title: Insert multiple lines into a file after specified pattern using shell script
body: <p>I want to insert multiple lines into a file using shell script.
  Let us consider my input file contents are:
  <strong>input.txt:</strong></p>
  
  <pre><code>abcd
  accd
  cdef
  line
  web
  </code></pre>
  
  <p>Now I have to insert four lines after the line 'cdef' in the <strong>input.txt</strong> file.
  After inserting my file should change like this:</p>
  
  <pre><code>abcd
  accd
  cdef
  line1
  line2
  line3
  line4
  line
  web
  </code></pre>
  
  <p>The above insertion I should do using the shell script. Can any one help me?</p>