title: Need of a specific trick to manage bash eval cmd & <<< input
body: <p>I want to use several instances of a spider object of scrapy with several instances of polipo proxies.</p>
  
  <p>For this, it is quite simple:</p>
  
  <pre><code>for i in `seq 1 100`
      do
          numeroPortProxy=$(($i+30000))
          command="scrapy crawl courses_PT ... -s HTTP_PROXY=http://127.0.0.1:${numeroPortProxy}"
          eval $command&amp;
      done
  </code></pre>
  
  <p>My issue is I need to answer automatically <code>"o"</code> to the command.</p>
  
  <p>I tried this <code>eval $command&amp;&lt;&lt;&lt;"o"</code>, it does not work. The logfile indicates: <code>EOFError: EOF when reading a line</code></p>
  
  <p>I tried this too <code>eval $command&lt;&lt;&lt;"o" &amp;</code>, it does not work too. It gives this error in the terminal:</p>
  
  <pre><code>Usage
  =====
    scrapy crawl [options] &lt;spider&gt;
  
  crawl: error: Invalid -s value, use -s NAME=VALUE
  </code></pre>
  
  <p>Well it does not appreciate.</p>
  
  <p>So, how can I do to launch several instances of command at one time like <code>&amp;</code> operator allows and to answer the prompt of each several instances like <code>&lt;&lt;&lt;</code> allows.</p>