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/*
* build-from-scratch.c - Building YAML documents programmatically
*
* Demonstrates:
* - Creating empty documents
* - Building nodes using printf-style formatting
* - Setting document root
* - Adding fields programmatically
* - Emitting as both JSON and YAML
*
* Copyright (c) 2019-2025 Pantelis Antoniou <pantelis.antoniou@konsulko.com>
*
* SPDX-License-Identifier: MIT
*/
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <libfyaml.h>
int main(void)
{
struct fy_document *fyd = NULL;
struct fy_node *root = NULL;
time_t now = time(NULL);
struct tm *tm_info = localtime(&now);
char timestamp[32];
int ret = EXIT_FAILURE;
strftime(timestamp, sizeof(timestamp), "%Y-%m-%d %H:%M:%S", tm_info);
// Create empty document
fyd = fy_document_create(NULL);
if (!fyd) {
fprintf(stderr, "Failed to create document\n");
return EXIT_FAILURE;
}
// Build root mapping using printf-style formatting
root = fy_node_buildf(fyd,
"application: MyApp\n"
"version: %d.%d.%d\n"
"build_date: %s\n"
"settings:\n"
" debug: %s\n"
" max_connections: %d\n"
" allowed_hosts:\n"
" - localhost\n"
" - 127.0.0.1\n",
1, 2, 3,
timestamp,
"true",
100);
if (!root) {
fprintf(stderr, "Failed to build root node\n");
goto cleanup;
}
// Set as document root
fy_document_set_root(fyd, root);
// Add more fields programmatically
if (fy_document_insert_at(fyd, "/settings", FY_NT,
fy_node_buildf(fyd, "log_level: info"))) {
fprintf(stderr, "Failed to add log_level\n");
goto cleanup;
}
if (fy_document_insert_at(fyd, "/settings", FY_NT,
fy_node_buildf(fyd,
"database:\n"
" host: localhost\n"
" port: 5432\n"
" name: myapp_db\n"))) {
fprintf(stderr, "Failed to add database config\n");
goto cleanup;
}
// Add feature flags
if (fy_document_insert_at(fyd, "/", FY_NT,
fy_node_buildf(fyd,
"features:\n"
" authentication: enabled\n"
" api_v2: disabled\n"
" metrics: enabled\n"))) {
fprintf(stderr, "Failed to add features\n");
goto cleanup;
}
// Output as JSON
printf("=== JSON Output ===\n");
if (fy_emit_document_to_fp(fyd, FYECF_MODE_JSON, stdout)) {
fprintf(stderr, "Failed to emit as JSON\n");
goto cleanup;
}
printf("\n\n");
// Output as YAML with sorted keys
printf("=== YAML Output (sorted) ===\n");
if (fy_emit_document_to_fp(fyd, FYECF_MODE_BLOCK | FYECF_SORT_KEYS, stdout)) {
fprintf(stderr, "Failed to emit as YAML\n");
goto cleanup;
}
ret = EXIT_SUCCESS;
cleanup:
fy_document_destroy(fyd);
return ret;
}
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