In this class, we learn and gain experience with File Descriptor, socket file and redirection.

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The students are expected to have a Linux system available, also be capable of opening a terminal. I have a classes that provided detailed instruction for those who are completely new to Linux

Installing and running Linux on a USB drive.
The basics command line
What does it mean: Everything is a file.

The following commands are used through out the videos, click on the link for more information, only basic details about the commands are provided in this video.

Learning resources for subject at hand:
Detailed introduction to I/O and I/O Redirection
TCP/UDP Socket
Process Substitution

Before we get to play in our terminal, we have to first glance at a few required topics:

File Descriptor and Data Stream
Learn the basic of what file descriptor are, and data stream.
There are reserved and default file descriptor that allows us to manipulate the data stream. We can also create our own. We also looks at what data streams are and perform a simple redirection.
Redirecting stdout & stderr
In the previous session we proved that there are 2 data stream leaving a process by piping stdout. Now we look in more details how to redirect stdout & stderr
Basic of redirection https://www.gnu.org/software/bash/manual/html_node/Redirections.html
Here we look more into the redirection symbols with some input & output redirection and how to use file descriptor to redirect.

After we have the basics with the above subject, we can enter the practical section.

Creating and using file descriptor
In this practical session, we create local file description, we create some for reading, writing and both. We demonstrate the scope of file descriptor, we test and see what happens if a file is deleted while descriptors are still pointing to it.
How to open a socket
Here we do a quick demonstration to show how we open a socket.
Introduction to netcat
In order to open a socket to a remote computer, the remote computer needs to be listening to that port. Here I introduce you to netcat. Netcat will be our listener for all our exercise. More information on NetCat can be found here: https://en.wikipedia.org/wiki/Netcat
In this practice session we create a 2 way messaging stream. Messages received gets stored in a temporary file. Bash alias is used to retrieve unread messages on demand.
How to quickly transfer directory tree to another computer.
Here we use tar, netcat, file descriptors and socket to transfer a directory and all its content from 1 computer to another.
Input process substitution
Learn about process substitution and practice input process substitution.

Eric Simard

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