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PUTMSG(P)			    POSIX Programmer's Manual				PUTMSG(P)

NAME
       putmsg, putpmsg - send a message on a STREAM (STREAMS)

SYNOPSIS
       #include <stropts.h>

       int putmsg(int fildes, const struct strbuf *ctlptr,
	      const struct strbuf *dataptr, int flags);
       int putpmsg(int fildes, const struct strbuf *ctlptr,
	      const struct strbuf *dataptr, int band, int flags);

DESCRIPTION
       The putmsg() function shall create a message from a process buffer(s) and send the message
       to a STREAMS file. The message may contain either a data part, a control  part,	or  both.
       The  data  and  control	parts  are  distinguished  by  placement  in separate buffers, as
       described below. The semantics of each  part  are  defined  by  the  STREAMS  module  that
       receives the message.

       The  putpmsg()  function  is equivalent to putmsg(), except that the process can send mes-
       sages in different priority bands. Except where noted, all requirements on  putmsg()  also
       pertain to putpmsg().

       The fildes argument specifies a file descriptor referencing an open STREAM. The ctlptr and
       dataptr arguments each point to a strbuf structure.

       The ctlptr argument points to the structure describing the control part,  if  any,  to  be
       included in the message. The buf member in the strbuf structure points to the buffer where
       the control information resides, and the len member indicates the number of  bytes  to  be
       sent. The maxlen member is not used by putmsg(). In a similar manner, the argument dataptr
       specifies the data, if any, to be included in the message. The  flags  argument	indicates
       what type of message should be sent and is described further below.

       To  send  the  data  part of a message, the application shall ensure that dataptr is not a
       null pointer and the len member of dataptr is 0 or greater. To send the control part of	a
       message, the application shall ensure that the corresponding values are set for ctlptr. No
       data (control) part shall be sent if either dataptr( ctlptr) is a null pointer or the  len
       member of dataptr( ctlptr) is set to -1.

       For putmsg(), if a control part is specified and flags is set to RS_HIPRI, a high priority
       message shall be sent.  If no control part is specified, and flags  is  set  to	RS_HIPRI,
       putmsg()  shall	fail  and  set errno to [EINVAL].  If flags is set to 0, a normal message
       (priority band equal to 0) shall be sent. If a control part and data part are  not  speci-
       fied and flags is set to 0, no message shall be sent and 0 shall be returned.

       For putpmsg(), the flags are different. The flags argument is a bitmask with the following
       mutually-exclusive flags defined: MSG_HIPRI and MSG_BAND. If flags is set to 0,	putpmsg()
       shall  fail and set errno to [EINVAL].  If a control part is specified and flags is set to
       MSG_HIPRI and band is set to 0, a high-priority message shall be sent. If flags is set  to
       MSG_HIPRI  and  either  no  control  part is specified or band is set to a non-zero value,
       putpmsg() shall fail and set errno to [EINVAL]. If flags is set to MSG_BAND, then  a  mes-
       sage shall be sent in the priority band specified by band. If a control part and data part
       are not specified and flags is set to MSG_BAND, no message shall be sent and  0	shall  be
       returned.

       The  putmsg()  function shall block if the STREAM write queue is full due to internal flow
       control conditions, with the following exceptions:

	* For high-priority messages, putmsg() shall not block on this	condition  and	continues
	  processing the message.

	* For  other  messages,  putmsg()  shall not block but shall fail when the write queue is
	  full and O_NONBLOCK is set.

       The putmsg() function shall also block, unless prevented by lack  of  internal  resources,
       while waiting for the availability of message blocks in the STREAM, regardless of priority
       or whether O_NONBLOCK has been specified. No partial message shall be sent.

RETURN VALUE
       Upon successful completion, putmsg() and putpmsg() shall return 0; otherwise,  they  shall
       return -1 and set errno to indicate the error.

ERRORS
       The putmsg() and putpmsg() functions shall fail if:

       EAGAIN A  non-priority  message	was specified, the O_NONBLOCK flag is set, and the STREAM
	      write queue is full due to internal flow control conditions; or buffers  could  not
	      be allocated for the message that was to be created.

       EBADF  fildes is not a valid file descriptor open for writing.

       EINTR  A signal was caught during putmsg().

       EINVAL An  undefined value is specified in flags, or flags is set to RS_HIPRI or MSG_HIPRI
	      and no control part is supplied, or the STREAM or multiplexer referenced by  fildes
	      is  linked  (directly or indirectly) downstream from a multiplexer, or flags is set
	      to MSG_HIPRI and band is non-zero (for putpmsg() only).

       ENOSR  Buffers could not be allocated for the message that was to be created due to insuf-
	      ficient STREAMS memory resources.

       ENOSTR A STREAM is not associated with fildes.

       ENXIO  A hangup condition was generated downstream for the specified STREAM.

       EPIPE or EIO
	      The fildes argument refers to a STREAMS-based pipe and the other end of the pipe is
	      closed. A SIGPIPE signal is generated for the calling thread.

       ERANGE The size of the data part of the message does not fall within the  range	specified
	      by the maximum and minimum packet sizes of the topmost STREAM module. This value is
	      also returned if the control part of the message is larger than the maximum config-
	      ured  size  of  the  control part of a message, or if the data part of a message is
	      larger than the maximum configured size of the data part of a message.

       In addition, putmsg() and putpmsg() shall fail if the STREAM head had processed	an  asyn-
       chronous  error	before	the  call.  In this case, the value of errno does not reflect the
       result of putmsg() or putpmsg(), but reflects the prior error.

       The following sections are informative.

EXAMPLES
   Sending a High-Priority Message
       The value of fd is assumed to refer to an open STREAMS file.  This call to  putmsg()  does
       the following:

	1. Creates a high-priority message with a control part and a data part, using the buffers
	   pointed to by ctrlbuf and databuf, respectively.

	2. Sends the message to the STREAMS file identified by fd.

	      #include <stropts.h>
	      #include <string.h>
	      ...
	      int fd;
	      char *ctrlbuf = "This is the control part";
	      char *databuf = "This is the data part";
	      struct strbuf ctrl;
	      struct strbuf data;
	      int ret;

	      ctrl.buf = ctrlbuf;
	      ctrl.len = strlen(ctrlbuf);

	      data.buf = databuf;
	      data.len = strlen(databuf);

	      ret = putmsg(fd, &ctrl, &data, MSG_HIPRI);

   Using putpmsg()
       This example has the same effect as the previous example. In this  example,  however,  the
       putpmsg() function creates and sends the message to the STREAMS file.

	      #include <stropts.h>
	      #include <string.h>
	      ...
	      int fd;
	      char *ctrlbuf = "This is the control part";
	      char *databuf = "This is the data part";
	      struct strbuf ctrl;
	      struct strbuf data;
	      int ret;

	      ctrl.buf = ctrlbuf;
	      ctrl.len = strlen(ctrlbuf);

	      data.buf = databuf;
	      data.len = strlen(databuf);

	      ret = putpmsg(fd, &ctrl, &data, 0, MSG_HIPRI);

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       STREAMS	,  getmsg()  ,	poll()	,  read()  ,  write()  ,  the  Base Definitions volume of
       IEEE Std 1003.1-2001, <stropts.h>

COPYRIGHT
       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					PUTMSG(P)
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