command line

Mastering the Linux Shell : Killing Processes and Dire Warnings

Today's installment of Mastering the Linux Shell comes with a warning. Actually, it comes with a few warnings. .And a viewer advisory. Well, actually a reader advisory. 

Mastering The Linux Shell - Processes

So what constitutes a process on your Linux system?  The short answer is : Everything

In your long and illustrious career as Linux gurus, you are going to hear a lot about processes, process status, monitoring processes, or even killing processes. Gasp! Reducing the whole discussion to its simplest form, all you have to remember is that any command we run is a process.  Processes are also sometimes referred to as jobs. 

The session program which executes our typed commands (the shell, or terminal if you prefer) is a process.  The tools I am using to write this article such as my desktop, the browser, the server somewhere out on the internet . . . these are creating several processes and sub-processes.  Every terminal session you have open, every link to the Internet, every game you have running, the little clock in the corner; all these programs will generate one or more processes on your system.  In fact, there can be hundreds, even thousands of processes running on your system at any given time.   To see your own processes, try the following command.

Mastering The Linux Shell - Finding Anything

You know how you get those emails that suggest you can find out anything about anyone? They claim to be able to locate any person and tell you who they are, where they are from, the date they were born, and what their background is . . . You'll be happy to know this isn't the subject of this article. It's a lot more fun than that.

Mastering The Linux Shell : Standard In, Out, and Error

Welcome to part four in my Mastering The Linux Shell series where we will wander wistfully into a land where three terribly under-appreciated but vitally important files live. You will remember that everything is a file, including directories which some people call folders. What you may not know is that your keyboard is a file, as is the screen on which you read these words.

Mastering The Linux Shell : Making Things Disappear

Information begets information and eventually, there's just too much of it. I don't really believe that -- I'm an information junkie -- but there's no question that if you never delete anything, eventually, you will either use up all your disk space, or you'll have a terrible mess on your hands.

Mastering the Linux Shell : Files and Directories

Let me tell you the secret of computers, of operating systems, and of the whole industry that surrounds these things: Everything is data. Information is the be all and end all of everything we do with computers. Files are the storehouses for that information and learning how to manipulate them, use and abuse them, and otherwise play with them will still be the point of computers 20 years from now. There's a saying in the Linux world that "everything is a file" (a comment attributed to Ken Thompson, the developer of UNIX). That includes directories. Directories are just files with lists of files inside them. All these files and directories are organized into a hierarchical file system, starting from the root directory and branching out.

For the record, and to make things easier, you can safely assume that folders and directories are the same thing. The terms can be used interchangeably, but I will usually refer to them directories. If you are more comfortable thinking of them as folders, don't worry. Depending on the application, you'll see both terms used.

The root directory (referred to as slash, or /) is actually aptly named. If you consider your file system as a tree's root system spreading out below the surface, you start to get an idea of just what things look like.

Under the root directory, you'll find folders called usr, bin, etc, tmp, and so on.  And then we have the three invisible, often overlooked, but completely indispensible files on your system: standard in, standard out, and standard error. I'll tell you more about those three later. Suffice it to say that understanding and knowing how to work with all these “files” will provide you with amazing flexibility when it comes to doing your work. 

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