title: Wget: Skip download if file already exists?
body: <p>Answers to <a href="https://stackoverflow.com/questions/4944295/skip-download-if-files-exist-in-wget">Skip download if files exist in wget?</a> say to use <code>-nc</code>, or <code>--no-clobber</code>, but <code>-nc</code> doesn't prevent the sending of the HTTP request and subsequent downloading of the file. It just doesn't do anything after downloading the file if the file has already been fully retrieved. Is there anyway to prevent making the HTTP request if the file already exists?</p>
  
  <p>I installed <a href="https://github.com/Homebrew/homebrew/blob/master/Library/Formula/wget.rb" rel="noreferrer"><code>wget</code> 1.16.3 with Homebrew</a>. After running the command below, <code>wget</code> said something like <code>making HTTP request</code> for each file that already existed, appeared to download it, and then said something like: <code>file already retrieved, nothing to do</code>.</p>
  
  <pre><code>wget --user-agent='Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) AppleWebKit/600.7.12 (KHTML, like Gecko) Version/8.0.7 Safari/600.7.12' \
       --tries=1 \
       --no-clobber \
       --continue \
       --wait=0.3 \
       --random-wait \
       --adjust-extension \
       --load-cookies cookies.txt \
       --save-cookies cookies.txt \
       --keep-session-cookies \
           --recursive \
           --level=inf \
           --convert-links \
           --page-requisites \
           --reject=edit,logout,rate \
           --domains=example.com,s3.amazonaws.com \
           --span-hosts \
           --exclude-directories=/admin \
       http://example.com/
  </code></pre>