== Description
   Adds the wait3, wait4, waitid, pause, sigsend, and getrusage methods to
   the Process module.

== Synopsis
   require 'proc/wait3'

   pid = fork{ sleep 1; exit 2 }
   p Time.now
   Process.wait3
   p $?

== Module Methods
Proc.pause(signals=nil)
   Pauses the current process. If the process receives any of the signals
   you pass as arguments it will return from the pause and continue with
   the execution of your code. Otherwise, it will exit.
   
   Note that you must leave out the 'SIG' prefix for the signal name, e.g.
   use 'INT', not 'SIGINT'.

   Returns the result of the pause() function, which should always be -1.
   
Process.sigsend(idtype, id, signal=0)
   Sends a signal of type "idtype" to a process or process group "id". This
   is more versatile method of sending signals to processes than Process.kill.
   
   For a list of valid idtype values, see the "Process type constants" below.
   Not supported on all platforms.
   
Proc.wait3(flags=0)
   Delays its caller until a signal is received or one of its child processes
   terminates or stops due to tracing.

   The return value is a ProcStat structure and sets the $last_status global
   variable. The special global $? is also set. Raises a SystemError if there
   are no child processes.

Proc.wait4(pid, flags=0)
   Waits for the given child process to exit. Returns a ProcStat structure.
   The $last_status global variable is set. Also sets the $? special global
   variable.
   
Proc.waitid(id_type, id_num=nil, options=nil)
   Suspends the calling process until one of its children changes state,
   returning immediately if a child process changed state prior to the call.
   The state of a child process will change if it terminates, stops because
   of a signal, becomes trapped or reaches a breakpoint.

   The id_num corresponds to a process ID or process group ID, depending on
   the value of +id_type+, which may be Process::P_PID, Process::P_PGID or
   Process::P_ALL. If +id_type+ is Process::P_ALL, then the +id_num+ is ignored.

   The options argument is used to specify which state changes are to be
   waited for. It is constructed from the bitwise-OR of one or more of the
   following constants:

   Process::WCONTINUED
   Process::WEXITED
   Process::WNOHANG
   Process::WNOWAIT
   Process::WSTOPPED
   Process::WTRAPPED (not supported on all platforms)

   If Process::WNOHANG is set as an option, this method will return
   immediately, whether or not a child has changed state.

   Calling this method with an +id_type+ of Process::P_ALL and the options set
   to 'Process::EXITED | Process::WTRAPPED' is equivalent to calling
   Process.wait.

   Returns a Proc::SigInfo struct and sets $?.

   Not supported on all platforms.

== Constants
=== Standard
Process::WAIT3_VERSION
   Returns the version of this package as a string.

=== Process type constants
==== All platforms
Process::P_ALL
   All non-system process.

Process::P_PID
   A standard process id.

Process::P_PGID
   Any non-system process group id.

==== Not supported on all platforms
Process::P_CID
   A scheduler process id.

Process::P_GID
   Any non-system effective process group id.

Process::P_PROJID
   A project process id. Solaris 8 or later only.

Process::P_SID
   A session process id.

Process::P_TASKID
   A task process id. Solaris 8 or later only.

Process::P_UID
   Any non-system effective process user id.

=== The following additional constants are defined if the waitid function is
    supported on your system.
   
Process::WCONTINUED
   Return the status for any child that was stopped and has been continued.

Process::WEXITED
   Wait for process(es) to exit.

Process::WNOWAIT
   Keep the process in a waitable state.

Process::WSTOPPED
   Wait for and return the process status of any child that has stopped upon
   receipt of a signal.

Process::WTRAPPED
   Wait for traced process(es) to become trapped or reach a breakpoint.

   Not supported on all platforms.
   
=== RLIMIT constants
Process::RLIMIT_AS
   A synonym for RLIMIT_VMEM
   
Process::RLIMIT_CORE
   The maximum size of a core file, in bytes, that may be created.
   
Process::RLIMIT_CPU
   The maximum amount of CPU time, in seconds, the process is allowed to use.
   
Process::RLIMIT_DATA
   The maximum size of the process' heap size, in bytes.
   
Process::RLIMIT_FSIZE
   The maximum size of a file, in bytes, that the process may create.
   
Process::RLIMIT_NOFILE
   The maximum value that the kernel may assign to a file descriptor,
   effectively limiting the number of open files for the calling process.
   
Process::RLIMIT_STACK
   The maximum size of the process' stack in bytes.
   
Process::RLIMIT_VMEM
   The maximum size of the process' mapped address space.
   
Process::RLIM_INFINITY
   A infinite limit.
   
Process::RLIM_SAVED_CUR
   Current soft limit.
   
Process::RLIM_SAVED_MAX
   Current hard limit.

== Notes
   The wait3 and wait4 methods are similar to the wait2 and waitpid2
   methods, except that they return much more information via the rusage
   struct.

== Known Bugs
   None that I'm aware of. Please log any bugs on the Github project
   page at https://github.com/djberg96/proc-wait3.

== License
   Artistic 2.0

== Copyright
   (C) 2003-2014 Daniel J. Berger
   All Rights Reserved.

== Warranty
   This package is provided "as is" and without any express or
   implied warranties, including, without limitation, the implied
   warranties of merchantability and fitness for a particular purpose.

== Author
   Daniel J. Berger

== See also
   wait3, wait4, waitid, pause, sigsend