首先在linux下打开一个文件，然后将该文件上写入锁，并写入hello字符串。接着在解锁后再将该文件上读取锁，并读取刚才写好的内容。最后模拟多进程，同时读写一个文件时的情况。-First, open a file under linux, and then write lock on the file and write the string hello. Then, after unlocking the file lock on the read and write just to read