envy is a small header-only library to deserialize environment variables into type-safe structs.
Quick Start
Start by creating a struct where to store the values of environment variables.
#include <envy/envy.hpp>
struct ServerConfig {
int server_alive_interval = 45;
bool compression = false;
int compression_level = 0;
bool forward_x11 = true;
};
ENVY_STRUCT(ServerConfig, server_alive_interval, compression, compression_level, forward_x11);For each field in the struct, envy will look for an environment variable with the same name in upper case, e.g., for the field named forward_x11, envy will look for an environment variable named FORWARD_X11.
Use envy::get<T>() to get a deserialized, type-safe struct.
int main() {
auto config = envy::get<ServerConfig>();
std::cout << "Server Alive Interval : " << config.server_alive_interval << "\n";
std::cout << "Compression Enabled? : " << std::boolalpha << config.compression << "\n";
std::cout << "Compression Level : " << config.compression_level << "\n";
std::cout << "Forward X11? : " << std::boolalpha << config.forward_x11 << "\n";
}Here's the stdout of the above program:
▶ ./main
Server Alive Interval : 45
Compression Enabled? : false
Compression Level : 0
Forward X11? : true
▶ SERVER_ALIVE_INTERVAL=90 COMPRESSION=1 COMPRESSION_LEVEL=9 FORWARD_X11=0 ./main
Server Alive Interval : 90
Compression Enabled? : true
Compression Level : 9
Forward X11? : falseDeserialize comma-separated values
Comma-separated values can be deserialized into an std::vector:
#include <envy/envy.hpp>
struct Config {
std::vector<int> values;
};
ENVY_STRUCT(Config, values);
int main() {
auto config = envy::get<Config>();
for (auto& v : config.values) {
std::cout << v << " ";
}
}▶ ./main
▶ VALUES=1,2,3,4,5 ./main
1 2 3 4 5Deserialize JSON
JSON can be deserialized into std::map, std::unordered_map or even nlohmann::json:
#include <envy/envy.hpp>
struct Config {
std::map<std::string, int> values;
};
ENVY_STRUCT(Config, values);
int main() {
auto config = envy::get<Config>();
for (auto& kv : config.values) {
std::cout << kv.first << " : " << kv.second << "\n";
}
}▶ ./main
▶ VALUES='{"a": 1, "b": 2, "c": 3}' ./main
a : 1
b : 2
c : 3Application Prefix for Environment Variables
#include <envy/envy.hpp>
struct Config {
int foo = 0;
float bar = 0.0f;
bool baz = false;
};
ENVY_STRUCT(Config, foo, bar, baz);
int main() {
auto config = envy::get<Config>("APP_"); // prefix for env vars
std::cout << "foo : " << config.foo << "\n";
std::cout << "bar : " << config.bar << "\n";
std::cout << "baz : " << std::boolalpha << config.baz << "\n";
}▶ ./main
foo : 0
bar : 0
baz : false
▶ APP_FOO=1 APP_BAR=3.14 APP_BAZ=1 ./main
foo : 1
bar : 3.14
baz : trueGenerating Single Header
python3 utils/amalgamate/amalgamate.py -c single_include.json -s .Contributing
Contributions are welcome, have a look at the CONTRIBUTING.md document for more information.
License
The project is available under the MIT license.