PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

NAME

       posix_fallocate — file space control (ADVANCED REALTIME)

SYNOPSIS

       #include <fcntl.h>

       int posix_fallocate(int fd, off_t offset, off_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_fallocate() 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; otherwise,  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  is less than zero, or the offset argument is less than zero, or the underlying
              file system does not support this operation.

       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 posix_fallocate() function may fail if:

       EINVAL The len argument is zero.

       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 ALSO

       creat(), ftruncate(), open(), unlink()

       The Base Definitions volume of POSIX.1‐2017, <fcntl.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 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 .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                               POSIX_FALLOCATE(3POSIX)