PORT_ASSOCIATE(3C) Standard C Library Functions PORT_ASSOCIATE(3C)


port_associate, port_dissociate - associate or dissociate the object with
the port


#include <port.h>

int port_associate(int port, int source, uintptr_t object,
int events, void *user);

int port_dissociate(int port, int source, uintptr_t object);


The port_associate() function associates specific events of a given
object with a port. Only objects associated with a particular port are
able to generate events that can be retrieved using port_get(3C) or
port_getn(3C). The delivery event has its portev_user member set to the
value specified in the user parameter. If the specified object is already
associated with the specified port, the port_associate() function serves
to update the events and user arguments of the association. The
port_dissociate() function removes the association of an object with a

The objects that can be associated with a port by way of the
port_associate() function are objects of type PORT_SOURCE_FD and
PORT_SOURCE_FILE. Objects of other types have type-specific association
mechanisms. A port_notify_t structure, defined in <port.h>, is used to
specify the event port and an application-defined cookie to associate
with these event sources. See port_create(3C) and signal.h(3HEAD).

The port_notify_t structure contains the following members:

int portnfy_port; /* bind request(s) to port */
void *portnfy_user; /* user defined cookie */

Objects of type PORT_SOURCE_FD are file descriptors. The event types for
PORT_SOURCE_FD objects are described in poll(2). At most one event
notification will be generated per associated file descriptor. For
example, if a file descriptor is associated with a port for the
POLLRDNORM event and data is available on the file descriptor at the time
the port_associate() function is called, an event is immediately sent to
the port. If data is not yet available, one event is sent to the port
when data first becomes available.

When an event for a PORT_SOURCE_FD object is retrieved, the object no
longer has an association with the port. The event can be processed
without the possibility that another thread can retrieve a subsequent
event for the same object. After processing of the file descriptor is
completed, the port_associate() function can be called to reassociate the
object with the port.

Objects of type PORT_SOURCE_FILE are pointer to the structure file_obj
defined in <sys/port.h>. This event source provides event notification
when the specified file/directory is accessed, modified, truncated or
when its status changes. The path name of the file/directory to be
watched is passed in the struct file_obj along with the access,
modification, and change time stamps acquired from a stat(2) call. If the
file name is a symbolic link, it is followed by default. The
FILE_NOFOLLOW needs to be passed in along with the specified events if
the symbolic link itself needs to be watched and lstat() needs to be used
to get the file status of the symbolic link file.

The struct file_obj contains the following elements:

timestruc_t fo_atime; /* Access time from stat() */
timestruc_t fo_mtime; /* Modification time from stat() */
timestruc_t fo_ctime; /* Change time from stat() */
char *fo_name; /* Pointer to a null terminated path name */

At the time the port_associate() function is called, the time stamps
passed in the structure file_obj are compared with the file or
directory's current time stamps and, if there has been a change, an event
is immediately sent to the port. If not, an event will be sent when such
a change occurs.

The event types that can be specified at port_associate() time for
FILE_TRUNC. The first three of these correspond to the three time stamps:
an fo_atime change results in the FILE_ACCESS event, an fo_mtime change
results in the FILE_MODIFIED event, and an fo_ctime change results in the
FILE_ATTRIB event. If the operation that induced the time stamp update
also truncated the file, FILE_TRUNC will be set in the resulting event.

The following exception events are delivered when they occur. These event
types cannot be filtered.

FILE_DELETE /* Monitored file/directory was deleted */
FILE_RENAME_TO /* Monitored file/directory was renamed */
FILE_RENAME_FROM /* Monitored file/directory was renamed */
UNMOUNTED /* Monitored file system got unmounted */
MOUNTEDOVER /* Monitored file/directory was mounted over */

At most one event notification will be generated per associated file_obj.
When the event for the associated file_obj is retrieved, the object is no
longer associated with the port. The event can be processed without the
possibility that another thread can retrieve a subsequent event for the
same object. The port_associate() can be called to reassociate the
file_obj object with the port.

The association is also removed if the port gets closed or when
port_dissociate() is called.

The parent and child processes are allowed to retrieve events from file
descriptors shared after a call to fork(2). The process performing the
first association with a port (parent or child process) is designated as
the owner of the association. Only the owner of an association is allowed
to dissociate the file descriptor from a port. The association is removed
if the owner of the association closes the port .

On NFS file systems, events from only the client side (local)
access/modifications to files or directories will be delivered.


Upon successful completion, 0 is returned. Otherwise, -1 is returned and
errno is set to indicate the error.


