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.TH POSIX_FALLOCATE 3  2014-06-03 "GNU" "Linux Programmer's Manual"
.SH NAME
posix_fallocate \- allocate file space
.SH SYNOPSIS
.nf
.B #include <fcntl.h>
.sp
.BI "int posix_fallocate(int " fd ", off_t " offset ", off_t " len );
.fi
.sp
.ad l
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR posix_fallocate ():
.RS 4
_XOPEN_SOURCE\ >=\ 600 || _POSIX_C_SOURCE\ >=\ 200112L
.RE
.ad
.SH DESCRIPTION
The function
.BR posix_fallocate ()
ensures that disk space is allocated for the file referred to by the
descriptor
.I fd
for the bytes in the range starting at
.I offset
and continuing for
.I len
bytes.
After a successful call to
.BR posix_fallocate (),
subsequent writes to bytes in the specified range are
guaranteed not to fail because of lack of disk space.

If the size of the file is less than
.IR offset + len ,
then the file is increased to this size;
otherwise the file size is left unchanged.
.SH RETURN VALUE
.BR posix_fallocate ()
returns zero on success, or an error number on failure.
Note that
.I errno
is not set.
.SH ERRORS
.TP
.B EBADF
.I fd
is not a valid file descriptor, or is not opened for writing.
.TP
.B EFBIG
.I offset+len
exceeds the maximum file size.
.TP
.B EINVAL
.I offset
was less than 0, or
.I len
was less than or equal to 0.
.TP
.B ENODEV
.I fd
does not refer to a regular file.
.TP
.B ENOSPC
There is not enough space left on the device containing the file
referred to by
.IR fd .
.TP
.B ESPIPE
.I fd
refers to a pipe.
.SH VERSIONS
.BR posix_fallocate ()
is available since glibc 2.1.94.
.SH ATTRIBUTES
.SS Multithreading (see pthreads(7))
The
.BR posix_fallocate ()
function is thread-safe.
.SH CONFORMING TO
POSIX.1-2001.

POSIX.1-2008 says that an implementation
.I shall
give the
.B EINVAL
error if
.I len
was 0, or
.I offset
was less than 0.
POSIX.1-2001 says that an implementation
.I shall
give the
.B EINVAL
error if
.I len
is less than 0, or
.I offset
was less than 0, and
.I may
give the error if
.I len
equals zero.
.SH SEE ALSO
.BR fallocate (1),
.BR fallocate (2),
.BR lseek (2),
.BR posix_fadvise (2)
.SH COLOPHON
This page is part of release 3.74 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%http://www.kernel.org/doc/man\-pages/.