named parameters in C

name_params.c

#include <stdio.h>
#include <stdlib.h>

typedef struct {
  char *name;
  size_t len;
  int value;
} option_t;

void display_cmd_fn(option_t opt);

// macro to set defaults and allow for overwrites
#define display_cmd(...) \
  display_cmd_fn((option_t){ .name = "default", .len = 7, __VA_ARGS__ })

void display_cmd_fn(option_t opt) {
  if (opt.name != NULL) {
    printf("name = %s\n", opt.name);
  } else {
    printf("name = NULL\n");
  }
  printf("len = %lu\n", opt.len);
  printf("value = %d\n", opt.value);

}

int main (void) {
  // using default values.
  display_cmd(.value = 10);

  // overwriting values.
  display_cmd(.name = "scale", .len = 5, .value = 42);
}