in spawned processes, both $$ and $PPID are wrong

[skt]

Bash does not represent current pid and parent process-id correctly
in spawned processes.

The configuration information below is from a RedHat 9.0 system,
but I have confirmed the problem still exists using
bash version 3.1.17(1)-release on Fedora Core 6.


Configuration Information [Automatically generated, do not change]:
Machine: i386
OS: linux-gnu
Compiler: i386-redhat-linux-gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i386-redhat-linux-gnu' 
-DCONF_VENDOR='redhat' -DSHELL -DHAVE_CONFIG_H  -I.  -I. -I./include -I./lib 
-D_GNU_SOURCE  -O2 -march=i386 -mcpu=i686 -g
uname output: Linux skywalker.ca.boeing.com 2.4.20-8 #1 Thu Mar 13 17:54:28 EST 
2003 i686 i686 i386 GNU/Linux
Machine Type: i386-redhat-linux-gnu

Bash Version: 2.05b
Patch Level: 0
Release Status: release

Description:
        [Detailed description of the problem, suggestion, or complaint.]
        The shell variables $$ and $PPID are not correct in child shell
        processes spawned by a parent shell process.

Repeat-By:
        [Describe the sequence of events that causes the problem
        to occur.]
This script will demonstrate the problem:
-----------------------------cut here----------------------------------
#!/bin/sh
#
# 4/9/07 - Stan Tazuma
#
# demo of bash bugs in the use of:
#       $$  $PPID

demo1() {
    echo function in forked process shows pid='$$' of original process,
    echo not the new child process

    echo demo1: pid=$$, PPID=$PPID
}

demo2() {
    echo pipe situation -- the processes in the pipe should be able to
    echo determine their own pid, but they cannot

    some_var='some'

    (echo demo2/pipe-writer: pid = $$, PPID = $PPID) |
        (
        read line
        echo $line

        # neither $$ nor $PPID appear to be evaluated at run-time,
        # but are just kept as they were from the parent shell;
        # since neither are environment variables, that is strange
        echo demo2/pipe-reader: pid = $$, PPID = $PPID

        # the next few lines show that other variables
        # are being evaluated at run time
        echo some_var=$some_var
        some_var=something
        echo some_var=$some_var
        )
}


echo ==========================================================
echo parent pid = $$, PPID = $PPID
echo ==========================================================

echo calling demo1 in a background process ...
demo1 &
wait

echo ''
echo ==========================================================

echo calling demo2 ...
demo2

echo ''
echo ==========================================================
echo A situation where you need an accurate listing of pids:
echo You have a tree of processes for a system service, and you
echo want a reliable way of killing off all the processes started
echo for that service.  I would like to have each process write its
echo own pid to a pid file.
echo ''

-----------------------------cut here----------------------------------

Running the above script results in:

==========================================================
parent pid = 8291, PPID = 30730
==========================================================
calling demo1 in a background process ...
function in forked process shows pid=$$ of original process,
not the new child process
demo1: pid=8291, PPID=30730

==========================================================
calling demo2 ...
pipe situation -- the processes in the pipe should be able to
determine their own pid, but they cannot
demo2/pipe-writer: pid = 8291, PPID = 30730
demo2/pipe-reader: pid = 8291, PPID = 30730
some_var=some
some_var=something

==========================================================
A situation where you need an accurate listing of pids:
You have a tree of processes for a system service, and you
want a reliable way of killing off all the processes started
for that service. I would like to have each process write its
own pid to a pid file.