Lesson 3: Linux Guide
Linux generally has four main parts: kernel, shell, file structure, and utility. Linux kernel
The kernel is the heart of the system, which is a core program for running procedures and management like disks and printers. It accepts commands there and delivers the command to the kernel. 2. Linux shell
The shell is a user interface of the system, providing a user with a user to interact with the kernel. It receives the command input command and feed it into the kernel.
In fact, shell is a command interpreter that explains the command entered by the user and sent them to the kernel. Not only that, but shell has its own programming language for editing of the command, which allows users to write programs consisting of shell commands. The shell programming language has a lot of characteristics of normal programming languages, such as the cyclic structure and branch control structure, etc., the shell program written in this programming language has the same effect as other applications.
Linux provides a visual command input interface (GUI) like Microsoft Windows. It provides a lot of window manager, which is like Windows, with windows, icons, and menus, all management through mouse control. Nowadays, the popular window manager is KDE and GNOME.
Users of each Linux system can have his own user interface or shell to meet their own special shell needs.
Like Linux itself, SHELL also has a variety of different versions. At present, there are mainly the following versions of the shell:
Bourne Shell: It is developed by Bell Lab. Bash: It is a GNU's Bourne Again Shell, which is the default shell on the GNU operating system. Korn Shell: It is the development of Bourne Shell and is compatible with Bourne Shell on most of the content. C shell: is the BSD version of Sun's shell. 3. Linux file structure
The file structure is an organizational method on the storage device stored in the file. Mainly reflected in the organization of documents and catalogs. The directory provides a convenient and effective way to manage files. We can switch from a directory to another, and you can set the permissions of the directory and files, setting the level of sharing files.
With Linux, users can set permissions for directory and files to allow or reject other people to access them. The Linux directory features a multi-stage tree structure, and Figure 1.1 shows this tree level structure. Users can browse the entire system, you can enter any directory where you have authorized enters, access the files there.
The interrelation of the file structure makes the shared data easier, and several users can access the same file. Linux is a multi-user system that stores the operating system itself in a dedicated directory starting with the root directory, sometimes specified as the system directory. The directory in the root directory in Figure 1.1 is the system directory.
The kernel, shell and file structure form a basic operating system structure. They allow users to run programs, manage files, and use systems. In addition, the Linux operating system also has many programs called utility, and secondary users complete some specific tasks.
4. Linux utility
The standard Linux system has a program called utility, which are special procedures, such as editors, executing standard calculation operations, and more. Users can also produce their own tools.
Practical tools can be divided into three categories:
Editor: Used to edit files. Filter: Used to receive data and filter data. Interactive: Allows users to send information or receive information from other users.
The editor of Linux has: ED, EX, VI, and Emacs. ED and EX are line editors, VI and Emacs are full screen editors.
Linux's Filter Reads Enter, checks, and processing data from user files or elsewhere, and then outputs the result. In this sense, they filtered through their data. Linux has different types of filters, and some filter is used to edit commands to output an edited file. Other filters are looking for files by pattern and output partial data in this mode. There are also some execution word processing operations, detect formats in a file, output a formatted file. The filter of the filter can be a file, or the user typed from the keyboard, and can also be the output of another filter. The filter can be connected to each other, so the output of a filter may be an input to another filter. In some cases, users can write their own filter programs. The interactive program is the user's information interface with the machine. Linux is a multi-user system that must keep in touch with all users. Information can be sent or received by different users on the system. There are two ways to send information, one way is to talk to other users one-to-one link, and the other is that a user communicates with multiple users at the same time, the so-called broadcast communication. Lesson 4 Linux development
Linux is an operating system designed for a personal computer. It was the first designed by Linus Torvalds. At that time, Linux was a personal research project in his purpose to design a more effective UNIX PC version for Minix users. Linus Torvalds call it Linux. MINIX is developed by Professor Andrew Tannebaum, published on the Internet, and is used by students around the world. Minix has more Unix features, but is incompletely compatible with Unix, Linus intends to design a more complete UNIX PC version for minix users, issued Linux 0.11 version in 1991, and released it on the Internet, free to use people .
In the next few years, other Linux enthusiasts use their own usage, integrated the features, modifications and add some contents, modifications, and add some content in the existing UNIX standards and UNIX systems, making Linux more perfect.
Linux designs interfaces with all major window managers, providing a large number of Internet tools such as FTP, Telnet, and SLIP.
Linux provides a relatively complete program development tool that is the most commonly used C compiler and debugger.
Although Linux has all the features and features of UNIX, it is the smallest, most stable and fastest operating system. Under the minimum configuration, it can run on only 4MB of memory.
Linux is developed in the Internet Open environment, which is constantly perfect by programmers around the world, and free for users. Despite this, it still follows the standard of commercial UNIX version. Portable operating system interface (PSoix). This standard defines how UNIX systems operates, and the system call has also been specifically discussed. PSOIX limits all UNIX versions must rely on mass standards. The existing general Unix and popular versions are followed by POSIX standards, while Linux follows the POSIX standard from the beginning.
