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LLSEEK(2) Linux Programmer's Manual LLSEEK(2)


_llseek - reposition read/write file offset


#include <sys/types.h>
#include <unistd.h>
int _llseek(unsigned int fd, unsigned long offset_high,
            unsigned long offset_low, loff_t *result,
            unsigned int whence);

Note: There is no glibc wrapper for this system call; see NOTES.


Note: for information about the llseek(3) library function, see lseek64(3).

The _llseek() system call repositions the offset of the open file description associated with the file descriptor fd to the value

(offset_high << 32) | offset_low

This new offset is a byte offset relative to the beginning of the file, the current file offset, or the end of the file, depending on whether whence is SEEK_SET, SEEK_CUR, or SEEK_END, respectively.

The new file offset is returned in the argument result. The type loff_t is a 64-bit signed type.

This system call exists on various 32-bit platforms to support seeking to large file offsets.


Upon successful completion, _llseek() returns 0. Otherwise, a value of -1 is returned and errno is set to indicate the error.


fd is not an open file descriptor.
Problem with copying results to user space.
whence is invalid.


This function is Linux-specific, and should not be used in programs intended to be portable.


Glibc does not provide a wrapper for this system call. To invoke it directly, use syscall(2). However, you probably want to use the lseek(2) wrapper function instead.


lseek(2), open(2), lseek64(3)


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2020-12-21 Linux