streamio - STREAMS ioctl commands
#include <sys/types.h> #include <sys/stropts.h>
int ioctl(
int fildes,
int command,
... /* arg */); );
Interfaces documented on this reference page conform to
industry standards as follows:
ioctl(): XSH4.2
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Contains the open file descriptor for the Stream to be
operated on. Specifies the STREAM ioctl() command function
to be performed on the Stream. Contains additional
information that the specified command may need for performing
its function. This is usually an integer, or a
pointer to a command-specific structure, but can be of any
type.
The STREAMS ioctl commands perform control operations on
Streams. User processes can use these commands on all
STREAMS file types.
When the Stream head receives a STREAMS ioctl function, it
interprets the command parameter and arg parameter, when
specified, into an M_IOCTL message. In some cases, the
command and arg parameters are passed onto a module or
driver in the Stream.
The modules or drivers in a Stream can also detect errors.
When they do, they send an error message containing an
error number to the Stream head. Subsequent calls to the
functions will fail with errno set to this number.
ioctl Commands
The STREAMS ioctl commands are the following: Lets the
user process see if the message currently on the Stream
head read queue is marked by a downstream module. A message
is marked when its b_flag field has MSGMARK ORed in
by a module/driver. The arg field specifies how the checking
is done when there are multiple marked messages on the
queue. The legal values of arg are: Checks if the message
is marked. Checks if the message is the last one that is
marked on the queue.
The command returns a value of 1 if the mark condition
is satisfied; otherwise, a 0 (zero) is
returned. Checks if the specified priority band is
currently writable. The arg parameter specifies the
priority band to check.
The command returns a value of 0 (zero) if the priority
band is being flow controlled; otherwise, a
value of 1 is returned. Checks if a certain priority
band's message is currently on the Stream head
read queue. The arg parameter specifies the priority
band being checked.
If a message of the priority band is on the Stream
head read queue, the command returns a value of 1;
otherwise, a value of 0 (zero) is returned. Creates
a message from one or more user specified
buffers, includes information about another Stream,
and sends the message downstream. The message contains
a control part and a data part (which is
optional). These parts are placed in separate
buffers, ctlbuf and databuf, pointed to by arg.
These buffers are contained in an strfdinsert
structure (defined in the stropts.h header file),
whose members are as follows:
struct strbuf ctlbuf; struct strbuf databuf; long
flags; int fildes; int offset;
The strbuf structure pointed to by ctlbuf and
databuf has the following members:
int maxlen; int len; char *buf
The len field of the strbuf structure for ctlbuf
must specify the size of a pointer, plus the number
of information control bytes to be sent in the message.
The fildes field in the strfdinsert structure specifies
the file descriptor of the Stream in which
the message will be sent.
The offset field needs to be properly aligned. This
field specifies the number of bytes after the
beginning of the control buffer where the I_FDINSERT
command will store a pointer. This pointer
will be the address of the read queue structure of
the device driver for the Stream designated by
fildes in the strfdinsert structure.
The len field in the strbuf structure for databuf
must contain the number of bytes of data information
to be sent with the message, or to 0 (zero) if
no data part is to be sent.
The flags field specifies the type of message to be
created. When this field contains 0 (zero), the
I_FDINSERT command creates an ordinary message.
When the field is set to RS_HIPRI, the I_FDINSERT
command creates a high priority message. This command
will block for an ordinary message if the
named Stream's read queue is full because of internal
flow control conditions. It will not block on
these conditions for a high priority message. For
ordinary messages, the ioctl will not block when
the write queue is full and O_NDELAY or O_NONBLOCK
(see the open() function) is specified. It will
fail instead. Compares the names of all modules
currently present on the Stream to the name specified
in arg. The command returns a value of 1 value
if the module is present and a value of 0 (zero)
value if the the module is not present. Flushes
the input and output queues of the Stream head and
all of the modules and drivers on the Stream,
according to the value of arg. The arg parameter
value can specify one of the following operations:
Flushes write and read queues. Flushes write
queues. Flushes read queues.
The command has the following effects on pipes: If
a pipe does not have pushed modules, then, according
to the value of arg, the read queue of the
Stream head at either end is flushed. When arg is
FLUSHRW and fildes specifies a pipe, the read
queues at both ends are flushed. When arg is
FLUSHW and fildes specifies a pipe, and the other
end of the pipe exists (for example, the other end
is not closed), the read queue for the other end of
the pipe, and the write queue for this end, are
flushed. When arg is FLUSHR and fildes specifies a
pipe, both the read queue for the end which issued
the I_FLUSH, and the write queue for the other end,
are flushed.
