boost::program_options::parse_environment通过环境变量来设置options

这里需要注意的是需要注意的是:一定要将所需要的环境变量加入到options中。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
#include <iostream>
#include <string>
#include <boost/program_options.hpp>

using namespace std;
using namespace boost::program_options;

// compile: g++ boostprogramoption.cpp -o boostprogramoption -lboost_program_options

// envs
const string ENVS[] = {
"HOME",
"PKG_CONFIG_PATH",
"PATH",
"http_proxy",
};

const int ENVCOUNT = 4;

static std::string name_mapper(const std::string &var_name){
for (int i = 0; i < ENVCOUNT; ++i) {
if (var_name == ENVS[i])
return var_name;
}

return "";
}

int main(int argc, char** argv)
{

// need to pass the buffer size to constructor (e.g. 1024), otherwise:
// undefined reference to 'boost::program_options::options_description::m_default_line_length'
options_description desc("Allowed options", 1024);
desc.add_options()
("help,h", "produce help message")
("compression,c", value<int>(), "set compression level")

// need to use the env as option, otherwise exception throwed:
("HOME,m", value<string>()->default_value(""), "home dir")
("PATH,p", value<string>()->default_value(""), "path")
("PKG_CONFIG_PATH,k", value<string>()->default_value(""), "pkg config")
("http_proxy", value<string>()->default_value(""), "http proxy");
;

variables_map vm;
store(parse_command_line(argc, argv, desc), vm);
store(parse_environment(desc, name_mapper), vm);
notify(vm);

if (vm.count("help")) {
cout << desc << endl;
return 1;
}

if (vm.count("compression")) {
cout << "Compression level was set to "
<< vm["compression"].as<int>() << endl;
} else {
cout << "Compression level was not set." << endl;
}

for (int i = 0; i < ENVCOUNT; ++i) {
if (vm.count(ENVS[i])) {
cout << ENVS[i] << " is "
<< vm[ENVS[i]].as<string>() << endl;
}
}

return 0;
}
知识共享授权条款
本著作Chen, Zai-Chun制作,以知识共享 姓名标示-相同方式分享 4.0 国际 授权条款释出

留言

Jun 1 2010