Hopefully, the previous Bash crash course chapter provided more than a hint of the utility and power of Bash. On the other hand, this chapter introduces several bolt-on technologies to make Bash even more extensive when searching for items and text, or automating file explorer/file system operations. 

By itself, Bash is merely a powerful scripting language, but much of Bash's flexibility comes from being able to "glue" other technologies (tools or languages) together to make the output more useful. In other words, Bash is a base platform similar to how some auto/car lovers choose a particular platform before making their modifications. Will a modified car do everything, even with enhancements? Certainly not, but it can make it more powerful or useful in specific cases, and at least provides four wheels for movement.

Not only do common scripts...

Imagine searching for a four leaf clover in a big garden. It would be really hard (and it is still really hard for computers). Thankfully, words are not images and text on a computer is easily searchable depending on the format. The term format has to be used because if your tool cannot understand a given type of text (encoding), then you might have trouble recognizing a pattern or even detecting that there is text at all!

Typically, when you are looking at the console, text files, source code (C, C++, Bash, HTML), spreadsheets, XML, and other types, you are looking at it in ASCII or UTF. ASCII is a commonly used format in the *NIX world on the console. There is also the UTF encoding scheme, which is an improvement upon ASCII and can support a variety of extended characters that were not present in computing originally...

As we saw in the previous section, there was this new concept of recursive functions and the introduction of wildcards. This section will extend upon those same fundamental primitives to create more advanced searches using regexes and globbing.

It will also extend them with a number of built-in Bash features, and some one-liners (nifty tricks) to enhance our searches. In short:

• A wildcard can be: *, {*.ooh,*.ahh}, /home/*/path/*.txt, [0-10], [!a], ?, [a,p] m
• A regex can be: $, ^, *, [], [!], | (be careful to escape this)

Globbing basically refers to a far more computer-eccentric term, which can be simply described in layman terms as extended pattern matching. Wildcards are the symbols used to describe patterns, and regex is short for regular expression, which are terms used to describe the pattern that is to match a series...

After a grueling introduction to the world of wildcards and regexes for searches, we're going to move on to being able to perform some basic mathematical operations at the console. If you haven't already tried, what happens when you run something like the following in the Bash shell? Does it look like this?

$ 1*5
1*5: command not found

Command not found? Certainly, we know the computer can do math, but clearly Bash is unable to interpret mathematical operations in this way. We have to ensure that Bash is able to interpret these operations correctly through the use of:

• The expr command (antiquated)
• The bc command
• POSIX Bash shell expansion
• Another language/program to do the dirty work

Let's try again, but using the POSIX Bash shell expansion:

$ echo $((1*5))
5

We got the expected answer of 5, but where does...

So far, we have seen inkling of the power of commands available in Linux, and some of these are among the most powerful: sed and grep. However, while we can easily use these commands together, sed by itself or even using another very useful command called awk, we can leverage Bash itself to shave time and reduce external dependencies in a portable way!

So, how can we do this? Let's begin with a few examples using this Bash syntax:

#!/bin/bash
# Index zero of VARIABLE is the char 'M' & is 14 bytes long
VARIABLE="My test string"
# ${VARIABLE:startingPosition:optionalLength}
echo ${VARIABLE:3:4}

In the preceding example, we can see a special way of calling special substring functionality using ${...} , where VARIABLE is a string variable within your script (or even global)...

Again, when we need to remove a pesky character or remove sections of strings upon occurrence, we can always rely on these two powerful commands: sed and awk. And while we saw that Bash does indeed have a similar functionality built-in, the full tools are able to offer the same and more complex functionality. So, when should we use these tools?

• When we care less about the speed that might be gained by using the built-in functionality of Bash
• When more complex features are needed (when programming constructs like multi-dimensional arrays are required or editing streams)
• When we are focused on portability (Bash might be embedded or a limited version and standalone tools may be required)

Sometimes, finding the string or the exact data you are looking for is the easy part of your task, but formatting the output data is tricky. For example, here are some situations that have subtle elements that need to be altered:

• Echoing output without the newline terminator (\n)
• Echoing raw hexadecimal (hex) data
• Printing raw hexadecimal values and printable ASCII characters
• Concatenating strings
• Escaping specific characters
• Aligning text
• Printing horizontal rules

In addition to tricks, we can also print values to the screen that are also floats as well (in addition to the recipe for math). Wait, what is a hexadecimal number? Yes, another type of data or at least a representation exists. To understand what hexadecimals are, we first need to remember that computers use binary, which consists of 1s and 0s (ones and zeros...

Great, so you have this awesome script, but it's written in standard English and you would like to target those nice people who speak other languages. In some countries like Canada, they (we) have two official languages: English and French. Sometimes, the dual-language component is enforced with legislature and localized language laws. 

To get around this, let's imagine a scenario where you are an individual who has written a script that prints out specific strings, but in English first. He/she wishes to have all of the strings inside of variables so that they can be swapped in and out dynamically using system language variables. Here are the basics:

• Create a shell script that utilizes gettext and sets the appropriate variables
• Build a po file that contains the necessary...