C/C++ 命令行参数的实现方法

解析从命令行提供的参数可以使用 getopt函数.
To use this facility, your program must include the header file unistd.h

unistd.h 是系统头文件, 并非由C/C++提供.

下面的介绍来自此链接.

首先要理解 option 和 option argument 这两个概念.

The getopt and getopt_long functions automate some of the chore involved in parsing typical unix command line options.

int getopt(int argc, char * const *argv, const char *options)

The getopt function gets the next option argument from the argument list specified by the argv and argc arguments. Normally these values come from the arguments received by main.

The options argument is a string that specifies the option characters that are valid for this program. An option character in this string can be followed by a colon (':') to indicate that it takes a required argument. If an option character is followed by two colons ('::'), its argument is optional; this is a GNU extension (这段话读了两遍才懂, reading 真是遭透了).