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
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