Okay, there exists a getpid() in a variety of programming
languages, and shells, and there exists a getppid() to
get the parent process ID in a variety of languages and shells.
But how can I get my grandparent pid, in some way that is
portable?  The only thing I can think of is to read the ouput
of a 'ps' command, because there doesn't seem to be any standard
calls or commands that give me that.

Ideally, it would be nice if there was some sort of getppid command
that instead of just returning YOUR parent, would return the parent
of a pid you give it as an argument.  Again, I don't care if
this is something in a shell or a more low-level language like C,
I just want to know if anyone out there has seen some sort of a
way to do this, in any language or any shell.

I want to avoid 'ps' because it's flags differ so much from
one UNIX to another, as does its output format.

Actually,  thanks to XPG4, ps has actually converged.  For instance,
the same works for both HP-UX 10.x &11.x and Linux Red Hat 6.1 (under ksh):

   UNIX95=1 ps -p $PPID -o ppid=

(don't forget the trailing "=").  On some systems,  xpg4 compliant
utilities will be in a separate bin directory, /usr/xpg4/bin for
example.

--
Dan Mercer
damer...@uswest.net

How about looking in the /proc directory?  (or is this linux-centric?)

--

Remove 'wakawaka' and 'invalid' to e-mail me.  You can thank spammers for this
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I didn't do it!  Nobody saw anything!  You can't prove anything! -- bart

: How about looking in the /proc directory?  (or is this linux-centric?)

All /proc directory layouts are vendor-specific.

: Actually,  thanks to XPG4, ps has actually converged.  For instance,
: the same works for both HP-UX 10.x &11.x and Linux Red Hat 6.1 (under ksh):

:    UNIX95=1 ps -p $PPID -o ppid=

: (don't forget the trailing "=").  On some systems,  xpg4 compliant
: utilities will be in a separate bin directory, /usr/xpg4/bin for
: example.

I'm afraid I have no idea what this XPG4 is.  (There is no /usr/xpg4
in any of the unix system I have access to.)

There isn't on SCO OpenServer 5 either but I thought I'd try it anyway. It
works. Just try it.

What systems are you going to be using this on?

--
Richard Howlett

mailto:rich...@howie.org.uk

Thanks for the heads up.  Should I worry about changes w/ a specific vendor?
(elinux on the etrax100 board in this case)

--

Remove 'wakawaka' and 'invalid' to e-mail me.  You can thank spammers for this
inconvenience.

I didn't do it!  Nobody saw anything!  You can't prove anything! -- bart

  >> All /proc directory layouts are vendor-specific.

  n> Thanks for the heads up.  Should I worry about changes w/ a
  n> specific vendor?  (elinux on the etrax100 board in this case)

Generally, yes.  The Linux kernel (which is what you care about) has,
can, and will continue to change the format of the contents of /proc
files.

They don't like to do it, but they aren't nearly as concerned about
keeping backward-compatibility here as they are about getting a correct,
usable interface.

--
-------------------------------------------------------------------------------
 Paul D. Smith <psm...@baynetworks.com>    HASMAT--HA Software Methods & Tools
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist
-------------------------------------------------------------------------------
   These are my opinions---Nortel Networks takes no responsibility for them.

XPG4 is a standard.  Some vendors use a separate directory path
to hold the compliant function.  Most just build the compliance in
(like Linux and HP-UX 10/11) but some of those (HP-UX) rely on
the UNIX95 env var being set (to any value) to trigger the new
functionality.  Under any circumstances,  setting UNIX95 for the
ps command does no harm.  Check your man pages for the ps
command and pay particular attention to the "Standards Compliance" section:

Name
     ps - report process status

...

Standards Compliance
     ps: SVID2, XPG2, XPG3, XPG4

Did you try the command to see if it works?  There is no portable
API for reading the process table.

--
Dan Mercer
damer...@uswest.net

Uh, *why* do you need a grandparent PID anyways?  "Grandparents" have
no particular relation to their "grandchildren" and there is not
generally a need for a process to need this information, which is why
there's no easy way to get it.

                               Chris Mattern

                       Chris Mattern