diff options
Diffstat (limited to 'doc/DetachPids.3')
| -rw-r--r-- | doc/DetachPids.3 | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/doc/DetachPids.3 b/doc/DetachPids.3 new file mode 100644 index 0000000..153649b --- /dev/null +++ b/doc/DetachPids.3 @@ -0,0 +1,62 @@ +'\" +'\" 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. +'\" +'\" SCCS: @(#) DetachPids.3 1.15 96/08/26 12:59:44 +'\" +.so man.macros +.TH Tcl_DetachPids 3 "" Tcl "Tcl Library Procedures" +.BS +.SH NAME +Tcl_DetachPids, Tcl_ReapDetachedProcs \- manage child processes in background +.SH SYNOPSIS +.nf +\fB#include <tcl.h>\fR +.sp +\fBTcl_DetachPids\fR(\fInumPids, pidPtr\fR) +.sp +\fBTcl_ReapDetachedProcs\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. +.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. + +.SH KEYWORDS +background, child, detach, process, wait |