streamio(7)

Allows the user to see if the current message on the stream head read queue is "marked" by some module downstream. arg determines how the checking is done when there are multiple marked messages on the stream head read queue. It may take the following values:

If both ANYMARK and LASTMARK are set, ANYMARK supersedes LASTMARK.

The return value is 1 if the mark condition is satisfied and 0 otherwise.

Checks if a certain band is writable. arg is set to the priority band in question. The return value is 0 if the priority band arg is flow controlled, 1 if the band is writable, or -1 on error.

Check if the message of a given priority band exists on the stream head read queue. This returns 1 if a message of a given priority exists, or -1 on error. arg should be an integer containing the value of the priority band in question.

Creates a message from user specified buffer(s), adds information about another stream and sends the message downstream. The message contains a control part and an optional data part. The data and control parts to be sent are distinguished by placement in separate buffers, as described below.

arg points to a strfdinsert structure which contains the following members:

The len field in the ctlbuf strbuf structure (see putmsg(2)) must be set to the size of a pointer plus the number of bytes of control information to be sent with the message. fildes in the strfdinsert structure specifies the file descriptor of the other stream. offset, which must be word-aligned, specifies the number of bytes beyond the beginning of the control buffer where I_FDINSERT will store a pointer. This pointer will be the address of the read queue structure of the driver for the streams corresponding to fildes in the strfdinsert structure. The len field in the databuf strbuf structure must be set to the number of bytes of data information to be sent with the message or zero if no data part is to be sent.

flags specifies the type of message to be created. An ordinary (non-priority) message is created if flags is set to 0, a high priority message is created if flags is set to RS_HIPRI. For normal messages, I_FDINSERT will block if the stream write queue is full due to internal flow control conditions. For high priority messages, I_FDINSERT does not block on this condition. For normal messages, I_FDINSERT does not block when the write queue is full and the O_NONBLOCK is set. Instead, it fails and sets errno to EAGAIN.

I_FDINSERT also blocks, unless prevented by the lack of internal resources, waiting for the availability of message blocks, regardless of priority or whether O_NONBLOCK has been specified. No partial message is sent.

I_FDINSERT can also fail if an error message was received by the stream head of the stream corresponding to fildes in the strfdinsert structure. In this case, errno will be set to the value in the message.

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 module is not present.

This request flushes all input and/or output queues, depending on the value of arg. Valid arg values are:

If a pipe or FIFO does not have any modules pushed, the read queue of the streams head on either end is flushed depending on the value of arg.

If FLUSHR is set and fildes is a pipe, the read queue for that end of the pipe is flushed and the write queue for the other end is flushed. If fildes is a FIFO, both queues are flushed.

If FLUSHW is set and fildes is a pipe and the other end of the pipe exists, the read queue for the other end of the pipe is flushed and the write queue for this end is flushed. If fildes is a FIFO, both queues of the FIFO are flushed.

If FLUSHRW is set, all read queues are flushed, that is the read queue for the FIFO and the read queue of boths ends of the pipe are flushed.

Correct flushing handling of a pipe or FIFO with modules pushed is achieved via the pipemod module. This module should be the first module pushed onto a pipe so that it is at the midpoint of the pipe itself.

Flushes a particular band of messages. arg points to a bandinfo structure that has the following members:

The value of the bi_flag field can be FLUSHR, FLUSHW, or FLUSHRW as described for the I_FLUSH command.

Returns the priority band of the first message on the stream head read queue in the integer referenced by arg.

Returns the close time delay in the long pointed by arg.

Allows the user to set the time that the stream head will delay when a stream is closing, and there is data on the write queues. Before closing each module and driver, the stream head will delay for the specified amount of time to allow the data to drain. If, after the delay, data is still present, data will be flushed. arg is a pointer to the number of milliseconds to delay, rounded up to the nearest valid value on the system. The default is fifteen seconds.

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 in an int pointed to by the argument arg. Read modes are described in read(2).

Returns the current write mode setting, as described in I_SWROPT, in the int that is pointed to by the argument arg.

Connects two streams, where fildes is the file descriptor of the stream connected to the multiplexing driver, and arg is the file descriptor of the stream connected to another driver. The stream designated by arg gets connected below the multiplexing driver. I_LINK requires the multiplexing driver to send an acknowledgement message to the stream head regarding the linking operation. This call returns a multiplexor ID number (an identifier used to disconnect the multiplexor, see I_UNLINK) on success, and -1 on failure.

