76 lines
3.0 KiB
Groff
76 lines
3.0 KiB
Groff
|
'\"
|
||
|
|
'\" 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.
|
||
|
|
'\"
|
||
|
|
.TH Tcl_DetachPids 3 "" Tcl "Tcl Library Procedures"
|
||
|
|
.so man.macros
|
||
|
|
.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, statusPtr, options\fR)
|
||
|
|
.SH ARGUMENTS
|
||
|
|
.AS Tcl_Pid *statusPtr out
|
||
|
|
.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 *statusPtr out
|
||
|
|
The result of waiting on a process (pipe). Either 0 or ECHILD.
|
||
|
|
.AP int options in
|
||
|
|
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 does not
|
||
|
|
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 has not exited yet,
|
||
|
|
\fBTcl_ReapDetachedProcs\fR does not 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 is not 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
|