link :
trap n [condition...] trap [action condition...]
If the first operand is an unsigned decimal integer, the shell shall treat all operands as conditions, and shall reset each condition to the default value. Otherwise, if there are operands, the first is treated as an action and the remaining as conditions.
If action is '-', the shell shall reset each condition to the default value.
Qual é a sintaxe trap n ? Não é basicamente as mesmas coisas que trap - ?