/* ncpus.c - find number of CPUs on a Solaris machine
 * Andrew Ho (andrew@zeuscat.com)
 *
 * Displays the number of CPUs on the local machine; works at least on
 * Solaris systems, where its output should agree with the output of
 * psrinfo(1). Compile with -DDEBUG to get some debug output when
 * walking the kstat(3) struct.
 * 
 * Build: gcc -Wall -lkstat -o ncpus ncpus.c
 * Usage: ncpus
 */

#include <stdio.h>
#include <string.h>
#include <kstat.h>
#include <fcntl.h>
#include <sys/var.h>
#include <sys/sysinfo.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <unistd.h>

#define ME "ncpus"

static kstat_ctl_t *kctl = NULL;
struct kstat_list {
    kstat_t *k;
    struct kstat_list *next;
};

int main(int argc, char **argv) {
    int cpunum, pgsize, ncpu = 0;
    kstat_t *k;
    struct kstat_list *cpu = NULL, *cpucur, *newone;

    /* Open the kstat interface */
    pgsize = sysconf(_SC_PAGESIZE);
    pgsize /= 1024; /* Page size in kb */
    if(NULL == (kctl = kstat_open())) {
        perror("kstat");
        exit(1);
    }
    for(k = kctl->kc_chain; k; k = k->ks_next) {

#ifdef DEBUG
printf("%s [debug]: statistic = \"%s\"\n", ME, k->ks_name);
#endif

        if(!strncmp(k->ks_name, "cpu_stat", 8)) {

#ifdef DEBUG
printf("%s [debug]: found CPU statistic = \"%s\"\n", ME, k->ks_name);
#endif

            (void)sscanf(k->ks_name, "cpu_stat%d", &cpunum);
            newone = (struct kstat_list *)malloc(sizeof(struct kstat_list));
            newone->k = k;
            newone->next = NULL;
            if(NULL == cpu) {
                cpu = newone;
                cpucur = newone;
            } else {
                cpucur->next = newone;
                cpucur = newone;
            }
            ncpu++;
        }
    }
    printf("%s: found %d CPU%s\n", ME, ncpu, ncpu == 1 ? "" : "s");
    return 0;
}