The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> stropts.h - STREAMS interface (STREAMS)

#### SYNOPSIS

> `[OB XSR] #include <stropts.h>`

#### DESCRIPTION

> The <stropts.h> header shall define the bandinfo structure, which shall include at least the following members:

>     int            bi_flag  Flushing type.
>     unsigned char  bi_pri   Priority band.

> The <stropts.h> header shall define the strpeek structure, which shall include at least the following members:

>     struct strbuf  ctlbuf   The control portion of the message.
>     struct strbuf  databuf  The data portion of the message.
>     t_uscalar_t    flags    RS_HIPRI or 0.

> The <stropts.h> header shall define the strbuf structure, which shall include at least the following members:

>     char  *buf     Pointer to buffer.
>     int    len     Length of data.
>     int    maxlen  Maximum buffer length.

> The <stropts.h> header shall define the strfdinsert structure, which shall include at least the following members:

>     struct strbuf  ctlbuf   The control portion of the message.
>     struct strbuf  databuf  The data portion of the message.
>     int            fildes   File descriptor of the other STREAM.
>     t_uscalar_t    flags    RS_HIPRI or 0.
>     int            offset   Relative location of the stored value.

> The <stropts.h> header shall define the strioctl structure, which shall include at least the following members:

>     int    ic_cmd     ioctl() command.
>     char  *ic_dp      Pointer to buffer.
>     int    ic_len     Length of data.
>     int    ic_timout  Timeout for response.

> The <stropts.h> header shall define the strrecvfd structure, which shall include at least the following members:

>     int    fd   Received file descriptor.
>     gid_t  gid  GID of sender.
>     uid_t  uid  UID of sender.

> The <stropts.h> header shall define the uid_t and gid_t types through typedef, as described in <sys/types.h>.

> The <stropts.h> header shall define the t_scalar_t and t_uscalar_t types, respectively, as signed and unsigned opaque types of equal length of at least 32 bits.

> The <stropts.h> header shall define the str_list structure, which shall include at least the following members:

>     struct str_mlist  *sl_modlist  STREAMS module names.
>     int                sl_nmods    Number of STREAMS module names.

> The <stropts.h> header shall define the str_mlist structure, which shall include at least the following member:

>     char  l_name[FMNAMESZ+1]  A STREAMS module name.

> The <stropts.h> header shall define at least the following symbolic constants for use as the request argument to ioctl():

> I_ATMARK
>   Is the top message "marked''?
> I_CANPUT
>   Is a band writable?
> I_CKBAND
>   See if any messages exist in a band.
> I_FDINSERT
>   Send implementation-defined information about another STREAM.
> I_FIND
>   Look for a STREAMS module.
> I_FLUSH
>   Flush a STREAM.
> I_FLUSHBAND
>   Flush one band of a STREAM.
> I_GETBAND
>   Get the band of the top message on a STREAM.
> I_GETCLTIME
>   Get close time delay.
> I_GETSIG
>   Retrieve current notification signals.
> I_GRDOPT
>   Get the read mode.
> I_GWROPT
>   Get the write mode.
> I_LINK
>   Connect two STREAMs.
> I_LIST
>   Get all the module names on a STREAM.
> I_LOOK
>   Get the top module name.
> I_NREAD
>   Size the top message.
> I_PEEK
>   Peek at the top message on a STREAM.
> I_PLINK
>   Persistently connect two STREAMs.
> I_POP
>   Pop a STREAMS module.
> I_PUNLINK
>   Dismantle a persistent STREAMS link.
> I_PUSH
>   Push a STREAMS module.
> I_RECVFD
>   Get a file descriptor sent via I_SENDFD.
> I_SENDFD
>   Pass a file descriptor through a STREAMS pipe.
> I_SETCLTIME
>   Set close time delay.
> I_SETSIG
>   Ask for notification signals.
> I_SRDOPT
>   Set the read mode.
> I_STR
>   Send a STREAMS ioctl().
> I_SWROPT
>   Set the write mode.
> I_UNLINK
>   Disconnect two STREAMs.

> The <stropts.h> header shall define at least the following symbolic constant for use with I_LOOK:

> FMNAMESZ
>   The minimum size in bytes of the buffer referred to by the arg argument.

> The <stropts.h> header shall define at least the following symbolic constants for use with I_FLUSH:

> FLUSHR
>   Flush read queues.
> FLUSHRW
>   Flush read and write queues.
> FLUSHW
>   Flush write queues.

