[OpenSPARC-T2-SAM] / sam-t2 / devtools / v9 / man / man3 / Tcl_WaitPid.3

'\"
'\" Copyright (c) 1989-1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\" RCS: @(#) $Id: DetachPids.3,v 1.3 2001/04/03 14:53:45 andreas_kupries Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
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.TH Tcl_DetachPids 3 "" Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_DetachPids, Tcl_ReapDetachedProcs, Tcl_WaitPid \- manage child processes in background
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
\fBTcl_DetachPids\fR(\fInumPids, pidPtr\fR)
.sp
\fBTcl_ReapDetachedProcs\fR()
.sp
Tcl_Pid
\fBTcl_WaitPid\fR(\fIpid, statPtr, options\fR)
.SH ARGUMENTS
.AS int *statusPtr
.AP int numPids in
Number of process ids contained in the array pointed to by \fIpidPtr\fR.
.AP int *pidPtr in
Address of array containing \fInumPids\fR process ids.
.AP Tcl_Pid pid in
The id of the process (pipe) to wait for.
.AP int* statPtr out
The result of waiting on a process (pipe). Either 0 or ECHILD.
.AP int options
The options controlling the wait. WNOHANG specifies not to wait when
checking the process.
.BE
.SH DESCRIPTION
.PP
\fBTcl_DetachPids\fR and \fBTcl_ReapDetachedProcs\fR provide a
mechanism for managing subprocesses that are running in background.
These procedures are needed because the parent of a process must
eventually invoke the \fBwaitpid\fR kernel call (or one of a few other
similar kernel calls) to wait for the child to exit.  Until the
parent waits for the child, the child's state cannot be completely
reclaimed by the system.  If a parent continually creates children
and doesn't wait on them, the system's process table will eventually
overflow, even if all the children have exited.
.PP
\fBTcl_DetachPids\fR may be called to ask Tcl to take responsibility
for one or more processes whose process ids are contained in the
\fIpidPtr\fR array passed as argument.  The caller presumably
has started these processes running in background and doesn't
want to have to deal with them again.
.PP
\fBTcl_ReapDetachedProcs\fR invokes the \fBwaitpid\fR kernel call
on each of the background processes so that its state can be cleaned
up if it has exited.  If the process hasn't exited yet,
\fBTcl_ReapDetachedProcs\fR doesn't wait for it to exit;  it will check again
the next time it is invoked.
Tcl automatically calls \fBTcl_ReapDetachedProcs\fR each time the
\fBexec\fR command is executed, so in most cases it isn't necessary
for any code outside of Tcl to invoke \fBTcl_ReapDetachedProcs\fR.
However, if you call \fBTcl_DetachPids\fR in situations where the
\fBexec\fR command may never get executed, you may wish to call
\fBTcl_ReapDetachedProcs\fR from time to time so that background
processes can be cleaned up.
.PP
\fBTcl_WaitPid\fR is a thin wrapper around the facilities provided by
the operating system to wait on the end of a spawned process and to
check a whether spawned process is still running. It is used by
\fBTcl_ReapDetachedProcs\fR and the channel system to portably access
the operating system.

.SH KEYWORDS
background, child, detach, process, wait
Commit	Line	Data
920dae64 AT	1	'\"
	2	'\" Copyright (c) 1989-1993 The Regents of the University of California.
	3	'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
	4	'\"
	5	'\" See the file "license.terms" for information on usage and redistribution
	6	'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
	7	'\"
	8	'\" RCS: @(#) $Id: DetachPids.3,v 1.3 2001/04/03 14:53:45 andreas_kupries Exp $
	9	'\"
	10	'\" The definitions below are for supplemental macros used in Tcl/Tk
	11	'\" manual entries.
	12	'\"
	13	'\" .AP type name in/out ?indent?
	14	'\" Start paragraph describing an argument to a library procedure.
	15	'\" type is type of argument (int, etc.), in/out is either "in", "out",
	16	'\" or "in/out" to describe whether procedure reads or modifies arg,
	17	'\" and indent is equivalent to second arg of .IP (shouldn't ever be
	18	'\" needed; use .AS below instead)
	19	'\"
	20	'\" .AS ?type? ?name?
	21	'\" Give maximum sizes of arguments for setting tab stops. Type and
	22	'\" name are examples of largest possible arguments that will be passed
	23	'\" to .AP later. If args are omitted, default tab stops are used.
	24	'\"
	25	'\" .BS
	26	'\" Start box enclosure. From here until next .BE, everything will be
	27	'\" enclosed in one large box.
