介绍一个命令行解析库：TCLAP，属于一个比较好用的命令行解析库，Envoy中也用到了这个库，整理出来，方便后续查看。
详细介绍参考：https://tclap.sourceforge.net/html/classTCLAP_1_1SwitchArg.html
使用方法分成几步： 先初始化一些默认的参数数值，parse传递过来的参数之后，会使用传递进来的参数代替掉这些默认值。
代码语言：javascript复制// step 1: 实例化CmdLine
TCLAP::CmdLine cmd("Command description message", ' ', "0.9");
// step 2: 参数实现和添加
TCLAP::ValueArg<std::string> nameArg("n","name","Name to print",true,"homer","string");
cmd.add( nameArg );
// step 3: 解析参数
cmd.parse( argc, argv );
// step 4: 获取对应的命令行
std::string name = nameArg.getValue();
bool reverseName = reverseSwitch.getValue();例子：代码如下
代码语言：javascript复制#include <string>
#include <iostream>
#include <algorithm>
#include <tclap/CmdLine.h>
int main(int argc, char** argv)
{
// Wrap everything in a try block. Do this every time,
// because exceptions will be thrown for problems.
try {
// Define the command line object, and insert a message
// that describes the program. The "Command description message"
// is printed last in the help text. The second argument is the
// delimiter (usually space) and the last one is the version number.
// The CmdLine object parses the argv array based on the Arg objects
// that it contains.
TCLAP::CmdLine cmd("Command description message", ' ', "0.9");
// Define a value argument and add it to the command line.
// A value arg defines a flag and a type of value that it expects,
// such as "-n Bishop".
// homer 是默认的name的数值。
TCLAP::ValueArg<std::string> nameArg("n","name","Name to print",true,"homer","string");
// Add the argument nameArg to the CmdLine object. The CmdLine object
// uses this Arg to parse the command line.
cmd.add( nameArg );
// Define a switch and add it to the command line.
// A switch arg is a boolean argument and only defines a flag that
// indicates true or false. In this example the SwitchArg adds itself
// to the CmdLine object as part of the constructor. This eliminates
// the need to call the cmd.add() method. All args have support in
// their constructors to add themselves directly to the CmdLine object.
// It doesn't matter which idiom you choose, they accomplish the same thing.
TCLAP::SwitchArg reverseSwitch("r","reverse","Print name backwards", cmd, false);
// Parse the argv array.
cmd.parse( argc, argv );
// Get the value parsed by each arg.
std::string name = nameArg.getValue();
bool reverseName = reverseSwitch.getValue();
// Do what you intend.
if ( reverseName )
{
std::reverse(name.begin(),name.end());
std::cout << "My name (spelled backwards) is: " << name << std::endl;
}
else
std::cout << "My name is: " << name << std::endl;
} catch (TCLAP::ArgException &e) // catch any exceptions
{ std::cerr << "error: " << e.error() << " for arg " << e.argId() << std::endl; }
}输出：
代码语言：javascript复制% test1 -n mike // 指定了mike之后，name就被替换成mike了
My name is: mike
% test1 -n mike -r
My name (spelled backwards) is: ekim
% test1 -r -n mike
My name (spelled backwards) is: ekim
% test1 -r
PARSE ERROR:
One or more required arguments missing!
Brief USAGE:
test1 [-r] -n <string> [--] [-v] [-h]
For complete USAGE and HELP type:
test1 --help
% test1 --help
USAGE:
test1 [-r] -n <string> [--] [-v] [-h]
Where:
-r, --reverse
Print name backwards
-n <string> --name <string>
(required) (value required) Name to print
--, --ignore_rest
Ignores the rest of the labeled arguments following this flag.
-v, --version
Displays version information and exits.
-h, --help
Displays usage information and exits.
Command description message参考下面三篇文章： https://tclap.sourceforge.net/html/classTCLAP_1_1SwitchArg.html https://dtai.cs.kuleuven.be/krr/files/gidl2docs/code/pcsolver/lib/tclap/docs/manual.html https://blog.csdn.net/youngpan1101/article/details/73742209
