'\" te
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.TH POSIX_FADVISE 3C "Jul 14, 2008"
.SH NAME
posix_fadvise \- file advisory information
.SH SYNOPSIS
.LP
.nf
#include <fcntl.h>

\fBint\fR \fBposix_fadvise\fR(\fBint\fR \fIfd\fR, \fBoff_t\fR \fIoffset\fR, \fBoff_t\fR \fIlen\fR, \fBint\fR \fIadvice\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBposix_fadvise()\fR function advises the system on the expected behavior
of the application with respect to the data in the file associated with the
open file descriptor, \fIfd\fR, starting at \fIoffset\fR and continuing for
\fIlen\fR bytes. The specified range need not currently exist in the file. If
\fIlen\fR is zero, all data following offset is specified. The system may use
this information to optimize handling of the specified data. The
\fBposix_fadvise()\fR function has no effect on the semantics of other
operations on the specified data, although it may affect the performance of
other operations.
.sp
.LP
The advice to be applied to the data is specified by the \fIadvice\fR parameter
and may be one of the following values:
.sp
.ne 2
.na
\fB\fBPOSIX_FADV_NORMAL\fR\fR
.ad
.RS 25n
Specifies that the application has no advice to give on its behavior with
respect to the specified data. It is the default characteristic if no advice is
given for an open file.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_FADV_SEQUENTIAL\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified data
sequentially from lower offsets to higher offsets.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_FADV_RANDOM\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified data in a random
order.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_FADV_WILLNEED\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified data in the near
future.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_FADV_DONTNEED\fR\fR
.ad
.RS 25n
Specifies that the application expects that it will not access the specified
data in the near future.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_FADV_NOREUSE\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified data once and
then not reuse it thereafter.
.RE

.sp
.LP
These values are defined in \fB<fcntl.h>\fR
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBposix_fadvise()\fR returns zero. Otherwise, an
error number is returned to indicate the error.
.SH ERRORS
.sp
.LP
The \fBposix_fadvise()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIfd\fR argument is not a valid file descriptor.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIadvice\fR is invalid, or the value of \fIlen\fR is less than
zero.
.RE

.sp
.ne 2
.na
\fB\fBESPIPE\fR\fR
.ad
.RS 10n
The \fIfd\fR argument is associated with a pipe or FIFO.
.RE

.SH USAGE
.sp
.LP
The \fBposix_fadvise()\fR function has a transitional interface for 64-bit file
offsets. See \fBlf64\fR(5).
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBposix_madvise\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)