ATTR_SET(3)

✨ ATTR_SET — set the value of a user attribute of a filesystem object ✨

okay bestie, listen up 💖 this is the XFS Compatibility API version of attr_set, and she's a whole vibe. Two functions, one mission: making attributes exist and changing what they say. Let's get into it 🦋

---

🌸 C SYNOPSIS 🌸

#include <attr/attributes.h>

int attr_set (const char *path, const char *attrname,
              const char *attrvalue, const int valuelength,
              int flags);

int attr_setf (int fd, const char *attrname,
               const char *attrvalue, const int valuelength,
               int flags);

---

👑 DESCRIPTION 👑

So like, attr_set and attr_setf are literally the way you create attributes and set/change their values. That's it, that's the job 🫶

path points to a path name for a filesystem object, and fd refers to the file descriptor associated with a file. Okay so here's the tea: if the attribute attrname does not exist, an attribute with the given name and value gets created and associated with that indicated filesystem object. And if an attribute with that name already exists on that filesystem object? The existing value is replaced with the new value given in this call. Iconic. The new attribute value is copied from the attrvalue buffer for a total of valuelength bytes. No cap 📏

Now the flags argument can contain the following symbols bitwise OR'ed together — yes, bitwise, we're doing bit math, slay:

💅 ATTR_ROOT

Look for attrname in the root address space, not in the user address space. (limited to use by super-user only) — so like, don't try it unless you're Him.

💅 ATTR_DONTFOLLOW

Do not follow symbolic links when resolving a path on an attr_set function call. The default is to follow symbolic links. So yeah, this is the "leave my symlinks alone" button 🧚

💅 ATTR_CREATE

Return an error (EEXIST) if an attribute of the given name already exists on the indicated filesystem object, otherwise create an attribute with the given name and value. This flag is used to implement a pure create operation. Heads up though: without this flag, attr_set will create the attribute if it does not already exist. And an error (EINVAL) will be returned if both ATTR_CREATE and ATTR_REPLACE are set in the same call. Pick a lane, bestie 😭

💅 ATTR_REPLACE

Return an error (ENOATTR) if an attribute of the given name does not already exist on the indicated filesystem object, otherwise replace the existing attribute's value with the given value. This flag is used to implement a pure replacement operation. And again, without this flag, attr_set will create the attribute if it does not already exist. An error (EINVAL) will be returned if both ATTR_CREATE and ATTR_REPLACE are set in the same call. Same energy as above, fr fr.

---

🚨 so when does attr_set fail? 🚨

attr_set will fail if one or more of the following are true:

• [ENOATTR] — The attribute name given is not associated with the indicated filesystem object and the ATTR_REPLACE flag bit was set.
• [E2BIG] — The value of the given attribute is too large, it exceeds the maximum allowable size of an attribute value.
• [EEXIST] — The attribute name given is already associated with the indicated filesystem object and the ATTR_CREATE flag bit was set.
• [ENOENT] — The named file does not exist.
• [EPERM] — The effective user ID does not match the owner of the file and the effective user ID is not super-user.
• [ENOTDIR] — A component of the path prefix is not a directory.
• [EACCES] — Search permission is denied on a component of the path prefix.
• [EINVAL] — A bit was set in the flag argument that is not defined for this system call, or both the ATTR_CREATE and ATTR_REPLACE flags bits were set.
• [EFAULT] — path, attrname, or attrvalue points outside the allocated address space of the process.
• [ELOOP] — A path name lookup involved too many symbolic links. (the symlink spiral 💀)
• [ENAMETOOLONG] — The length of path exceeds {MAXPATHLEN}, or a pathname component is longer than {MAXNAMELEN}.

---

🚨 and attr_setf will fail if: 🚨

• [ENOATTR] — The attribute name given is not associated with the indicated filesystem object and the ATTR_REPLACE flag bit was set.
• [E2BIG] — The value of the given attribute is too large, it exceeds the maximum allowable size of an attribute value.
• [EEXIST] — The attribute name given is already associated with the indicated filesystem object and the ATTR_CREATE flag bit was set.
• [EINVAL] — A bit was set in the flag argument that is not defined for this system call, or both the ATTR_CREATE and ATTR_REPLACE flags bits were set, or fd refers to a socket, not a file. (a socket, girl?? not today 🙈)
• [EFAULT] — attrname, or attrvalue points outside the allocated address space of the process.
• [EBADF] — fd does not refer to a valid descriptor.

---

🩺 DIAGNOSTICS 🩺

On success, zero is returned. ✨ On error, -1 is returned, and errno is set appropriately. That's the whole mood ring, bestie.

---

👀 SEE ALSO 👀

attr(1), attr_get(3), attr_list(3), attr_multi(3), attr_remove(3)

---

and that's the page!! 🎀 this one came from the XFS Compatibility API, dated Dec 2001, filed under Extended Attributes — go forth and set those attributes, you absolute icon 👑💜