UNLINK(2) System Calls UNLINK(2)

NAME

unlink, unlinkat - remove directory entry

SYNOPSIS

#include <unistd.h>

int unlink(const char *path);


int unlinkat(int dirfd, const char *path, int flag);

DESCRIPTION

The unlink() function removes a link to a file. If path names a symbolic
link, unlink() removes the symbolic link named by path and does not
affect any file or directory named by the contents of the symbolic link.
Otherwise, unlink() removes the link named by the pathname pointed to by
path and decrements the link count of the file referenced by the link.


The unlinkat() function also removes a link to a file. See fsattr(7). If
the flag argument is 0, the behavior of unlinkat() is the same as
unlink() except in the processing of its path argument. If path is
absolute, unlinkat() behaves the same as unlink() and the dirfd argument
is unused. If path is relative and dirfd has the value AT_FDCWD, defined
in <fcntl.h>, unlinkat() also behaves the same as unlink(). Otherwise,
path is resolved relative to the directory referenced by the dirfd
argument.


If the flag argument is set to the value AT_REMOVEDIR, defined in
<fcntl.h>, unlinkat() behaves the same as rmdir(2) except in the
processing of the path argument as described above.


When the file's link count becomes 0 and no process has the file open,
the space occupied by the file will be freed and the file is no longer
accessible. If one or more processes have the file open when the last
link is removed, the link is removed before unlink() or unlinkat()
returns, but the removal of the file contents is postponed until all
references to the file are closed.


If the path argument is a directory and the filesystem supports unlink()
and unlinkat() on directories, the directory is unlinked from its parent
with no cleanup being performed. In UFS, the disconnected directory will
be found the next time the filesystem is checked with fsck(8). The
unlink() and unlinkat() functions will not fail simply because a
directory is not empty. The user with appropriate privileges can orphan a
non-empty directory without generating an error message.


If the path argument is a directory and the filesystem does not support
unlink() and unlink() on directories (for example, ZFS), the call will
fail with errno set to EPERM.


Upon successful completion, unlink() and unlinkat() will mark for update
the st_ctime and st_mtime fields of the parent directory. If the file's
link count is not 0, the st_ctime field of the file will be marked for
update.

RETURN VALUES

Upon successful completion, 0 is returned. Otherwise, -1 is returned,
errno is set to indicate the error, and the file is not unlinked.

ERRORS

The unlink() and unlinkat() functions will fail if:

EACCES
Search permission is denied for a component of the path
prefix, or write permission is denied on the directory
containing the link to be removed.


EACCES
The parent directory has the sticky bit set and the file
is not writable by the user, the user does not own the
parent directory, the user does not own the file, and the
user is not a privileged user.


EBUSY
The entry to be unlinked is the mount point for a mounted
file system.


EFAULT
The path argument points to an illegal address.


EILSEQ
The path argument includes non-UTF8 characters and the
file system accepts only file names where all characters
are part of the UTF-8 character codeset.


EINTR
A signal was caught during the execution of the unlink()
function.


ELOOP
Too many symbolic links were encountered in translating
path.


ENAMETOOLONG
The length of the path argument exceeds PATH_MAX, or the
length of a path component exceeds NAME_MAX while
_POSIX_NO_TRUNC is in effect.


ENOENT
The named file does not exist or is a null pathname.


ENOLINK
The path argument points to a remote machine and the link
to that machine is no longer active.


ENOTDIR
A component of the path prefix is not a directory or the
provided directory descriptor for unlinkat() is not
AT_FDCWD or does not reference a directory.


EPERM
The named file is a directory and {PRIV_SYS_LINKDIR} is
not asserted in the effective set of the calling process,
or the filesystem implementation does not support
unlink() or unlinkat() on directories.


EROFS
The directory entry to be unlinked is part of a read-only
file system.


The unlink() and unlinkat() functions may fail if:

ENAMETOOLONG
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds {PATH_MAX}.


ETXTBSY
The entry to be unlinked is the last directory entry to a
pure procedure (shared text) file that is being executed.

USAGE

Applications should use rmdir(2) to remove a directory.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+------------------------+
|Interface Stability | unlink() is Standard; |
| | unlinkat() is Evolving |
+--------------------+------------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+------------------------+

SEE ALSO

rm(1), close(2), link(2), open(2), rmdir(2), remove(3C), attributes(7),
fsattr(7), privileges(7)

May 18, 2007 UNLINK(2)