shells是什么意思英语翻译（Introduction to Shells）

Introduction to Shells

Shells are an essential component of the Unix-based operating systems, but what exactly are they? At its core, a shell is a command-line interface that allows users to interact with the operating system by typing in text-based commands. In simpler terms, it's the software that enables communication between the user and the computer. In this article, we will go over the basics of shells and explore their importance in the Unix-based operating systems.

Types of Shells

There are several types of shells available, including Bourne shell (sh), Korn shell (ksh), C shell (csh), and Bourne-again shell (bash). Different shells have their own set of commands and features, but they all serve the same purpose: to provide a command-line interface for users to interact with the operating system. Many modern Unix-based systems use bash shell as their default shell because of its support for scripting and flexible configuration options. However, users can change their default shell to other options if they prefer different features or syntax.

Bash Shell

Bash shell is probably the most widely-used shell in Unix-based operating systems. It is open-source software and is developed by the GNU Project. Bash offers a wide range of functionalities, such as command-line editing, job control, history, and programmable completion. In addition to running interactive commands, bash is also used for creating shell scripts, which are a series of commands executed in sequence. User-defined functions and aliases can also be created in bash to simplify frequently used commands.

Korn Shell

Korn shell, commonly known as ksh, is another popular shell that's available in Unix-based operating systems. It was developed by David G. Korn at Bell Laboratories and is an enhanced version of the Bourne shell. Ksh offers many features similar to bash, such as command history, line editing, job control, and programmable completion. However, users who are familiar with the Bourne shell syntax will find ksh more comfortable to use than bash because of its structural similarity to the original shell. Ksh also supports advanced programming features such as associative arrays, regular expressions, and floating-point arithmetic.

Conclusion

Shells are a fundamental part of Unix-based operating systems, providing a command-line interface for users to communicate with the system. The different types of shells available provide users with a variety of choices when it comes to syntax and features. Regardless of which shell is used, they all serve the same purpose: to provide a powerful and flexible means of interacting with the operating system through text-based commands.