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UNLINK(2) FreeBSD System Calls Manual UNLINK(2)
NAME unlink, unlinkat, funlinkat - remove directory entry
LIBRARY Standard C Library (libc, -lc)
SYNOPSIS #include <unistd.h>
int unlink(const char *path);
int unlinkat(int dfd, const char *path, int flag);
int funlinkat(int dfd, const char *path, int fd, int flag);
DESCRIPTION The unlink() system call removes the link named by path from its directory and decrements the link count of the file which was referenced by the link. If that decrement reduces the link count of the file to zero, and no process has the file open, then all resources associated with the file are reclaimed. If one or more process have the file open when the last link is removed, the link is removed, but the removal of the file is delayed until all references to it have been closed. The path argument may not be a directory.
The unlinkat() system call is equivalent to unlink() or rmdir() except in the case where path specifies a relative path. In this case the directory entry to be removed is determined relative to the directory associated with the file descriptor dfd instead of the current working directory.
The values for flag are constructed by a bitwise-inclusive OR of flags from the following list, defined in <fcntl.h>:
AT_REMOVEDIR Remove the directory entry specified by fd and path as a directory, not a normal file.
AT_RESOLVE_BENEATH Only walk paths below the directory specified by the fd descriptor. See the description of the O_RESOLVE_BENEATH flag in the open(2) manual page.
If unlinkat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the behavior is identical to a call to unlink or rmdir respectively, depending on whether or not the AT_REMOVEDIR bit is set in flag.
The funlinkat() system call can be used to unlink an already-opened file, unless that file has been replaced since it was opened. It is equivalent to unlinkat() in the case where path is already open as the file descriptor fd. Otherwise, the path will not be removed and an error will be returned. The fd can be set the FD_NONE. In that case funlinkat() behaves exactly like unlinkat(). The unlink() succeeds unless:
[ENOTDIR] A component of the path prefix is not a directory.
[EISDIR] The named file is a directory.
[ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
[ENOENT] The named file 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 link to be removed.
[ELOOP] Too many symbolic links were encountered in translating the pathname.
[EPERM] The named file is a directory.
[EPERM] The named file has its immutable, undeletable or append-only flag set, see the chflags(2) manual page for more information.
[EPERM] The parent directory of the named file has its immutable or append-only flag set.
[EPERM] The directory containing the file is marked sticky, and neither the containing directory nor the file to be removed are owned by the effective user ID.
[EIO] An I/O error occurred while deleting the directory entry or deallocating the inode.
[EINTEGRITY] Corrupted data was detected while reading from the file system.
[EROFS] The named file resides on a read-only file system.
[EFAULT] The path argument points outside the process's allocated address space.
[ENOSPC] On file systems supporting copy-on-write or snapshots, there was not enough free space to record metadata for the delete operation of the file.
In addition to the errors returned by the unlink(), the unlinkat() may fail if:
[EBADF] The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
[ENOTEMPTY] The flag parameter has the AT_REMOVEDIR bit set and the path argument names a directory that is not an empty directory, or there are hard links to the directory other than dot or a single entry in dot-dot. neither AT_FDCWD nor a file descriptor associated with a directory.
[ENOTCAPABLE] path is an absolute path, or contained a ".." component leading to a directory outside of the directory hierarchy specified by fd, and the process is in capability mode or the AT_RESOLVE_BENEATH flag was specified.
In addition to the errors returned by unlinkat(), funlinkat() may fail if:
[EDEADLK] The file descriptor is not associated with the path.
SEE ALSO chflags(2), close(2), link(2), rmdir(2), symlink(7)
STANDARDS The unlinkat() system call follows The Open Group Extended API Set 2 specification.
HISTORY The unlink() function appeared in Version 1 AT&T UNIX. The unlinkat() system call appeared in FreeBSD 8.0. The funlinkat() system call appeared in FreeBSD 13.0.
The unlink() system call traditionally allows the super-user to unlink directories which can damage the file system integrity. This implementation no longer permits it.
FreeBSD 14.0-RELEASE-p11 February 23, 2021 FreeBSD 14.0-RELEASE-p11