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().
RETURN VALUES
The unlink() function returns the value 0 if successful; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.
ERRORS
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.
[ENOTDIR] The flag parameter has the AT_REMOVEDIR bit set and
path does not name a directory.
[EINVAL] The value of the flag argument is not valid.
[ENOTDIR] The path argument is not an absolute path and fd is
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 13.1-RELEASE-p6 February 23, 2021 FreeBSD 13.1-RELEASE-p6
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