posix_fallocate — pre-allocate storage for a range in a file
Standard C Library (libc, -lc)
posix_fallocate(int fd, off_t offset, off_t len);
Required storage for the range offset to offset + len in the file
referenced by fd is guaranteed to be allocated upon successful return.
That is, if posix_fallocate() returns successfully, subsequent writes to
the specified file data will not fail due to lack of free space on the
file system storage media. Any existing file data in the specified range
is unmodified. If offset + len is beyond the current file size, then
posix_fallocate() will adjust the file size to offset + len. Otherwise,
the file size will not be changed.
Space allocated by posix_fallocate() will be freed by a successful call
to creat(2) or open(2) that truncates the size of the file. Space
allocated via posix_fallocate() may be freed by a successful call to
ftruncate(2) that reduces the file size to a size smaller than offset +
If successful, posix_fallocate() returns zero. It returns -1 on failure,
and sets errno to indicate the error.
Possible failure conditions:
[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
[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.
creat(2), ftruncate(2), open(2), unlink(2)
The posix_fallocate() system call conforms to IEEE Std 1003.1-2004
The posix_fallocate() function appeared in FreeBSD 9.0.
posix_fallocate() and this manual page were initially written by Matthew