The port_associate() and port_dissociate() functions will fail if:

The port identifier is not valid.

The source argument is of type PORT_SOURCE_FD and the object
argument is not a valid file descriptor.

The source argument is not valid.

The port_associate() function will fail if:

The source argument is PORT_SOURCE_FILE and, Search permission
is denied on a component of path prefix or the file exists and
the permissions, corresponding to the events argument, are

The maximum number of objects associated with the port was
exceeded. The maximum allowable number of events or
association of objects per port is the minimum value of the
process.max-port-events resource control at the time
port_create(3C) was used to create the port. See setrctl(2)
and rctladm(1M) for information on using resource controls.

The number of objects associated with a port is composed of
all supported resource types. Some of the source types do not
explicitly use the port_associate() function.

The source argument is PORT_SOURCE_FILE and the file does not
exist or the path prefix does not exist or the path points to
an empty string.

The physical memory limits of the system have been exceeded.

The source argument is PORT_SOURCE_FILE and the file system on
which the specified file resides, does not support watching
for file events notifications.

The port_dissociate() function will fail if:

The process is not the owner of the association.

The specified object is not associated with the port.


Example 1: Retrieve data from a pipe file descriptor.

The following example retrieves data from a pipe file descriptor.

#include <port.h>

int port;
int fd;
int error;
int index;
void *mypointer;
port_event_t pev;
struct timespec_t timeout;
char rbuf[STRSIZE];
int fds[MAXINDEX];

/* create a port */
port = port_create();

for (index = 0; index < MAXINDEX; index++) {
error = mkfifo(name[index], S_IRWXU | S_IRWXG | S_IRWXO);
if (error)
/* handle error code */
fds[index] = open(name[index], O_RDWR);

/* associate pipe file descriptor with the port */
error = port_associate(port, PORT_SOURCE_FD, fds[index],
POLLIN, mypointer);
timeout.tv_sec = 1; /* user defined */
timeout.tv_nsec = 0;

/* loop to retrieve data from the list of pipe file descriptors */
for (...) {
/* retrieve a single event */
error = port_get(port, &pev, &timeout);
if (error) {
/* handle error code */
fd = pev.portev_object;
if (read(fd, rbuf, STRSIZE)) {
/* handle error code */
if (fd-still-accepting-data) {
* re-associate the file descriptor with the port.
* The re-association is required for the
* re-activation of the data detection.
* Internals events and user arguments are set to the
* new (or the same) values delivered here.
error = port_associate(port, PORT_SOURCE_FD, fd, POLLIN,
} else {
* If file descriptor is no longer required,
* - it can remain disabled but still associated with
* the port, or
* - it can be dissociated from the port.

Example 2: Bind AIO transaction to a specific port.

The following example binds the AIO transaction to a specific port.

#include <port.h>

int port;
port_notify_t pn;
aiocb_t aiocb;
aiocb_t *aiocbp;
void *mypointer;
int error;
int my_errno;
int my_status;
struct timespec_t timeout;
port_event_t pev;

port = port_create();
/* fill AIO specific part */
aiocb.aio_fildes = fd;
aiocb.aio_nbytes = BUFSIZE;
aiocb.aio_buf = bufp;
aiocb.aio_offset = 0;

/* port specific part */
pn.portnfy_port = port;
pn.portnfy_user = mypointer;
aiocb.aio_sigevent.sigev_notify = SIGEV_PORT;
aiocb.aio_sigevent.sigev_value.sival_ptr = &pn

* The aio_read() function binds internally the asynchronous I/O
* transaction with the port delivered in port_notify_t.
error = aio_read(&aiocb);

timeout.tv_sec = 1; /* user defined */
timeout.tv_nsec = 0;

/* retrieve a single event */
error = port_get(port, &pev, &timeout);
if (error) {
/* handle error code */

* pev.portev_object contains a pointer to the aiocb structure
* delivered in port_notify_t (see aio_read()).
aiocbp = pev.portev_object;

/* check error code and return value in
my_errno = aio_error(aiocbp);
my_status = aio_return(aiocbp);


See attributes(5) for descriptions of the following attributes:

|Architecture | all |
|Interface Stability | Committed |
|MT-Level | Safe |


rctladm(1M), poll(2), setrctl(2), port_alert(3C), port_create(3C),
port_get(3C), port_send(3C), signal.h(3HEAD), attributes(5)

April 9, 2016 PORT_ASSOCIATE(3C)