Environment-what is stored in the environment?

Although shell stores two basic types of data in the environment, there is basically no difference between the two types in bash.

Introduction

Although shell stores two basic types of data in the environment, there is basically no difference between the two types in bash.

The two data types are environment variables and shell variables.

Shell variables are a small amount of data stored by bash. Environment variables are other variables.

In addition to variables, shell functions also store some programming data, that is, aliases and shell functions.

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Check environment

To understand the content stored in the environment, you need to use the set command or printenv program integrated in bash.

The difference is that the set command displays both shell variables and environment variables, while printenv only displays environment variables.

Because the content of the environment may be lengthy, it is best to redirect the output of these two commands to the less command in the form of pipelines.

For example

[Allyes_op @ allyes ~] $ Set

BASH =/bin/bash

BASH_ARGC = ()

BASH_ARGV = ()

BASH_LINENO = ()

BASH_SOURCE = ()

BASH_VERSINFO = ([0] = "3" [1] = "2" [2] = "25" [3] = "1" [4] = "release" [5] = "x86_64-redhat-linux-gnu ")

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View the value of a single variable

[Allyes_op @ allyes ~] $ Echo $ BASH

/Bin/bash

[Allyes_op @ allyes ~] $

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View aliases

[Allyes_op @ allyes ~] $ Alias

Alias l. = 'ls-d. * -- color = tty'

Alias ll = 'ls-l -- color = tty'

Alias ls = 'ls -- color = tty'

Alias vi = 'vim'

Alias which = 'Alias |/usr/bin/which -- tty-only -- read-alias -- show-dot -- show-tilde'

[Allyes_op @ allyes ~] $

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Some interesting environment variables

EDITOR	Program name used for text editing
SHELL	Shell name of the local machine
HOME	Path name of the local main directory
LANG	Defines the character set of the local language
OLD_PWD	Previous working directory
PAGER	Program name used for paging output
PWD	Current working directory
USER	User name