pcntl_waitpid
Waits on or returns the status of a forked child
Description
int pcntl_waitpid(
int $process_id,
int &$status,
int $flags = 0,
array &$resource_usage = []
)
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_id can be one of the following:
possible values for process_id
< -1 |
wait for any child process whose process group ID is equal to
the absolute value of process_id.
|
-1 |
wait for any child process; this is the same behaviour that
the wait function exhibits.
|
0 |
wait for any child process whose process group ID is equal to
that of the calling process.
|
> 0 |
wait for the child whose process ID is equal to the value of
process_id.
|
Note:
Specifying -1 as the process_id is
equivalent to the functionality pcntl_wait provides
(minus flags).
-
status
-
pcntl_waitpid will store status information
in the status parameter 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 flags is the value of zero
or more of the following two global constants
OR'ed together:
possible values for flags
WNOHANG |
return immediately if no child has exited.
|
WUNTRACED |
return 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
- pcntl_signal
- pcntl_wifexited
- pcntl_wifstopped
- pcntl_wifsignaled
- pcntl_wexitstatus
- pcntl_wtermsig
- pcntl_wstopsig