POSIX_FALLOCATE(3P)                                 POSIX Programmer's Manual                                POSIX_FALLOCATE(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult 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, size_t len);


DESCRIPTION
       The  posix_fallocate()  function shall ensure that any required storage for regular file data starting at offset and con-
       tinuing for len bytes is allocated on the file system storage media. If posix_fallocate()  returns  successfully,  subse-
       quent 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 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.


       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 implementa-
       tions.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       creat(), ftruncate(), open(), unlink(), the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                           POSIX_FALLOCATE(3P)