POSIX_FALLOCATE
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
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.
NAME
posix_fallocate
--- file space control
(
ADVANCED REALTIME)
SYNOPSIS
#include <fcntl.h>
int posix_fallocate(int fd, off_t offset, off_t len);
DESCRIPTION
The
posix_fallocate()
function shall ensure that any required storage for regular file data
starting at
offset
and continuing for
len
bytes is allocated on the file system storage media. If
posix_fallocate()
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.
If the
offset+len
is beyond the current file size, then
posix_fallocate()
shall adjust the file size to
offset+len.
Otherwise, the file size shall not be changed.
It is implementation-defined whether a previous
posix_fadvise()
call influences allocation strategy.
Space allocated via
posix_fallocate()
shall be freed by a successful call to
creat()
or
open()
that truncates the size of the file. Space allocated via
posix_fallocate()
may be freed by a successful call to
ftruncate()
that reduces the file size to a size smaller than
offset+len.
RETURN VALUE
Upon successful completion,
posix_fallocate()
shall return zero; otherwise, an error number shall be returned to
indicate the error.
ERRORS
The
posix_fallocate()
function shall fail if:
- EBADF
-
The
fd
argument is not a valid file descriptor.
- EBADF
-
The
fd
argument references a file that was opened without write permission.
- EFBIG
-
The value of
offset+len
is greater than the maximum file size.
- EINTR
-
A signal was caught during execution.
- EINVAL
-
The
len
argument is less than zero, or the
offset
argument is less than zero, or the underlying file system does not
support this operation.
- EIO
-
An I/O error occurred while reading from or writing to a file system.
- ENODEV
-
The
fd
argument does not refer to a regular file.
- ENOSPC
-
There is insufficient free space remaining on the file system storage
media.
- ESPIPE
-
The
fd
argument is associated with a pipe or FIFO.
The
posix_fallocate()
function may fail if:
- EINVAL
-
The
len
argument is zero.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The
posix_fallocate()
function is part of the Advisory Information option and need not be
provided on all implementations.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
creat(),
ftruncate(),
open(),
unlink()
The Base Definitions volume of POSIX.1-2017,
<fcntl.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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 .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .