POSIX_FALLOCATE(P) POSIX Programmer's Manual POSIX_FALLOCATE(P)NAMEposix_fallocate - file space control (ADVANCED REALTIME)
SYNOPSIS
#include <fcntl.h>
int posix_fallocate(int fd, off_t offset, size_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_fallo‐
cate() 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; other‐
wise, 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 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.
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 ALSOcreat() , ftruncate() , open() , unlink() , the Base Definitions volume
of IEEE Std 1003.1-2001, <fcntl.h>
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 .
IEEE/The Open Group 2003 POSIX_FALLOCATE(P)