Allows the user to list all the module names on the stream, up to and including the topmost driver name. If arg is NULL, the return value is the number of modules, including the driver, that are on the stream pointed to by fildes. This allows the user to allocate enough space for the module names. If arg is not NULL, it should point to a str_list structure that has the following members:

The str_mlist structure has the following member:

sl_nmods indicates the number of entries the user has allocated in the array. On success, the return value is 0, sl_modlist contains the list of module names, and sl_nmods indicates the number of entries that have been filled in.

Retrieves the name of the module located just below the streams head of the stream pointed to by fildes, and places it in a null terminated character string pointed at by arg. The buffer pointed to by arg should be at least FNAMESZ+1 bytes long. A #include <stropts.h> declaration is required.

Counts the number of data bytes in data blocks in the first message on the stream head read queue, and places this value in the location pointed to by arg. The return value for the command is the number of messages on the stream head read queue. For example, if zero is returned in arg, but the ioctl return value is greater than zero, this indicates that a zero-length message is next on the queue.

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:

The strbuf structure pointed to by ctlbuf and databuf has the following members:

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, where fildes is the file descriptor of the stream connected to the multiplexing driver, and arg is the file descriptor of the stream connected to another driver. The stream designated by arg gets connected via a persistent link below the multiplexing driver. I_PLINK requires the multiplexing driver to send an acknowledgement message to the stream head regarding the linking operation. This call creates a persistent link which can exist even if the file descriptor associated with the upper stream to the multiplexing driver is closed. This call returns a multiplexor ID number (an identifier that may be used to disconnect the multiplexor, see I_PUNLINK) on success and -1 on failure.

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_IOACK or M_IONAK message. When these occur, the I_PLINK fails with errno set to the value in the message.

Removes the module just below the stream head of the stream pointed to by fildes. To remove a module from a pipe requires that the module was pushed on the side it is being removed from. arg should be 0 in an I_POP request.

Disconnects the two streams specified by fildes and arg that are connected with a persistent link. fildes is the file descriptor of the stream connected to the multiplexing driver. arg is the multiplexor ID number that was returned by I_PLINK when a stream was linked below the multiplexing driver. If arg is MUXID_ALL, then all streams which are persistent links to fildes are disconnected. As in I_PLINK, this command requires the multiplexing driver to acknowledge the unlink.

Pushes the module whose name is pointed by arg onto the top of the current stream, just below the stream head. If the stream is a pipe, the module will be inserted between the streams heads of both ends of the pipe. It then calls the open routine of the newly-pushed module.

Retrieves the file descriptor associated with the message sent by an I_SENDFD ioctl over a stream pipe. arg is a pointer to a data buffer large enough to hold a strrecvfd data structure containing the following members:

fd is an integer file descriptor. uid and gid are the user ID and group ID, respectively, of the sending stream.

If O_NONBLOCK is clear, I_RECVFD will block until a message is present at the stream head. If O_NONBLOCK is set, I_RECVFD will fail with errno set to EAGAIN if no message is present at the stream head.

If the message at the stream head is a message sent by a I_SENDFD, a new user file descriptor is allocated for the file pointer contained in the message. The new file descriptor is placed in the fd field of the strrecvfd structure. The structure is copied into the user data buffer pointed to by arg.

Requests the stream associated with fildes to send a message, containing a file pointer, to the stream head at the other end of a stream pipe. The file pointer corresponds to arg, which must be an open file descriptor.

I_SENDFD converts arg into the corresponding system file pointer. It allocates a message block and inserts the file pointer in the block. The user ID and group ID associated with the sending process are also inserted. This message is placed directly on the read queue of the stream head at the other end of the stream pipe to which it is connected.

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 STREAMS 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.

Informs the stream head that the user wants the kernel to issue the SIGPOLL signal (see signal(2)) when a particular event has occurred on the stream associated with fildes. I_SETSIG supports an asynchronous processing capability in STREAMS. The value of arg is a bitmask that specifies the events for which the user should be signaled. It is the bitwise-OR of any combination, except where noted, of the following constants:

A user process may choose to be signaled only of high priority messages by setting arg bitmask to the value S_HIPRI.

