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WAIT4(2) Linux Programmer's Manual WAIT4(2)
NAME
wait3, wait4 - wait for process to change state, BSD style
SYNOPSIS
#include <sys/wait.h>
pid_t wait3(int *wstatus, int options, struct rusage *rusage);
pid_t wait4(pid_t pid, int *wstatus, int options,
struct rusage *rusage);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
wait3():
Since glibc 2.26:
_DEFAULT_SOURCE
|| (_XOPEN_SOURCE >= 500 &&
! (_POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 600))
From glibc 2.19 to 2.25:
_DEFAULT_SOURCE || _XOPEN_SOURCE >= 500
Glibc 2.19 and earlier:
_BSD_SOURCE || _XOPEN_SOURCE >= 500
wait4():
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE
DESCRIPTION
These functions are nonstandard; in new programs, the use of waitpid(2) or waitid(2) is preferable.
The wait3() and wait4() system calls are similar to waitpid(2), but additionally return resource usage information about the child in the structure pointed to by
rusage.
Other than the use of the rusage argument, the following wait3() call:
wait3(wstatus, options, rusage);
is equivalent to:
waitpid(-1, wstatus, options);
Similarly, the following wait4() call:
wait4(pid, wstatus, options, rusage);
is equivalent to:
waitpid(pid, wstatus, options);
In other words, wait3() waits of any child, while wait4() can be used to select a specific child, or children, on which to wait. See wait(2) for further de‐
tails.
If rusage is not NULL, the struct rusage to which it points will be filled with accounting information about the child. See getrusage(2) for details.
RETURN VALUE
As for waitpid(2).
ERRORS
As for waitpid(2).
CONFORMING TO
4.3BSD.
SUSv1 included a specification of wait3(); SUSv2 included wait3(), but marked it LEGACY; SUSv3 removed it.
NOTES
Including <sys/time.h> is not required these days, but increases portability. (Indeed, <sys/resource.h> defines the rusage structure with fields of type struct
timeval defined in <sys/time.h>.)
C library/kernel differences
On Linux, wait3() is a library function implemented on top of the wait4() system call.
SEE ALSO
fork(2), getrusage(2), sigaction(2), signal(2), wait(2), signal(7)
Linux 2021-03-22 WAIT4(2)