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.
