Question

case声明的standard description说：

The format for the case construct is as follows:

case word in
  [(]pattern1) compound-list;;
  [[(]pattern[ | pattern] ... ) compound-list;;] ...
  [[(]pattern[ | pattern] ... ) compound-list]
esac

The ";;" is optional for the last compound-list.

为什么pattern1也不能成为多重模式？它似乎相当随意，但我很确定它一定不是。

谢谢！

Answer 1

我认为你误解了他们所说的话。您链接到的页面上的语法没有显示出这样的区别：

case_clause      : Case WORD linebreak in linebreak case_list    Esac
                 | Case WORD linebreak in linebreak case_list_ns Esac
                 | Case WORD linebreak in linebreak              Esac
                 ;
case_list_ns     : case_list case_item_ns
                 |           case_item_ns
                 ;
case_list        : case_list case_item
                 |           case_item
                 ;
case_item_ns     :     pattern ')'               linebreak
                 |     pattern ')' compound_list linebreak
                 | '(' pattern ')'               linebreak
                 | '(' pattern ')' compound_list linebreak
                 ;
case_item        :     pattern ')' linebreak     DSEMI linebreak
                 |     pattern ')' compound_list DSEMI linebreak
                 | '(' pattern ')' linebreak     DSEMI linebreak
                 | '(' pattern ')' compound_list DSEMI linebreak
                 ;
pattern          :             WORD         /* Apply rule 4 */
                 | pattern '|' WORD         /* Do not apply rule 4 */

为什么shell case语句中的第一个模式不能是多重模式？

1 个答案: