Linux Basic Concepts-----Environment variables

Shell Environment variables

Shell is also an application, working with user mode

Variable type

Plastic

Floating point Type

Character type

Boolean type

Bash Variable type

Local variable: Valid only for the current shell

Local variables: Valid only for local code snippets (functions)

Environment variable: Expor var_name=value, valid for current shell and child shell

Position variable: $1;$2 ....

Special variables: $?; $!; $$ ....

View environment variables

Printenv

Export

View all variables

Set

Bash's Quotes

Double quotation mark: Weak reference, can realize variable substitution;

Single quotes: Strong references, not replacements, and display of the string itself;

Anti-Quote =$ (): Command Reference

Liezi:

[Email protected] ~]#name=tom

[Email protected] ~]# echo "I is $name"

[Email protected] ~]# I is Tom

[Email protected] ~]# echo ' I is $name '

[Email protected] ~]# I is $name

[Email protected] ~]# date=$ (date +%f-%t)

[Email protected] ~]#Echo $date

[Email protected] ~]# 2014-07-07-17:27:33

Bash features

Variable

Shortcut keys

Command aliases

Command line expansion

Pipeline

Input and output redirection

Programming

Command line completion

Path completion

This article is from the "Hanging Sword" blog, please be sure to keep this source http://sublime.blog.51cto.com/8856101/1439609