WAIT4(2) Linux Programmer's Manual WAIT4(2)
NAME
 wait3, wait4 - wait for process to change state, BSD style
SYNOPSIS
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #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 ad-
 ditionally 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 details.
 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 porta-
 bility. (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)
COLOPHON
 This page is part of release 5.10 of the Linux man-pages project. A
 description of the project, information about reporting bugs, and the
 latest version of this page, can be found at
 https://www.kernel.org/doc/man-pages/.
Linux 2020年06月09日 WAIT4(2)