File Metadata

std::fs::Metadata represents the filesystem attributes of a file, directory, or symbolic link—including its byte length, entry type (FileType), permissions (Permissions), and modification/access/creation timestamps (SystemTime).

Three Ways to Query `Metadata` (Symlink-Following vs. Non-Following)

Function / Method	Follows Symbolic Links?	OS Syscall Equivalent	When to Use
`fs::metadata(path)`	Yes (queries the target of a symlink; fails with `NotFound` on a broken symlink)	`stat` (Unix) / `GetFileAttributesEx`	Inspecting the actual file a path resolves to
`fs::symlink_metadata(path)`	No (queries the symlink entry itself!)	`lstat` (Unix)	Detecting symlinks (`meta.is_symlink()`) or inspecting broken symlinks
`file.metadata()`	Queries the already-open file descriptor	`fstat` (Unix)	Avoids path lookup overhead and TOCTOU path races when a `File` is already open!

Given Symlink: `latest.log -> app-2026.log` (1,024 bytes)

  `fs::metadata("latest.log")`
    +-- Follows symlink to `app-2026.log`:
        `.is_file() == true`, `.is_symlink() == false`, `.len() == 1024`

  `fs::symlink_metadata("latest.log")`
    +-- Inspects symlink entry itself:
        `.is_file() == false`, `.is_symlink() == true`

Key Methods on `std::fs::Metadata`

Method	Return Type	Description
`.len()`	`u64`	Size of the file in bytes
`.is_file()`	`bool`	`true` if regular file
`.is_dir()`	`bool`	`true` if directory
`.is_symlink()`	`bool`	`true` if symbolic link (only possible via `fs::symlink_metadata` or `DirEntry::metadata`!)
`.file_type()`	`FileType`	Detailed file type (extensible via `std::os::unix::fs::FileTypeExt` for sockets/FIFOs/devices)
`.permissions()`	`Permissions`	Read-only flag and OS permission mode
`.modified()`	`io::Result<SystemTime>`	Last modification timestamp (`mtime`)
`.accessed()`	`io::Result<SystemTime>`	Last access timestamp (`atime`)
`.created()`	`io::Result<SystemTime>`	Creation / birth timestamp (`btime`, supported on macOS, Windows, and modern Linux `statx`)

use std::fs::{self, File};
use std::io::{self, Write};
use std::time::SystemTime;

fn main() -> io::Result<()> {
    let path = std::env::temp_dir().join("rust_ch50_metadata_demo.txt");

    {
        let mut f = File::create(&path)?;
        f.write_all(b"0123456789ABCDEF")?;
        // Query metadata directly on the open file descriptor (`fstat`):
        let fd_meta = f.metadata()?;
        println!("via file.metadata() -> len = {} bytes", fd_meta.len());
    }

    let meta = fs::metadata(&path)?;
    let modified_age = SystemTime::now()
        .duration_since(meta.modified()?)
        .unwrap_or_default();

    println!(
        "is_file: {}, is_dir: {}, is_symlink: {}, modified <= 5s ago: {}",
        meta.is_file(),
        meta.is_dir(),
        meta.is_symlink(),
        modified_age.as_secs() <= 5
    );

    fs::remove_file(&path)?;
    Ok(())
}

via file.metadata() -> len = 16 bytes
is_file: true, is_dir: false, is_symlink: false, modified <= 5s ago: true

Three Ways to Query Metadata (Symlink-Following vs. Non-Following)

Key Methods on std::fs::Metadata

Three Ways to Query `Metadata` (Symlink-Following vs. Non-Following)

Key Methods on `std::fs::Metadata`