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。-In the Linux environment. Write a console application, in the program have a Shared shared_var integer variables, the initial value of 0　Create a thread and make it with the main thread immediately execute concurrently. The newly created thread and the main thread are continuously circulation, and the value of output shared_var. The main thread in a loop to add 1 shared_var continuously operating, namely each loop shared_var added 1　While the newly created thread continuously to minus 1 shared_var operation, namely each loop shared_var was minus 1. Observe the result of the program is running, and to explain the phenomenon of you see.