--file-allocation=METHOD Specify file allocation method.
'none' doesn't pre-allocate file space. 'prealloc'
pre-allocates file space before download begins.
This may take some time depending on the size of
the file.
If you are using newer file systems such as ext4
(with extents support), btrfs, xfs or NTFS
(MinGW build only), 'falloc' is your best
choice. It allocates large(few GiB) files
almost instantly. Don't use 'falloc' with legacy
file systems such as ext3 and FAT32 because it
takes almost same time as 'prealloc' and it
blocks aria2 entirely until allocation finishes.
'falloc' may not be available if your system
doesn't have posix_fallocate() function.
'trunc' uses ftruncate() system call or
platform-specific counterpart to truncate a file
to a specified length.
