title: How to search a keyword then list all lines about this keyword?
body: <p>I use standard shell to write a phone book program which can add, delete and search contacts you looking for. 
  I store the information of one contact by using 4 variable, name, address, city and phonenumber. I put them into a txt file line by line. When I do the search, for example:</p>
  
  <pre><code>Bill
  2 wood st.
  city
  123-4323
  </code></pre>
  
  <p>when I search no matter Bill or wood or 4323, I need to print all these 4 lines.
  sed and awk are not allowed to use, how to do it?</p>
  
  <p>I used grep which can only output one line.</p>
  
  <pre><code>echo -e "\nEnter name to look up: \c"
  read search
  grep -i $search book
  </code></pre>