title: Shortest command to calculate the sum of a column of output on Unix?
body: <p>I'm sure there is a quick and easy way to calculate the sum of a column of values on Unix systems (using something like <code>awk</code> or <code>xargs</code> perhaps), but writing a shell script to parse the rows line by line is the only thing that comes to mind at the moment.</p>
  
  <p>For example, what's the simplest way to modify the command below to compute and display the total for the SEGSZ column (70300)?</p>
  
  <pre><code>ipcs -mb | head -6
  IPC status from /dev/kmem as of Mon Nov 17 08:58:17 2008
  T         ID     KEY        MODE        OWNER     GROUP      SEGSZ
  Shared Memory:
  m          0 0x411c322e --rw-rw-rw-      root      root        348
  m          1 0x4e0c0002 --rw-rw-rw-      root      root      61760
  m          2 0x412013f5 --rw-rw-rw-      root      root       8192
  </code></pre>