.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "POSIX_FALLOCATE" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" posix_fallocate 
.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
posix_fallocate \- file space control (\fBADVANCED REALTIME\fP)
.SH SYNOPSIS
.LP
\fB#include <fcntl.h>
.br
.sp
int posix_fallocate(int\fP \fIfd\fP\fB, off_t\fP \fIoffset\fP\fB,
size_t\fP \fIlen\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIposix_fallocate\fP() function shall ensure that any required
storage for regular file data starting at \fIoffset\fP and
continuing for \fIlen\fP bytes is allocated on the file system storage
media. If \fIposix_fallocate\fP() returns successfully,
subsequent writes to the specified file data shall not fail due to
the lack of free space on the file system storage media.
.LP
If the \fIoffset\fP+ \fIlen\fP is beyond the current file size, then
\fIposix_fallocate\fP() shall adjust the file size to
\fIoffset\fP+ \fIlen\fP. Otherwise, the file size shall not be changed.
.LP
It is implementation-defined whether a previous \fIposix_fadvise\fP()
call
influences allocation strategy.
.LP
Space allocated via \fIposix_fallocate\fP() shall be freed by a successful
call to \fIcreat\fP() or \fIopen\fP() that truncates the size of the
file. Space allocated via \fIposix_fallocate\fP() may be freed by
a successful call to \fIftruncate\fP() that reduces the file size
to a size smaller than \fIoffset\fP+
\fIlen\fP.
.SH RETURN VALUE
.LP
Upon successful completion, \fIposix_fallocate\fP() shall return zero;
otherwise, an error number shall be returned to indicate
the error.
.SH ERRORS
.LP
The \fIposix_fallocate\fP() function shall fail if:
.TP 7
.B EBADF
The \fIfd\fP argument is not a valid file descriptor.
.TP 7
.B EBADF
The \fIfd\fP argument references a file that was opened without write
permission.
.TP 7
.B EFBIG
The value of \fIoffset\fP+ \fIlen\fP is greater than the maximum file
size.
.TP 7
.B EINTR
A signal was caught during execution.
.TP 7
.B EINVAL
The \fIlen\fP argument was zero or the \fIoffset\fP argument was less
than zero.
.TP 7
.B EIO
An I/O error occurred while reading from or writing to a file system.
.TP 7
.B ENODEV
The \fIfd\fP argument does not refer to a regular file.
.TP 7
.B ENOSPC
There is insufficient free space remaining on the file system storage
media.
.TP 7
.B ESPIPE
The \fIfd\fP argument is associated with a pipe or FIFO.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
The \fIposix_fallocate\fP() function is part of the Advisory Information
option and need not be provided on all
implementations.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIcreat\fP(), \fIftruncate\fP(), \fIopen\fP(), \fIunlink\fP(),
the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, \fI<fcntl.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 .