grep 在 nc 输出中不匹配

Question

我正在使用nc扫描开放端口，但我扫描的范围很广，并且显示的结果太多。grep出于某种原因，尝试使用“成功”这个词是行不通的：

$ nc -zv localhost 31000-32000 | grep succeeded
...
nc: connect to localhost port 31957 (tcp) failed: Connection refused
nc: connect to localhost port 31958 (tcp) failed: Connection refused
nc: connect to localhost port 31959 (tcp) failed: Connection refused
Connection to localhost 31960 port [tcp/*] succeeded!
nc: connect to localhost port 31961 (tcp) failed: Connection refused
nc: connect to localhost port 31962 (tcp) failed: Connection refused
nc: connect to localhost port 31963 (tcp) failed: Connection refused
nc: connect to localhost port 31964 (tcp) failed: Connection refused
...

（我也考虑过将错误消息发送到/dev/null：nc -zv localhost 31000-32000 2>/dev/null。但在那种情况下，没有任何结果。似乎所有nc端口状态消息都是错误/调试消息）

Answer 1

nc 将其输出写入标准错误，您需要：

nc -zvv localhost 31000-32000 2>&1 | grep succeeded

在2>&1将标准错误重定向到标准输出，所以你可以再管它grep。