The latest articles on Forem by Iván Naranjo Ortega (@ivannaranjo999). https://forem.com/ivannaranjo999 https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3909543%2F5c3bc8af-744d-4ede-99dc-15bd64b3000e.jpeg https://forem.com/ivannaranjo999 en Iván Naranjo Ortega Sun, 03 May 2026 08:26:44 +0000 https://forem.com/ivannaranjo999/i-build-a-simple-file-archiver-in-c-sar-535b https://forem.com/ivannaranjo999/i-build-a-simple-file-archiver-in-c-sar-535b <p>I wanted to sharpen my file management skills in C, not just reading and writing, but also creating, seeking, metadata preservation and compression/decompression with <strong>zlib</strong>. So I built <strong>SAR</strong> (<strong>Simple ARchiver</strong>), a command-line tool to pack and unpack files and directories to a single archive, with optional gzip compression.</p> <p>It's heavily inspired by <em>tar</em>, but stripped down to the essentials. Just a clean binary and a list of focused actions to perform in this archives, compressed or not.</p> <h2> The format </h2> <p>The archive, <code>.sar</code> format, is just a binary file which consists of a secuence of blocks:</p> <p><code>[ FileHeader | raw bytes ][ FileHeader | raw bytes ] ...</code></p> <p>Each <code>FileHeader</code> is a fixed-size C struct that stores the filename, file size, permissions and modification timestamp. To read the archive you just walk it linearly: read header, skip forward by file size bytes and repeat until EOF.</p> <h2> Compression </h2> <p>When using <code>pz</code>, SAR compresses the entire archive using zlib's deflate into a standard gzip envelope, the same format produce by <code>gzip</code> tool. This means you can actually decompress SAR compressed files, <code>.sgz</code> or <code>.sar.gz</code>, with <code>gunzip</code> if desired.</p> <p>Compression if applied to the whole SAR archive after packing, not per file. This gives better compression ratios.</p> <p>For all other actions, SAR detects whether the archive is compressed or not.</p> <h2> Dependencies </h2> <p>The only dependency is zlib. </p> <h2> Final thoughts </h2> <p>This project is <a href="https://github.com/ivannaranjo999/sar" rel="noopener noreferrer">on Github</a>, feedback is very welcome! 🐦.</p> <p>Happy to answer questions about the implementation, this was a great exercise in low-level file management and I am starting to use it as an real alternative to <code>tar</code> myself.</p> linux c tooling opensource