putmsg.2 (2010 09)

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putmsg(2) putmsg(2)

NAME

putmsg, putpmsg - send a message on a stream

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 creates a message from a process buffer(s) and sends the message to a

STREAMS ﬁle. The message may contain either a data part, a control part, or both. The data and con-

trol parts are distinguished by placement in separate buffers, as described below. The semantics of each

part is deﬁned by the STREAMS module that receives the message.

The

putpmsg() function does the same things as putmsg(), but the process can send messages 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 argu-

ments each point to a

strbuf structure.

The ctlptr argument points to the structure describing the control part, if any, to be included in the mes-

sage. 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 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, dataptr must not be a null pointer and the len member of dataptr

must be 0 or greater. To send the control part of a message, the corresponding values must be set for

ctlptr . No data (control) part will 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 is

sent. If no control part is speciﬁed, and ﬂags is set to RS_HIPRI, putmsg() fails and sets errno to

[EINVAL]. If ﬂags is set to 0, a normal message (priority band equal to 0) is sent. If a control part and

data part are not speciﬁed and ﬂags is set to 0, no message is sent and 0 is returned.

The stream head guarantees that the control part of a message generated by

putmsg() is at least 64

bytes in length.

For

putpmsg(), the ﬂags are different. The ﬂags argument is a bitmask with the following mutually-

exclusive ﬂags deﬁned: MSG_HIPRI and MSG_BAND.Ifﬂags is set to 0, putpmsg() fails and sets

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 is 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() fails and set errno to [EINVAL]. If ﬂags is set to MSG_BAND,

then a message is 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 is sent and 0 is returned.

The

putmsg() function blocks if the stream write queue is full due to internal ﬂow control conditions.

For high-priority messages, putmsg() does not block on this condition. For other messages, putmsg()

does not block when the write queue is full and O_NONBLOCK is set.

The

putmsg() function also blocks, unless prevented by lack of internal resources, while for the availa-

bility of message blocks in the stream, regardless of priority of whether O_NONBLOCK has been speciﬁed.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

PAGE 1
putmsg(2) putmsg(2) NAME putmsg, putpmsg - send a message on a stream SYNOPSIS #include 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 creates a message from a process buffer(s) and sends the message to a STREAMS file. The message may contain either a data part, a control part, or both.
PAGE 2
putmsg(2) putmsg(2) No partial message is sent. RETURN VALUE putmsg() and putpmsg() return the following values: 0 Successful completion. -1 Error. errno is set to indicate the error. ERRORS On failure, errno may be set to one of the following values: A [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.