title: How do I grep multiple lines (output from another command) at the same time?
body: <p>I have a Linux driver running in the background that is able to return the current system data/stats. I view the data by running a console utility (let's call it <strong>dump-data</strong>) in a console. <strong>All</strong> data is dumped every time I run <strong>dump-data</strong>. The output of the utility is like below</p>
  
  <pre><code>Output:
  - A=reading1
  - B=reading2
  - C=reading3
  - D=reading4
  - E=reading5
  ...
  - variableX=readingX
  ...
  </code></pre>
  
  <p>The list of readings returned by the utility can be really long. Depending on the scenario, certain readings would be useful while everything else would be useless. </p>
  
  <p>I need a way to grep only the useful readings whose names might have have nothing in common (via a bash script). I.e. Sometimes I'll need to collect A,D,E; and other times I'll need C,D,E.</p>
  
  <p>I'm attempting to graph the readings over time to look for trends, so I can't run something like this:</p>
  
  <pre><code># forgive my pseudocode
  Loop
      dump-data | grep A
      dump-data | grep D
      dump-data | grep E
  End Loop
  </code></pre>
  
  <p>to collect A,D,E as that would actually give me readings from 3 separate calls of dump-data as that would not be accurate.</p>