查找具有重复模式的行

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，括号外面的IP与里面的相同，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

您可以使用反向引用到一个编号的捕获组：

$ 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 .....