POSIX_FALLOCATE(2)           BSD System Calls Manual          POSIX_FALLOCATE(2)

     posix_fallocate — pre-allocate storage for a range in a file

     Standard C Library (libc, -lc)

     #include <fcntl.h>

     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 + len.

     If successful, posix_fallocate() returns zero.  It returns an error on
     failure, without setting errno.

     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
                        file size.

     [EINTR]            A signal was caught during execution.

     [EINVAL]           The len argument was less than or equal to zero, the
                        offset argument was less than zero, or the operation is
                        not supported by the file system.

     [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.

     [ENOTCAPABLE]      The file descriptor fd has insufficient rights.

     [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
     Fleming <mdf@FreeBSD.org>.

BSD                             November 4, 2017                             BSD