waitid - Wait for child process to change state
#include <sys/wait.h>
int waitid(
idtype_t idtype,
id_t id,
siginfo_t *infop,
int options );
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.
Identifies the type of process to be affected. Used with
the id parameter, it suspends execution for the specified
child process. 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.
Specifies a pointer to a siginfo_t structure.
Specifies the conditions that must occur before a wait
operation is performed by the waitid() function.
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: Return the status
for any child that was stopped and has been continued.
Wait for processes to exit. Return immediately if no
child processes in the requested state are present. 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. Wait for and return the process
status of any child that has stopped upon receipt of a
signal. [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.
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.
The waitid() function sets errno to the specified values
for the following conditions: The calling process has no
unwaited-for child processes. [Tru64 UNIX] The infop
parameter points to an invalid address. The waitid()
function was interrupted due to the receipt of a signal by
the calling process. An invalid value was used with the
options parameter, or the idtype and id parameters specify
an invalid set of processes.
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)
waitid(2)
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