POSIX_FALLOCATE(P) POSIX Programmer's Manual POSIX_FALLOCATE(P)
posix_fallocate - file space control (ADVANCED REALTIME)
int posix_fallocate(int fd, off_t offset, size_t len);
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 stor-
age 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
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.
Upon successful completion, posix_fallocate() shall return zero; otherwise, an error num-
ber shall be returned to indicate the error.
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 was zero or the offset argument was less than zero.
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 following sections are informative.
The posix_fallocate() function is part of the Advisory Information option and need not be
provided on all implementations.
creat() , ftruncate() , open() , unlink() , the Base Definitions volume of
IEEE Std 1003.1-2001, <fcntl.h>
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 POSIX_FALLOCATE(P)