title: Shell Jenkins job reading text from file with variables
body: <p>I am implementing Jenkins job in bash shell script. Jenkins jobs is using the variable <code>AS_OF_DATE</code> which can be used as input for users. </p>
  
  <p>I also have some files on zone with text that I grep during the execution of this jenkins job. </p>
  
  <p>So user will start the jobs and given parameters is:
  <code>AS_OF_DATE: "20180331"</code></p>
  
  <p>Then during the job I grep some text from <code>test.txt</code> file.</p>
  
  <pre><code>TEXT_FROM_FILE="This is my text, where i used ${AS_OF_DATE}"
  </code></pre>
  
  <p>And when I do the echo of <code>$TEXT_FROM_FILE</code>, variable <code>$AS_OF_DATE</code> is not changed with the date that user added. </p>
  
  <p><strong>My outcome is:</strong></p>
  
  <pre><code>"This is my text, where i used ${AS_OF_DATE}"
  </code></pre>
  
  <p><strong>What it should be:</strong> </p>
  
  <p><code>"This is my text, where i used 20180331"</code></p>
  
  <p>I assume that I am not declaring the variable inside the file correctly, so my question is hot to correctly specified the variable in file that will actually use the value that variable has instead of just outputting the text. </p>
  
  <p>Thank you in advance. </p>