HPUX streamio[7]
streamio(7) streamio(7)
NAME
streamio - STREAMS ioctl commands
SYNOPSIS
#include <sys/types.h>
#include <stropts.h>
int ioctl( int fildes, int command, [void arg ])
DESCRIPTION
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 optional arg parameter, when specified, into
an M_IOCTL message. In some cases, the command and optional arg
parameters are passed onto a module or driver in the stream.
The modules or drivers in a stream can detect errors in the ioctl
command. When they do, they send an error message containing an error
number to the stream head. Subsequent calls to functions fail with
errno set to this number.
Parameters
fildes Contains the open file descriptor for the stream to be
operated on.
command Specifies the STREAMS ioctl() command function to be
performed on the stream.
arg 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 must be of the type required for the
specific command.
ioctl Commands
The STREAMS ioctl commands are the following:
I_ATMARK Lets the user process determine whether 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. Acceptable values
of arg are:
ANYMARK Checks if the message is
marked.
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LASTMARK 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.
I_CANPUT Checks if the specified priority band is currently
writeable. 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.
I_CKBAND Checks if a priority band 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.
I_FDINSERT 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. 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 options;
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.
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The fildes field in the strfdinsert structure
specifies the file descriptor of the stream to
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 is the address of the read queue 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 0
(zero) if no data part is to be sent.
The options 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 messges, the ioctl
will not block when the write queue is full and
O_NDELAY or O_NONBLOCK (see open(2) or fcntl(2) )
is specified. It will fail instead.
I_FIND Compares the names of all modules currently
present on the stream to the name specified in
arg. The command returns a value of 1 if the
module is present and a value of 0 (zero) if the
the module is not present.
I_FLUSH Flushes the read and write 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:
FLUSHRW Flushes write and read queues.
FLUSHW Flushes write queues.
FLUSHR Flushes read queues.
I_FLUSHBAND Flushes a band of messages. The band of messages
to be flushed is defined in the bandinfo structure
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pointed to by arg. This structure (in the
<stropts.h> header file) has the following
members:
unsigned char bi_pri:
int bi_option;
The value of the bi_option field can be FLUSHR,
FLUSHW, or FLUSHRW, as described for the I_FLUSH
command.
I_GETBAND Returns the priority of the first message on the
stream head read queue. The priority is returned
as an integer in the arg parameter.
I_GETCLTIME 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.
I_GETSIG 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.
I_GRDOPT Returns the current read mode setting of the
stream (see read(2)) in an integer pointed to by
arg.
I_GWROPT Returns the current write mode setting for a
stream in the integer pointed to by arg. See the
I_SWROPT command for a description of write modes.
I_LINK 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.
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I_LIST 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 l_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 pointed to be
the sl_modlist field. On return, the array
pointed to by the sl_modlist field contains the
list of module names.
The return value for the I_LIST ioctl indicates
the number of entries that have been filled in the
array.
I_LOOK 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 <stropts.h> file
contains the definition for FMNAMESZ.
I_NREAD 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.
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I_PEEK 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 messsage. 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 options;
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 options 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
options contains RS_HIPRI or 0 (zero).
I_PLINK 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
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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
fails with errno set to the value in the message.
I_POP 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.
I_PUNLINK 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.
I_PUSH Pushes the module whose name is pointed to by arg
onto the stream just below the stream head, then
calls the open routine of the module.
I_RECVFD 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:
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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
gid fields contain the user ID and group ID of the
sending stream. If the O_ONDELAY or O_NONBLOCK
options (see open(2) or fcntl(2)) function) are
not set, the I_RECVFD ioctl blocks until a message
is present at the stream head. If the O_ONDELAY
or O_NONBLOCK options are set, the I_RECVFD ioctl
fails 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.
I_SENDFD 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.
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.
I_SETCLTIME 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 delays for the specified amount of
time. This allows the data on the write queues to
drain. If data is still present on the writes
queues after the delay, the queues are flushed.
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I_SETSIG 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:
S_BANDURG 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 is generated.
If S_BANDURG is also set, then
a SIGURG signal is generated.)
S_ERROR Specifies that an M_ERROR
message has reached the front
of the stream head read queue.
S_HANGUP Specifies that an M_HANGUP
message has reached the stream
head.
S_HIPRI Specifies a high priority
message has arrived on the
read queue of the stream head.
A SIGPOLL signal is issued
even for zero-length messages.
S_INPUT Specifies that a message,
which is not a M_PCPROTO type
message, has reached the front
of the stream head read queue.
