Shell Introduction Linux written by what language

1.shell Introduction

The shell itself is a program written in C, which is a bridge for users to use Linux. The shell is both a command language and a programming language. As a command language, it interprets and executes user-entered commands interactively, and as a programming language, it defines variables and parameters and provides many control structures in high-level languages, including loops and branches. Although not part of the kernel of the Linux system, it invokes most of the system's core functions to execute programs, create files, and coordinate the operation of individual programs in parallel. Therefore, for the user, the shell is the most important utility program, in-depth understanding and proficiency in the shell features extremely use of the method is the key to good Linux system.

It can be said that the proficiency of the shell's use reflects the user's proficiency in using Linux.

So, what is a shell?

when a user logs on to a Linux system, the system initialization program Init runs a program called a shell (shell) for each user. So, what is the shell? To be exact, the shell is a command-line interpreter that provides the user with an interface system-level program that sends a request to the Linux kernel to run the program, and the user can start, suspend, stop, or even write some programs with the shell.

when the user is using Linux, it is done by command to complete the required work. A command is the basic unit of a conversation between a user and a shell, which is a string of characters consisting of a newline ending. The shell interprets the commands entered by the user, just as the DOS Command.com do, except that there is only one command.com in DOS, and there are several more popular shells under Linux, each with a different shell. Typical Linux systems use bash as the default shell.

2.linux is mainly written in what language

Linux operating system mainly includes kernel and component system. Most of the kernel is written in C, but some are written in assembly language, because on the hardware, the Assembly has better performance and speed. Some Linux component systems and additional applications are mostly written in C, C + +, Python, Perl, and other languages.

3.unix features

2. Unix system is a multi-user, multi-task time-sharing operating system.

4. UNIX's system structure can be divided into three parts: the operating system kernel (is the UNIX system core management and control center, in the system startup or resident memory), System call (for program developers to invoke system components when developing applications, including process management, file management, device status, etc.), applications (including various development tools, Compilers, network communication handlers, and so on, all applications are managed and controlled by the shell to serve the user).

6. Most Unix systems are written in C, which makes the system easy to read, easy to modify, and easy to transplant.

8. UNIX provides a rich, well-chosen system call, the entire system is very compact and concise implementation.

10. UNIX provides a powerful, programmable shell language (shell language) as a user interface with a concise, efficient feature.

12. The UNIX system uses a tree-like directory structure, which has good security, confidentiality and maintainability.

14. The UNIX system uses the process swap (swapping) memory management mechanism and the request paging storage method, realizes the virtual memory management, greatly improves the memory utilization efficiency.

16. UNIX system provides a variety of communication mechanisms, such as: Pipeline communication, soft interrupt communication, message communication, shared memory communication, signal traffic.

Shell Introduction Linux written by what language