utsname.c

/*
 * prints something like:
 * sysname: Darwin
 * release: 16.7.0
 * version: Darwin Kernel Version 16.7.0: Wed Feb 27 00:29:57 PST 2019; root:xnu-3789.73.43~1/RELEASE_X86_64
 * machine: x86_64
 */
#include <stdio.h>
#include <sys/utsname.h>

int main(void)
{
    struct utsname n;
    uname(&n);
    printf("sysname: %s\nrelease: %s\nversion: %s\nmachine: %s\n", n.sysname, n.release, n.version, n.machine);
    return 0;
}