echo命令

• 概述
  用於在shell中打印shell變量的值，或者直接輸出指定的字符串。
• 選項
  -n：不進行換行
  -e：讓轉義符生效
  \n：換行
  \t：製表符
  STRING可使用引號，單引號和雙引號都可用
  單引號：強引用，變量引用不執行替換
  ~]# echo '$SHELL'
  雙引號：弱引用，變量引用會被替換
  ~]# echo "$SHELL"
  注意：變量引用的正規符號
  ${name}
• 實例

  [root@localhost ~]# echo how are you doing.How do you do?
  how are you doing.How do you do?
  [root@localhost ~]# echo -e "how are you doing.\tHow do you do?"
  how are you doing.  How do you do?
  [root@localhost ~]# echo -e "how are you doing.\nHow do you do?"
  how are you doing.
  How do you do?