^(?<user>.+)这个到底匹配什么啊？

[13378333]

试了一下 <user>33 好像不行啊，

[枫叶饭团]

代码： 全选

ef>echo '<user>33' |grep -E '^(?<user>.+)'
<user>33

哪里不行了

[枫叶饭团]

If name is a valid sub pattern name but it didn't match anything (e.g. sub pattern "X", matching "b" against "(?P<X>a)?b") then an empty string is returned.

[13378333]

代码： 全选

ef>echo '<user>33' |grep -E '^(?<user>.+)'
<user>33

哪里不行了

感谢大神指点，感谢送出

[13378333]

If name is a valid sub pattern name but it didn't match anything (e.g. sub pattern "X", matching "b" against "(?P<X>a)?b") then an empty string is returned.

?起啥作用啊