Installation guide

Chapter 12. Managing Files and Directories 125
12.2.3. System Files
• .conf — a configuration file
• .lock — a lock file; determines whether a program or device is in use
• .rpm — a Red Hat Package Manager file used to install software
12.2.4. 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
• .so — a library file
• .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 instance, 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
It will display ASCII text, telling you it is a text file. Any file that is designated a text file should be
readable using the cat, more, or less commands.
Tip
To learn more about file, read the man page by typing man file.
For more information on helpful commands for reading files, see Chapter 11.
12.3. File Compression and Archiving
Sometimes it is useful to store a group of files in one file so that they can be backed up, easily
transferred to another directory, or even transferred to a different computer. It is also sometimes useful
to compress files into one file so that they use less disk space and download faster.
It is important to understand the difference and relationship between an archive file and a compressed
file. An archive file is a collection of files and directories that are stored in one file. The archive file
is not compressed — it uses the same amount of disk space as all the individual files and directories
combined. A compressed file is a collection of files and directories that are stored in one file and
stored in a way that uses less disk space than all the individual files and directories combined. If you
do not have enough disk space on your computer, you can compress files that you do not use very