我有一个文本文件，我想从后面的每一行中提取字符串 "OS="
input file line
A0A0A9PBI3_ARUDO Uncharacterized protein OS=Arundo donax OX=35708 PE=4 SV=1
K3Y356_SETIT ATP-dependent DNA helicase OS=Setaria italica OX=4555 PE=3 SV=1
所需的输出
OS=Arundo donax
OS=Setaria italica
或者
Arundo donax
Setaria italica