title: How to merge two files line by line in Bash
body: <p>I have two text files, each of them contains an information by line such like that</p>
  
  <pre><code>file1.txt            file2.txt
  ----------           ---------
  linef11              linef21
  linef12              linef22
  linef13              linef23
   .                    .
   .                    .
   .                    .
  </code></pre>
  
  <p>I would like to merge theses files lines by lines using a bash script in order to obtain:</p>
  
  <pre><code>fileresult.txt
  --------------
  linef11     linef21
  linef12     linef22
  linef13     linef23
   .           .
   .           .
   .           .
  </code></pre>
  
  <p>How can this be done in Bash?</p>