Pthread-of-linux

说明：  在linux环境下编写一个控制台应用程序，程序中有一个共享的整型变量shared_var，初始值为0；创建一个线程并使其立即与主线程并发执行。新创建的线程与主线程均不断地循环，并输出shared_var 的值。主线程在循环中不断地对shared_var 进行加1操作，即每次循环shared_var 被加1；而新创建的线程则不断地对shared_var 进行减1 操作，即每次循环shared_var 被减1。观察程序运行的结果，并对你看到的现象进行解释。
(Written in the linux environment a console application, the program has a shared integer variable shared_var, the initial value of 0 create A thread and make it run concurrently with the main thread immediately. The newly created thread and main thread are constantly circulating, and the output shared_var Value. The main thread in a loop constantly on shared_var are incremented, that is plus 1 for each cycle shared_var and the new line created Process is constantly on the shared_var decremented, that is, each cycle shared_var is decreased by 1. Observe the results of running the program, and you To explain the phenomenon seen.)