title: Is it necessary to specify traps other than EXIT?
body: <p>I see a lot of shell scripts that do:</p>
  
  <pre>
  trap cmd 0 1 2 3 13 15 # EXIT HUP INT QUIT PIPE TERM
  </pre>
  
  <p>In every shell I have access to at the moment, all the traps other than 0 are redundant, and cmd will be executed upon receipt of a signal if the trap is simply specified:</p>
  
  <pre>
  trap cmd 0
  </pre>
  
  <p>Is the latter specification sufficient, or do some shells require the other signals to be specified?</p>