strqset.9

7号信令功能代码,为开源代码

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.TH STRQSET 9 "2004/01/12 23:33:12" "LiS-2_16_18-8" "Linux STREAMS DDI/DKI"
.SH NAME
.B strqset, lis_strqset
\- sets attributes of a \fISTREAMS\fR message queue
.SH SYNOPSIS
.PP
.B #include <sys/stream.h>
.HP 8
.BI "int " retval " = strqset(queue_t *" q ", qfields_t " what ", unsigned char " band ", long " val );
.SH DESCRIPTION
.PP
.BR strqset ()
sets the attribute requested by
.I what
for the queue pointed to by
.I q
and band specified by
.I band
to the value specified by
.IR val .
The value set can be either a scalar or a pointer.
.PP
When
.I band
is zero,
.BR strqset ()
will set the attribute specified by
.I what
for the queue.
When
.I band
is non-zero (between 1 and 255),
.BR strqset ()
will set the attribute specified by
.I what
for the queue band specified by
.IR band .
.PP
The argument
.I what
specifies the queue (or queue band if
.I band
is non-zero) attribute to be set.
.I what
can be one of the following values.
.TP 12
.B QHIWAT
Sets the high water mark associated with the
.I q
or queue
.IR band .
.TP 12
.B QLOWAT
Sets the low water mark associated with the
.I q
or queue
.IR band .
.TP 12
.B QMAXPSZ
Sets the maximum packet size associated with the
.IR q .
For this operation
.I band
must be zero (0).
.TP 12
.B QMINPSZ
Sets the minimum packet size associated with the
.IR q .
For this operation
.I band
must be zero (0).
.PP
.BR strqset ()
provides a mechanims whereby a
.IR STREAMS (4)
module or driver can change information
about a queue or queue band without directly accessing the
.B queue
or
.B qband
structures.
Values set by
.BR strqset ()
are equivalent to directly accessing the
.B queue
or
.B qband
structure members described below.
.PP
The
.B queue
structure contains at least the following members:
.HP
.BI "ulong " q_hiwat
\- the high water mark for the queue.
.HP
.BI "ulong " q_lowat
\- the low water mark for the queue.
.HP
.BI "long " q_maxpsz
\- the maximum message size accepted by the queue.
.HP
.BI "long " q_minpsz
\- the minimum message size accepted by the queue.
.PP
The
.B qband
structure contains at least the following members:
.HP
.BI "ulong " qb_hiwat
\- the high water mark for the band.
.HP
.BI "ulong " qb_lowat
\- the low water mark for the band.
.SH "RETURN VALUES"
.PP
Upon success,
.BR strqset ()
returns zero (0) and sets the appropriate attribute to the appropriate value.
.PP
Upon failure,
.BR strqset ()
returns a non-zero error number.
The requested attribute is remains unchanged.
.SH ERRORS
.PP
When
.BR strqset ()
fails,
it returns one of the following errors:
.TP 12
.RB [ EINVAL ]
The queue pointer
.I q
is
.BR NULL;
.I q
does not point to a valid queue structure;
the queue band specified in
.I band
does not exist;
.BR QMAXPSZ " or " QMINPSZ
was specified for
.I what
and
.I band
was non-zero;
.I what
is not a valid queue or queue band attribute.
.TP 12
.RB [ EPERM ]
.I what
specified an attribute that is appropriate for
.BR strqget (9),
but which is invalid for
.BR strqset ():
.BR QCOUNT ", " QFIRST ", " QLAST " or " QFLAG .
.SH CAVEATS
.PP
None.
.SH "SEE ALSO"
.PP
.BR strqget (9).
.SH VERSIONS
.PP
This manpage was written for
.B LiS\c
.
.[
LiS
.]
.PP
.BR strqset ()
first appeared in SVR 3.
.[
svr3
.]
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