Shell basic Syntax (iii)

For statement

Basic format:

For variable name in condition; Do ...; Done

Example: Traversing a directory or file

#!/bin/bashcd/etc/# #脚本中如果查询的目录在多级目录下, first go to the directory, or directly with the absolute path for a in ' ls/etc/' # #遍历目录do if [-D $a ] # #一个一个的去判断是否为目录 then ls-d $a # #如果是目录, view the files and subdirectories in the directory below Fidone

While statement

Basic format:

While condition;

Do ...;

Done

Example: real-time monitoring of load-sending messages

#!/bin/bashwhile: # #: Represents the perpetual loop, and true one meaning do load= ' w|head-1|awk-f ' load average: ' {print $} ' |cut-d.-f1 ' If [ $load-gt]then top|mail-s "Load is High: $load" [email protected] # #这里也可以执行python发邮件的脚本fisleep 30done

Break

Jump out of the loop and execute the instructions after the loop code.

Continue

Skip this cycle and proceed to the next cycle.

Exit

Exits the entire script.

Function

Basic format:

function Fun () {# #定义函数

......

}

Fun 1 2 3 # #传入参数, call function

Variable meaning:

$: First parameter

$ A: The second parameter

$ A: The third parameter

$ A: The name of the script itself

$#: Number of parameters passed in

[Email protected]: all parameters

Sample: View network card IP address

#!/bin/baship () {ifconfig | grep-a1 "$e" |tail-1 | awk ' {print $} '}read-p "Please input the ETH name:" emyip= ' IP $e ' E Cho "$e address is $myip"

Array

Defined:

# a= (1 2 3) # #定义一个数组a并赋值 1 2 3# echo ${a[*]} # #注意输出a的值的格式1 2 3# Echo ${a[1]} # #输出单个a数组中的值2 # echo ${a[ 2]}3# echo ${a[0]} # #注意第一个其实是 01# echo ${#a [@]} # #获取数组的元素个数3

Change:

# a[3]=a # #给第三个数组赋值一个a # echo ${a[*]}1 2 3 a# a[3]=aaa # #修改赋值为aaa # echo ${a[*]}1 2 3 Aaa#echo ${A[@]/5/ASD} # #替换1 2 3 4 ASD 6 7 8

Delete:

# unset A[2] # #删除a数组中第2位的值 # unset a # #删除a数组

Sharding:

# a= (' seq 1 8 ') # #给a赋值8个数 # echo ${a[*]}1 2 3 4 5 6 7 8# Echo ${a[@]:3:3} # #从第3个数组开始, intercept 3. 4 5 6# Echo ${a[@]:0-3:2} # #从倒数第三个开始, fetch two numbers 6 7

Shell basic Syntax (iii)