Stefan Graupner eFrane

File Magic Numbers

Magic numbers are the first bits of a file which uniquely identify the type of file. This makes programming easier because complicated file structures need not be searched in order to identify the file type.

For example, a jpeg file starts with ffd8 ffe0 0010 4a46 4946 0001 0101 0047 ......JFIF.....G ffd8 shows that it's a JPEG file, and ffe0 identify a JFIF type structure. There is an ascii encoding of "JFIF" which comes after a length code, but that is not necessary in order to identify the file. The first 4 bytes do that uniquely.

This gives an ongoing list of file-type magic numbers.

	// Creates a new promise that automatically resolves after some timeout:
	Promise.delay = function (time) {
	return new Promise((resolve, reject) => {
	setTimeout(resolve, time)
	})
	}

	// Throttle this promise to resolve no faster than the specified time:
	Promise.prototype.takeAtLeast = function (time) {
	return new Promise((resolve, reject) => {

	#!/usr/bin/env bash
	# MIT © Sindre Sorhus - sindresorhus.com

	# git hook to run a command after `git pull` if a specified file was changed
	# Run `chmod +x post-merge` to make it executable then put it into `.git/hooks/`.

	changed_files="$(git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD)"

	check_run() {
	echo "$changed_files" \| grep --quiet "$1" && eval "$2"

	<!DOCTYPE html>

	<title>Beispiel für die Benutzung des Audio-Elements in HTML5</title>

	<audio controls>
	<source src="elvis.mp3">
	<source src="elvis.oga">
	<a href="elvis.mp3">Download (mp3)</a>
	<a href="elvis.oga">Download (Ogg Vorbis)</a>
	</audio>

Stefan Graupner eFrane

File Magic Numbers

Image Files