title: Regular expression for specific file mask
body: <p>I want to have 2 regex patterns that checks files after specific file mask. The way I like to do it is written below.</p>
  
  <p>Pattern 1:</p>
  
  <ol>
  <li><p>check if the left side of <code>_</code> has 7 digits.</p></li>
  <li><p>checks if the right side of <code>_</code> is numeric.</p></li>
  <li><p>checks for the specified extension is there.</p></li>
  </ol>
  
  <p>the input will look like this : <code>1234567_1.jpg</code></p>
  
  <p>Pattern 2:</p>
  
  <ol>
  <li>check if there is 10 digits to the left of a "Space" char</li>
  <li>check if there is 4 digits to the right of a "Space" char</li>
  <li>check to the right side of <code>_</code> is numeric</li>
  <li>check for the specified extension is there.</li>
  </ol>
  
  <p>The input will look like this: <code>1234567891 1234_1.png</code></p>
  
  <p>As stated above this is to be used to check for a specific file mask.</p>
  
  <p>i have been playing around with ideas like : ^[0-9]<em>[0-9].jpg$
  and ^[0-9] [0-9]</em>[0-9].jpg$ is my first tries.</p>
  
  <p>i do apologies for not providing my tries.</p>