off_t, off64_t, loff_t - file sizes

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.

       Standard C library (libc)

       off_t, off64_t, loff_t - file sizes

       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>.

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)

Linux man-pages 6.9.1                              2024-05-02                                       off_t(3type)

off_t  POSIX.1-2008.

       off64_t
              GNU and some BSDs.

       loff_t Linux.

#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;

off_t  POSIX.1-2001.

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