title: need hint with a custom Linux/UNIX command line utlity "cal" in C
body: <p>Ok I need to make this program to display "<code>cal</code>" 3 month(one month before and one month after) side by side, rather than just one single month it displays in any Linux/UNIX. I got it working to display 3 calendar by using "<code>system(customCommand)</code>" three times; but then it's not side by side. </p>
  
  <p>I got some hint to use the following system calls:</p>
  
  <pre><code>close(..) pipe(..) dup2(..) read(..) and write(..)
  </code></pre>
  
  <p>my question is what should I start with? Do I need to create child process and than catch it in <code>pipe(..)</code>? </p>
  
  <p>How can I display three calendar side by side. </p>
  
  <p>ex.</p>
  
  <pre><code>    February 2009          March 2009             April 2009
   S  M Tu  W Th  F  S    S  M Tu  W Th  F  S    S  M Tu  W Th  F  S
   1  2  3  4  5  6  7    1  2  3  4  5  6  7             1  2  3  4
   8  9 10 11 12 13 14    8  9 10 11 12 13 14    5  6  7  8  9 10 11
  15 16 17 18 19 20 21   15 16 17 18 19 20 21   12 13 14 15 16 17 18
  22 23 24 25 26 27 28   22 23 24 25 26 27 28   19 20 21 22 23 24 25
                         29 30 31               26 27 28 29 30
  </code></pre>