找到具有重复图案的线

Question

我有一个这样的日志文件

123.123.123.123 (456.456.456.456) abc def .....
123.123.123.123 (123.123.123.123) abc def .....
123.123.123.123 (456.456.456.456) abc def .....
455.455.455.455 (456.456.456.456) abc def .....
555.555.555.555 (555.555.555.555) efc bbb .....

在某些行中，括号外的IP与内部相同，我想输出这些行：

123.123.123.123 (123.123.123.123) abc def .....
555.555.555.555 (555.555.555.555) efc bbb .....

我怎样才能用 grep 或 sed 做到这一点？

Answer 1

您可以使用对编号捕获组的反向引用：

$ grep '\([0-9.]*\) (\1)' file.log
123.123.123.123 (123.123.123.123) abc def .....
555.555.555.555 (555.555.555.555) efc bbb .....