title: Batch file to replace a line
body: <p>Many examples here for replace subsring or string, but i need replace all line what contains some string with another line with constant text. For example i have a file:</p>
  
  <pre><code>aaa=111
  bbb=222
  ccc=333
  aaa=444
  </code></pre>
  
  <p>I need to replace "aaa=" to "aaa=000". The output file should look like this:</p>
  
  <pre><code>aaa=000
  bbb=222
  ccc=333
  aaa=000
  </code></pre>
  
  <p>All this must be done without party tools like sed,awk,etc</p>