Shell---If statement

Shell tip:

1. Need to add ' $ ' when referencing variables

2.shell variable viewing and deletion

Set | grep variable name//view Set Variable unset variable name//delete variable

The difference between single and double quotes in 3.shell

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Note : Single quotation marks are assigned to variables; double quotation mark cancels the function of the space

4. Anti-quotes, assigning a shell command to a variable

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5.read: Read data, assign to variable

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6.EXPR: Arithmetic operations on integer variables

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Note: Notice the space, \ is escaped, cancels the special meaning of *

If statement:

vim if.sh#!/bin/bash     //specifies that the shell   //script that runs the script begins #file: if.sh      echo  ' Hello, how old are you? ' echo  ' please input your age: ' read age                  //read-in data if [  $age  -eq 28 ];  then        echo  "You ' re at the age of  marriage! " elif [  $age  -gt 28 -a  $age  -lt 35 ]; then      //Judging age between 28 to 35         echo  "You must go  on a blind date now. " elif [  $age  -lt 28 ]; then        echo   "You ' re still young and good to learn!" else        echo  "Sorry, i don ' t kown your age!" fi                                        //script End chmod +x if.sh     //gives execute permission ./if.sh      //script execution script under current path

This article from "Experience from pain" blog, declined reprint!

Shell---If statement