The pipemod module performs flushing operations on
pipes. This module should be the first one pushed
on the Stream for a pipe so that it will be located
at the midpoint of the pipe. Flushes a band of
messages. The band of messages to be flushed is
defined in the bandinfo structure pointed to by
arg. This structure (in the stropts.h header file)
has the following members:
unsigned char bi_pri: int bi_flag;
The value of the bi_flag field can be FLUSHR,
FLUSHW, or FLUSHRW, as described for the I_FLUSH
command. Returns the priority of the first message
on the Stream head read queue. The arg parameter
specifies the priority band being checked. Returns
the time delay for closing a Stream (see the I_SETCLTIME
ioctl command). The time value is returned
in the long pointed to by arg. This value may, or
may not, have been set by a previously issued
I_SETCLTIME ioctl. Returns the events for which
the calling process has registered to receive a
SIGPOLL signal. Events are returned as in arg bitmask
as defined for the I_SETSIG command. Returns
the current read mode setting of the Stream (see
the read() function reference page) in an integer
pointed to by arg. Returns the current write mode
setting for a Stream in the integer pointed to by
arg. The value of the integer returned in arg is
SNDZERO as described for the I_SWROPT command.
Connects two Streams: the file descriptor of the
Stream associated with the multiplexing driver
(where fildes is the file descriptor) and the
Stream associated with another driver (where arg is
the file descriptor). The Stream referred to by arg
is connected below the multiplexing driver.
The I_LINK ioctl requires a multiplexing driver to
send an acknowledgement message (M_IOCACK or M_IOCNAK)
to the Stream head about the linking operation.
Upon successful completion, the call returns
a multiplexor ID number, which is an identifier
that is used to disconnect the link (see the
I_UNLINK command). If the request fails, a value
of -1 is returned. Lets the user process list the
names of all the modules present on a Stream. This
includes the names up to and including the topmost
driver name. If the arg parameter is a null value,
the command returns the number of modules, plus the
driver, which are present on the Stream referred to
by fildes. The user can use this information to
allocate enough space for the module and driver
names in user space. If the arg parameter is not a
null value, its value should point to an str_list
structure (in the stropts.h header file), with the
following members:
int sl_nmods; struct str_mlist *sl_modlist;
The str_mlist structure (also in the stropts.h
header file) has the following member:
char 1_name[FMNAMESZ+1];
The sl_nmods field of the str_list structure indicates
the number of entries that the user process
has allocated in the array and on return. The
sl_modlist field contains the list of module names.
The return value for the I_STR ioctl indicates the
number of entries that have been filled in the
array. Retrieves the name of the module located
just below the Stream head, placing it in a null
terminated character string pointed to by arg. The
Stream is referred to by fildes. The arg parameter
should point to a buffer, whose size is at least
FMNAMESZ+1 bytes. The <sys/stropts.h> file contains
the definition for FMNAMESZ. Counts the
bytes in the data blocks of the first message on
the Stream head read queue. This command places
this value in the location pointed to by arg. The
command returns the number of messages on the
queue. For example, if the command call results in
a value of 0 (zero) in arg, but a return value
greater than 0 (zero) is returned by the ioctl()
function, the first message on the queue contains 0
(zero) bytes. Allows the user process to look
(peek) at the contents of the first message on the
Stream head read queue. This is done without taking
the message off the queue. The I_PEEK ioctl
operates the same way as the getmsg() function,
except that it does not remove the message. The arg
parameter points to a strpeek structure (in the
stropts.h header file) with the following members:
struct strbuf ctlbuf; struct strbuf databuf; long
flags;
The strbuf structure pointed to by ctlbuf and
databuf has the following members:
int maxlen; int len; char *buf
The maxlen field of the strbuf structure must specify
the number of bytes of control or data information
to be retrieved. The flags field can be set to
RS_HIPRI or 0 (zero). If this field is set to
RS_HIPRI, the I_PEEK ioctl looks for a high priority
message on the queue. If the field is set to 0,
the I_PEEK ioctl looks at the first message on the
queue.
