This appendix lists and describes common Linux file extensions. Also included is a section explaining how to get your system to properly identify a file with no extension, an incorrect one, or one that you are uncertain about.
.tar - an archive file (short for tape archive)
.gz - a compressed file (gzipped)
.tgz - a tarred and gzipped file
.txt - a plain ASCII text file
.html/.htm - an HTML file
.ps - a PostScript file; formatted for printing
.au - an audio file
.wav - an audio file
.xpm - an image file
.jpg - a graphical or image file, such as a photo or artwork
.gif - a graphical or image file
.png - a graphical or image file
.pdf - an electronic image of a document
.rpm - a Red Hat Package Manager file
.conf - a configuration file
.a - an archive file
.lock - a "lock" file; determines whether a program is in use
.h - a C or C++ program language header file
.c - a C program language source code file
.cpp - a C++ program language source code file
.o - a program object file
.pl - a Perl script
.tcl - a TCL script
.so - a library file