flux_fd_watcher_create.rst

flux_fd_watcher_create(3)

.. default-domain:: c

SYNOPSIS

#include <flux/core.h>

typedef void (*flux_watcher_f)(flux_reactor_t *r,
                               flux_watcher_t *w,
                               int revents,
                               void *arg);

flux_watcher_t *flux_fd_watcher_create (flux_reactor_t *r,
                                        int fd,
                                        int events,
                                        flux_watcher_f callback,
                                        void *arg);

int flux_fd_watcher_get_fd (flux_watcher_t *w);

Link with :command:`-lflux-core`.

DESCRIPTION

:func:`flux_fd_watcher_create()` creates a :type:`flux_watcher_t` object which can be used to monitor for events on a file descriptor :var:`fd`. When events occur, the user-supplied :var:`callback` is invoked.

The :var:`events` and :var:`revents` arguments are a bitmask containing a logical OR of the following bits. If a bit is set in :var:`events`, it indicates interest in this type of event. If a bit is set in :var:`revents`, it indicates that this event has occurred.

FLUX_POLLIN

The file descriptor is ready for reading.

FLUX_POLLOUT

The file descriptor is ready for writing.

FLUX_POLLERR

The file descriptor has encountered an error. This bit is ignored if it is set in the create events argument.

Events are processed in a level-triggered manner. That is, the callback will continue to be invoked as long as the event has not been fully consumed or cleared, and the watcher has not been stopped.

:func:`flux_fd_watcher_get_fd` is used to obtain the file descriptor from within the :type:`flux_watcher_f callback`.

RETURN VALUE

:func:`flux_fd_watcher_create` returns a :type:`flux_watcher_t` object on success. On error, NULL is returned, and :var:`errno` is set appropriately.

:func:`flux_fd_watcher_get_fd` returns the file descriptor associated with the watcher.

ERRORS

ENOMEM

Out of memory.

RESOURCES

SEE ALSO

:man3:`flux_watcher_start`, :man3:`flux_reactor_run`