> The <stropts.h> header shall define at least the following symbolic constants for use with I_SETSIG:

> S_BANDURG
>   When used in conjunction with S_RDBAND, SIGURG is generated instead of SIGPOLL when a priority message reaches the front of the STREAM head read queue.
> S_ERROR
>   Notification of an error condition reaches the STREAM head.
> S_HANGUP
>   Notification of a hangup reaches the STREAM head.
> S_HIPRI
>   A high-priority message is present on a STREAM head read queue.
> S_INPUT
>   A message, other than a high-priority message, has arrived at the head of a STREAM head read queue.
> S_MSG
>   A STREAMS signal message that contains the SIGPOLL signal reaches the front of the STREAM head read queue.
> S_OUTPUT
>   The write queue for normal data (priority band 0) just below the STREAM head is no longer full. This notifies the process that there is room on the queue for sending (or writing) normal data downstream.
> S_RDBAND
>   A message with a non-zero priority band has arrived at the head of a STREAM head read queue.
> S_RDNORM
>   A normal (priority band set to 0) message has arrived at the head of a STREAM head read queue.
> S_WRBAND
>   The write queue for a non-zero priority band just below the STREAM head is no longer full.
> S_WRNORM
>   Equivalent to S_OUTPUT.

> The <stropts.h> header shall define at least the following symbolic constant for use with I_PEEK:

> RS_HIPRI
>   Only look for high-priority messages.

> The <stropts.h> header shall define at least the following symbolic constants for use with I_SRDOPT:

> RMSGD
>   Message-discard mode.
> RMSGN
>   Message-non-discard mode.
> RNORM
>   Byte-STREAM mode, the default.
> RPROTDAT
>   Deliver the control part of a message as data when a process issues a read().
> RPROTDIS
>   Discard the control part of a message, delivering any data part, when a process issues a read().
> RPROTNORM
>   Fail read() with [EBADMSG] if a message containing a control part is at the front of the STREAM head read queue.

> The <stropts.h> header shall define at least the following symbolic constant for use with I_SWOPT:

> SNDZERO
>   Send a zero-length message downstream when a write() of 0 bytes occurs.

> The <stropts.h> header shall define at least the following symbolic constants for use with I_ATMARK:

> ANYMARK
>   Check if the message is marked.
> LASTMARK
>   Check if the message is the last one marked on the queue.

> The <stropts.h> header shall define at least the following symbolic constant for use with I_UNLINK:

> MUXID_ALL
>   Unlink all STREAMs linked to the STREAM associated with fildes.

> The <stropts.h> header shall define the following symbolic constants for getmsg(), getpmsg(), putmsg(), and putpmsg():

> MORECTL
>   More control information is left in message.
> MOREDATA
>   More data is left in message.
> MSG_ANY
>   Receive any message.
> MSG_BAND
>   Receive message from specified band.
> MSG_HIPRI
>   Send/receive high-priority message.

> The <stropts.h> header may make visible all of the symbols from <unistd.h>.

> The <stropts.h> header may also define macros for message types using names that start with M_ .

> The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

>     int    fattach(int, const char *);
>     int    fdetach(const char *);
>     int    getmsg(int, struct strbuf *restrict, struct strbuf *restrict,
>                int *restrict);
>     int    getpmsg(int, struct strbuf *restrict, struct strbuf *restrict,
>                int *restrict, int *restrict);
>     int    ioctl(int, int, ...);
>     int    isastream(int);
>     int    putmsg(int, const struct strbuf *, const struct strbuf *, int);
>     int    putpmsg(int, const struct strbuf *, const struct strbuf *, int,
>                int);

The following sections are informative.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> <sys/types.h>, <unistd.h>

> XSH close, fattach, fcntl, fdetach, getmsg, ioctl, isastream, open, pipe, read, poll, putmsg, signal, write

#### CHANGE HISTORY

> First released in Issue 4, Version 2.

#### Issue 5

> The flags members of the strpeek and strfdinsert structures are changed from type long to t_uscalar_t.

#### Issue 6

> This header is marked as part of the XSI STREAMS Option Group.

> The restrict keyword is added to the prototypes for getmsg() and getpmsg().

#### Issue 7

> SD5-XBD-ERN-87 is applied, correcting an error in the strrecvfd structure.

> The <stropts.h> header is marked obsolescent.

> This reference page is clarified with respect to macros and symbolic constants.

> POSIX.1-2008, Technical Corrigendum 2, XBD/TC2-2008/0076 [801] is applied.

End of informative text.

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