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WAIT4 !!!WAIT4 NAME SYNOPSIS DESCRIPTION RETURN VALUE ERRORS NOTE CONFORMING TO SEE ALSO ---- !!NAME wait3, wait4 - wait for process termination, BSD style !!SYNOPSIS __#define _USE_BSD #include __''status''__, int__ ''options''__, struct rusage *__''rusage''__) 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 '' The value of ''pid'' can be one of: 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__. 0 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!): __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()__ 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 '''' 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. !!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__. !!NOTE Including '''' is not required these days, but increases portability. (Indeed, '''' defines the ''rusage'' structure with fields of type ''struct timeval'' defined in ''''.) !!CONFORMING TO SVr4, POSIX.1 !!SEE ALSO signal(2), getrusage(2), wait(2), signal(7) ----
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