If you are new to Linux, file names may look strange to you.
Linux file names may include extensions you haven't seen before,
may have multiple extensions, or may not have any at all. File
names may begin with a "." or may have other
symbols in their names, including spaces. Below are some
guidelines regarding file names in Linux.
3.3.1. File Types
Below are the most common file types in Red Hat Enterprise Linux.
3.3.1.1. 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 or .tar.bz — a tarred
and bzipped file
.tgz or .tar.gz — 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
.gif — a GIF image file
(short for Graphics Interchange Format)
.html or .htm — an HTML
file (short for Hyper Text Markup Language)
.jpg — a JPEG image file
(short for Joint Photographic Experts Group)
.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 (short for X Pixelmap)
3.3.1.3. 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
3.3.1.4. 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
3.3.2. Naming Conventions
3.3.2.1. Dot Files
Files whose name begins with a ".", called
"dot" files, are hidden files. These files can be
viewed in both graphical file managers like
Nautilus and from the shell
prompt, but require an extra step to reveal them. In
Nautilus, select
View => Show Hidden
Files. From a shell prompt, list the files
in your home directory by entering the command ls
-al. If you view the hidden files in your home
directory, you may be surprised by the number of files in
what you thought was an empty directory. These hidden files
are usually configuration files for applications. They are
hidden to prevent accidental changes and to remove clutter from
the user's home directory.
3.3.2.2. Using Spaces in File Names
While Linux allows file names with spaces in them,
manipulating these files from a shell prompt can be quite
cumbersome. The shell prompt expects a space to separate
two files or commands, and may mis-interpret such a
filename. To manipulate files with spaces in their names,
surround the name with quotation marks.
3.3.2.3. Using Symbols in File Names
It is possible to use punctuation marks in your file names.
However, be aware that these special characters have special
meaning to the shell and may cause errors at a shell prompt.
It is generally recommended that you avoid using special
characters in file names for this reason. If you choose to
use file names with special characters, use quotes around
the file names when manipulating them from a shell prompt.
There are a few special characters you cannot use in file names.
You cannot use a "/" — this indicates a
directory. You cannot name a file "." or
"..", for reasons discussed in Section 3.2.1 Paths.
3.3.2.4. Files with Multiple Extensions
Filenames can have multiple extensions. There may be a
"." in the middle of a file name, or there may
actually be multiple extensions. These multiple extensions
usually arise when processing a file through multiple
programs or commands. The most common file type with
multiple extensions is a compressed archive. Compresed
files are discussed in detail in Section 3.4 File Compression and Archiving.
3.3.3. Finding the Correct File Extension
File extensions are not always used, or used consistently.
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. The
file command enables you to see what type
of file it is. Enter file saturday at
a shell prompt. In this example, the command responds with
ASCII text. 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. Refer to Section 4.8 Viewing text files from the shell prompt for more information on
cat, more, and
less. Refer to Chapter 9 Working with Other Text Applications
for more information on gedit and
vi.
