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

#ifdef __FreeBSD__
#include <fcntl.h>
#include <kvm.h>
#include <paths.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <sys/user.h>
#endif

int main (int ac, char **av)
{
    if (ac != 2) {
        fprintf(stderr,"Usage: %s pid (0 for current pid)\n",av[0]);
        exit(0);
    }

    int pid;
    long vsize,rss;

    pid = strtol(av[1],NULL,10);
    pid = pid ? pid : getpid();
#ifdef __FreeBSD__
    kvm_t *kd;
    char *err = (char *)malloc(64*sizeof(char));
    bzero(err,64);
    struct kinfo_proc *ki;
    int pagesize,cnt,size;

    size = sizeof(pagesize);
    sysctlbyname("hw.pagesize",&pagesize,&size,NULL,0);

    kd = kvm_open(getbootfile(),"/dev/null",NULL,O_RDONLY,err);
    ki = kvm_getprocs(kd,KERN_PROC_PID,pid,&cnt);

    vsize = ki->ki_size/1024;
    rss = (ki->ki_rssize*pagesize)/1024;
    kvm_close(kd);
    free(err);
#else
    char path[64];
    sprintf(path,"/proc/%d/stat",pid);
    FILE *proc_stat = fopen(path,"r");
    if (!proc_stat) return -1;

    fscanf(proc_stat,"%*d %*s %*c %*d %*d %*d %*d %*d %*u %*u %*u %*u %*u %*u %*u %*d %*d %*d %*d %*d %*d %*u %lu %ld %*u %*u %*u %*u %*u %*u %*u %*u %*u %*u %*u %*u %*u %*d %*d",&vsize,&rss);
    fclose(proc_stat);
    vsize /= 1024;
    rss *= 4;
#endif

    printf("Memory usage for pid %d:\nVsize: %ld\nRSS: %ld\n",pid,vsize,rss);
    return 0;
}