用__text__替换％（text）s

Question

关于sed / awk的一些问题：

1. How to replace %(text)s with __text__

Example:

    %(vehicle)s -> __vehicle__

第二个问题：

2. How to make reverse operation: replace __text__ with %(text)s ?

Example:  

    __vehicle__ -> %(vehicle)s

Answer 1

$ cat test.txt
How to replace %(text)s with __text__
How to make backward operation: replace __text__ with %(text)s

$ sed 's#%(\([^)]*\))s#__\1__#g' test.txt
How to replace __text__ with __text__
How to make backward operation: replace __text__ with __text__

$ sed 's#__\([^_]*\)__#%(\1)s#g' test.txt
How to replace %(text)s with %(text)s
How to make backward operation: replace %(text)s with %(text)s

请注意，捕获组parantheses需要在sed中转义。