Linux Shell Types Simple Introduction

The shell is actually a program that has a special function, mainly to provide a user interface with the kernel to interoperate. It is located between the user interface and the kernel, the workflow is to receive commands entered by the user and interpreted (converted to mechanical code that the computer can understand), and then the command into the kernel to execute. We usually telnet to the system via SSH and open the shell, and there are some ways to open the shell directly on the graphical interface. The latter is mainly used in Ubuntu systems.

Here are some of the most popular or historically existing shell types, the current popular shell has ash, bash, Ksh, CSH, zsh, and so on, different shells have their own characteristics and use.

Use the following command to see which shell programs are installed on the system.

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The current popular

Currently the popular Shell has ash, bash, Ksh, csh, zsh, etc., using different shells because they each have their own characteristics, the following is a simple introduction:

# sh

SH is actually a shortcut.

# Bash

This is the default shell for most Linux systems, and the full name is Bourneagain shell, with 40 commands in total. The included functionality covers almost all of the functionality that the shell has, so a generic shell script specifies that it is the execution path. The first line of the generic shell script is as follows:

#！ /bin/bash

Bash also has a feature that can be viewed with help commands.

# Ksh

Ksh has 42 internal commands, which are somewhat restrictive compared to bash. But Ksh is mainly used for UNIX such as Hp-uinx

#/bin/nologin

This generally means that the user cannot log on.

# Dash

Dash is for running scripts, with more efficiency than bash, but with poor interaction performance. Now it's mostly used on Debian and Ubuntu. Its internal commands and parameters are somewhat different from bash, and some scripts written with the Bash command can be faulted.

# tcsh & CSH

Put Tcsh and CSH together because the two SH is actually the same, TCSH is the csh of the enhanced version, and fully compatible with CSH. As the name implies CSH, is actually a C language style of a shell, its internal command has 52, relatively large. Not much is being used at the moment.

# Pdksh

Pdksh is a shell of Oracle itself, primarily used in Oracle database management. This shell is typically used by DBAs. It does not coexist with ksh, and if Ksh is installed in the system, an error is encountered when installing Pdksh.

# zsh

At last, it introduces one of the largest shell:zsh in Linux. It has 84 internal commands and is more complex to use. In general, the shell is not used.

We'll introduce you to the advantages and limitations of using the shell and shell scripts later.

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Linux Shell Types Simple Introduction