pcntl_waitpid
(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)
pcntl_waitpid — Waits on or returns the status of a forked child
Description
int
$process_id,int
&$status,int
$flags = 0,array
&$resource_usage = []): int
Suspends execution of the current process until a child as specified by
the process_id 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 process_id 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.
Please see your system's waitpid(2) man page for specific details as to
how waitpid works on your system.
Parameters
-
process_id -
The value of
process_idcan be one of the following:possible values for process_id< -1wait for any child process whose process group ID is equal to the absolute value of process_id.-1wait for any child process; this is the same behaviour that the wait function exhibits. 0wait for any child process whose process group ID is equal to that of the calling process. > 0wait for the child whose process ID is equal to the value of process_id.Note:
Specifying
-1as theprocess_idis equivalent to the functionality pcntl_wait() provides (minusflags). -
status -
pcntl_waitpid() will store status information in the
statusparameter which can be evaluated using the following functions: pcntl_wifexited(), pcntl_wifstopped(), pcntl_wifsignaled(), pcntl_wexitstatus(), pcntl_wtermsig() and pcntl_wstopsig(). -
flags -
The value of
flagsis the value of zero or more of the following two global constantsOR'ed together:possible values for flagsWNOHANGreturn immediately if no child has exited. WUNTRACEDreturn for children which are stopped, and whose status has not been reported.
Return Values
pcntl_waitpid() returns the process ID of the
child which exited, -1 on error or zero if WNOHANG was used and no
child was available
See Also
- pcntl_fork() - Forks the currently running process
- pcntl_signal() - Installs a signal handler
- pcntl_wifexited() - Checks if status code represents a normal exit
- pcntl_wifstopped() - Checks whether the child process is currently stopped
- pcntl_wifsignaled() - Checks whether the status code represents a termination due to a signal
- pcntl_wexitstatus() - Returns the return code of a terminated child
- pcntl_wtermsig() - Returns the signal which caused the child to terminate
- pcntl_wstopsig() - Returns the signal which caused the child to stop