The I_PEEK returns a 1 if a message was retrieved,
and returns a value of 0 (zero) if no message was
found; it does not wait for a message. Upon successful
completion, ctlbuf specifies control information
in the control buffer, databuf specifies
data information in the data buffer, and flags contains
RS_HIPRI or 0 (zero). Connects two Streams:
the file descriptor of the Stream associated with
the multiplexing driver (where fildes is the file
descriptor) and the Stream associated with another
driver (where arg is the file descriptor). The
Stream referred to by arg is connected via a persistent
link below the multiplexing driver. A persistent
link is a link that can exist even if the
file descriptor fildes referring to the Stream
associated with the multiplexing driver is closed.
The I_PLINK ioctl requires a multiplexing driver to
send an acknowledgement message (M_IOCACK or M_IOCNAK)
to the Stream head about the linking operation.
On successful completion, the command returns a
multiplexor ID number, which is an identifier that
is used to disconnect the multiplexing driver (see
the I_PUNLINK command). Otherwise, a -1 is
returned.
The I_PLINK ioctl can also fail if it is waiting
for the multiplexing driver to acknowledge the link
request and an error (M_ERROR) message, or hangup
(M_HANGUP) message is received at the Stream head
for fildes. In addition, an error can be returned
in an M_IOCACK or M_IOCNAK message. When these
occur, the I_PLINK ioctl will fail with errno set
to the value in the message. Removes the module
just below the Stream head. The Stream is referred
to by the fildes parameter. The arg parameter must
be set to the value 0 (zero) in the request.
In the case of pipes, the module must be popped
from the side on which it was pushed. Disconnects
two Streams that are connected via a persistent
link, where fildes is the file descriptor of the
Stream associated with a multiplexing driver and
arg is the multiplexor ID number returned by the
I_PLINK ioctl. If arg is MUXID_ALL (as defined in
the stropts.h header file), then all Streams that
are connected by persistent links to the Stream
referred to by fildes are disconnected.
The I_PUNLINK ioctl requires a multiplexing driver
to send an acknowledgement message (M_IOCACK or
M_IOCNAK) to the Stream head about the unlinking
operation. Pushes the module whose name is pointed
to by arg on to the Stream, just below the Stream
head, then calls the open routine of the module. In
the case of pipes, the module is effectively pushed
between the Stream head at each end. Gets the file
descriptor associated with the message sent by the
I_SENDFD command over a Stream pipe.
The arg parameter points to a data buffer large
enough to hold a strrecvfd structure (in the
stropts.h header file), which contains user data.
This structure has the following members:
int fd; uid_t uid; gid_t gid; char
fill[8]
The fd field of the strrecvfd structure contains
the integer for the file descriptor. The uid and
guid fields contain the user ID and group ID of the
sending Stream. If the O_ONDELAY or O_NONBOCK flags
(see the open() function) are not set, the I_RECVFD
ioctl will block until a message is present at the
Stream head. If the O_ONDELAY or O_NONBOCK flags
are set, the I_RECVFD ioctl will fail if no message
is present at the Stream head.
If the I_SENDFD command sent the message at the
Stream head, the I_RECVFD command allocates a new
file descriptor for the file pointer contained in
the message. The new file descriptor is placed in
the fd field of the strrecvfd structure, and the
structure is copied into the data buffer pointed to
by arg. Requests the Stream referred to by fildes
to send a message M_PASSFP to the Stream head at
the other end of a Stream pipe. The file pointer
corresponds to the value of arg, which specifies an
open file descriptor.
The I_SENDFD command changes the arg value into a
system file pointer, allocates a message data
block, and inserts the file pointer in the block.
It also places the user id and group id associated
with the calling process are also placed in the
block. The message is then placed directly on the
read queue of the Stream head at the other end of
the Stream pipe. It does not go through the Stream
of the pipe. Lets the user process set the time
that the Stream head delays when the Stream is
closing and the write queues contain data. The arg
parameter contains a pointer to the number of milliseconds
to delay, rounded up to the nearest legal
value on the system. The default time is 15 seconds.
Before Stream modules and drivers are closed, the
Stream head will delay for the specified amount of
time. This allows the data on the write queues to
drain. If data are still present on the writes
queues after the delay, the queues are flushed.
Tells the Stream head that the user process wants a
SIGPOLL signal to be issued by the kernel for a
particular event that can occur on a Stream. This
command provides support for asynchronous processing
in STREAMS.
The arg parameter contains a bitmask specifying the
particular events that SIGPOLL is to be sent for.
The value is the bitwise-OR of any combination of
the following constants: Indicates that, when used
with S_RDBAND, a priority message has reached the
front of the Stream head read queue. (If only
S_RDBAND is set, only a SIGPOLL signal will be generated.
