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 by way of the
wait(3C), waitid(2), or waitpid(3C) system call. In the normal course
of system operation, zombies can occur, but are typically short-
lived. This can 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(8), which periodically
reaps such processes.


An irresponsible parent process can 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(2)
for pid, if pid represents a defunct process.


preap attempts 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(8).

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.

USAGE

Caution should be exercised when using the -F flag. Imposing two
controlling processes on one victim process can lead to chaos. Safety
is assured only if the primary controlling process, typically a
debugger, has stopped the victim process and the primary controlling
process is doing nothing at the moment of application of the proc
tool in question.

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.

SEE ALSO

proc(1), waitid(2), wait(3C), waitpid(3C), proc(5), attributes(7),
init(8)

WARNINGS

preap should be applied sparingly and only in situations in which the
administrator or developer has confirmed that defunct processes are
not reaped by the parent process. Otherwise, applying preap can
damage the parent process in unpredictable ways.

June 19, 2006 PREAP(1)