Learn advanced concepts of Bash shell programming.

Bash Programming

After going through the basics of Bash programming in the previous module, we’ll now learn some important key concepts of Bash, such as tests, exit codes, job controls, traps, subshell, and more. In this module, the interactive nature of the module instills the knowledge in a way we will not forget!

Master the Bash Shell

Bash is a *shell program*.

A *shell program* is typically an executable **binary** that takes commands that you
type and (once you hit return), translates those commands into (ultimately)
system calls to the Operating System API.

> Note:
A binary is a file that contains the instructions for a program, ie it is a ‘program’ file, rather than a ‘text’ file, or an ‘application’ file
(such as a Word document).

If you're not sure what an Operating System API is, then don't worry. You only need to know that
a shell program is a program that allows you to tell the computer what to do. In that way, it's not much different to many other kinds of programming languages.

What makes bash different from some other languages is that it is a language
designed to 'glue' together other programs.

### How Important is this Lesson? 

This lesson will delve into the history of bash. This information isn’t essential for the topics covered in the rest of the course. However, it’ll be useful for a thorough understanding of the subject.


### Other shells

Bash is not the only kind of shell. Other shells include:

- `sh`

- `ash`

- `dash`

- `ksh`

- `tcsh`

- `zsh`

- `tclsh`

You might have heard about some of them or may have used them before. 
The other shells mentioned have different rules, conventions, logic, and
histories meaning they can look similar, however, can differ in subtle ways.

Since other shells are also programs, they can be run from within one another!

In the following code sample you run `tcsh` from within the terminal. Note that you will get a different prompt after the `tcsh` command is run.

Bash is a *shell program*.

A *shell program* is typically an executable **binary** that takes commands that you
type and (once you hit return), translates those commands into (ultimately)
system calls to the Operating System API.

> Note:
A binary is a file that contains the instructions for a program, ie it is a ‘program’ file, rather than a ‘text’ file, or an ‘application’ file
(such as a Word document).

If you're not sure what an Operating System API is, then don't worry. You only need to know that
a shell program is a program that allows you to tell the computer what to do. In that way, it's not much different to many other kinds of programming languages.

What makes bash different from some other languages is that it is a language
designed to 'glue' together other programs.

# How Important is this Lesson? 

This lesson will delve into the history of bash. This information isn’t essential for the topics covered in the rest of the course. However, it’ll be useful for a thorough understanding of the subject.


# Other shells

Bash is not the only kind of shell. Other shells include:

- `sh`

- `ash`

- `dash`

- `ksh`

- `tcsh`

- `zsh`

- `tclsh`

You might have heard about some of them or may have used them before. 
The other shells mentioned have different rules, conventions, logic, and
histories meaning they can look similar, however, can differ in subtle ways.

Since other shells are also programs, they can be run from within one another!

In the following code sample you run `tcsh` from within the terminal. Note that you will get a different prompt after the `tcsh` command is run.

The first lesson gives you a high-level view of what bash is, and a little on its history.



Before We Begin

Core Bash

Scripting Bash

Bash in Practice

Advanced Bash

Conclusion

What is Bash?