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mediumiofilesdirectoriesrecursionstd::fs

Directory Traversal

Traversing directories is a fundamental operation when working with filesystems. Whether you're building a file search tool, calculating disk usage, or processing batches of files, you need to navigate directory trees efficiently. Rust's std::fs module provides read_dir() for listing directory contents and metadata() for inspecting file properties.

Reading Directory Contents

The std::fs::read_dir() function returns an iterator over directory entries:

rust
use std::fs;
 
for entry in fs::read_dir("./src")? {
    let entry = entry?;
    let path = entry.path();
    println!("{}", path.display());
}

Each DirEntry provides access to the file's path, name, metadata, and file type without additional system calls for basic information.

Recursive Traversal

To traverse subdirectories, you need to implement recursion yourself. Check if each entry is a directory using entry.file_type()?.is_dir() and recurse into it:

rust
fn visit_dirs(dir: &Path) -> io::Result<()> {
    for entry in fs::read_dir(dir)? {
        let entry = entry?;
        let path = entry.path();
        if path.is_dir() {
            // Recurse into subdirectory
            visit_dirs(&path)?;
        } else {
            println!("File: {}", path.display());
        }
    }
    Ok(())
}

Filtering Files

You can filter entries by extension, name pattern, or other criteria as you iterate:

rust
for entry in fs::read_dir(".")? {
    let path = entry?.path();
    if path.extension().map_or(false, |ext| ext == "rs") {
        println!("Rust file: {}", path.display());
    }
}

Your Task

Implement the following directory traversal functions:

  1. list_files(dir: &Path) -> io::Result<Vec<PathBuf>>
    • List all files (not directories) in a directory (non-recursive)
  2. list_directories(dir: &Path) -> io::Result<Vec<PathBuf>>
    • List all subdirectories in a directory (non-recursive)
  3. list_all_recursive( dir: &Path ) -> io::Result<Vec<PathBuf>>
    • Recursively list all files and directories
  4. find_by_extension( dir: &Path, ext: &str ) -> io::Result<Vec<PathBuf>>
    • Find all files with a given extension (recursive)
  5. find_by_name( dir: &Path, name: &str ) -> io::Result<Vec<PathBuf>>
    • Find all files/directories matching a name exactly (recursive)
  6. calculate_dir_size(dir: &Path) -> io::Result<u64>
    • Calculate total size of all files in a directory (recursive)
  7. count_files_recursive( dir: &Path ) -> io::Result<usize>
    • Count all files in a directory tree

Examples
rust
use std::path::Path;
 
// List only files in a directory
// (not subdirectories or their contents)
let files = list_files(Path::new("./src"))?;
// Returns: ["./src/main.rs", "./src/lib.rs"]
 
// List only immediate subdirectories
let dirs = list_directories(Path::new("./project"))?;
// Returns: ["./project/src", "./project/tests"]
 
// Recursively list everything
let all = list_all_recursive(Path::new("./src"))?;
// Returns all files and directories at all levels
 
// Find all Rust source files
let rust_files = find_by_extension(Path::new("./"), "rs")?;
// Returns all .rs files recursively
 
// Find files or directories named "Cargo.toml"
let cargo_files = find_by_name(
    Path::new("./"),
    "Cargo.toml"
)?;
// Returns all paths ending in "Cargo.toml"
 
// Calculate total size of a directory
let size = calculate_dir_size(Path::new("./src"))?;
// Returns total bytes of all files
 
// Count files in directory tree
let count = count_files_recursive(Path::new("./src"))?;
// Returns number of files (not directories)

Hints
Click here for hints
  • Use std::fs::read_dir(path) to get an iterator over directory entries
  • Each entry from read_dir() is a Result<DirEntry, io::Error> - handle errors with ?
  • Use entry.path() to get the full PathBuf for an entry
  • Use entry.file_type()?.is_dir() or entry.path().is_dir() to check if it's a directory
  • For recursive functions, call the function on subdirectories and combine results
  • Use entry.metadata()?.len() to get the file size in bytes
  • For extension matching, use path.extension().map_or( false, |e| e == ext )
  • For name matching, use path.file_name().map_or( false, |n| n == name )
  • Remember that read_dir() only lists immediate children, not nested contents
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