title: Ways to read only select columns from a file into R? (A happy medium between `read.table` and `scan`?)
body: <p>I have some very big delimited data files and <strong>I want to process only certain columns in R</strong> without taking the time and memory to create a <code>data.frame</code> for the whole file.</p>
  
  <p>The only options I know of are <code>read.table</code> which is very wasteful when I only want a couple of columns or <code>scan</code> which seems too low level for what I want.</p>
  
  <p>Is there a better option, either with pure R or perhaps calling out to some other shell script to do the column extraction and then using scan or read.table on it's output? (Which leads to the question how to call a shell script and capture its output in R?).</p>