Differences between version 2 and revision by previous author of wait4(2).
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| Newer page: | version 2 | Last edited on Wednesday, February 12, 2003 12:46:24 am | by PerryLorier | Revert |
| Older page: | version 1 | Last edited on Tuesday, June 4, 2002 12:23:49 am | by perry | Revert |
@@ -1,201 +1,52 @@
-WAIT4
-!!!WAIT4
-NAME
-SYNOPSIS
-DESCRIPTION
-RETURN VALUE
-ERRORS
-NOTE
-CONFORMING TO
-SEE ALSO
-----
!!NAME
-
-
-wait3,
wait4 - wait for process termination, BSD style
+wait4 - wait for process termination, BSD style
!!SYNOPSIS
-
-
-__
#define _USE_BSD
-#include
-__''status''__, int__ ''options''__,
-struct rusage *__''rusage''__)
-
-
-
+ #include <sys/types.h>
+ #include <sys/time.h>
+ #include <sys/resource.h>
+ #include <sys/wait.h>
+ __pid_t wait4(pid_t__ ''pid''__, int *__''status''__, int__ ''options''__, struct rusage *__''rusage''__)__
!!DESCRIPTION
-
-
-The __wait3__ function suspends execution of the current
-process until a child has exited, or until a signal is
-delivered whose action is to terminate the current process
-or to call a signal handling function. If a child has
-already exited by the time of the call (a so-called
-__
-
-
-
-
-
-
-
-
-
-''
-
+The __wait4__ function suspends execution of the current process until a child as specified by the ''pid'' argument has exited, or until a signal is delivered whose action is to terminate the current process or to call a signal handling function. If a child as requested by ''pid'' has already exited by the time of the call (a so-called "zombie" process), the function returns immediately. Any system resources used by the child are freed.
The value of ''pid'' can be one of:
+;<-1:which means to wait for any child process whose process group ID is equal to the absolute value of ''pid''.
+;-1:which means to wait for any child process; this is equivalent to calling wait3(2).
+;0:which means to wait for any child process whose process group ID is equal to that of the calling process.
+;>0:which means to wait for the child whose process ID is equal to the value of ''pid''.
+The value of ''options'' is a bitwise OR of zero or more of the following constants:
+;__WNOHANG__: which means to return immediately if no child is there to be waited for.
+;__WUNTRACED__: which means to also return for children which are stopped, and whose status has not been reported.
+If ''status'' is not __NULL__, __wait3__ or __wait4__ store status information in the location pointed to by ''status''.
+This status can be evaluated with the following macros (these macros take the stat buffer (an __int__) as an argument -- not a pointer to the buffer!):
-which means to wait for any child process whose process
-group ID is equal to the absolute value of
-''pid''.
-
-
--1
-
-
-which means to wait for any child process
; this is
-equivalent to calling __wait3__.
-
-
-
-
-
-which means to wait for any child process whose process
-group ID is equal to that of the calling
-process.
-
-
-
-
-which means to wait for the child whose process ID is equal
-to the value of ''pid''.
-
-
-The value of ''options'' is a bitwise OR of zero or more
-of the following constants:
-
-
-__WNOHANG__
-
-
-which means to return immediately if no child is there to be
-waited for.
-
-
-__WUNTRACED__
-
-
-which means to also return for children which are stopped,
-and whose status has not been reported.
-
-
-If ''status'' is not __NULL__, __wait3__ or
-__wait4__ store status information in the location
-pointed to by ''status''.
-
-
-This status can be evaluated with the following macros
-(these macros take the stat buffer (an __int__) as an
-argument -- not a pointer to the buffer!):
-
-
-
-
-
-
-
-
-
-
-
-
-
-__
exit()__
or as the
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+;__WIFEXITED(__''status''__)__;
is non-zero if the child exited normally.
+;
__WEXITSTATUS(__''status''__)__:
evaluates to the least significant eight bits of the return code of the child which terminated, which may have been set as the argument to a call to exit(3
) or as the argument for a __return__ statement in the main program. This macro can only be evaluated if __WIFEXITED__ returned non-zero.
+;
__WIFSIGNALED(__''status''__)__:
returns true if the child process exited because of a signal which was not caught.
+;
__WTERMSIG(__''status''__)__:
returns the number of the signal that caused the child process to terminate. This macro can only be evaluated if
__WIFSIGNALED__ returned non-zero.
-
-
-
-
-
-
-
+;
__WIFSTOPPED(__''status''__)__:
returns true if the child process which caused the return is currently stopped; this is only possible if the call was
done using __WUNTRACED__.
-
-
-
-
-
-
-
+;
__WSTOPSIG(__''status''__)__:
returns the number of the signal which caused the child to stop. This macro can only be evaluated if __WIFSTOPPED__
returned non-zero.
-
-
-
-
+If ''rusage'' is not __NULL__, the __struct rusage__ as defined in ''<sys/resource.h>
'' it points to will be filled with accounting information. See
getrusage(2) for details.
+
!!RETURN VALUE
+The process ID of the child which exited, -1 on error (in particular, when no unwaited-for child processes of the specified kind exist) or zero if __WNOHANG__ was used and no child was available yet. In the latter two cases ''errno'' will be set appropriately.
-
-The process ID of the child which exited, -1 on error (in
-particular, when no unwaited-for child processes of the
-specified kind exist) or zero if __WNOHANG__ was used and
-no child was available yet. In the latter two cases
-''errno'' will be set appropriately.
!!ERRORS
+;[ECHILD]: No unwaited-for child process as specified does exist.
+;[ERESTARTSYS]: if __WNOHANG__ was not set and an unblocked signal or a [SIGCHLD] was caught. This error is returned by the system call. The library interface is not allowed to return [ERESTARTSYS], but will return [EINTR].
-
-__ECHILD__
-
-
-No unwaited-for child process as specified does
-exist.
-
-
-__ERESTARTSYS__
-
-
-if __WNOHANG__ was not set and an unblocked signal or a
-__SIGCHLD__ was caught. This error is returned by the
-system call. The library interface is not allowed to return
-__ERESTARTSYS__, but will return
-__EINTR__.
!!NOTE
-
-
-
-
-
-
-
+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>
''.)
!!CONFORMING TO
+SVr4, POSIX.1
-
-SVr4, POSIX.1
!!SEE ALSO
-
-
-
-
-----
+signal(2), getrusage(2), wait(2), signal(7)
