Shell Common Sense

　　

 1 #!/bin/bash 2: <<! 3 #使用变量 4 Your_name= "QINJX" 5 echo $your _name 6 echo ${your_name} 7 #只卖变量 8 myurl= "HT tp://www.w3cschool.cc "9 readonly myurl myurl=" http://www.runoob.com "one #删除变量 unset Variab                                  Le_name #数据类型: Numbers and strings #定义字符串 str1= ' This is a string ' #单引号里的任何字符都会原样输出, the variable in the string is not valid for str2= "Hello, I know your is \" $str 1\ "! \ n "#双引号里可以有变量和转义字符 #读取字符串长度 string=" ABCD "Echo ${#string} # Output 4 #分割提取子字符串 string= "Runoob is a great site" "Echo ${stri                 Ng:1:4} # Output Unoo, 4 characters starting from the 2nd character of the string: #查找子字符串 string= "Runoob is a great company" 26 echo ' expr index ' $string ' is ' # output 8 27! : <<! #数组 #定义数组 array_name= (value0 value1 value2 value3) #或者 array_name= (VALUE0 35                 Value1 value2 Notoginseng value3 38) 39                         #单独定义各数组变量 Rray_name[0]=value0 array_name[1]=value1 #读取数组 43                 Valuen=${array_name[n]} #读取单个数组44 echo ${array_name[@]} #读取多个数组 45                         #数组的长度 46 # Gets the number of array elements length=${#array_name [@]} 48                         # or length=${#array_name [*]} 50 # Gets the length of the array single element 51                 lengthn=${#array_name [n]} #基本运算 #加算 val= ' expr 2 + 2 ' 55 echo "Sum of two numbers: $val" #减算 "expr $a-$b ' \* #乖算 ' expr $a ' 6        0 #除算 61         ' Expr $b/$a ' #除余 "expr $b% $a ' a= #赋值 66 #相等 [$a = = $b] #返回布尔值 #不相等 [$a! = $b] #返回布尔值 70!         #if判断 a=10 b=20, if [$a! = $b] and echo "A not equal to B" 77  Fi 78 79 80

　　

Shell Common Sense