From: Daniel Berger <djberg96@...>
Date: 2008-08-29T07:04:03+09:00
Subject: Re: Unraveling binary data out of the proc filesystem on Solaris



On Aug 26, 8:16 am, Daniel Berger <djber...@gmail.com> wrote:
> On Aug 25, 7:59 pm, "Heesob Park" <pha...@gmail.com> wrote:
>
>
>
> > Hi,
>
> > 2008/8/26 DanielBerger<djber...@gmail.com>:
>
> > > Hi all,
>
> > > Ruby 1.8.6
> > >Solaris10
>
> > > I'm trying to get process information on aSolarisusing 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.

<snip>

The bad news is that it requires pread() after all as far as I can
tell. The good news is that I've added pread and pwrite support to the
io-extra library, and it's available in io-extra-1.1.0 and later.

Here's a snippet:

require 'io/extra'

# Mozilla on Solaris. Use whatever pid you wish.
#
# ps -ef shows the args to be "/bin/ksh", "-p", and "/usr/sfw/bin/
mozilla"
#
pid = 2253

# First, get the psinfo struct data and unravel some information we
need
psinfo = IO.read("/proc/#{pid}/psinfo")
pr_argc = psinfo[188, 4].unpack("L")[0]
pr_argv = psinfo[192, 4].unpack("L")[0]

# Second, get our initial address from /proc/<pid>/as
fd = File.open("/proc/#{pid}/as")
addr = IO.pread(fd.fileno, pr_argc * 4, pr_argv).unpack("L")[0]

# Third, get each command argument, incrementing the address as
needed. I've
# hard coded the read limit at 128. Adjust as you see fit.
0.upto(pr_argc - 1){ |i|
   data = IO.pread(fd.fileno, 128, addr)
   addr += data.length + 1 # Add 1 for the space
   p data
}

# Finally, close our file descriptor
fd.close

On my system, that prints "/bin/ksh", "-p" and "/usr/sfw/bin/mozilla"
as expected.

Regards,

Dan

PS - Doing this also helped me realize that there's a bug in the C
implementation, too. :/