Processes that want to receive SIGPOLL signals must explicitly register to receive them using I_SETSIG. If several processes register to receive the signal for the same event on the same stream, each process will be signaled when the event occurs.

If the value of arg is zero, the calling process will be unregistered and will not receive further SIGPOLL signals.

Sets the read mode (see read(2)) using the value of the argument arg. Valid arg values are:

Setting both RMSGD and RMSGN is an error. RMSGD and RMSGN override NORM.

In addition, treatment of control messages by the stream head may be changed by setting the following flags in arg:

Constructs an internal STREAMS ioctl message from the data pointed to by arg, and sends that message downstream.

This mechanism is provided to send user ioctl requests to downstream modules and drivers. It allows information to be sent with the ioctl, and will return to the user any information sent upstream by the downstream recipient. I_STR blocks until the system responds with either a positive or negative acknowledgement message, or until the request "times out" after some period of time. If the request times out, it fails with errno set to ETIME.

At most, one I_STR can be active on a stream. Further I_STR calls will block until the active I_STR completes at the stream head. The default timeout intervals for these requests is 15 seconds. The O_NONBLOCK (see open(2)) flags have no effect on this call.

To send requests downstream, arg must point to a strioctl structure which contains the following members:

ic_cmd is the internal ioctl command intended for the downstream module or driver and ic_timout is the number of seconds (-1 =infinite, 0 = use default, >0 = as specified) an I_STR request will wait for acknowledgement before timing out. The default timeout is infinite. ic_len is the number of bytes in the data argument and ic_dp is a pointer to the data argument. The ic_len field has two uses: on input, it contains the length of the data argument passed in, and on return from the command, it contains the number of bytes being returned to the user (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). The stream head will convert the information pointed to by strioctl structure to an internal ioctl command message and send it downstream.

Sets the write mode using the value of the argument arg. Legal bit settings for arg are:

Disconnects the two streams specified by fildes and arg. fildes is the file descriptor of the stream connected to the multiplexing driver. arg is the multiplexor ID number that was returned by the I_LINK. If arg is MUXID_ALL, then all streams which were linked to fildes are disconnected. As in I_LINK, this command requires the multiplexing driver to acknowledge the unlink.

arg has an illegal value.

arg has an illegal value.

arg has an illegal value.

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.

offset does not specify a properly aligned location in the data buffer.

flags contains an undefined value.

arg 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_NONBLOCK option 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 top-most module on the stream.

The value of the len field for the buffer specified through databuf is larger than 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 than 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.

arg does not contain a valid module name.

arg points outside the allocated address space.

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.

The bi_pri parameter value exceeds the maximum band, or the bi_flag parameter is not FLUSHR, FLUSHW, or FLUSHRW.

No message exists on the stream head read queue.

User process is not registered to receive the SIGPOLL signal.

arg points outside the allocated address space.

arg is pointing outside the allocated address space.

Temporarily unable to allocate storage to perform the linking operation.

The arg parameter not a valid 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

Not enough STREAMS memory resources to allocate storage for this command.

Acknowledgement message not received at stream head before timeout.

sl_nmods is less than 1.

Could not allocate buffers.

There are no modules in the stream.

arg points outside the allocated address space.

arg is pointing outside the allocated address space.

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.

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.

arg is not a valid open file descriptor.

The stream referred to by fildes does not support multiplexing.

The file referred to by arg 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 arg is linked into the configuration at multiple places.

There are not modules in the stream.

Error value returned by the module being popped.

A hangup was received on fildes.

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.

arg is an invalid multiplexor ID number.

fildes is the file descriptor of a pipe.

An invalid module name was used.

arg points outside the allocated address space.

Error value returned by the module being pushed. The push has failed.

A hangup was received on fildes.

The O_NONBLOCK option 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.

Too many open files. No more file descriptors are permitted to be opened.

A hangup was received on fildes.

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 not a valid open file descriptor.

The fildes parameter does not refer to a stream.

A hangup was received on fildes.

arg has an illegal value.

The user process is not registered to receive the SIGPOLL signal.

A data structure to store the signal request could not be allocated.

arg contains an illegal value.

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_timout field is less than -1.

arg 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 arg parameter is an illegal value.

A hangup was received on fildes.

A timeout occurred before an acknowledgement message was received at the stream head.

arg is an invalid multiplexor ID number, or fildes is already linked under a multiplexing driver.