The Extent File System (efs) is Silicon Graphics' early block-device filesystem, widely used on pre-6.0 versions of IRIX. Since 6.0, xfs has been bundled with IRIX and users are being encouraged to migrate to xfs filesystems. IRIX support for efs will be read-only in versions of IRIX beyond 6.5, however efs is still very much in use on SGI software distribution CDs.
Efone is a distributed internet phone system. It features a voice sending/receiving client (an internet phone) and a central server (administered via the Web) where users' information (name, nick, password, current IP) is stored. It resembles a combination of ICQ and Internet phone.
Eev.el is a simple Emacs Lisp library that lets you treat portions of a text file as shell commands, chunks of code for programming languages or as hyperlinks; its intention is to let people record into plain ASCII files their interaction with the computer, and to let them edit and play back any block of code in those files easily. The hyperlinks can point to places in manpages, Info pages and text or HTML files, and they are seen as comments by all programming languages; using them you can place pointers to all relevant online sources of information inside the code.
eDB is a very simple and easy-to-use collection of Perl 5 CGI scripts to perform searches on a flat-file database. Search results are displayed using HTML templates that can be modified to fit the user's needs. Pattern-based searches can be refined by using a range of values of a user-specified field. If desired, search results can be displayed using a paging procedure.
eCos (Embedded Configurable OS) is an open source, configurable, portable, and royalty-free embedded Real Time Operating System. It is written in C++, provides all the usual OS things. You configure the OS so that the parts you don't need aren't loaded to the embedded system. eCos is released under a modified GPL that allows for its use in embedded systems without having to GPL the embedded application.