Ubuntu: Up and Running

File Extensions

Another difference between Linux and Windows files is that Linux imposes no requirement for program files to use any particular extension, such as .exe or .dll. Instead, each file has an extended set of attributes that tell the operating system what it can do with the file. So, as well as having attributes for read-only, hidden, and system, such as you would use on Windows, there is also an executable attribute.

However, Linux does make good use of file extensions for data files, and they often use full terms such as .html and .jpeg instead the truncated, three-letter versions .htm and .jpg that grew up because of restrictions imposed by early Windows systems. Graphic files such as .gif, .tif, and .png files also retain their extensions, as do many other file types. Table 5-1 lists the main extension types and what they are generally used for in Ubuntu.

Table 5-1. Typical file extensions used in Ubuntu Linux

Extension	Type of file
.0–.9	Help pages for the man program, and old logfiles
.asm	Assembly language program
.au	Audio file
.bmp	Graphic image
.bz2	A file compressed using the bzip2 program
.c	C language program
.class	Java language compiled program
.cfg / .conf	Configuration file
.cc / .cpp	C++ language program
.css	Cascading style sheet
.csv	Comma-separated value data file
.db	Berkeley DB data file
.deb	Debian application package
.diff	File of differences generated by the diff program
.dtd	Document type definition for XML data
.gif	Graphic image
.gz	File compressed using the gzip program
.h	Header ...