我有一个prova.txt这样的文件：
Start to grab from here: 1
fix1
fix2
fix3
fix4
random1
random2
random3
random4
extra1
extra2
bla
Start to grab from here: 2
fix1
fix2
fix3
fix4
random1546
random2561
extra2
bla
bla
Start to grab from here: 1
fix1
fix2
fix3
fix4
random1
random22131
我需要从“开始抓住这里”到第一个空行。输出应该是这样的：
Start to grab from here: 1
fix1
fix2
fix3
fix4
random1
random2
random3
random4
Start to grab from here: 2
fix1
fix2
fix3
fix4
random1546
random2561
Start to grab from here: 1 …