From: Daniel Berger <djberg96@...>
Date: 2008-08-26T06:50:47+09:00
Subject: Unraveling binary data out of the proc filesystem on Solaris

Hi all,

Ruby 1.8.6
Solaris 10

I'm trying to get process information on a Solaris using pure Ruby.
For the basic information, this is fairly straightforward, as I read
out of /proc/<pid>/psinfo.

However, where I'm having trouble is getting the command line
arguments out of /proc/<pid>/as. Basically, I need to know how to
unravel the data I'm reading into a human readable string.

Here's some sample code:

# sunos.rb
module Sys
   class ProcTable
      def self.ps(pid = nil)
         Dir.foreach("/proc") do |file|
            next if file =~ /\D/
            next if pid && file.to_i != pid

            psinfo = IO.read("/proc/#{file}/psinfo")

            pid = psinfo[8,4].unpack("L")[0]
            puts "PID: #{pid}"

            argc = psinfo[188,4].unpack("L")[0] # pr_argc
            addr = psinfo[192,4].unpack("L")[0] # pr_argv

            size = argc * 4 # 4 is the sizeof(caddr32_t)
            asinfo = IO.read("/proc/#{file}/as", size, addr)

            # How do I unravel asinfo?
            p asinfo
         end
      end
   end
end

if $0 == __FILE__
   include Sys
   ProcTable.ps(2764) # or whatever pid you prefer
end

The C code I'm trying to simulate, which I pulled from a post by Roger
Faulkner on comp.unix.questions, looks something like this:

addr_args = p.pr_argv; /* from the psinfo struct */
arg_count = p.pr_argc; /* from the psinfo struct */

if((fd = open(as_file, O_RDONLY)) < 0){
   /* Do nothing - you can only get info on processes you rights to */
}
else
{
   arg_vec = malloc(arg_count * sizeof(uintptr_t));
   (void)pread(fd, arg_vec, arg_count * sizeof (uintptr_t),
addr_args);

   arg_len = 16;
   arg = malloc(arg_len+1);

   for(i = 0; i < arg_count; i++) {
      if(pread(fd, arg, arg_len, arg_vec[i]) < 0)
         continue;

      arg[arg_len] = '\0';
      if(strlen(arg) == arg_len){
         arg_len *= 2;
         arg = realloc(arg, arg_len + 1);
         i--;
         continue;
      }
      rb_ary_push(v_cmd_array, rb_str_new2(arg));
   }
   free(arg);
   free(arg_vec);
}

close(fd);

Any ideas how to get the string(s) I need out of /proc/<pid>/as ?

Thanks,

Dan