If S_BANDURG is also set, then a SIGURG
signal will be generated.) However, SIGURG is generated
instead of SIGPOLL. Specifies that an
M_ERROR message has reached the front of the Stream
head read queue. The SIGPROC signal is posted to
the user. Specifies that an M_HANGUP message has
reached the Stream head. The SIGPROC signal is
posted, in addition to a SIGHUP signal. Specifies
a high priority message has arrived on the readd
queue of the Stream head. This bit is set even zero
length messages. Specifies that a message, which
is not a M_PCPROTO type message, has arrived on the
read queue of the Stream head. This bit is set even
for zero length messages. The S_INPUT event is
maintained for compatibility with SVID 2. Specifies
that a STREAMS signal (M_SIG) signal containing
the SIGPOLL signal has reached the front of the
Stream head read queue. The SIGPROC signal will be
posted to the user. If S_MSG is not enabled, SIGPROC
will not be sent. Specifies that the write
queue of the module just below the Stream head is
not full any more. There is room on the queue for
the user process to send (write) data to the
Stream. Specifies a priority band message (where
band is greater than 0 (zero)) has arrived on the
read queue of the Stream head. This bit is set even
zero length messages. Specifies that an ordinary
message has arrived on the read queue of the Stream
head. This bit is set even for zero length messages.
Specifies that a priority band (where band
is greater than 0 (zero)) exists on a queue downstream.
The user can send (write)a priority data
message on the queue. Specifies that this event is
the same as S_OUTPUT.
User processes must register explicitly using the
I_SETSIG command to receive SIGPOLL (or SIGURG)
signals. This is noted by the Stream head. When
more than one user process registers to receive the
signal for the same event on a Stream, each is signaled
when the event occurs. If the value of arg is
0 (zero), the calling process is deregistered and
does not receive the signal.
A user process can set the arg bitmask to the
S_HIPRI value, thus allowing itself to be signaled
only of high priority messages. Sets the read mode
of the Stream (see the read() reference page)
according to the value of arg. The arg value specifies
the following read modes related to data and
message boundaries: Byte-stream mode (the default).
The read() function completes when the byte count
is satisfied, the Stream head read queue is empty,
or a zero length message is encountered. In the
case of a zero length message, the message is
placed back on the queue, and a subsequent read()
returns 0 bytes. Message-discard mode. The read()
function completes when the byte count is satisfied,
or a message boundary is reached. Any
remaining data in the message are discarded. Message-nondiscard
mode. The read() function completes
when the byte count is satisfied, or a message
boundary is reached. Any data remaining in the
message are put back on the read queue.
If the following value are set in arg, the Stream
head treats control (protocol) messages accordingly:
The read() function fails, returning
EBADMSG, if a control message is at the front of
the read queue (the default behavior). The read()
function delivers the control portion of the message
as data to the user process. The read() function
discard the control portion of a message and
send the data portion to the user process. Builds
a STREAMS ioctl (M_IOCTL) message from the data
pointed to by arg and sends the message downstream
to a module or driver. The command allows a user
process to send data with an ioctl request, and to
receive any information that the downstream recipient
of the message returns. The I_STR ioctl blocks
until the intended recipient of the M_IOCTL message
responds with a positive acknowledgement (M_IOCACK)
message or negative acknowledgement (M_IOCNAK) message,
or until the request times out (default time
= 15 seconds). If the request times out, it fails.
Only one I_STR ioctl can be active on a Stream at a
time. Other requests must wait until the active
request completes at the Stream head. The O_NDELAY
and O_NONBLOCK flags (see the open() function) have
no effect on the call.
User values for the I_STR ioctl request are supplied
by a strioctl structure (in the stropts.h
header file), to which the arg parameter points.
The members of strioctl structure are the following:
int ic_cmd; int ic_timeout; int ic_len; char
*ic_dp;
The ic_cmd field of the strioctl structure contains
the ioctl command to be sent to the downstream module
or driver. The ic_timeout field specifies the
number of seconds that the I_STR request will wait
for an acknowledgement before timing out: Indicates
infinite number of seconds. Indicates that the
default number of seconds should be used (which is
infinite). Indicates that the specified number of
seconds should be used.
On input, the ic_len field contains the length of
the data argument. On return, it contains the number
of bytes being returned to the user process,
(the buffer pointed to by ic_dp). The buffer
pointed to by ic_dp should be large enough to contain
the maximum amount of data able to be returned
by any module or driver in the Stream. Sets the
stream write mode according to the arg parameter
value. The legal value for arg is: When set, the
Stream head sends a zero length message downstream
upon the occurrence of a write of 0 (zero) bytes.
