Standard C Library Functions wait3(3C)
NAME
wait3, wait4 - wait for process to terminate or stop
SYNOPSIS
#include
#include
#include
pid_t wait3(int *statusp, int options, struct rusage *rusage);
pid_t wait4(pid_t pid, int *statusp, int options, struct rusage *rusage);
DESCRIPTION
The wait3() function delays its caller until a signal is received or one of its child processes terminates or stops due to tracing. If any child process has died or stopped due to tracing and this has not already been reported, return is immediate, returning the process ID and status of one ofthose children. If that child process has died, it is dis-
carded. If there are no children, -1 is returned immedi-
ately. If there are only running or stopped but reported children, the calling process is blocked.If statusp is not a null pointer, then on return from a suc-
cessful wait3() call, the status of the child process isstored in the integer pointed to by statusp. *statusp indi-
cates the cause of termination and other information about the terminated process in the following manner:o If the low-order 8 bits of *statusp are equal to
0177, the child process has stopped; the 8 bitshigher up from the low-order 8 bits of *statusp
contain the number of the signal that caused the process to stop. See signal.h(3HEAD).o If the low-order 8 bits of *statusp are non-zero
and are not equal to 0177, the child process ter-
minated due to a signal; the low-order 7 bits of
*statusp contain the number of the signal that ter-
minated the process. In addition, if the low-order
seventh bit of *statusp (that is, bit 0200) is set, a ``core image'' of the process was produced; see signal.h(3HEAD). o Otherwise, the child process terminated due to anexit() call; the 8 bits higher up from the low-
order 8 bits of *statusp contain the low-order 8
bits of the argument that the child process passed to exit(); see exit(2).SunOS 5.11 Last change: 4 Nov 2005 1
Standard C Library Functions wait3(3C) The options argument is constructed from the bitwise inclusive OR of zero or more of the following flags, defined in: WNOHANG Execution of the calling process is not suspended if status is not immediately avail-
able for any child process. WUNTRACED The status of any child processes that are stopped, and whose status has not yet been reported since they stopped, are also reported to the requesting process. If rusage is not a null pointer, a summary of the resources used by the terminated process and all its children is returned. Only the user time used and the system time usedare currently available. They are returned in the ru_utime
and ru_stime, members of the rusage structure, respectively.
When the WNOHANG option is specified and no processes havestatus to report, wait3() returns 0. The WNOHANG and WUN-
TRACED options may be combined by the bitwise OR operation of the two values.The wait4() function is an extended interface. If pid is 0,
wait4() is equivalent to wait3(). If pid has a nonzero
value, wait4() returns status only for the indicated process
ID, but not for any other child processes. If pid has anegative value, wait4() return status only for child
processes whose process group ID is equal to the absolute value of pid. The status can be evaluated using the macros defined by wait.h(3HEAD).RETURN VALUES
If wait3() or wait4() returns due to a stopped or terminated
child process, the process ID of the child is returned tothe calling process. Otherwise, -1 is returned and errno is
set to indicate the error.If wait3() or wait4() return due to the delivery of a signal
to the calling process, -1 is returned and errno is set to
EINTR. If WNOHANG was set in options, it has at least one child process specified by pid for which status is not available, and status is not available for any processspecified by pid, 0 is returned. Otherwise, -1 is returned
and errno is set to indicate the error.SunOS 5.11 Last change: 4 Nov 2005 2
Standard C Library Functions wait3(3C)The wait3() and wait4() functions return 0 if WNOHANG is
specified and there are no stopped or exited children, and return the process ID of the child process if they return due to a stopped or terminated child process. Otherwise,they return -1 and set errno to indicate the error.
ERRORS
The wait3() and wait4() functions will fail and return
immediately if:ECHILD The calling process has no existing unwaited-for
child processes.EFAULT The statusp or rusage arguments point to an ille-
gal address. EINTR The function was interrupted by a signal. The value of the location pointed to by statusp is undefined. EINVAL The value of options is not valid.The wait4() function may fail if:
ECHILD The process specified by pid does not exist or is not a child of the calling process.The wait3()and wait4() functions will terminate prematurely,
return -1, and set errno to EINTR upon the arrival of a sig-
nal whose SA_RESTART bit in its flags field is not set (see
sigaction(2)).ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:SunOS 5.11 Last change: 4 Nov 2005 3
Standard C Library Functions wait3(3C)____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | Async-Signal-Safe |
|_____________________________|_____________________________|
SEE ALSO
kill(1), exit(2), waitid(2), waitpid(3C), getrusage(3C), signal(3C), signal.h(3HEAD), wait(3C), wait.h(3HEAD), proc(4), attributes(5) NOTESIf a parent process terminates without waiting on its chil-
dren, the initialization process (process ID = 1) inherits the children.The wait3() and wait4() functions are automatically res-
tarted when a process receives a signal while awaiting ter-
mination of a child process, unless the SA_RESTART bit is
not set in the flags for that signal.SunOS 5.11 Last change: 4 Nov 2005 4