lseek64(3) Library Functions Manual lseek64(3)

lseek64 - reposition 64-bit read/write file offset

Standard C library (libc-lc)

#define _LARGEFILE64_SOURCE     /* See feature_test_macros(7) */
#include <sys/types.h>
#include <unistd.h>
[[deprecated]] off64_t lseek64(int fd, off64_t offset, int whence);

This function is equivalent to lseek(2) if one compiles with


#define _FILE_OFFSET_BITS 64

Use lseek(2) instead.

For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
lseek64 () Thread safety MT-Safe

glibc 2.1.

lseek64() is one of the functions that was specified in the Large File Summit (LFS) specification that was completed in 1996. The purpose of the specification was to provide transitional support that allowed applications on 32-bit systems to access files whose size exceeds that which can be represented with a 32-bit off_t type.

_llseek(2), lseek(2)

2026-06-13 Linux man-pages 6.19