2018-03-23

"apue.h"

是一个非常常用的头文件。其包括一些标准的系统头文件和定义了多种常量和函数。

想要使用这个头文件，需要现在系统中进行编译。
过程参考：http://www.cnblogs.com/52php/p/5681701.html
编译时要链接-lapue

Process Control

There are three primary functions for process control: fork, exec, and waitpid. (The exec function has seven variants, but we often refer to them collectively as simply the exec function.)

Error handing

There are two rules to be aware of with respect to errno. First, its value is never
cleared by a routine if an error does not occur. Therefore, we should examine its value
only when the return value from a function indicates that an error occurred. Second,
the value of errno is never set to 0 by any of the functions, and none of the constants
defined in <errno.h> has a value of 0

Signal

signals are a technique used to notify a process that some condition has occurred.