A SIGPOLL signal is issued
even for zero-length messages.
The S_INPUT event is
maintained for compatibility
with SVID2.
S_MSG Specifies that a STREAMS
signal (M_SIG) signal
containing the SIGPOLL signal
has reached the front of the
stream head read queue.
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S_OUTPUT 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.
S_RDBAND Specifies a priority band
message (where band is greater
than 0 (zero)) has reached the
front of the stream head read
queue. A SIGPOLL signal is
issued even for zero-length
messages.
S_RDNORM Specifies that an ordinary
message has reached the front
of the stream head read queue.
A SIGPOLL signal is issued
even for zero-length messages.
S_WRBAND 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.
S_WRNORM 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 when high priority messages reach the stream
head read queue.
I_SRDOPT Sets the read mode of the stream (see read(2))
according to the value of arg. The arg value
specifies the following read modes related to data
and message boundaries:
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RNORM Byte-stream mode (default).
The read(2) 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(2) returns 0 bytes.
RMSGD Message-discard mode. The
read(2) function completes
when the byte count is
satisfied, or a message
boundary is reached. Any
remaining data in the message
is discarded.
RMSGN Message-nondiscard mode. The
read(2) 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 any of the following values are set in arg, the
stream head treats control (protocol) messages
accordingly:
RPROTNORM read(2) fails, returning
[EBADMSG], if a control
message is at the front of the
read queue (default behavior).
RPROTDAT read(2) delivers the control
portion of the message as data
to the user process.
RPROTDIS read(2) discards the control
portion of a message and sends
the data portion to the user
process.
I_STR 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
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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 options (see open(2) or
fcntl(2)) 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:
-1 Indicates infinite number of seconds.
0 Indicates that the default number of
seconds should be used (15 seconds).
>0 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 that any module
or driver in the stream can return.
I_SWROPT Sets the stream write mode according to the arg
parameter value. The legal value for arg is:
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SNDZERO 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.
I_UNLINK 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
that 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
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.
ERRORS
A STREAMS ioctl command fails without performing the function and with
errno set to [EINVAL] if:
o The stream referred to by fildes is linked below a
multiplexing driver.
o 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
[EINVAL] arg has an illegal value.
I_CANPUT
[EINVAL] arg has an illegal value.
I_CKBAND
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[EINVAL] arg has an illegal value.
I_FDINSERT
[EINVAL] The fildes parameter in the strfdinsert structure
is an invalid open file descriptor.
[EINVAL] The size of the pointer plus offset exceeds the
value of the len field for the buffer specified
through ctlptr.
[EINVAL] offset does not specify a properly aligned
location in the data buffer.
[EINVAL] options contains an undefined value.
[EFAULT] arg points, or ctrlbuf or databuf is outside the
allocated address space.
[EAGAIN] The ioctl request failed because a non-priority
message was to be created, the O_NDELAY or
O_NONBLOCK option was set, and the stream's write
queue was full because of internal flow control
conditions.
[ENOSR] Buffers could not be allocated for the message
that was to be created due to insufficient STREAMS
memory resources.
[ENXIO] 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.
[ERANGE] 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 top-most module on the stream.
[ERANGE] 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.
[ERANGE] 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.
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I_FIND
[EINVAL] arg does not contain a valid module name.
[EFAULT] arg points outside the allocated address space.
I_FLUSH
[ENOSR] Could not allocate buffers for flush operation
because of a lack of STREAMS memory resources.
[EINVAL] The arg parameter is an invalid value.
[ENXIO] A hangup was received on fildes.
I_FLUSHBAND
[EINVAL] The bi_pr parameter value exceeds the maximum
band, or the bi_option parameter is not FLUSHR,
FLUSHW, or FLUSHRW.
I_GETBAND
[ENODATA] No message exists on the stream head read queue.
I_GETSIG
[EINVAL] User process is not registered to receive the
SIGPOLL signal.
[EFAULT] arg points outside the allocated address space.
I_GRDOPT
[EFAULT] arg is pointing outside the allocated address
space.
I_LINK
[EAGAIN] Temporarily unable to allocate storage to perform
the linking operation.
[EBADF] The arg parameter not a valid open file
descriptor.
[ENXIO] A hangup was received on fildes.
[EINVAL] The stream referred to by fildes does not support
multiplexing.
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[EINVAL] The file referred to by arg is not a stream, or
the stream is already linked under a multiplexor.
[EINVAL] 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
[ENOSR] Not enough STREAMS memory resources to allocate
storage for this command.
[ETIME] Acknowledgement message not received at stream
head before timeout.
