Shell Process Control-IF statement

1. Single-branch If condition statement
   

   If [conditional judgment]; Then
   Program
   Fi

   Example: Judging partition usage

   #!/bin/bash# Author:huangrui (email:[email protected]) rate=$(DF-H |grep "sda1"|awk '{print $}'|Cut-F1-D"%") if[$rate-GT the]; Then   Echo "warning! disk is full!!!"fi

   Code

2. Dual-Branch IF condition statement
   If [conditional judgment]; Then
   When a condition is executed, the statement executed
   Else
   Conditional execution is not valid, the executed statement
   Fi

   Example: Backing up a site directory file

   #!/bin/bash# Author Huangrui (email:[email protected])Date=$(Date+%y%m%d) Size=$(du-SH/home/test.com)if[-d/home/test.com]; Then    Echo "date is: $date">/tmp/dbback/Db.txtEcho "size is: $size">>/tmp/dbback/db.txt CD/tmp/DbbackTar-ZCF web_$Date.Tar. gz/home/test.com db.txt&>/dev/NULL    RM-rf/tmp/dbback/Db.txtElse    mkdir/tmp/DbbackEcho "date is: $date">/tmp/dbback/Db.txtEcho "size is: $size">>/tmp/dbback/db.txt CD/tmp/DbbackTar-ZCF web_$Date.Tar. gz/home/test.com db.txt&>/dev/NULL    RM-rf/tmp/dbback/Db.txtfi

   Code

   To determine if Apache is starting, use Nmap command

   #!/bin/bash# Author Huangrui (email:[email protected]) port=$ (nmap-st172.16.193.128|grepTCP |grepHTTP |awk '{print $}') if["$port"=="Open"]; Then   Echo "$ (date) httpd is ok!">>/tmp/autostart-Acc.logElse/ETC/RC.D/INIT.D/HTTPD Restart &>/dev/NULL   Echo "$ (date) httpd is restart!!">>/tmp/autostart-Err.logfi

   Code

4. Multi-branch IF condition statement
   If [conditional judgment 1]; Then
   When the conditional judgment 1 is established, the execution of the program 1
   elif [Conditional judgment type 2]; Then
   When the conditional Judgment 2 is established, the execution of the program 2
   ... Omit more conditions ...
   Else
   When all conditions are not set, the final execution of this program
   Fi

Shell Process Control-IF statement