if[ xxx ]echo" xxx "fi# space in the brackets and semi colon is important
Example
#! /bin/bash echo"hello ..."if[ 3 -eq 3 ];then
echo"yes, boolean is ture!"fi# make sure space on both side of the content [ xx ]if[ 3 -eq 5 ];then
echo"this boolean is not ture, it won't output in the terminal"fi
echo"bye for now"# interpretation# 3 -eq 3 => 3 = 3# 3 -ne 4 => 3 is not 4 # 3 -gt 1 => 3 greater than 1 # 3 -lt 7 => 3 less than 7 # 3 -ge 3 => 3 greater equal 3 # 3 -le 3 => 3 less equal 3