4.2. Identifying and Working with File Types
If you are new to Linux, you may see certain file types that you do not recognize because of their unfamiliar extension. A file's extension is the last part of a file's name after the final dot (in the file sneakers.txt, "txt" is that file's extension).
Here is a brief listing of file extensions and their meanings:
4.2.1. Compressed and Archived Files
.bz2 — a file compressed with bzip2
.gz — a file compressed with gzip
.tar — a file archived with tar (short for tape archive), also known as a tar file
.tbz — a tarred and bzipped file
.tgz — a tarred and gzipped file
.zip — a file compressed with ZIP compression, commonly found in MS-DOS applications; most compressed files for Linux use the gzip compression, so finding a .zip archive for Linux files is rare
For information on working with bzip2, gzip, and tar files, refer to Section 4.3 File Compression and Archiving.
4.2.2. File Formats
.au — an audio file
.gif — a GIF image file
.html/.htm — an HTML file
.jpg — a JPEG image file
.pdf — an electronic image of a document; PDF stands for Portable Document Format
.png — a PNG image file (short for Portable Network Graphic)
.ps — a PostScript file; formatted for printing
.txt — a plain ASCII text file
.wav — an audio file
.xpm — an image file
4.2.3. System Files
.conf — a configuration file; configuration files sometimes use the .cfg extension, as well
.lock — a lock file; determines whether a program or device is in use
.rpm — a Red Hat Package Manager file used to install software
4.2.4. Programming and Scripting Files
.c — a C program language source code file
.cpp — a C++ program language source code file
.h — a C or C++ program language header file
.o — a program object file
.pl — a Perl script
.py — a Python script
.so — a library file
.sh — a shell script
.tcl — a TCL script
But file extensions are not always used, or used consistently. So what happens when a file does not have an extension, or the file does not seem to be what the extension says it is supposed to be?
That is when the file command can be helpful.
For example, you find a file called saturday without an extension. Using the file command, you can tell what type of file it is by typing:
file saturday |
In the example, the command file saturday displays ASCII text, telling you it is a text file. Any file that is designated as a text file should be readable by using the cat, more, or less commands, or by using a text editor such as gedit or vi.
 | Tip |
|---|---|
To learn more about file, read the man page by typing man file. |
For more information on helpful commands for reading files, refer to Chapter 3 Shell Prompt Basics.