What is wrong with my sysctl()?

When I compile the following:

Code:

#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <kvm.h>

int main(void)
{
/*ttypf*/

    struct stat sb;
    int mib[4];
    size_t len;
    struct kinfo_proc  *p; 
    static char buffer[1024];
    int count;
    struct kinfo_proc *kp;


    if (stat("/dev/ttypf", &sb) != 0) {
        perror("stat");
        return 1;
    }
        

    mib[0] = CTL_KERN;
    mib[1] = KERN_PROC;
    mib[2] = KERN_PROC_TTY;
    mib[3] = sb.st_rdev;

    len = 0;
    if (sysctl(mib, sizeof(mib)/sizeof(int), NULL , &len, NULL, 0) == -1) 
{
        perror("sysctl test");
        return 1;
    }

   p =(struct kinfo_proc *)malloc(len); 
   if (sysctl(mib, sizeof(mib)/sizeof(int), p, &len, NULL, 0) == -1) 
    {
        perror("sysctl real");
        return 1;
    }

    /*count = len / sizeof(kp);*/
    kp = p; 

    printf("The pid is: %u\n", kp.ki_pid);

    return 0;
}

I get...

root@robotics.eecs.berkeley.edu# gcc -g RobotSex.c -o RobotSex -lkvm
RobotSex.c: In function `main':
RobotSex.c:52: error: request for member `ki_pid' in something not a structure or union

What did I do wrong?

Try "kp->ki_pid".

gg

I'm not sure why you are malloc()'ing the kinfo_proc. Why not just declare:

Code:

struct kinfo_proc p;

And then do:

Code:

if (sysctl(mib, sizeof(mib)/sizeof(int), &p, &len, NULL, 0) == -1)

And why do you alias the p pointer with kp before you access it?

I made the changes...

Code:

#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <utmp.h>
#include <kvm.h>

int main(void)
{
/*ttypf*/

    struct stat sb;
    int mib[4];
    size_t len;
    int count;
    struct kinfo_proc p;

    if (stat("/dev/ttypq", &sb) != 0) {
        perror("stat");
        return 1;
    }
        

    mib[0] = CTL_KERN;
    mib[1] = KERN_PROC;
    mib[2] = KERN_PROC_TTY;
    mib[3] = sb.st_rdev;

    len = 0;
    if (sysctl(mib, sizeof(mib)/sizeof(int), NULL , &len, NULL, 0) == -1) 
{
        perror("sysctl test");
        return 1;
    }

   /*p =(struct kinfo_proc *)malloc(len); */
   if (sysctl(mib, sizeof(mib)/sizeof(int), &p, &len, NULL, 0) == -1) 
    {
        perror("sysctl real");
        return 1;
    }

    /*count = len / sizeof(kp);*/
   /* kp = p; */

    printf("The pid is: %u\n", p.ki_pid);

    return 0;
}

And now I get

RobotSex.c: In function `main':
RobotSex.c:20: error: storage size of 'p' isn't known

Apparently the structure struct kinfo_proc is in some other header file. I have no idea which one.

What OS are you compiling/running this on?

gg