一个简单的shell，能够实现管道，外部命令，内部命令，bu-A simple shell, can be achieved pipes, external commands, internal commands, buaa

a program that creates three threads. These threads access a shared integer, called buer, one at a time. The buer will initially be set to 0. Each thread should print its thread ID, process ID and the buer s current value in one statement, t