default_handler

The default log handler set up by GLib; [func@GLib.

log_set_default_handler] allows to install an alternate default log handler.

This is used if no log handler has been set for the particular log domain and log level combination. It outputs the message to `stderr` or `stdout` and if the log level is fatal it calls [func@GLib.BREAKPOINT]. It automatically prints a new-line character after the message, so one does not need to be manually included in message.

The behavior of this log handler can be influenced by a number of environment variables:

• `G_MESSAGES_PREFIXED`: A `:`-separated list of log levels for which messages should be prefixed by the program name and PID of the application.
• `G_MESSAGES_DEBUG`: A space-separated list of log domains for which debug and informational messages are printed. By default these messages are not printed. If you need to set the allowed domains at runtime, use [func@GLib.log_writer_default_set_debug_domains].

`stderr` is used for levels [flags@GLib.LogLevelFlags.LEVEL_ERROR], [flags@GLib.LogLevelFlags.LEVEL_CRITICAL], [ flags@GLib.LogLevelFlags.LEVEL_WARNING] and [flags@GLib.LogLevelFlags.LEVEL_MESSAGE]. `stdout` is used for the rest, unless `stderr` was requested by [func@GLib.log_writer_default_set_use_stderr].

This has no effect if structured logging is enabled; see [Using Structured Logging](logging.html#using-structured-logging).

Parameters:

log_domain	the log domain of the message, or `NULL` for the default `""` application domain
log_level	the level of the message
message	the message
unused_data	data passed from [func@GLib.log] which is unused