"The Bash shell is available on many Linux and UNIX systems
today, and is a common default shell on Linux. Bash includes
powerful programming capabilities, including extensive functions
for testing file types and attributes, as well as the arithmetic
and string comparisons available in most programming languages.
Understanding the various tests and knowing that the shell can also
interpret some operators as shell metacharacters is an important
step to becoming a power shell user. This article, excerpted from
the developerWorks tutorial LPI exam 102 prep: Shells, scripting,
programming, and compiling, shows you how to understand and use the
test and comparison operations of the Bash shell..."