有如下的文本内容：

*********

123123

123123

*********

321321

321321

*********

456456

456456

*********

123123

123123

********

匹配123，取出******区间的内容：

awk -vRS="*+" '/123/{print RT$0}' file

说明：

RS The input record separator, by default a newline(n).

RT The record terminator. Gawk sets RT to the input text that matched the character or regular expression specified by RS.