This post covers the utilities those start with J. Part of the useful ubuntu utility glossary series.
- jablicator (System Administration) : creates a metapackage with all current packages as the dependencies. So you can edit the dependencies to limit metapackage, or take a snapshot of your packages for easy restoring after an update.
- jardiff (Utilities) : tool to help visualise API differences in JAR files between two different versions of a project.
- jclassinfo (Development) : Reads Java class files and extract useful information from them, such as:
- the classes/methods/constants/fields provided
- their dependencies
- the version of the virtual machine necessary to run them
- a full disassembly of the bytecode
- other attributes
Its main advantage over other similar programs is that it is written in C, which makes it much faster and more suitable for scripting.
- jed (Editors) : A small, fast (faster startup than bash) and powerful text editor.
- jeex (Editors) : A simple hexadecimal editor which allows user to create, open and edit files in hexadecimal, binary, octal and ASCII. The features include insert, delete, copy-and-paste, search and many others. It also shows several information about the opened file, like file mode bits, ownership, last access and modification timestamps, difference with other files.
- jekyll (Ruby Programming Language) : Simple, blog aware, static site generator.
- jets3t (Networking) : The JetS3t toolkit provides several applications for interacting and managing data stored in Amazon Simple Storage Service and Amazon CloudFront content delivery network.
- jhead (Graphics) : Utility for extracting digital camera settings from the Exif format files used by many digital cameras. It handles the various confusing ways these can be expressed, and displays them as F-stop, shutter speed, etc. It is also able to reduce the size of digital camera JPEGs without loss of information, by deleting integral thumbnails that digital cameras put into the Exif header.
- jigl (World Wide Web) : Perl script that generates a static html photo gallery from one or more directories of gif/jpg/png images. It supports themes and is very customizable. It includes the ability to display comments and EXIF info for each image in a simple clean layout.
- jitsi (Networking) : JAVA based VoIP and IM client.
- jnettop (Networking) : Traffic visualizer. Captures network traffic information and displays streams sorted by bandwidth they use. Result is a nice listing of communication on network by host and port, how many bytes went through this transport and the bandwidth it is consuming.
- john (System Administration) : John the Ripper is a tool designed to help systems administrators to find weak (easy to guess or crack through brute force) passwords, and even automatically mail users warning them about it, if it is desired.
Besides several crypt(3) password hash types most commonly found on various Unix flavors, supported out of the box are Kerberos AFS and Windows NT/2000/XP/2003 LM hashes, plus several more with contributed patches.
- jp2a (Graphics) : Small utility that converts JPG images to ASCII using libjpeg. jp2a is very flexible. It can use ANSI colors and html in output. jp2a can also download and convert images from the internet via the command line.
- jpegjudge (Graphics) : Try to determine which same picture was saved at a higher quality even if the picture was saved at low quality and later at a higher quality.
- jpegoptim (Graphics) : Optimize or compress jpeg files. Supports lossless optimization, which is based on optimizing the Huffman tables. So called, “lossy” optimization (compression) is done by re-encoding the image using user specified image quality factor.
- juffed (Editors) : Text editor written using the Qt 4 toolkit and the QScintilla library. It supports most features found in modern text editors, including syntax highlighting, bracket matching, switching encodings, sessions, and a plugin API.
- junit (Development) : a simple framework for writing and running automated tests for JAVA.