RS续篇

文本内容
  a.txt
        type {
          sfjslkfjslfjslf
          lsjflsfjslfjs
          sljfslfjslf
      }aa

      type {
          sfkhsfkshf
          141414lsjflsfjmb
          s474ljfslfjslfm54
      }bb

      type {
          098dgs
          vnxvsb
          zczgmvs
      }cc

     type {
          blddgdlgj
          d;gkdgkd
         lkdjgld
      }bb

  ...

现从文本a.txt中取出 type{...}bb的内容
 
zj@zj:~/Script/cushell/08.11.18$ awk 'BEGIN{RS=""}/}bb/{print $0}' awk.data
      type {
          sfkhsfkshf
          141414lsjflsfjmb
          s474ljfslfjslfm54
      }bb
     type {
          blddgdlgj
          d;gkdgkd
         lkdjgld
      }bb
zj@zj:~/Script/cushell/08.11.18$ awk 'BEGIN{RS=""}/}bb/{print $1,$2,$3}' awk.dat
type { sfkhsfkshf
type { blddgdlgj
可以看出这个时候FS把\n也当作一个分割符了.实际上

When RS is set to the null string, the newline character always acts as a field separator, in addition to whatever value FS may have.

设置RS为"\n\n"是一样的^_^