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All Rights Reserved. .\" Copyright (c) 2004, Sun Microsystems, Inc. All Rights Reserved. .\" .TH WAITID 2 "Jun 8, 2018" .SH NAME waitid \- wait for child process to change state .SH SYNOPSIS .LP .nf #include \fBint\fR \fBwaitid\fR(\fBidtype_t\fR \fIidtype\fR, \fBid_t\fR \fIid\fR, \fBsiginfo_t *\fR\fIinfop\fR, \fBint\fR \fIoptions\fR); .fi .SH DESCRIPTION .LP The \fBwaitid()\fR function suspends the calling process until one of its child processes changes state. It records the current state of a child in the structure pointed to by \fIinfop\fR. It returns immediately if a child process changed state prior to the call. .sp .LP The \fIidtype\fR and \fIid\fR arguments specify which children \fBwaitid()\fR is to wait for, as follows: .RS +4 .TP .ie t \(bu .el o If \fIidtype\fR is \fBP_PID\fR, \fBwaitid()\fR waits for the child with a process \fBID\fR equal to \fB(pid_t)\fR\fIid\fR. .RE .RS +4 .TP .ie t \(bu .el o If \fIidtype\fR is \fBP_PGID\fR, \fBwaitid()\fR waits for any child with a process group \fBID\fR equal to \fB(pid_t)\fR\fIid\fR. .RE .RS +4 .TP .ie t \(bu .el o If \fIidtype\fR is \fBP_ALL\fR, \fBwaitid()\fR waits for any child and \fIid\fR is ignored. .RE .sp .LP The \fIoptions\fR argument is used to specify which state changes \fBwaitid()\fR is to wait for. It is formed by bitwise \fBOR\fR operation of any of the following flags: .sp .ne 2 .na \fB\fBWCONTINUED\fR\fR .ad .RS 14n Return the status for any child that was stopped and has been continued. .RE .sp .ne 2 .na \fB\fBWEXITED\fR\fR .ad .RS 14n Wait for process(es) to exit. .RE .sp .ne 2 .na \fB\fBWNOHANG\fR\fR .ad .RS 14n Return immediately. .RE .sp .ne 2 .na \fB\fBWNOWAIT\fR\fR .ad .RS 14n Keep the process in a waitable state. .RE .sp .ne 2 .na \fB\fBWSTOPPED\fR\fR .ad .RS 14n Wait for and return the process status of any child that has stopped upon receipt of a signal. .RE .sp .ne 2 .na \fB\fBWTRAPPED\fR\fR .ad .RS 14n Wait for traced process(es) to become trapped or reach a breakpoint (see \fBptrace\fR(3C)). .RE .sp .LP The \fIinfop\fR argument must point to a \fBsiginfo_t\fR structure, as defined in \fBsiginfo.h\fR(3HEAD). If \fBwaitid()\fR returns because a child process was found that satisfies the conditions indicated by the arguments \fIidtype\fR and \fIoptions\fR, then the structure pointed to by \fIinfop\fR will be filled by the system with the status of the process. The \fBsi_signo\fR member will always be equal to \fBSIGCHLD\fR. .sp .LP One instance of a \fBSIGCHLD\fR signal is queued for each child process whose status has changed. If \fBwaitid()\fR returns because the status of a child process is available and \fBWNOWAIT\fR was not specified in \fIoptions\fR, any pending \fBSIGCHLD\fR signal associated with the process ID of that child process is discarded. Any other pending \fBSIGCHLD\fR signals remain pending. .SH RETURN VALUES .LP If \fBwaitid()\fR returns due to a change of state of one of its children and \fBWNOHANG\fR was not used, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is returned and \fBerrno\fR is set to indicate the error. If \fBWNOHANG\fR was used, \fB0\fR can be returned (indicating no error); however, no children may have changed state if \fBinfop->si_pid\fR is \fB0\fR. .SH ERRORS .LP The \fBwaitid()\fR function will fail if: .sp .ne 2 .na \fB\fBECHILD\fR\fR .ad .RS 10n The set of processes specified by \fIidtype\fR and \fIid\fR does not contain any unwaited processes. .RE .sp .ne 2 .na \fB\fBEFAULT\fR\fR .ad .RS 10n The \fIinfop\fR argument points to an illegal address. .RE .sp .ne 2 .na \fB\fBEINTR\fR\fR .ad .RS 10n The \fBwaitid()\fR function was interrupted due to the receipt of a signal by the calling process. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n An invalid value was specified for \fIoptions\fR, or \fIidtype\fR and \fIid\fR specify an invalid set of processes. .RE .SH USAGE .LP With \fIoptions\fR equal to \fBWEXITED\fR | \fBWTRAPPED\fR, \fBwaitid()\fR is equivalent to \fBwaitpid\fR(3C). With \fIidtype\fR equal to \fBP_ALL\fR and \fIoptions\fR equal to \fBWEXITED\fR | \fBWTRAPPED\fR, \fBwaitid()\fR is equivalent to \fBwait\fR(3C). .SH ATTRIBUTES .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS box; c | c l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Standard _ MT-Level Async-Signal-Safe .TE .SH SEE ALSO .LP \fBIntro\fR(2), \fBexec\fR(2), \fBexit\fR(2), \fBfork\fR(2), \fBpause\fR(2), \fBsigaction\fR(2), \fBptrace\fR(3C), \fBsignal\fR(3C), \fBsiginfo.h\fR(3HEAD), \fBwait\fR(3C), \fBwaitpid\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)