基本使用 方法
https://www.cnblogs.com/ctaixw/p/5860221.html
高級方法
https://blog.csdn.net/itsenlin/article/details/21129405
https://blog.csdn.net/zr1076311296/article/details/51277915
eg
file.ini
[section1]
param1=123
param2=345
param3=678
[section2]
param1=abc
param2=def
param3=ghi
[section3]
param1=000
param2=111
param3=222
sed -nr "/^\[section2\]/ { :l /^param2[ ]*=/ { s/.*=[ ]*//; p; q;}; n; b l;}" ./file.ini
result:
def