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



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

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(3)
