tarThe term 'tar' stands for 'Tape Archive' and refers to a file format and a corresponding command-line utility used to bundle multiple files and directories into a single archive file. Crucially, `tar` itself is not a compression utility; its primary purpose is to aggregate files while preserving their metadata, such as permissions, timestamps, and directory structures. This makes it an ideal format for distribution, backup, and packaging of software or data.
A `tar` archive is essentially a sequence of file entries, where each entry consists of a header block (containing metadata like filename, size, owner, permissions, and modification time) followed by the actual file data. Directory entries are also stored, ensuring the hierarchy is maintained upon extraction.
Because `tar` only bundles and does not compress, it is very common to combine `tar` archives with compression algorithms. This typically involves piping the output of `tar` to a compression utility like `gzip`, `bzip2`, or `xz`. This results in common file extensions like `.tar.gz` (or `.tgz`), `.tar.bz2`, or `.tar.xz`, which are compressed `tar` archives.
In Rust, the `tar` crate provides robust functionality for working with `tar` archives. It allows developers to:
* Create archives: Bundle files and directories into a new `.tar` file.
* Extract archives: Unpack files and directories from an existing `.tar` file to a specified location.
* Read archive entries: Iterate through the contents of a `tar` archive without necessarily extracting all of them.
* Write archive entries: Add individual files or entire directory trees to an archive, with control over metadata.
When working with compressed `tar` archives (e.g., `.tar.gz`), the `tar` crate is typically used in conjunction with other crates that provide compression/decompression capabilities, such as `flate2` for GZIP, `bzip2` for BZ2, or `xz2` for XZ. These compression crates provide `Read` and `Write` wrappers that can be layered around the underlying `tar::Archive` or `tar::Builder` objects, allowing seamless creation and extraction of compressed archives.
The `tar` format's simplicity and widespread adoption across Unix-like systems make it an essential tool in many software ecosystems, from deployment pipelines to data archival.
Example Code
use std::io::{self, Write, Read};
use std::fs::{self, File};
use std::path::{Path, PathBuf};
use flate2::write::GzEncoder;
use flate2::read::GzDecoder;
use flate2::Compression;
use tempfile::{tempdir, Builder as TempFileBuilder}; // For creating temporary directories
fn main() -> io::Result<()> {
// 1. Setup: Create a temporary directory for source files
let source_dir = tempdir()?;
let file1_path = source_dir.path().join("file1.txt");
let file2_path = source_dir.path().join("subdir/file2.log");
let subdir_path = source_dir.path().join("subdir");
fs::create_dir(&subdir_path)?;
fs::write(&file1_path, "This is the content of file 1.")?;
fs::write(&file2_path, "Log entry 1.\nLog entry 2.")?;
println!("Source directory created at: {}", source_dir.path().display());
println!(" - Created file: {}", file1_path.display());
println!(" - Created file: {}", file2_path.display());
// Define the output tar.gz archive path
let archive_path = TempFileBuilder::new().suffix(".tar.gz").tempfile()?.path().to_path_buf();
println!("Archive will be created at: {}", archive_path.display());
// --- Part 1: Create a .tar.gz archive ---
println!("\n--- Creating .tar.gz archive ---");
create_tar_gz_archive(source_dir.path(), &archive_path)?;
println!("Archive created successfully.");
// --- Part 2: Extract the .tar.gz archive ---
println!("\n--- Extracting .tar.gz archive ---");
let extract_dir = tempdir()?;
println!("Archive will be extracted to: {}", extract_dir.path().display());
extract_tar_gz_archive(&archive_path, extract_dir.path())?;
println!("Archive extracted successfully.");
// --- Part 3: Verify extracted files ---
println!("\n--- Verifying extracted files ---");
let extracted_file1_path = extract_dir.path().join("file1.txt");
let extracted_file2_path = extract_dir.path().join("subdir/file2.log");
assert!(extracted_file1_path.exists());
assert!(extracted_file2_path.exists());
assert_eq!(fs::read_to_string(&extracted_file1_path)?, "This is the content of file 1.");
assert_eq!(fs::read_to_string(&extracted_file2_path)?, "Log entry 1.\nLog entry 2.");
println!("Verification successful: Files exist and content matches.");
// The temporary directories and files will be automatically cleaned up when `source_dir`, `extract_dir`, and `archive_file` go out of scope.
Ok(())
}
/// Creates a gzipped tar archive from a source directory.
fn create_tar_gz_archive(source_path: &Path, archive_path: &Path) -> io::Result<()> {
let tar_gz = File::create(archive_path)?;
let enc = GzEncoder::new(tar_gz, Compression::default());
let mut tar = tar::Builder::new(enc);
// Add the entire source directory to the archive.
// The path argument 'source_path' determines the base directory for the archive entries.
// The `.` indicates that the contents of `source_path` should be added directly at the archive's root.
tar.append_dir_all(".", source_path)?;
// `finish()` consumes the builder and returns the underlying writer (GzEncoder),
// which then needs to be explicitly finished to write the GZIP footer.
tar.into_inner()?.finish()?;
Ok(())
}
/// Extracts a gzipped tar archive to a destination directory.
fn extract_tar_gz_archive(archive_path: &Path, dest_path: &Path) -> io::Result<()> {
let tar_gz = File::open(archive_path)?;
let dec = GzDecoder::new(tar_gz);
let mut archive = tar::Archive::new(dec);
archive.unpack(dest_path)?;
Ok(())
}