UNDELETE(2)

💅 UNDELETE(2) — System Calls Manual, but make it cute ✨

✨ NAME ✨

undelete — attempt to recover a deleted file 🫶

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📚 LIBRARY 📚

Standard C Library (libc, -lc) — yes bestie, that’s the one 💖

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🧾 SYNOPSIS 🧾

#include <unistd.h>

int
undelete(const char *path);

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💫 DESCRIPTION 💫

Okay so the undelete() system call attempts to recover the deleted file named by path. That’s the whole main-character mission 🌸.

Currently, this works only when the named object is a whiteout in a union file system. The system call removes the whiteout causing any objects in a lower layer of the union stack to become visible once more. Literally bringing the lower-layer vibes back into view 🦋.

Eventually, the undelete() functionality may be expanded to other file systems able to recover deleted files such as the log-structured file system. Future icon behavior, no cap ✨.

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🎀 RETURN VALUES 🎀

The undelete() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error. Classic success/fail energy 💅.

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💀 ERRORS 💀

The undelete() succeeds unless one of these gremlins shows up:

• [ENOTDIR] — A component of the path prefix is not a directory.
• [ENAMETOOLONG] — A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
• [EEXIST] — The path does not reference a whiteout.
• [ENOENT] — The named whiteout does not exist.
• [EACCES] — Search permission is denied for a component of the path prefix.
• [EACCES] — Write permission is denied on the directory containing the name to be undeleted.
• [ELOOP] — Too many symbolic links were encountered in translating the pathname.
• [EPERM] — The directory containing the name is marked sticky, and the containing directory is not owned by the effective user ID.
• [EINVAL] — The last component of the path is ‘..’.
• [EIO] — An I/O error occurred while updating the directory entry.
• [EINTEGRITY] — Corrupted data was detected while reading from the file system.
• [EROFS] — The name resides on a read-only file system.
• [EFAULT] — The path argument points outside the process's allocated address space.

Yes, there are two [EACCES] entries — both are real, both matter, not me making it up 💅

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👀 SEE ALSO 👀

• unlink(2)
• mount_unionfs(8)

Go peek, iykyk 🧚

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🌸 HISTORY 🌸

The undelete() system call first appeared in 4.4BSD-Lite. Vintage but still iconic 🔥.

xoxo, Debian 💖 March 30, 2020 — UNDELETE(2) out. 🎀