PCNTL Functions
PHP Manual

pcntl_wait

Waits on or returns the status of a forked child

Description

int pcntl_wait ( int &$status [, int $options = 0 ] )

The wait 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 "zombie" process), the function returns immediately. Any system resources used by the child are freed. Please see your system's wait(2) man page for specific details as to how wait works on your system.

Note:

This function is equivalent to calling pcntl_waitpid with a -1 pid and no options.

Parameters

status

pcntl_wait 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.

options

If wait3 is available on your system (mostly BSD-style systems), you can provide the optional options parameter. If this parameter is not provided, wait will be used for the system call. If wait3 is not available, providing a value for options will have no effect. The value of options is the value of zero or more of the following two constants OR'ed together:

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.

Return Values

pcntl_wait returns the process ID of the child which exited, -1 on error or zero if WNOHANG was provided as an option (on wait3-available systems) and no child was available.

See Also

  • pcntl_fork
  • pcntl_signal
  • pcntl_wifexited
  • pcntl_wifstopped
  • pcntl_wifsignaled
  • pcntl_wexitstatus
  • pcntl_wtermsig
  • pcntl_wstopsig
  • pcntl_waitpid