The I_LINK ioctl can also fail if M_ERROR or M_HANGUP message is
received at the stream head for fildes before receiving the
driver acknowledgement. In addition, an error can be returned in
an M_IOCACK or M_IOCNAK message. When these occur, the I_LINK
ioctl fails with errno set to the value in the message.
I_LIST
[EINVAL] sl_nmods is less than 1.
[EAGAIN] Could not allocate buffers.
I_LOOK
[EINVAL] There are no modules in the stream.
[EFAULT] arg points outside the allocated address space.
I_NREAD
[EFAULT] arg is pointing outside the allocated address
space.
I_PEEK
[EINVAL] The options parameter is an illegal value.
[EFAULT] arg points, or ctrlbuf or databuf is, outside the
allocated address space.
[EBADMSG] Message to be looked at is not valid for the
I_PEEK command.
I_PLINK
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[ENXIO] A hangup was received on the stream referred to by
the fildes parameter.
[ETIME] A timeout occured before an acknowledgement
message was received at the stream head.
[EAGAIN] Temporarily unable to allocate storage to perform
the linking operation.
[EBADF] arg is not a valid open file descriptor.
[EINVAL] The stream referred to by fildes does not support
multiplexing.
[EINVAL] The file referred to by arg is not a stream, or is
already linked under a multiplexing driver.
[EINVAL] The link operation would cause a "cycle" in the
resulting multiplexing configuration. In other
words, the driver referred to by arg is linked
into the configuration at multiple places.
I_POP
[EINVAL] There are not modules in the stream.
[ENXIO] Error value returned by the module being popped.
[ENXIO] A hangup was received on fildes.
I_PUNLINK
[ENXIO] A hangup was received on fildes.
[ETIME] A timeout occured before an acknowledgement
message was received at the stream head.
[EAGAIN] Temporarily unable to allocate storage to perform
the linking operation.
[EINVAL] arg is an invalid multiplexor ID number.
[EINVAL] 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 P_UNLINK
ioctl fails with errno set to the value in the message.
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streamio(7) streamio(7)
I_PUSH
[EINVAL] An invalid module name was used.
[EFAULT] arg points outside the allocated address space.
[ENXIO] Error value returned by the module being pushed.
The push has failed.
[ENXIO] A hangup was received on fildes.
I_RECVFD
[EAGAIN] The O_ONDELAY or O_NONBLOCK option was set, and a
message was not present on the stream head read
queue.
[EFAULT] The arg parameter points outside the allocated
address space.
[EBADMSG] The message present on the stream head read queue
did not contain a passed file descriptor.
[EMFILE] Too many open files. No more file descriptors are
permitted to be opened.
[ENXIO] A hangup was received on fildes.
I_SENDFD
[EAGAIN] The sending stream head could not allocate a
message block for the file pointer.
[EAGAIN] The read queue of the receiving stream head was
full and could not accept the message.
[EBADF] The arg parameter is not a valid open file
descriptor.
[EINVAL] The fildes parameter does not refer to a stream.
[ENXIO] A hangup was received on fildes.
I_SETCLTIME
[EINVAL] arg has an illegal value.
I_SETSIG
[EINVAL] The user process is not registered to receive the
SIGPOLL signal.
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streamio(7) streamio(7)
[EAGAIN] A data structure to store the signal request could
not be allocated.
I_SRDOPT
[EINVAL] arg contains an illegal value.
I_STR
[EINVAL] 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).
[EINVAL] The ic_timeout field is less than -1.
[EFAULT] arg points, or the buffer area specified by ic_dp
or ic_len is, outside the allocated address space.
[ENOSR] Buffers could not be allocated for the ioctl
request because of a lack of STREAMS memory
resources.
[ENXIO] A hangup was received on the stream referred to by
fildes.
[ETIME] 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 fails with errno set to the
error value in the message.
I_SWROPT
[EINVAL] The arg parameter is an illegal value.
I_UNLINK
[ENXIO]
A hangup was received on fildes.
[ETIME]
A timeout occured before an acknowledgement message was
received at the stream head.
[EINVAL]
arg is an invalid multiplexor ID number, or fildes is
already linked under a multiplexing driver.
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streamio(7) streamio(7)
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 fails with errno set to the value in the message.
NOTES
For portability purposes, it is recommended that O_NONBLOCK be used
instead of O_NDELAY.
SEE ALSO
close(2), fcntl(2), getmsg(2), ioctl(2), open(2), poll(2), putmsg(2),
read(2), write(2), signal(4).
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