HPUX wait[2]
wait in anderen Kapiteln des hpux Handbuch:
wait.3f
wait.1
wait(2) wait(2)
NAME
wait, waitpid, wait3 - wait for child or traced process to stop or
terminate
SYNOPSIS
#include <sys/wait.h>
pid_t wait(int *stat_loc);
pid_t waitpid(pid_t pid, int *stat_loc, int options);
pid_t wait3(int *stat_loc, int options, int *reserved);
DESCRIPTION
wait() suspends the calling process until one of the immediate
children terminates or until a process being traced stops because that
traced process has hit a break point. A process being traced can be
either a child or a process attached by the ptrace() request PT_ATTACH
(see ptrace(2)). The wait() system call returns prematurely if a
signal is received. If a child or traced process stops or terminates
prior to the call on wait, return is immediate.
If stat_loc is not a null pointer, status information is stored in the
location pointed to by stat_loc. The status can be used to
differentiate between stopped and terminated processes. If the
process terminates, the status identifies the cause of termination and
passes useful information to the calling process. This is
accomplished using the following macros defined in <sys/wait.h>, with
the status value stored at *stat_loc as an argument:
WIFEXITED(stat_val) If the process terminated because of an
exit() or _exit() system call, this
macro evaluates to a non-zero value.
WEXITSTATUS(stat_val) If the value of WIFEXITED(stat_val) is
non-zero, this macro evaluates to the
low-order 8 bits of the argument that
the process passed to exit() or _exit()
(see exit(2)).
WIFSIGNALED(stat_val) If the process terminated due to the
default action of a signal (see
signal(5)), this macro evaluates to a
non-zero value.
WTERMSIG(stat_val) If the value of WIFSIGNALED(stat_val) is
non-zero, this macro evaluates to the
number of the signal that caused the
termination.
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WCOREDUMP(stat_val) If the value of WIFSIGNALED(stat_val) is
non-zero, this macro evaluates to a
non-zero value if a ``core image'' was
produced (see signal(5)).
WIFSTOPPED(stat_val) If the process is stopped, this macro
evaluates to a non-zero value.
WSTOPSIG(stat_val) If the value of WIFSTOPPED(stat_val) is
non-zero, this macro evaluates to the
number of the signal that caused the
process to stop.
As a single special case, the value stored in *stat_loc is zero if and
only if status is being returned from a terminated process that called
exit() or _exit() with a value of zero.
If the information stored at the location pointed to by stat_loc was
stored there by a call to one of the wait() functions, exactly one of
the macros WIFEXITED(*stat_loc), WIFSIGNALED(*stat_loc), or
WIFSTOPPED(*stat_loc) evaluates to a non-zero value.
The waitpid() function behaves identically to wait() if pid has a
value of -1 and options has a value of zero. Otherwise its behavior
is modified by the values of the pid and options arguments.
The pid argument specifies the set of processes for which status is
requested. waitpid returns only the status of a child process from
this set.
o If pid is equal to -1, status is requested for any child
process or attached process. In this respect, waitpid() is
then equivalent to wait().
o If pid is greater than zero, it specifies the process ID of a
single child or attached process for which status is
requested.
o If pid is equal to zero, status is requested for any child or
attached process whose process group ID is equal to that of
the calling process.
o If pid is less than -1, status is requested for any child or
attached process whose process group ID is equal to the
absolute value of pid.
The options argument is constructed from the bit-wise inclusive OR of
zero or more of the following flags:
WNOHANG If this flag is set, waitpid() or wait3() is
prevented from suspending the calling process. A
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value of zero is returned indicating that no child
or traced processes have stopped or died.
WUNTRACED If and only if this flag is set, waitpid() or
wait3() returns information on child or attached
processes that are stopped but not traced (with
ptrace(2)) because they received a SIGTTIN,
SIGTTOU, SIGTSTP, or SIGSTOP signal, and whose
status has not yet been reported. Regardless of
this flag, status is returned for child or
attached processes that have terminated or are
stopped and traced and whose status has not yet
been reported.
Calling wait3() is equivalent to calling waitpid() with the value of
pid equal to zero. The third parameter to wait3() is currently unused
and must always be a null pointer.
If a parent process terminates without waiting for its child processes
to terminate, the parent process ID of each child process is set to 1.
This means the initialization process inherits the child processes.
Notes
Earlier HP-UX versions documented the bit encodings of the status
returned by wait() rather than the macros WIFEXITED, WEXITSTATUS,
WIFSIGNALED, WTERMSIG, WCOREDUMP, WIFSTOPPED, and WSTOPSIG.
Applications using those bit encodings will continue to work
correctly. However, new applications should use the macros for
maximum portability.
In earlier HP-UX versions, the macros WIFSTOPPED, WIFSIGNALED, and
WIFEXITED have the same definitions as the correspondingly named
macros in the BSD 4.3 and earlier systems. Existing applications that
depend on these definitions will continue to work correctly. However,
if the application is recompiled, the feature test macro _BSD must be
turned on for the compilation so that the old definitions of these
macros are obtained. New definitions of these macros are in effect by
default. The only difference between the old and new definitions is
the type of the argument. Type union wait is used in the BSD
definitions while type int is used in the default definitions.
ERRORS
wait() fails if one or more of the following is true:
[ECHILD] The calling process to wait() or wait3() has no
existing child or traced processes, or the calling
process to waitpid() has no existing unwaited-for
child or traced processes that match the pid
argument.
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[ECHILD] For waitpid(), the process or process group
specified by pid does not exist or is not a child
of the calling process.
[EFAULT] stat_loc points to an illegal address. The
reliable detection of this error is implementation
dependent.
[EINVAL] The options argument to waitpid() or wait3() is
invalid.
[EINVAL] wait3() was passed a non-null pointer value for
its third argument.
[EINTR] The function was interrupted by a signal. The
value of the location pointed to by stat_loc is
undefined.
RETURN VALUE
If wait() returns due to the receipt of a signal, a value of -1 is
returned to the calling process and errno is set to EINTR. If wait()
returns due to a stopped or terminated child or traced process, the
process ID of that process is returned to the calling process. If
waitpid() or wait3() is called, the WNOHANG option is used, and there
are no stopped or terminated child or traced processes (as specified
by pid in the case of waitpid()), a value of zero is returned.
Otherwise, a value of -1 is returned and errno is set to indicate the
error.
WARNINGS
The behavior of wait(), waitpid(), and wait3() is affected by setting
the SIGCLD signal to SIG_IGN. See WARNINGS section of signal(5).
Signal handlers that cause system calls to be restarted can affect the
EINTR condition described above (see sigaction(2), sigvector(2), and
bsdproc(2)).
AUTHOR
wait(), waitpid(), and wait3() were developed by HP, AT&T, and the
University of California, Berkeley.
SEE ALSO
Exit conditions ($?) in sh(1), exec(2), exit(2), fork(2), pause(2),
ptrace(2), signal(5).
STANDARDS CONFORMANCE
wait(): AES, SVID2, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1
waitpid(): AES, XPG3, XPG4, FIPS 151-2, POSIX.1
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