作业控制是操作系统的首要功能，是连接用户与操作系统内核的最主要的通道。UNIX的作业控制由shell程序实现，它接收终端用户的联机命令，或执行shell脚本程序，完成用户的作业。shell以用户进程的方式运行于用户模式，因此，用户可以选择自己喜欢的shell程序，也可以使用自行设计的个性化shell程序。-Job control is the primary function of the operating system is to connect the user with the operating system kernel of the main channel. UNIX operating control is provided by shell procedures for implementation, it receives end-user on-line orders, or perform shell scr ipt to complete the user' s job. shell user processes run in user mode, so users can choose their own favorite shell program can also be used to design personalized shell program.