RENAME(2)

💅 RENAME(2) — the rename(2) page, but make it make sense

okay bestie, pull up a chair because we're talking about the rename system call, aka the glow-up moment where a file gets a whole new name 💖 this is a System Calls Manual situation, so yes we are in the deep end of the pool, but don't panic, I got you 🫶

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✨ NAME ✨

rename — change the name of a file 🏷️✨ (yes, that's it, that's the whole vibe)

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📚 LIBRARY 📚

Standard C Library (libc, -lc) — so you're gonna want to link that, bestie 🎀

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🌸 SYNOPSIS 🌸

#include <stdio.h>

int
rename(const char *from, const char *to);

int
renameat(int fromfd, const char *from, int tofd, const char *to);

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🦋 DESCRIPTION 🦋

So the rename() system call causes the link named from to be renamed as to. Periodt. And if to already exists? it gets removed first 💀 like, bye girl, we're replacing you.

BUT — and this is the part where people get got — both from and to must be of the same type (that means both directories, or both non-directories), and they must reside on the same file system. no cross-filesystem shenanigans, i don't make the rules 😤

The rename() system call guarantees that if to already exists, an instance of to will always exist, even if the system should crash in the middle of the operation. like, that's genuinely iconic behavior — atomicity queen 👑

If the final component of from is a symbolic link, the symbolic link is renamed — not the file or directory to which it points. so don't come for me thinking it follows the link, because it does not 🙈

If from and to resolve to the same directory entry, or to different directory entries for the same existing file, rename() returns success without taking any further action. it's giving "nothing to do here, we're good" 💅

Now for the plot twist: renameat() is equivalent to rename() except in the case where either from or to specifies a relative path:

• If from is a relative path, the file to be renamed is located relative to the directory associated with the file descriptor fromfd instead of the current working directory.
• If to is a relative path, the same happens only relative to the directory associated with tofd.
• If renameat() is passed the special value AT_FDCWD in the fromfd or tofd parameter, the current working directory is used in the determination of the file for the respective path parameter.

so basically renameat() is rename() but with ✨directory-context awareness✨, iykyk.

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💫 RETURN VALUES 💫

• The rename() function returns the value 0 if successful — slay 🎉
• Otherwise the value -1 is returned and the global variable errno is set to indicate the error 😭

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🔥 ERRORS 🔥

The rename() system call will fail and neither of the argument files will be affected if:

• [ENAMETOOLONG] — A component of either pathname exceeded 255 characters, or the entire length of either path name exceeded 1023 characters. girl, that name is TOO long, chill 💀
• [ENOENT] — A component of the from path does not exist, or a path prefix of to does not exist.
• [EACCES] — A component of either path prefix denies search permission.
• [EACCES] — The requested link requires writing in a directory with a mode that denies write permission.
• [EACCES] — The directory pointed at by the from argument denies write permission, and the operation would move it to another parent directory.
• [EPERM] — The file pointed at by the from argument has its immutable, undeletable or append-only flag set, see the chflags(2) manual page for more information.
• [EPERM] — The parent directory of the file pointed at by the from argument has its immutable or append-only flag set.
• [EPERM] — The parent directory of the file pointed at by the to argument has its immutable flag set.
• [EPERM] — The directory containing from is marked sticky, and neither the containing directory nor from are owned by the effective user ID.
• [EPERM] — The file pointed at by the to argument exists, the directory containing to is marked sticky, and neither the containing directory nor to are owned by the effective user ID.
• [ELOOP] — Too many symbolic links were encountered in translating either pathname. loop loop loop, we're stuck bestie 🌀
• [ENOTDIR] — A component of either path prefix is not a directory.
• [ENOTDIR] — The from argument is a directory, but to is not a directory.
• [EISDIR] — The to argument is a directory, but from is not a directory.
• [EXDEV] — The link named by to and the file named by from are on different logical devices (file systems). Note that this error code will not be returned if the implementation permits cross-device links.
• [ENOSPC] — The directory in which the entry for the new name is being placed cannot be extended because there is no space left on the file system containing the directory.
• [EDQUOT] — The directory in which the entry for the new name is being placed cannot be extended because the user's quota of disk blocks on the file system containing the directory has been exhausted.
• [EIO] — An I/O error occurred while making or updating a directory entry.
• [EINTEGRITY] — Corrupted data was detected while reading from the file system. yikes 🫠
• [EROFS] — The requested link requires writing in a directory on a read-only file system.
• [EFAULT] — Path points outside the process's allocated address space.
• [EINVAL] — The from argument is a parent directory of to, or an attempt is made to rename ‘.’ or ‘..’. no, you cannot rename . or .., that's not a thing, stop it 😭
• [ENOTEMPTY] — The to argument is a directory and is not empty.
• [ECAPMODE] — rename() was called and the process is in capability mode.

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In addition to the errors returned by the rename(), the renameat() may fail if:

• [EBADF] — The from argument does not specify an absolute path and the fromfd argument is neither AT_FDCWD nor a valid file descriptor open for searching, or the to argument does not specify an absolute path and the tofd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
• [ENOTDIR] — The from argument is not an absolute path and fromfd is neither AT_FDCWD nor a file descriptor associated with a directory, or the to argument is not an absolute path and tofd is neither AT_FDCWD nor a file descriptor associated with a directory.
• [ECAPMODE] — AT_FDCWD is specified and the process is in capability mode.
• [ENOTCAPABLE] — path is an absolute path or contained a ".." component leading to a directory outside of the directory hierarchy specified by fromfd or tofd.
• [ENOTCAPABLE] — The fromfd file descriptor lacks the CAP_RENAMEAT_SOURCE right, or the tofd file descriptor lacks the CAP_RENAMEAT_TARGET right.

fr fr, capability mode is not the moment to be sloppy. read the error, respect the sandbox 🧚

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👀 SEE ALSO 👀

chflags(2), open(2), symlink(7) — go read these too, they're lowkey connected 🫶

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⭐ STANDARDS ⭐

• The rename() system call is expected to conform to ISO/IEC 9945-1:1996 (“POSIX.1”).
• The renameat() system call follows The Open Group Extended API Set 2 specification.

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🌈 HISTORY 🌈

The renameat() system call appeared in FreeBSD 8.0. a little baby newcomer, and look at her now 👑

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and that's the whole page, bestie 💜

this gem came from the Debian folks, dated March 30, 2020, and it lives in section RENAME(2) of the System Calls Manual.

go rename something (responsibly) ✨ mwah 💅