off_t(3type) — Linux manual page

off_t(3type)                                                 off_t(3type)

NAME         top

       off_t, off64_t, loff_t - file sizes

LIBRARY         top

       Standard C library (libc)

SYNOPSIS         top

       #include <sys/types.h>

       typedef /* ... */  off_t;

       #define _LARGEFILE64_SOURCE
       #include <sys/types.h>

       typedef /* ... */  off64_t;

       #define _GNU_SOURCE
       #include <sys/types.h>

       typedef /* ... */  loff_t;

DESCRIPTION         top

       off_t is used for describing file sizes.  It is a signed integer
       type.

       off64_t is a 64-bit version of the type, used in glibc.

       loff_t is a 64-bit version of the type, introduced by the Linux
       kernel.

STANDARDS         top

       off_t  POSIX.1-2008.

       off64_t
              GNU and some BSDs.

       loff_t Linux.

VERSIONS         top

       off_t  POSIX.1-2001.

       <aio.h> and <stdio.h> define off_t since POSIX.1-2008.

NOTES         top

       On some architectures, the width of off_t can be controlled with
       the feature test macro _FILE_OFFSET_BITS.

       The following headers also provide off_t: <aio.h>, <fcntl.h>,
       <stdio.h>, <sys/mman.h>, <sys/stat.h>, and <unistd.h>.

SEE ALSO         top

       copy_file_range(2), llseek(2), lseek(2), mmap(2),
       posix_fadvise(2), pread(2), readahead(2), sync_file_range(2),
       truncate(2), fseeko(3), lockf(3), lseek64(3), posix_fallocate(3),
       feature_test_macros(7)

COLOPHON         top

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Linux man-pages 6.15            2025-05-17                   off_t(3type)

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