examples/server-config.json is what FSON is for — a configuration file a person maintains.
// Example service configuration.
// Demonstrates the typical use of FSON for hand-edited config files.
{
service_name: "billing",
database: {
host: "db.internal.example", // production endpoint
port: 5432,
--user: "root", /* disabled credential, kept for reference */
"connection timeout": 2.50,
options: ["sslmode=require", "application_name=billing"]
},
retries: [
1,
2, // quick retries first
5,
30
// give up after the last delay
],
scale_factor: 1.2e+3,
enabled: true,
--debug: false,
motto: "zügig parsen 🚀"
/* end of configuration */
}
// reviewed 2026-06
Points of interest
| Construct | Note | Page |
|---|---|---|
two leading // lines | header comments — attached to the document, written back above the { | Document structure |
host: … // production endpoint | a trailing comment — stays on the member's line | Comments |
--user: "root" | a disabled member — the credential is kept for reference but invisible to queries | |
"connection timeout": | a key with a space — must be quoted; still reachable as a path: "database.connection timeout" | Keys, dotted paths |
retries[] with per-element comments and a dangling // give up… | array element trivia round-trips | Values |
2.50, 1.2e+3 | lexemes kept exactly | Numbers |
🚀 written as 🚀 in the source | surrogate pair → decoded to one code point; re-emitted as raw UTF-8 | Strings & escapes |
/* end of configuration */ before } and // reviewed 2026-06 after | dangling + footer comments | Comments |
Querying it
This is the file the User Guide › Querying page works against:
auto r = Fson::load( "server-config.json" );
auto& d = *r.document;
d.getString ( "database.host", "" ); // "db.internal.example"
d.getInteger( "database.port", 0 ); // 5432
d.getDouble ( "database.connection timeout", 0.0 ); // 2.5
d.getInteger( "retries[3]", 0 ); // 30
d.getString ( "database.user", "none" ); // "none" — disabled
d.getBoolean( "debug", true ); // true — disabled, fallback used
Editing it safely
d.setPath( "database.host", std::make_unique<String>( "db-eu.internal.example" ) );
Fson::save( d, "server-config.json" );
Only database.host changes on disk. Every comment — header, trailing, dangling, footer — and the exact spelling of 2.50 and 1.2e+3 are untouched.
