Syntax
int
pcntl_waitpid ( int pid, int &status [, int options] )
The pcntl_waitpid() 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. Please see your system's waitpid(2) man page for specific
details as to how waitpid works on your system.
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
The value of pid can be one of the following:
Table 1. possible values for pid
| < -1 |
wait for any child process whose process group ID is equal to
the absolute value of pid.
|
| -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
pid.
|
Note:
Specifying -1 as the pid is
equivalent to the functionality pcntl_wait() provides
(minus options).
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().
The value of options is the value of zero
or more of the following two global constants
OR'ed together:
Table 2. possible values for options
| WNOHANG |
return immediately if no child has exited.
|
| WUNTRACED |
return for children which are stopped, and whose status has
not been reported.
|
See also pcntl_fork(),
pcntl_signal(),
pcntl_wifexited(),
pcntl_wifstopped(),
pcntl_wifsignaled(),
pcntl_wexitstatus(),
pcntl_wtermsig() and
pcntl_wstopsig().