When not set, the Stream head does not send a zero
length message downstream when a write of 0 bytes
occurs, and returns 0 to the user process. Disconnects
two Streams, where fildes is the file
descriptor of the Stream associated with a multiplexing
driver and arg is the multiplexor identifier
number returned by the I_LINK ioctl, which
created the multiplexing configuration. If arg is
MUXID_ALL (defined in the stropts.h header file),
all Streams connected to the Stream referred to by
fildes are disconnected.
The I_UNLINK ioctl requires a multiplexing driver
to send an acknowledgement message (M_IOCACK or
M_IOCNAK) to the Stream head about the unlinking
operation.
RETURN VALUES [Toc] [Back]
Unless specified differently for a command, the return
value for a STREAMS ioctl() call is 0 (zero) on success
and -1 (minus one) on failure.
A STREAMS ioctl command fails without performing the function
and with errno set to [EINVAL] if: The Stream
referred to by fildes is linked below a multiplexing
driver. The command parameter is not a valid value for
the Stream.
In addition, if any of the following conditions occur, the
STREAMS ioctl commands return the corresponding value:
I_ATMARK The arg parameter has an illegal value.
I_CANPUT The arg parameter has an illegal value.
I_CKBAND The arg parameter has an illegal value.
I_FDINSERT The fildes parameter in the strfdinsert structure
is an invalid, open file descriptor. The size of the
pointer plus offset exceeds the value of the len field for
the buffer specified through ctlptr. The offset parameter
does not specify a properly aligned location in the data
buffer. The flags parameter contains an undefined value.
The arg parameter points, or ctrlbuf or databuf is, outside
the allocated address space. The ioctl request
failed because a non-priority message was to be created,
the O_NDELAY or O_NONBLOCK flag was set, and the Stream's
write queue was full because of internal flow control conditions.
Buffers could not be allocated for the message
that was to be created due to insufficient STREAMS memory
resources. A hangup was received on the Stream specified
by fildes in the I_FDINSERT ioctl call or on the Stream
specified by fildes in the strfdinsert. The value of the
len field for the buffer specified through databuf does
not fall within the range for the minimum and maximum
sizes of packets for the topmost module on the Stream.
The value of the len field for the buffer specified
through databuf is larger the the maximum allowable size
for the data part of a message. The value of the len
field for the buffer specified through ctlbuf is larger
the the maximum allowable size for the control part of a
message.
The I_FDINSERT ioctl can also fail if an error
(M_ERROR) message was received by the Stream specified
by the fildes field in the strfdinsert structure.
In this case, errno is set to the error value
in the error message.
I_FIND The arg parameter does not contain a valid module
name. The arg parameter points outside the allocated
address space.
I_FLUSH Could not allocate buffers for flush operation
because of a lack of STREAMS memory resources. The arg
parameter is an invalid value. A hangup was received on
fildes.
I_FLUSHBAND
The bi_pr parameter value exceeds the maximum band, or the
bi_flag parameter is not FLUSHR, FLUSHW, or FLUSHRW.
I_GETBAND No message exists on the Stream head read queue.
I_GETSIG User process is not registered to receive the
SIGPOLL signal. The arg parameter points outside the
allocated address space.
GRDOPT The arg parameter is pointing outside the allocated
address space.
I_LINK Temporarily unable to allocate storage to perform
the linking operation. The arg parameter is an invalid,
open file descriptor. A hangup was received on fildes.
The Stream referred to by fildes does not support multiplexing.
The file referred to by arg is not a Stream, or
the Stream is already linked under a multiplexor. The
link operation would cause a "cycle" in the resulting multiplexing
configuration. In other words, the driver
referred to by the arg parameter is linked into this configuration
at multiple places The fildes parameter is the
file descriptor of a pipe.
The I_LINK ioctl can also fail if it is waiting for
the multiplexing driver to acknowledge the link
request and an error (M_ERROR) message, or hangup
(M_HANGUP) message is received at the Stream head
for fildes. In addition, an error can be returned
in an M_IOCACK or M_IOCNAK message. When these
occur, the I_LINK ioctl will fail with errno set to
the value in the message.
I_LIST The sl_mods number members is less than 1. Could
not allocate buffers.
I_LOOK The named module is not present on the Stream. The
arg parameter points outside the allocated address space.
I_NREAD The arg parameter is pointing outside the allocated
address space.
