Man page - dispatch_once(3)

Packages contains this manual

Package:  libdispatch-dev
apt-get install libdispatch-dev

Manuals in package:
• dispatch_queue_create(3)
• dispatch_time(3)
• dispatch_read(3)
• dispatch_semaphore_create(3)
• dispatch_async(3)
• dispatch_io_create(3)
• dispatch_data_create(3)
• dispatch_source_create(3)
• dispatch_io_read(3)
• dispatch_once(3)
• dispatch_apply(3)
• dispatch_api(3)
• dispatch(3)
• dispatch_after(3)
• dispatch_object(3)
• dispatch_group_create(3)
Documentations in package:
• libdispatch-dev

Manual

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dispatch_once (3) Library Functions Manual dispatch_once (3)

NAME

dispatch_once — execute a block only once

SYNOPSIS

#include <dispatch/dispatch.h>

void

dispatch_once ( dispatch_once_t *predicate , void (ˆblock)(void) );

void

dispatch_once_f ( dispatch_once_t *predicate , void *context , void (*function)(void *) );

DESCRIPTION

The dispatch_once () function provides a simple and efficient mechanism to run an initializer exactly once, similar to pthread_once (3). Well designed code hides the use of lazy initialization. For example:

FILE *getlogfile(void)
{

	static dispatch_once_t pred;
	static FILE *logfile;
	dispatch_once(&pred, ˆ{
		logfile = fopen(MY_LOG_FILE, "a");
	});
	return logfile;

}

FUNDAMENTALS

The dispatch_once () function is a wrapper around dispatch_once_f ().

SEE ALSO

dispatch (3) Darwin May 1, 2009 dispatch_once (3)

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