.\" Copyright (c) 2020-2022 by Alejandro Colomar <alx@kernel.org>
.\" and Copyright (c) 2020 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\"
.TH off_t 3type 2022-10-30 "Linux man-pages 6.03"
.SH NAME
off_t, off64_t, loff_t \- file sizes
.SH LIBRARY
Standard C library
.RI ( libc )
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.PP
.BR typedef " /* ... */  " off_t;
.PP
.B #define _LARGEFILE64_SOURCE
.B #include <sys/types.h>
.PP
.BR typedef " /* ... */  " off64_t;
.PP
.B #define _GNU_SOURCE
.B #include <sys/types.h>
.PP
.BR typedef " /* ... */  " loff_t;
.fi
.SH DESCRIPTION
.I off_t
is used for describing file sizes.
It is a signed integer type.
.PP
.I off64_t
is a 64-bit version of the type,
used in glibc.
.PP
.I loff_t
is a 64-bit version of the type,
introduced by the Linux kernel.
.SH VERSIONS
.I <aio.h>
and
.I <stdio.h>
define
.I off_t
since POSIX.1-2008.
.SH STANDARDS
.PD 0
.IR off_t :
POSIX.1-2001 and later.
.PP
.IR off64_t :
Present in glibc and some BSDs.
.PP
.IR loff_t :
Linux-specific.
.PD
.SH NOTES
On some architectures,
the width of
.I off_t
can be controlled with the feature test macro
.BR _FILE_OFFSET_BITS .
.PP
The following headers also provide
.IR off_t :
.IR <aio.h> ,
.IR <fcntl.h> ,
.IR <stdio.h> ,
.IR <sys/mman.h> ,
.IR <sys/stat.h> ,
and
.IR <unistd.h> .
.SH SEE ALSO
.BR copy_file_range (2),
.BR llseek (2),
.BR lseek (2),
.BR mmap (2),
.BR posix_fadvise (2),
.BR pread (2),
.BR readahead (2),
.BR sync_file_range (2),
.BR truncate (2),
.BR fseeko (3),
.BR lockf (3),
.BR lseek64 (3),
.BR posix_fallocate (3),
.BR feature_test_macros (7)