Shell Basics Learning (ii) Shell variables

1. Data type:

String

Array

2. Naming conventions for variables:

Can only start with a-Z or a-Z

Cannot have spaces in the middle, you can use _

Punctuation cannot be used

Cannot use the SHELL keyword

3. Variable type:

Environment variables

Local variables

Shell variables

4. String

Strings are the most common and useful data types in shell programming (except numbers and strings, and no other type works well), strings can be in single quotes or double quotes, or without quotes. The difference between single and double quotes is similar to PHP.

Single quotes:

Output exactly as quoted, invalid internal variable, invalid escape character

Double quotes:

Internal variables can be parsed, escape characters can appear

Stitching characters

Name='liupf'echo"$name  Echo " Hello ${name} "　　　　

Get string length

Name="liupf"　　　　echo ${#name}

Intercept string

$name ='liupf'　　　　echo ${name:1:3}

Find sub-string location

　　　　string=My name is LIUPF  echo 'expr'$string" Is  '

Array

1, the shell uses () to represent the array, the elements are separated by a space. The basic form is expressed as:

A, array name = (value 0 value 1 value 2 value N)

B, array name = (

Value 0

···

Value n

）

C, array name [0]= value 0

Array name [...] =··· Value

Array name [n]= value 2

2. Reading the value of an array

${array name [table below]}

3. Get all the values of the array

${array name [@]}

4. Get the length of the array

${#数组名 {@}}

${#数组名 {*}}

${#数组名 {n}}

Shell Basics Learning (ii) Shell variables