expr

名称:expr
  
  ### 字串长度
  
  shell>> expr length "this is a test"
  14
  
  ### 数字商数
  
  shell>> expr 14 % 9
  5
  
  ### 从位置处抓取字串
  
  shell>> expr substr "this is a test" 3 5
  is is
  
  ### 数字串 only the first character
  
  shell>> expr index "testforthegame" e
  2
  
  ### 字串真实重现
  
  shell>> expr quote thisisatestformela
  thisisatestformela