找出指定分隔符中间的字符串

【问题】

Hi friends, I want to ask a question:
how can I extract all the text between two given strings str1 and str2? The returned results should be seperated by something such as a space line.
For example, my "input.txt" is:
abdeb .....  str1 aaaaaaaaaaaaaaaaa str2 bbbbbbbbbbbb str1 cccccccccccccccccc str2 ddddddddddddddddd ....
Then my output.txt should be:
aaaaaaaaaaaaaaaaa
cccccccccccccccccc 
Note that the text between str1 and str2 could be any length.
I think regular expression and egrep should be able to achieve this, but I am not familar with them. Hope anyone can help. Thanks! 

【回答】

       正则表达式可以解决这种问题，只是对于初学者来说太抽象不太容易掌握。这种较简单的情况也可以试试采用SPL，SPL既支持正则表达式，也支持直观的函数，比如：pos（取位置）、mid（按位置截取）。比如这个问题的脚本如下：

	A
1	=file("D:\\input.txt").read().split("str2")
2	=A1.select(pos(~,"str1"))
3	=A2.(mid(~,pos(~,"str1")+4))
4	=file("D:\\output.txt").write(A3)

A1：读取文本串，并按照”str2”分隔成序列

A2：选取含有”str1”子串的成员

A3：从A2的每个成员中截取”str1”后面的字符串

A4：将A3写入output.txt