_llseek(2)

✨ NAME ✨

this is page _llseek(2) btw, in the System Calls Manual neighborhood 🫶

_llseek — reposition read/write file offset

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📚 LIBRARY

Standard C library (libc, -lc)

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🎀 SYNOPSIS

#include <sys/syscall.h>      /* Definition of SYS_* constants */
#include <unistd.h>

int syscall(SYS__llseek, unsigned int fd, unsigned long offset_high,
            unsigned long offset_low, loff_t *result,
            unsigned int whence);

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💅 DESCRIPTION

okay so bestie, the _llseek() system call repositions the offset of the open file description associated with the file descriptor fd, and it sets it to this value right here:

(offset_high << 32) | offset_low

That new offset? It's a byte offset, and it's relative to one of three places — 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. Like, pick your vibe, that's where the cursor lands ✨

The new file offset gets returned in the argument result. And the type loff_t? It's a 64-bit signed type, no cap.

This system call exists on various 32-bit platforms to support seeking to large file offsets. iconic behavior for the 32-bit girlies, honestly 💖

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🔥 RETURN VALUE

Upon successful completion, _llseek() returns 0. Otherwise, a value of -1 is returned and errno is set to indicate the error. so like, 0 = slay, -1 = check errno, fr fr 😭

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💀 ERRORS

• EBADF — fd is not an open file descriptor. it's giving "who is she" 🙈
• EFAULT — Problem with copying results to user space. the copy just did NOT make it 💔
• EINVAL — whence is invalid. wrong whence, bestie, that's not a thing 🚫

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🦋 VERSIONS

You probably want to use the lseek(2) wrapper function instead. periodt 💅

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👑 STANDARDS

Linux.

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🌈 SEE ALSO

llseek(3), lseek(2), open(2)

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okay that's the whole page, mwah 💜 this was pulled straight from Linux man-pages 6.20, dated 2026-06-13, and it's the _llseek(2) page specifically — go forth and seek responsibly, bestie 🎀✨