The GNU library also provides these related facilities for compatibility
with BSD Unix. BSD uses the union wait
data type to represent
status values rather than an int
. The two representations are
actually interchangeable; they describe the same bit patterns. The GNU
C Library defines macros such as WEXITSTATUS
so that they will
work on either kind of object, and the wait
function is defined
to accept either type of pointer as its status-ptr argument.
These functions are declared in `sys/wait.h'.
int w_termsig
WTERMSIG
macro.
int w_coredump
WCOREDUMP
macro.
int w_retcode
WEXITSTATUS
macro.
int w_stopsig
WSTOPSIG
macro.
Instead of accessing these members directly, you should use the equivalent macros.
The wait3
function is the predecessor to wait4
, which is
more flexible. wait3
is now obsolete.
wait3
is equivalent to
waitpid (-1, status-ptr, options)
.
If usage is not null, wait3
stores usage figures for the
child process in *rusage
(but only if the child has
terminated, not if it has stopped). See section Resource Usage.
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