Explore the world of Linux in the second act of Linux

Article Title: the second act of Linux exploration enters the Linux World. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
1st judo black belts
　　
Since the previous "legend" was published in some forums, I have indeed received letters from some friends, hoping that I can talk about everything about Linux in more detail, of course, it is not limited to Linux itself. Yes, I want to tell you frankly here that there are too many Linux stories buried in my mind and in my computer hard drive, and these stories are fascinating. Among them, there is Richard Stallman, father of Free Software, Linus Torvalds, father of Linux, and Eric S, the number one theory of free software. raymond, CEO of Red Hat, the largest Linux distributor, Robert Young, founder of Tim o'reilly, the largest publisher of Free Software books, brian behlenddorf, co-founder and core engineer of the Apache community with the highest market share of Web servers, and so on.
　　
Without a doubt, the name of each person listed above carries a wonderful story and a little legend, but the author must be more frank with everyone, if the author puts the stories of these people in the articles in the Linux Exploration Series, so even the pen won't know when to enter the true topic of the Linux Exploration Series-learning Linux technology.
　　
Maybe one day in the future (maybe tomorrow), I will write a series of other articles dedicated to telling these exciting stories, here, we would like to ask you to "be cautious.
　　
Now, let's get started with the topic. Linux is the main character in this series of articles. What is Linux? I believe that you should have known the answer to the first three stories? If you want to introduce others (he or she may not know about Linux at all) to Linux, there is no need to tell such a lengthy story to him, one sentence: Linux is an operating system. What? Still not quite clear? To be more detailed, Linux is a platform that is the same as Windows and can help you complete your work. (Oh, if he or she doesn't even know about Windows, no matter what you do)
　　
I know that someone will ask: Is it better for Linux or Windows? MyGod, is this a classic problem? I think yes, because it is not easy to give a complete answer! So here I can only answer you like this: which is better for Linux and Windows? It depends on what you want to do and who you want to ask.
　　
Of course, the author knows that this is more like a "diplomatic nature" answer, that is, I did not say it. Well, don't worry. At the end of the second screen, I will give you a more accurate answer to satisfy your curiosity.
　　
Let's get to know about Linux: Linux is a free, open source code, and collaborative development UNIX-like operating system that can run on most hardware platforms. It provides a wide range of network support, many of the features required to exchange with other systems and a large number of applications that they own and introduce from other systems.
　　
Oh? Open source code? Our technicians are very excited to see such a word. Is it true? In the city where we are selfish, greedy, and greedy, someone will disclose the source code of a complete operating system? Yes! This is the GNU plan! Great ideal plan, a lifetime dream of many people! GNU is the abbreviation of the word "GNU is Not UNIX" (GNU's Not Unix. -- This recursive naming method is a humorous expression of computer veterans. If you do not understand what is ridiculous, it does not matter. It can only prove that you belong to the majority of people.
　　
Let's take two minutes to get to know the GNU program, although it seems that there is no room for survival in our country! GNU is a project of the Free Software Foundation. This project was started in 1984 with the goal of creating a free, UNIX-like operating system. After many years, they have compiled many GNU tools that are widely used by many commercial UNIX vendors. Of course, system administrators also use these tools to complete their tasks. Linus Torvalds's Linux kernel eventually turned the GNU dream (creating a completely free, UNIX-like operating system) into reality!
　　
Of course, just as if there is God and there will be Satan, there are always people in this world who like darkness. They enjoy the benefits of GNU, but they are not willing to (not sure) themselves) implement the GNU program. Such people exist in our country! And now it is still very "successful ". Let the readers know what it means.
　　
Now I can explain to you the meaning of the title "judo black belt. Think about DOS. Do you still remember this operating system? I met this operating system in 1993. Now, we think that Chinese information and education are indeed lagging behind. At that time, the Windows 3.1 operating system had been put on the market for more than a year, and we had just known Dos, but this was due to our national conditions, understandable and understandable. What impressed me most was that Dos + WPS gave China many more job opportunities! There is also the "Five-stroke style" that has been popular for decades, so many people have the illusion that learning computer is learning typing. It seems that there was also a popular editing tool before WPS, which had something to do with sitcom, but it was hard for me to recall it here due to memory limitations (I am too lazy to check the information ).
　　
DOS features command line operations. Dir, cd, md ...... This is the order of the three commands I learned when I first came into contact with Dos. What about you?
