NAME
os_log_create —
create an object that tracks the state
of logging for a given system.
SYNOPSIS
#include
<os/log.h>
os_log_t
os_log_create(const
char *subsystem, const
char *category);
DESCRIPTION
Use os_log_create to create an object that
can be passed to os_log(3) calls. Log messages to this object will be marked with the
object's subsystem and category name. The behavior of log messages to this
object can be configured using the
log(1) command
or with a logging configuration profile (see
os_log(5)).
The subsystem argument should be the identifier of the subsystem in reverse DNS form. The category argument should be the category within the subsystem, for differentiating by topic and settings. Neither argument may be NULL.
The logging runtime maintains a global collection of all os_log_t
objects, one per subsystem/category pair. The os_log_t for a given
subsystem/category is created upon the first call to
os_log_create and any subsequent calls return the
same object. These objects are never deallocated, so dynamic creation (e.g.
on a per-operation basis) is generally inappropriate.
RETURN VALUES
The os_log_t object for the subsystem and category. A valid, non-NULL object is always returned.
EXAMPLES
Create a new os_log_t object and log a message:
#include <os/log.h>
/* create a log object for the subsystem, specifically the "connections" category" */
os_log_t log = os_log_create("com.example.widget", "connections");
/* log a connection related message */
os_log(log, "connection state changed: %d interface: %s", if, interface);