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	39	'\" Begin vertical sidebar, for use in marking newly-changed parts
	40	'\" of man pages. The first argument is ignored and used for recording
	41	'\" the version when the .VS was added, so that the sidebars can be
	42	'\" found and removed when they reach a certain age. If another argument
	43	'\" is present, then a line break is forced before starting the sidebar.
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	56	'\" options follow on successive lines, in four columns separated
	57	'\" by tabs.
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	60	'\" End of list of standard options for a Tk widget.
	61	'\"
	62	'\" .OP cmdName dbName dbClass
	63	'\" Start of description of a specific option. cmdName gives the
	64	'\" option's name as specified in the class command, dbName gives
65	'\" the option's name in the option database, and dbClass gives
66	'\" the option's class in the option database.
67	'\"
68	'\" .UL arg1 arg2
69	'\" Print arg1 underlined, then print arg2 normally.
70	'\"
71	'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
72	'\"
73	'\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
74	.if t .wh -1.3i ^B
75	.nr ^l \n(.l
76	.ad b
77	'\" # Start an argument description
78	.de AP
79	.ie !"\\$4"" .TP \\$4
80	.el \{\
81	. ie !"\\$2"" .TP \\n()Cu
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107	..
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177	.el \h'-1.5n'\L'\|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'\|0u'\c
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208	.SH "STANDARD OPTIONS"
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219	See the \\fBoptions\\fR manual entry for details on the standard options.
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243	.de UL
244	\\$1\l'\|0\(ul'\\$2
245	..
246	.TH Tcl_DetachPids 3 "" Tcl "Tcl Library Procedures"
247	.BS
248	.SH NAME
249	Tcl_DetachPids, Tcl_ReapDetachedProcs, Tcl_WaitPid \- manage child processes in background
250	.SH SYNOPSIS
251	.nf
252	\fB#include <tcl.h>\fR
253	.sp
254	\fBTcl_DetachPids\fR(\fInumPids, pidPtr\fR)
255	.sp
256	\fBTcl_ReapDetachedProcs\fR()
257	.sp
258	Tcl_Pid
259	\fBTcl_WaitPid\fR(\fIpid, statPtr, options\fR)
260	.SH ARGUMENTS
261	.AS int *statusPtr
262	.AP int numPids in
263	Number of process ids contained in the array pointed to by \fIpidPtr\fR.
264	.AP int *pidPtr in
265	Address of array containing \fInumPids\fR process ids.
266	.AP Tcl_Pid pid in
267	The id of the process (pipe) to wait for.
268	.AP int* statPtr out
269	The result of waiting on a process (pipe). Either 0 or ECHILD.
270	.AP int options
271	The options controlling the wait. WNOHANG specifies not to wait when
272	checking the process.
273	.BE
274	.SH DESCRIPTION
275	.PP
276	\fBTcl_DetachPids\fR and \fBTcl_ReapDetachedProcs\fR provide a
277	mechanism for managing subprocesses that are running in background.
278	These procedures are needed because the parent of a process must
279	eventually invoke the \fBwaitpid\fR kernel call (or one of a few other
280	similar kernel calls) to wait for the child to exit. Until the
281	parent waits for the child, the child's state cannot be completely
282	reclaimed by the system. If a parent continually creates children
283	and doesn't wait on them, the system's process table will eventually
284	overflow, even if all the children have exited.
285	.PP
286	\fBTcl_DetachPids\fR may be called to ask Tcl to take responsibility
287	for one or more processes whose process ids are contained in the
288	\fIpidPtr\fR array passed as argument. The caller presumably
289	has started these processes running in background and doesn't
290	want to have to deal with them again.
291	.PP
292	\fBTcl_ReapDetachedProcs\fR invokes the \fBwaitpid\fR kernel call
293	on each of the background processes so that its state can be cleaned
294	up if it has exited. If the process hasn't exited yet,
295	\fBTcl_ReapDetachedProcs\fR doesn't wait for it to exit; it will check again
296	the next time it is invoked.
297	Tcl automatically calls \fBTcl_ReapDetachedProcs\fR each time the
298	\fBexec\fR command is executed, so in most cases it isn't necessary
299	for any code outside of Tcl to invoke \fBTcl_ReapDetachedProcs\fR.
300	However, if you call \fBTcl_DetachPids\fR in situations where the
301	\fBexec\fR command may never get executed, you may wish to call
302	\fBTcl_ReapDetachedProcs\fR from time to time so that background
303	processes can be cleaned up.
304	.PP
305	\fBTcl_WaitPid\fR is a thin wrapper around the facilities provided by
306	the operating system to wait on the end of a spawned process and to
307	check a whether spawned process is still running. It is used by
308	\fBTcl_ReapDetachedProcs\fR and the channel system to portably access
309	the operating system.
310
311	.SH KEYWORDS
312	background, child, detach, process, wait