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 .