xtc_cfg(3)

---

xtc_cfg(3)

typed runtime configuration registry

XTC_CFG(3) Library Functions Manual XTC_CFG(3)

xtc_cfg_register, xtc_cfg_unregister, xtc_cfg_register_bool, xtc_cfg_register_int, xtc_cfg_register_int64, xtc_cfg_register_double, xtc_cfg_register_string, xtc_cfg_register_enum, xtc_cfg_get, xtc_cfg_get_bool, xtc_cfg_get_int, xtc_cfg_get_int64, xtc_cfg_get_double, xtc_cfg_get_string, xtc_cfg_get_enum, xtc_cfg_set, xtc_cfg_set_bool, xtc_cfg_set_int, xtc_cfg_set_int64, xtc_cfg_set_double, xtc_cfg_set_string, xtc_cfg_set_enum, xtc_cfg_count, xtc_cfg_kind, xtc_cfg_load_file, xtc_cfg_reload — typed runtime configuration registry

#include <xtc.h>
#include <xtc_cfg.h>

int
xtc_cfg_register(const xtc_cfg_spec_t *spec);

int
xtc_cfg_unregister(const char *name);

int
xtc_cfg_register_bool(const char *name, int *out_var, int default_v, const char *help);

int
xtc_cfg_register_int(const char *name, int *out_var, int default_v, int min, int max, const char *help);

int
xtc_cfg_register_int64(const char *name, int64_t *out_var, int64_t default_v, int64_t min, int64_t max, const char *help);

int
xtc_cfg_register_double(const char *name, double *out_var, double default_v, double min, double max, const char *help);

int
xtc_cfg_register_string(const char *name, char *buf, size_t buflen, const char *default_v, const char *help);

int
xtc_cfg_set(const char *name, const char *value);

int
xtc_cfg_get_bool(const char *name, int *out);

int
xtc_cfg_get_int(const char *name, int *out);

int
xtc_cfg_get_int64(const char *name, int64_t *out);

int
xtc_cfg_get_double(const char *name, double *out);

int
xtc_cfg_get_string(const char *name, const char **out);

int
xtc_cfg_get_enum(const char *name, int *out);

int
xtc_cfg_set_bool(const char *name, int v);

int
xtc_cfg_set_int(const char *name, int v);

int
xtc_cfg_set_int64(const char *name, int64_t v);

int
xtc_cfg_set_double(const char *name, double v);

int
xtc_cfg_set_string(const char *name, const char *v);

int
xtc_cfg_set_enum(const char *name, int v);

int
xtc_cfg_count(void);

int
xtc_cfg_kind(const char *name, xtc_cfg_kind_t *out);

int
xtc_cfg_load_file(const char *path);

int
xtc_cfg_reload(void);

xtc_cfg is a typed runtime configuration registry, modeled on PostgreSQL's GUC system. Modules register named knobs at startup; operators set them by name; values get bound to live variables and validated against type and bounds.

Supported types: bool, int, int64, double, string, enum. Each () takes:

  • A canonical name (dot-separated, e.g. ‘rexis.max_clients’).
  • A backing storage pointer. When the cfg value changes, the storage is updated atomically.
  • A default and bounds (for numeric types).
  • A help string used in ‘cfg dump’ output.

() parses the string value to the registered type, validates against bounds, and updates the backing variable. An optional on-change callback fires.

Modules register a knob with (), passing an xtc_cfg_spec_t that carries name, type, backing storage, default and bounds; the type-specific (), (), (), (), (), and () wrappers fill that spec for one type. () removes a knob by name.

() parses the string value to the registered type, validates against bounds, and updates the backing variable. An optional on-change callback fires. The typed setters (), (), (), (), (), and () assign a value of the matching C type without going through the string parser.

() (via the typed accessors) reads the current value. Use (), (), (), (), (), or () for the corresponding registered kind.

() returns the number of registered knobs; () reports the xtc_cfg_kind_t type of a named knob.

static int g_max_clients = 1000;

xtc_cfg_register_int("rexis.max_clients", &g_max_clients,
                      1000, 1, 100000,
                      "Maximum concurrent client connections");

/* Operator runtime change: */
xtc_cfg_set("rexis.max_clients", "5000");

xtc_log(3), xtc_stats(3), xtc(7)

Appeared in xtc 0.1.

May 28, 2026 Debian

View the mdoc source