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     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

     [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 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

     [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 (“POSIX.1”).


     The posix_fallocate() function appeared in FreeBSD 9.0.


     posix_fallocate() and this manual page were initially written by Matthew Fleming