-E regex matching sub-class error or something else?

[Hearen]

• I have searched the issues of this repository and believe that this is not a duplicate.

No answer and details provided in #96

More details provided here to re-produce the issue.

Environment
Arthas version: 3.0.4
Operating System version: 15.6.0 Darwin Kernel Version 15.6.0
Java version of target JVM: jdk1.8.0_73
Java version of JVM used to attach: jdk1.8.0_73

Steps to reproduce this issue

1. follow this to start Arthas: https://github.com/Hearen/arthas/blob/doc-with-consistent-demo/site/src/site/sphinx/en/quick-start.md
2. select the demo to monitor
3. using command sc to locate class demo.Demo$Counter.

Expected

$ sc demo.Demo$Counter
demo.Demo$Counter
Affect(row-cnt:1) cost in 1 ms.

$ sc -E demo\.Demo\$Counter
demo.Demo$Counter
Affect(row-cnt:1) cost in 11 ms.

Actual Result

$ sc demo.Demo$Counter
demo.Demo$Counter
Affect(row-cnt:1) cost in 1 ms.

$ sc -E demo\.Demo\$Counter
Affect(row-cnt:0) cost in 2 ms.

$ sc -E demo\.Demo\\$Counter
demo.Demo$Counter
Affect(row-cnt:1) cost in 3 ms.

$ sc -E demo.Demo\\$Counter
demo.Demo$Counter
Affect(row-cnt:1) cost in 3 ms.

Questions

1. Why require \\ instead of a single \ here? Unlike this escaping rule Arthas的一些特殊用法文档说明 #71 (comment) and sc -E demo\.Demo\$Counter didn't work?
2. Why sc -E demo.Demo\\$Counter worked? Shouldn't it be sc -E demo\.Demo\$Counter?

[hengyunabc]

Refer to #302