　　
Dear reader, here is what you need to know: In this series of articles, I will put a lot of effort into the command line method. Of course, I know many people like beautiful things, such as fantastic interfaces. However, from the perspective of system management, the command line is actually a rule. It is always effective and flexible. Even through a slow jump-to-modem line, it can manipulate remote systems thousands of kilometers away. Let's face this reality: All graphics are the killer of slowing down network connections.
　　
Another reason is that the beautiful front-end GUI and graphical desktop are indeed good. It allows a new Administrator to complete the task after a small amount of training. But what we should really understand is: in fact, the power comes from what is happening under the surface (that is, under the friendly menu and graphical interface!
　　
Learning to use the command line is like getting a black belt in judo or getting an emergency certificate. However, this does not mean that you suddenly have a solution when encountering obstacles (or opponents), but that you will have confidence and knowledge to protect yourself, or handle it in case of an emergency. Remember: the command line is powerful! Available at any time!
　　
Of course, this doesn't mean we don't want to use graphical things. After all, pretty things are liked by everyone, aren't they? Especially when you are facing timid users, it is no good to put comfortable graphical tools in front of them. Similarly, one thing these users often do is to regard the fantastic window interface as a test of operating system performance. ("I want to fight for hegemony or CS") in this regard, I will also introduce graphical operations.
But I am an honest person and don't want to hide any facts. We still need to tell you that the command line operation is the first and the GUI is the second. After all, many GUI interfaces are actually just a front-end or packaged command line. For experienced system administrators, it is difficult for GUI tools to provide all optional parameters. To provide complete parameters, the GUI operation interface is generally as complicated as the corresponding command line program. The original GUI Design is to simplify operations. Therefore, experienced users basically return to the flexible capabilities of the command line.
　　
Well, I don't want to get into a debate here. After all, whether it's command line or GUI, their common purpose is to complete the work. Each type has its own advantages and disadvantages.
　　
Let's go back to the memories of DOS. Yes, I admit that when I first came into contact with Linux, I did think about how to learn DOS in 1993. Now, I recall DOS again, and I will work with you to learn about Linux Command Line operations through DOS, but it has been a decade. Time flies ......
　　
The second act enters the Linux World.
The beginning of 2nd command lines
　　
If you think you are familiar with basic Linux commands, you do not need to talk about these commands. After all, my article is not a "matrix revolution. ^_^ Of course, readers who want to know about Linux may still want to review the content. After all, what if you miss something? You know, in the world of system administrators, some "missed" means "wrong "! (In fact, in the long river of life, why not? If you miss it, it means you lose it. It's hard to find the old dream. The so-called compensation is often a wishful thinking .) The author will continue with a "bad" habit: Starting from the basic content, how far will it go? It depends on the situation.
　　
The content to be discussed in this article is some of the most basic commands. They will run through all the articles in this series, and will spend a wonderful time with you to use Linux. I hope you can understand how powerful and flexible these commands are, and continue to explore other "hidden" functions of these commands after learning these basic commands. Slight exploration is eager to reveal the real potential of daily commands to you! In Linux, the command line is always an eternal need in the life of the system administrator!
　　
When it comes to the command line, it means we have to get in touch with shell. Now we don't care where the shell comes from and where it will go. Now we only need to know that shell can explain the commands we entered. Is there any trace of DOS in your mind? If so, when you see shell, can you think of the past as well as the author? Yes, you can think of shell as the original DOS prompt. (It does not matter if you forget the appearance of the DOS prompt. In your Windows system, click "start", click "run", and enter "cmd" in the open column. OK, DOS is reproduced. Of course, strictly speaking, it cannot be called DOS in the operating system after Windows 2000, but it should be called "command console", which enhances many DOS commands, you will see it later. In fact, shell is more like a command.com program in the DOS era .)
　　
There are many shell types. We often use BASH shell (Bourne Again ). Note This Again word. If you have already guessed that there should be another shell before this shell, haha, you guessed it! Let's review the history: the first real Unix shell-"sh", also known as the 'Bourne shell', was born in 1975 by Steve Bourne. soon, other shells emerged, such as "ksh" and "zsh" based on the original 'Bourne shell'. The latter is often used as the standard shell in the exclusive Unix system; there are also shell derived from the C language, such as "csh" or "tcsh ".