Functions, arrays in 71.shell

One, the function in shell script?

• The function is to organize a piece of code into a small unit, and give the small unit a name, when the code is used to call the name of the small unit directly.
  Format: function F_name ()
  {
  command} function must be placed at the front
• Example 1 output the specified parameters

#!/bin/bashinput()  {    echo $1 $2 $# $0}input 1 a b

• Example 2 summation \

#!/bin/bashsum() {      s=$[$1+$2]      echo $s}sum 1 2

• Example 3 viewing network card IP

  #!/bin/baship() {ifconfig |grep -A1 "$1"|tail -1 |awk ‘{print $2}‘}read -p "Please input the eth name: " emyip=`ip $e`echo "$e address is $myip"

Ii. Arrays in the shell

• Define array a= (1 2 3 4 5);

  echo ${a[@]}                 显示整个数组echo ${#a[@]}              获取数组的元素个数 echo ${a[2]}                  读取第三个元素，数组从0开始echo ${a[*]} 等同于 ${a[@]}    显示整个数组数组赋值a[1]=100; echo ${a[@]}a[5]=2; echo ${a[@]}         如果下标不存在则会自动添加一个元素数组的删除unset a[1] ;echo ${a[*]}   //删除数组中第1个元素unset a;echo ${a[*]}       //清空数组

• Array shards

  a=(`seq 1 5`)echo ${a[@]:0:3} 从第一个元素开始，截取3个echo ${a[@]:1:4} 从第二个元素开始，截取4个echo ${a[@]:0-3:2} 从倒数第3个元素开始，截取2个数组替换echo ${a[@]/3/100}  //将数组a中的3替换成100（只显示到屏幕，并不更改数组）a=(${a[@]/3/100})   //将数组a中的3替换成100

  Three, Shell project-alarm system

• Requirements: Use the shell to customize a variety of personalized alarm tools, but the need for unified management, standardized management.
• Idea: Specify a script package that contains the main program, subroutine, configuration file, mail engine, output log, and so on.
• Main program: As the entire script portal, is the lifeblood of the entire system.
• Configuration file: is a control center that uses it to switch individual subroutines, specifying each associated log file.
• Subroutine: This is the real monitoring script, used to monitor each indicator.
• Mail Engine: It is implemented by a Python program that defines the server to which the message is sent, the person who sent it, and the sender's password
• Output log: The entire monitoring system should have a log output.
  

Functions, arrays

in 71.shell