'\" et
.TH POSIX_FALLOCATE "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH 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.
.\"
.SH NAME
posix_fallocate
\(em file space control
(\fBADVANCED REALTIME\fP)
.SH SYNOPSIS
.LP
.nf
#include <fcntl.h>
.P
int posix_fallocate(int \fIfd\fP, off_t \fIoffset\fP, off_t \fIlen\fP);
.fi
.SH DESCRIPTION
The
\fIposix_fallocate\fR()
function shall ensure that any required storage for regular file data
starting at
.IR offset
and continuing for
.IR len
bytes is allocated on the file system storage media. If
\fIposix_fallocate\fR()
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.
.P
If the
.IR offset +\c
.IR len
is beyond the current file size, then
\fIposix_fallocate\fR()
shall adjust the file size to
.IR offset +\c
.IR len .
Otherwise, the file size shall not be changed.
.P
It is implementation-defined whether a previous
\fIposix_fadvise\fR()
call influences allocation strategy.
.P
Space allocated via
\fIposix_fallocate\fR()
shall be freed by a successful call to
\fIcreat\fR()
or
\fIopen\fR()
that truncates the size of the file. Space allocated via
\fIposix_fallocate\fR()
may be freed by a successful call to
\fIftruncate\fR()
that reduces the file size to a size smaller than
.IR offset +\c
.IR len .
.SH "RETURN VALUE"
Upon successful completion,
\fIposix_fallocate\fR()
shall return zero; otherwise, an error number shall be returned to
indicate the error.
.SH ERRORS
The
\fIposix_fallocate\fR()
function shall fail if:
.TP
.BR EBADF
The
.IR fd
argument is not a valid file descriptor.
.TP
.BR EBADF
The
.IR fd
argument references a file that was opened without write permission.
.TP
.BR EFBIG
The value of
.IR offset +\c
.IR len
is greater than the maximum file size.
.TP
.BR EINTR
A signal was caught during execution.
.TP
.BR EINVAL
The
.IR len
argument is less than zero, or the
.IR offset
argument is less than zero, or the underlying file system does not
support this operation.
.TP
.BR EIO
An I/O error occurred while reading from or writing to a file system.
.TP
.BR ENODEV
The
.IR fd
argument does not refer to a regular file.
.TP
.BR ENOSPC
There is insufficient free space remaining on the file system storage
media.
.TP
.BR ESPIPE
The
.IR fd
argument is associated with a pipe or FIFO.
.P
The
\fIposix_fallocate\fR()
function may fail if:
.TP
.BR EINVAL
The
.IR len
argument is zero.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
The
\fIposix_fallocate\fR()
function is part of the Advisory Information option and need not be
provided on all implementations.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIcreat\fR\^(\|)",
.IR "\fIftruncate\fR\^(\|)",
.IR "\fIopen\fR\^(\|)",
.IR "\fIunlink\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<fcntl.h>\fP"
.\"
.SH 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 .
.PP
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 .