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.
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
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
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
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
EIO An I/O error occurred while reading from or writing to a file
ENODEV The fd argument does not refer to a regular file.
ENOSPC There is insufficient free space remaining on the file system
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.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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
IEEE/The Open Group 2013 POSIX_FALLOCATE(3P)