directories are followed.
* **`max_depth`** — Optional limit to recursion depth. `None` means unlimited.
* The root is always depth `0`.
* Files or subdirectories at one level below are depth `1`, and so on.
## 🔗 Entry API
```rust
pub struct Entry {
path: PathBuf,
depth: usize,
}
impl Entry {
pub fn path(&self) -> &Path;
pub fn depth(&self) -> usize;
pub fn metadata(&self) -> io::Result<fs::Metadata>;
pub fn symlink_metadata(&self) -> io::Result<fs::Metadata>;
pub fn file_type(&self) -> io::Result<fs::FileType>;
}
```
* `metadata()` calls `fs::metadata`, following symlinks.
* `symlink_metadata()` calls `fs::symlink_metadata`, **not** following symlinks.
* `file_type()` reports the symbolic link type correctly.
## 🦉 Error Handling
```rust
pub enum WalkError {
Io(io::Error),
LoopDetected(PathBuf),
}
```
* **`Io(io::Error)`** — Covers all I/O-related errors, including:
* Broken symbolic links (`ENOENT`)
* Permission-denied directories (`EACCES`)
* Filesystem read errors
* **`LoopDetected(PathBuf)`** — Reported when a cyclic symbolic link is
detected (only if loop detection is enabled).
## ⚙️ Default Behavior Summary
| **Broken symlink** | Yields `Err(WalkError::Io)` |
| **Permission denied directory** | Yields `Err(WalkError::Io)` and continues |
| **Loop via symlink** | Yields `Err(WalkError::LoopDetected)` if detection is on |
| **Regular file as root** | Returns file directly, no traversal |
| **Unreadable entry** | Returns `Err(WalkError::Io)` |
| **Exceeds `max_depth`** | Skips entry silently (depth-guarded) |
## 🔍 Technical Details
### 📌 Core Design
`walkdir_minimal` implements a depth-first directory traversal without relying on
any external dependencies, using only POSIX APIs available through Rust’s standard
library. The iterator is built around a manual stack-based traversal that mimics
recursion, avoiding stack overflows for deeply nested directories.
* **Stack-based iteration:** Uses an internal vector of `StackEntry` structs,
each holding an active `ReadDir` handle and its depth.
* **Loop detection:** Uses a `HashSet<(dev, ino)>` to detect and skip cyclic
symlinks, preventing infinite recursion.
* **Filter callbacks:** Optional user-provided closures (`filter_entry`) allow
pruning of the traversal tree dynamically.
* **Error resilience:** Each I/O operation is wrapped in `Result`, and errors
are surfaced as `WalkError` variants (`Io`, `LoopDetected`).
### 📌 Error Handling Philosophy
`walkdir_minimal` follows a **fail-soft** philosophy:
* Broken symlinks are returned as `Ok(Entry)` unless metadata is explicitly requested.
* Directories without permission to read (`EACCES`) return an `Err(WalkError::Io)`,
allowing iteration to continue with the next entry.
* Files disappearing mid-iteration yield `Err(WalkError::Io)` gracefully.
This mirrors `walkdir`’s behavior but keeps it predictable and minimal.
### 📌 Metadata Access
`Entry` deliberately does **not** cache metadata by default. This ensures:
* Minimal memory overhead.
* Consistent behavior with file system changes.
* Full control for users who may wish to query `metadata()` or
`symlink_metadata()` selectively.
```rust
let entry = Entry::new(path, depth);
if let Ok(meta) = entry.metadata() {
println!("File size: {} bytes", meta.len());
}
```
### 📌 Platform Scope
`walkdir_minimal` targets **POSIX systems only** — this includes:
* GNU/Linux
* *BSD family (FreeBSD, OpenBSD, NetBSD, DragonFly)
* Solaris and Illumos
It relies on `MetadataExt` for device/inode access, which is non-portable
to Windows. No attempt is made to support non-POSIX environments.
### 📌 Performance Characteristics
* Single `ReadDir` handle open at a time per stack frame.
* Minimal heap allocations aside from the stack and visited set.
* No synchronization primitives — designed for **single-threaded deterministic traversal**.
* Filtering and loop detection incur negligible overhead for typical file trees.
### 📌 Safety & Reliability
* No unsafe code.
* Uses standard library types exclusively (`HashSet`, `Vec`, `ReadDir`, etc.).
* All system calls are wrapped in safe Rust abstractions.
* Loop detection ensures full reliability even on pathological file systems.
## 📚 Practical Use Cases
* Static analysis tools.
* POSIX-friendly installers and archivers.
* File packers and dependency scanners.
* System recovery tools that must run without external crates.
Example: skipping hidden files and following symlinks safely:
```rust
use walkdir_minimal::WalkDir;
let iter = WalkDir::new("/usr")
.unwrap()
.follow_links(true)
.filter_entry(|e| !e.path().file_name().map(|n| n.to_string_lossy().starts_with('.')).unwrap_or(false));
for entry in iter {
match entry {
Ok(e) => println!("{}", e.path().display()),
Err(err) => eprintln!("Error: {}", err),
}
}
```
## 💡 Why Choose `walkdir_minimal`?
* Ideal for **small binaries**, **system utilities**, and **initramfs tools**.
* Zero build dependencies (fast compile times).
* Deterministic and predictable traversal order.
* Designed to be readable and hackable.
## 🧩 Implementation Notes
* Loop detection uses `(dev, ino)` pairs to identify unique directories.
* When `follow_links` is disabled, symlink loops are naturally impossible.
* `max_depth` limits traversal, excluding deeper entries.
* The iterator yields entries as soon as they are discovered — no preloading
or buffering.
## 🤝 Contributing
Contributions are very welcome! Whether it’s fixing a bug, improving
documentation, or adding new features that align with the minimalist and
POSIX-only philosophy, your input is appreciated.
Please follow these guidelines when contributing:
1. **Keep it minimal** — avoid adding dependencies or non-POSIX abstractions.
2. **Preserve safety** — no `unsafe` code will be accepted.
3. **Document behavior clearly** — especially for error cases and edge conditions.
4. **Add tests** — every feature or bug fix should include a minimal test.
If you find a bug or have a suggestion for improvement:
* Open an issue describing the behavior or proposal clearly.
* Include steps to reproduce (for bugs) or examples (for feature requests).
Pull requests should target the `main` branch and include clear commit messages.
## 🧪 Testing
`walkdir_minimal` includes tests for common scenarios:
* Regular files and nested directories.
* Symbolic link loops and detection.
* Permission-denied directories.
* Broken symbolic links.
* Filtered traversals and depth limits.
Run the test suite with:
```bash
cargo test
```
## 🧱 Project Structure
```
walkdir_minimal/
├── src/
│ ├── lib.rs # Main crate entry
│ ├── entry.rs # Defines the Entry type
│ ├── error.rs # WalkError and error utilities
│ ├── options.rs # WalkOptions definition
│ ├── tests.rs # Unit and integration tests
│ └── walkdir.rs # Core iterator implementation
├── README.md # Project documentation
├── LICENSE # License file (MIT)
└── Cargo.toml # Package metadata
```
## 📜 MIT License
This repository has scripts that were created to be free software.
Therefore, they can be distributed and/or modified within the terms of the ***MIT License***.
> ### See the [LICENSE](LICENSE) file for details.
## 📬 Contact & Support
* 📧 **Email:** [m10ferrari1200@gmail.com](mailto:m10ferrari1200@gmail.com)
* 📧 **Email:** [contatolinuxdicaspro@gmail.com](mailto:contatolinuxdicaspro@gmail.com)
