Processes

cfig

1.基本概念：
A RUNNING INSTANCE OF A PROGRAM IS CALLED A PROCESS.程序的一个运行实例，称为一个进程。
1.2查看进程：ps
查看所有进程ps -e
ps -e -o pid,ppid,command
1.3杀掉进程 kill  向某个进程发送SIGTERM信号

2 创建进程：Two Methods
2.1(1)system call: system("***"), 位于Standard C Lib
2.2(2)Using fork and exec function:
fork: makes a child process  that is an exact copy of its parent process.
exec family functions: cause a particular process to cease being an instance of one program and to instead become an instance of another program.
要这样建立一个进程：first use fork to make a copy of the current process, then use exec to transform one of these processes into an instance of the program you want to spawn.
2.3进程调度
系统命令调用：nice [OPTION] [COMMAND [ARG]...]用一个非零的niceness值来运行某个程序，
编程的方法：nice函数
#include
int nice(int inc);


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