.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "PUTMSG" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" putmsg 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
putmsg, putpmsg \- send a message on a STREAM (\fBSTREAMS\fP)
.SH SYNOPSIS
.LP
\fB#include <stropts.h>
.br
.sp
int putmsg(int\fP \fIfildes\fP\fB, const struct strbuf *\fP\fIctlptr\fP\fB,
.br
\ \ \ \ \ \  const struct strbuf *\fP\fIdataptr\fP\fB, int\fP \fIflags\fP\fB);
.br
int putpmsg(int\fP \fIfildes\fP\fB, const struct strbuf *\fP\fIctlptr\fP\fB,
.br
\ \ \ \ \ \  const struct strbuf *\fP\fIdataptr\fP\fB, int\fP \fIband\fP\fB,
int\fP
\fIflags\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIputmsg\fP() 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.
.LP
The \fIputpmsg\fP() function is equivalent to \fIputmsg\fP(), except
that the process can send messages in different priority
bands. Except where noted, all requirements on \fIputmsg\fP() also
pertain to \fIputpmsg\fP().
.LP
The \fIfildes\fP argument specifies a file descriptor referencing
an open STREAM. The \fIctlptr\fP and \fIdataptr\fP
arguments each point to a \fBstrbuf\fP structure.
.LP
The \fIctlptr\fP argument points to the structure describing the control
part, if any, to be included in the message. The
\fIbuf\fP member in the \fBstrbuf\fP structure points to the buffer
where the control information resides, and the \fIlen\fP
member indicates the number of bytes to be sent. The \fImaxlen\fP
member is not used by \fIputmsg\fP(). In a similar manner, the
argument \fIdataptr\fP specifies the data, if any, to be included
in the message. The \fIflags\fP argument indicates what type of
message should be sent and is described further below.
.LP
To send the data part of a message, the application shall ensure that
\fIdataptr\fP is not a null pointer and the \fIlen\fP
member of \fIdataptr\fP is 0 or greater. To send the control part
of a message, the application shall ensure that the
corresponding values are set for \fIctlptr\fP. No data (control) part
shall be sent if either \fIdataptr\fP( \fIctlptr\fP) is a
null pointer or the \fIlen\fP member of \fIdataptr\fP( \fIctlptr\fP)
is set to -1.
.LP
For \fIputmsg\fP(), if a control part is specified and \fIflags\fP
is set to RS_HIPRI, a high priority message shall be sent.
If no control part is specified, and \fIflags\fP is set to RS_HIPRI,
\fIputmsg\fP() shall fail and set \fIerrno\fP to [EINVAL].
If \fIflags\fP is set to 0, a normal message (priority band equal
to 0) shall be sent. If a control part and data part are not
specified and \fIflags\fP is set to 0, no message shall be sent and
0 shall be returned.
.LP
For \fIputpmsg\fP(), the flags are different. The \fIflags\fP argument
is a bitmask with the following mutually-exclusive
flags defined: MSG_HIPRI and MSG_BAND. If \fIflags\fP is set to 0,
\fIputpmsg\fP() shall fail and set \fIerrno\fP to [EINVAL].
If a control part is specified and \fIflags\fP is set to MSG_HIPRI
and \fIband\fP is set to 0, a high-priority message shall be
sent. If \fIflags\fP is set to MSG_HIPRI and either no control part
is specified or \fIband\fP is set to a non-zero value,
\fIputpmsg\fP() shall fail and set \fIerrno\fP to [EINVAL]. If \fIflags\fP
is set to MSG_BAND, then a message shall be sent in
the priority band specified by \fIband\fP. If a control part and data
part are not specified and \fIflags\fP is set to MSG_BAND,
no message shall be sent and 0 shall be returned.
.LP
The \fIputmsg\fP() function shall block if the STREAM write queue
is full due to internal flow control conditions, with the
following exceptions:
.IP " *" 3
For high-priority messages, \fIputmsg\fP() shall not block on this
condition and continues processing the message.
.LP
.IP " *" 3
For other messages, \fIputmsg\fP() shall not block but shall fail
when the write queue is full and O_NONBLOCK is set.
.LP
.LP
The \fIputmsg\fP() 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.
.SH RETURN VALUE
.LP
Upon successful completion, \fIputmsg\fP() and \fIputpmsg\fP() shall
return 0; otherwise, they shall return -1 and set
\fIerrno\fP to indicate the error.
.SH ERRORS
.LP
The \fIputmsg\fP() and \fIputpmsg\fP() functions shall fail if:
.TP 7
.B 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.
.TP 7
.B EBADF
\fIfildes\fP is not a valid file descriptor open for writing.
.TP 7
.B EINTR
A signal was caught during \fIputmsg\fP().
.TP 7
.B EINVAL
An undefined value is specified in \fIflags\fP, or \fIflags\fP is
set to RS_HIPRI or MSG_HIPRI and no control part is
supplied, or the STREAM or multiplexer referenced by \fIfildes\fP
is linked (directly or indirectly) downstream from a
multiplexer, or \fIflags\fP is set to MSG_HIPRI and \fIband\fP is
non-zero (for \fIputpmsg\fP() only).
.TP 7
.B ENOSR
Buffers could not be allocated for the message that was to be created
due to insufficient STREAMS memory resources.
.TP 7
.B ENOSTR
A STREAM is not associated with \fIfildes\fP.
.TP 7
.B ENXIO
A hangup condition was generated downstream for the specified STREAM.
.TP 7
.B EPIPE \fRor\fP EIO
The \fIfildes\fP 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.
.TP 7
.B 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 configured
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.
.sp
.LP
In addition, \fIputmsg\fP() and \fIputpmsg\fP() shall fail if the
STREAM head had processed an asynchronous error before the
call. In this case, the value of \fIerrno\fP does not reflect the
result of \fIputmsg\fP() or \fIputpmsg\fP(), but reflects the
prior error.
.br
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Sending a High-Priority Message
.LP
The value of \fIfd\fP is assumed to refer to an open STREAMS file.
This call to \fIputmsg\fP() does the following:
.IP " 1." 4
Creates a high-priority message with a control part and a data part,
using the buffers pointed to by \fIctrlbuf\fP and
\fIdatabuf\fP, respectively.
.LP
.IP " 2." 4
Sends the message to the STREAMS file identified by \fIfd\fP.
.LP
.sp
.RS
.nf

\fB#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;
.sp

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

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

ret = putmsg(fd, &ctrl, &data, MSG_HIPRI);
\fP
.fi
.RE
.SS Using putpmsg()
.LP
This example has the same effect as the previous example. In this
example, however, the \fIputpmsg\fP() function creates and
sends the message to the STREAMS file.
.sp
.RS
.nf

\fB#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;
.sp

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

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

ret = putpmsg(fd, &ctrl, &data, 0, MSG_HIPRI);
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fISTREAMS\fP, \fIgetmsg\fP(), \fIpoll\fP(), \fIread\fP(), \fIwrite\fP(),
the Base
Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<stropts.h>\fP
.SH 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 original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .