12-17-2002
Processes don't change process IDs. However, processes can spawn other processes and each of those will have a different process id.... in turn, those process ids do not change, they are born and they die.
Parent processes spawn child processes and children can also become parents, etc. (like RTM was explaining)
Because we call them parent and child processes and because processes die (and are killed), parent and child processes are the subject of many jokes about "forking children" "killing children" ... "parents killing their children" etc.
... these jokes are normally made by UNIX novices who have just discovered parent/child process relationships.... then after a short time, the vocabulary become natural and the jokes are not (generally) used by 'UNIX adults'...... (mature UNIX users)... we just do the work... so to speak.
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preap(1) User Commands preap(1)
NAME
preap - force a defunct process to be reaped by its parent
SYNOPSIS
preap [-F] pid...
DESCRIPTION
A defunct (or zombie) process is one whose exit status has yet to be reaped by its parent. The exit status is reaped via the wait(3C),
waitid(2), or waitpid(3C) system call. In the normal course of system operation, zombies may occur, but are typically short-lived. This may
happen if a parent exits without having reaped the exit status of some or all of its children. In that case, those children are reparented
to PID 1. See init(1M), which periodically reaps such processes.
An irresponsible parent process may not exit for a very long time and thus leave zombies on the system. Since the operating system destroys
nearly all components of a process before it becomes defunct, such defunct processes do not normally impact system operation. However, they
do consume a small amount of system memory.
preap forces the parent of the process specified by pid to waitid(3C) for pid, if pid represents a defunct process.
preap will attempt to prevent the administrator from unwisely reaping a child process which might soon be reaped by the parent, if:
o The process is a child of init(1M).
o The parent process is stopped and might wait on the child when it is again allowed to run.
o The process has been defunct for less than one minute.
OPTIONS
The following option is supported:
-F Forces the parent to reap the child, overriding safety checks.
OPERANDS
The following operand is supported:
pid Process ID list.
EXIT STATUS
The following exit values are returned by preap, which prints the exit status of each target process reaped:
0 Successfully operation.
non-zero Failure, such as no such process, permission denied, or invalid option.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWesu (32-bit) |
+-----------------------------+-----------------------------+
| |SUNWesxu (64-bit) |
+-----------------------------+-----------------------------+
SEE ALSO
proc(1), init(1M), waitid(2), wait(3C), waitpid(3C), proc(4), attributes(5)
WARNINGS
preap should be applied sparingly and only in situations in which the administrator or developer has confirmed that defunct processes will
not be reaped by the parent process. Otherwise, applying preap may damage the parent process in unpredictable ways.
SunOS 5.10 26 Mar 2001 preap(1)