FHREADLINK(2)

💅 FHREADLINK(2) — the system calls manual ✨

okay so bestie, we're in System Calls Manual territory today and this one is a little niche but it slaps once you get it, i promise 🫶

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🌸 NAME 🌸

fhreadlink — read the value of a symbolic link, but like… by file handle 🔗

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🎀 LIBRARY 🎀

Standard C Library (libc, -lc) — the classic, the icon, the one you already link against 💖

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✨ SYNOPSIS ✨

#include <sys/param.h>
#include <sys/mount.h>

int
fhreadlink(fhandle_t *fhp, char *buf, size_t bufsize);

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🦋 DESCRIPTION 🦋

okay so fhreadlink() is the system call that takes the contents of the symbolic link fhp and drops them straight into the buffer buf, which has size bufsiz 💫

and here's the part that gets people: fhreadlink() does not append a NUL character to buf. like, at all. no null terminator, no little gift at the end 🙈 so if you're planning to treat it like a string you gotta handle that yourself, bestie. that's on you.

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👑 RETURN VALUES 👑

if it works? the call returns the count of characters it placed in the buffer, slay 💅

if it doesn't? it returns a -1 and tucks the error code into the global variable errno so you can go look at what went wrong 😭

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🔥 ERRORS 🔥

the fhreadlink() system call will fail if any of these happen:

• [ENOENT] — the named file does not exist. it's giving ~nothing~ 💀
• [ELOOP] — too many symbolic links were encountered while translating the file handle fhp. link-ception, we're not doing that today 🌀
• [EINVAL] — the named file is not a symbolic link. wrong vibe entirely, not the main character you were looking for 🙅
• [EIO] — an I/O error occurred while reading from the file system. the filesystem is having a moment 🫠
• [EINTEGRITY] — corrupted data was detected while reading from the file system. something is rotten and it's not the algorithm 🍓
• [EFAULT] — the buf argument extends outside the process's allocated address space. you're colouring outside the lines, literally ⚠️
• [ESTALE] — the file handle fhp is no longer valid. expired, deceased, gone girl 💔

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💜 SEE ALSO 💜

fhlink(2), fhstat(2), readlink(2) — go read these next, you'll be obsessed 📚

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⭐ HISTORY ⭐

the fhreadlink() system call first appeared in FreeBSD 12.1 🎂 a Scorpio, presumably.

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ngl bestie, the whole "no NUL at the end" thing is the number one thing to remember here. everything else is just vibes and errno checks 💀

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mwah 💋 this page came to you from Debian, dated November 30, 2022 — consider this your cute little sign-off, take care of yourself, hydrate, and check your return values 🧚‍♀️