Number of Running Processes on a Minix system from C code

Question

So, this seemed simple at first, but after crawling Google and here, the answer doesn\'t seem as simple as I first thought.

Basically, I\'m editing a MINIX kernel as

Answer 1

So I have been having the same problem and found a solution. (MINIX 3.1) within the method to count the processes use this code: (This is ANSI C)

It simply runs through the process table and counts the number of processes.

I know this is an old thread but it might help someone in the future.

#include "../pm/mproc.h"

/* inside function */

struct mproc *mp;
int i, n=0;

printf("Number of running processes:\n");

getsysinfo(PM_PROC_NR, SI_PROC_TAB, mproc);

for (i = 0; i<NR_PROCS; i++) {
    mp = &mprocs[i];
    if (mp->mp_pid == 0 && i != PM_PROCS_NR) continue;
    n++;   
}

printf("%d", n);

/* function end */

Answer 2

Perhaps you could show us the code your wrote for capturing the result of system("ps -ax | wc -l"), or the code you wrote to use popen and we could help you diagnose the problem with it.

Regardless, the most efficient way I can think of to count the number of existing (not the same as running) processes on the system is to opendir("/proc") and count the number of entries that are strings of decimal digits. Each process in the system will be represented by a subdirectory of /proc, named after the decimal process id number of that process.

So, if you find "/proc/3432", for example, then you know that there exists a process with a pid of "3432". Simply count the number of subdirectories you find whose names are decimal numbers.

---

Assumptions:

• You are asking about Linux, not MINIX.
• You are writing a user-mode program, not modifiying the kernel.

Answer 3

Check this out: http://sourceforge.net/p/readproc/code/ci/master/tree/

#include"read_proc.h"
int main(void)
{
     struct Root * root=read_proc();
     printf("%lu\n",root->len);
     return 0;
}

Answer 4

try looking to see what ps does. Look at its source code; it knows how many processes there are

Answer 5

Check this out: http://procps.sourceforge.net/

It's got source to a number of small utilities that do these kinds of things. It'll be a good learning experience :) and I think PS is i n there as pm100 noted.

Answer 6

struct kinfo kinfo;
int nr_tasks, nr_procs;
getsysinfo(PM_PROC_NR, SI_KINFO, &kinfo);
nr_procs = kinfo.nr_pro;

This will get you the number of processes running