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waitid(2)
NAME
  waitid - Wait for child process to change state

SYNOPSIS
  #include <sys/wait.h>

  int waitid(
	  idtype_t idtype,
	  id_t id,
	  siginfo_t *infop,
	  int options );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  waitid(): XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  idtype
      Identifies the type of process to be affected.  Used with the id
      parameter, it suspends execution for the specified child process.

  id  Specifies either the process ID or process group ID of the child
      process.	Used with the idtype parameter, it suspends execution for the
      specified process.

  infop
      Specifies a pointer to a siginfo_t structure.

  options
      Specifies the conditions that must occur before a wait operation is
      performed by the waitid() function.

DESCRIPTION
  The waitid() function holds a calling process until the state of a child
  process changes.  The current state of the child is recorded in a structure
  pointed to by the infop parameter. If a child process changed state prior
  to the call to the waitid() function, the waitid() function returns
  immediately.

  The idtype and id parameters determine which child process the waitid()
  function is to act upon.

    ·  If the idtype parameter is P_PID, the waitid() function waits for the
       child with a process ID equal to (pid_t)id.

    ·  If the idtype parameter is P_PGID, the waitid() function waits for any
       child with a process group ID equal to (pid_t)id.

    ·  If the idtype parameter is P_ALL, the waitid function waits for any
       child and the id parameter is ignored.

  The options parameter specifies the conditions that must occur before a
  wait operation is performed by the waitid() function.	 To specify a
  condition, use at least one of the following flags in a logical OR
  operation:

  WCONTINUED
      Return the status for any child that was stopped and has been
      continued.

  WEXITED
      Wait for processes to exit.

  WNOHANG
      Return immediately if no child processes in the requested state are
      present.

  WNOWAIT
      Keep the child process whose status is returned in infop in a waitable
      state.  Another wait for that child may occur with the same results.

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

  WTRAPPED
      [Tru64 UNIX]  Wait for traced processes to become trapped or reach a
      breakpoint (see ptrace(2)).

  The infop parameter must point to a siginfo_t structure as defined in
  siginfo(5). This structure contains the status explaining why a process is
  in a wait state.

  The waitid() function returns if a child process is found that satisfies
  the conditions defined by the idtype and options parameters. In this case,
  the system fills in the structure pointed to by the infop parameter with
  the process status. The system always sets the si_signo structure member to
  SIGCHLD.

RETURN VALUE
  If the waitid() function returns because the state of a child process
  changes, it returns a value of zero (0).  Otherwise, a value of -1 is
  returned and errno is set to indicate the error.

ERRORS
  The waitid() function sets errno to the specified values for the following
  conditions:

  [ECHILD]
      The calling process has no unwaited-for child processes.

  [EFAULT]
      [Tru64 UNIX]  The infop parameter points to an invalid address.

  [EINTR]
      The waitid() function was interrupted due to the receipt of a signal by
      the calling process.

  [EINVAL]
      An invalid value was used with the options parameter, or the idtype and
      id parameters specify an invalid set of processes.

SEE ALSO
  Functions:  intro(2), exec(2), exit(2), fork(2), pause(3), ptrace(2),
  sigaction(2), signal(2), wait(2)

  Routines:  pause(3)

  Files:  siginfo(5)

  Standards:  standards(5)

Index for Section 2

Alphabetical listing for W

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