lseek64

lseek64 is a Unix-like system call wrapper that repositions the file offset of an open file descriptor using a 64-bit offset. It is designed to support large files whose sizes exceed 2 gigabytes.

Prototype (C): off64_t lseek64(int fd, off64_t offset, int whence); Offsets are interpreted according to whence (SEEK_SET, SEEK_CUR, SEEK_END).

On success, it returns the resulting offset from the beginning of the file. On error, it returns -1 and sets errno (examples: EBADF for a bad file descriptor, ESPIPE for an invalid seek on pipes, EINVAL for invalid whence, EOVERFLOW if the resulting offset cannot be represented).

In Linux, lseek64 provides 64-bit offsets for 32-bit applications; on 64-bit systems it is typically equivalent to lseek. It cannot be used on streams that do not support seeking, such as pipes, sockets, or character devices.

Related concepts include lseek, which uses the standard offset type, and fseeko/ftello, which use size-related types for 64-bit offsets in C libraries. lseek64 is part of large-file support, enabling portable handling of files larger than 2^31 bytes on systems where off_t may be 32-bit.