I_PEEK The flags parameter is an illegal value. arg
points, or ctrlbuf or databuf is, outside the allocated
address space. Message to be looked at is not valid for
the I_PEEK command.
I_PLINK A hangup was received on the Stream referred to by
the fildes parameter. A timeout occurred before an
acknowledgement message was received at the Stream head.
Temporarily unable to allocate storage to perform the
linking operation. The arg parameter is an invalid, open
file descriptor. The Stream referred to by the fildes
parameter does not support multiplexing. The file
referred to by the arg parameter is not a Stream, or is
already linked under a multiplexing driver. The link
operation would cause a "cycle" in the resulting multiplexing
configuration. In other words, the driver
referred to by the arg parameter is linked into the configuration
at multiple places. The fildes parameter is
the file descriptor of a pipe.
I_POP The named module is not present on the Stream.
Error value returned by the module being popped. A hangup
was received on fildes.
I_PUNLINK A hangup was received on fildes. A timeout
occurred before an acknowledgement message was received at
the Stream head. Temporarily unable to allocate storage
to perform the linking operation. The arg parameter is an
invalid multiplexor ID number. fildes is the file
descriptor of a pipe.
An I_PUNLINK ioctl can also fail if it is waiting
for the multiplexor to acknowledge the unlink
request and an error (M_ERROR) message, or hangup
(M_HANGUP) is received at the Stream head for
fildes. In addition, an error can be returned in an
M_IOCACK or M_IOCNAK message. When these occur, the
PUNI_LINK ioctl will fail with errno set to the
value in the message.
I_PUSH An invalid module name was used. The arg parameter
points outside the allocated address space. Error value
returned by the module being pushed. The push has failed.
A hangup was received on fildes.
I_RECVFD The O_ONDELAY or O_NONBOCK flag was set, and a
message was not present on the Stream head read queue, The
arg parameter points outside the allocated address space.
The message present on the Stream head read queue did not
contain a passed file descriptor. No more file descriptors
are permitted to be opened. A hangup was received on
fildes.
I_SENDFD The sending Stream head could not allocate a message
block for the file pointer. The read queue of the
receiving Stream head was full and could not accept the
message. The arg parameter is an invalid, open file
descriptor. The fildes parameter does not refer to a
Stream pipe. A hangup was received on fildes.
I_SETCLTIME The arg parameter has an illegal value.
I_SETSIG The user process is not registered to receive the
SIGPOLL signal. A data structure to store the signal
request could not be allocated.
I_SRDOPT The arg parameter contains an illegal value.
I_STR The ic_len field is less than 0 (zero) bytes or
larger than the maximum allowable size of the data part of
a message (ic_dp). The ic_timeout field is less than -1.
The arg parameter points, or the buffer area specified by
ic_dp or ic_len is, outside the allocated address space.
Buffers could not be allocated for the ioctl request
because of a lack of STREAMS memory resources. A hangup
was received on the Stream referred to by fildes. The
ioctl request timed out before an acknowledgement was
received.
The I_STR ioctl can also fail if the Stream head
receives a message indicating an error (M_ERROR) or
a hangup (M_HANGUP). In addition, an error can be
returned in an M_IOCACK or M_IOCNAK message. In
these cases, the ioctl will fail with errno set to
the error value in the message.
I_SWROPT The arg parameter is an illegal value.
I_UNLINK A hangup was received on fildes. A timeout
occurred before an acknowledgement message was received at
the Stream head. The arg parameter is an invalid multiplexor
ID number, or the fildes parameter is already
linked under a multiplexing driver. The fildes parameter
is the file descriptor of a pipe.
An I_UNLINK ioctl can also fail if it is waiting
for the multiplexor to acknowledge the unlink
request and an error (M_ERROR) message, or hangup
(M_HANGUP) is received at the Stream head for
fildes. In addition, an error can be returned in
M_IOCACK or M_IOCNAK message. When this occurs, the
I_UNLINK ioctl will fail with errno set to the
value in the message.
The system file containing all of the structure and constant
definitions for STREAMS. The system file that contains
type definitions used in STREAMS header files. The
system file that contains definitions of the arguments to
the STREAMS M_FLUSH message type required by users and
STREAMS modules and drivers.
Functions: close(2), fattach(3), fcntl(2), fdetach(3),
getmsg(2), ioctl(2), open(2), poll(2), putmsg(2), read(2),
sigaction(2), write(2)
Files: signal(4)
Standards: standards(5)
streamio(7)
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