unlink, unlinkat - delete a name and possibly the file it refers to
#include <unistd.h>
int unlink(const char *pathname);
#include <fcntl.h> /* Definition of AT_* constants */
#include <unistd.h>
int unlinkat(int dirfd, const char *pathname, int flags);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
unlinkat():
- Since glibc 2.10:
- _POSIX_C_SOURCE >= 200809L
- Before glibc 2.10:
- _ATFILE_SOURCE
unlink() deletes a name from the filesystem. If that name was the last
link to a file and no processes have the file open, the file is deleted and
the space it was using is made available for reuse.
If the name was the last link to a file but any processes still have the file
open, the file will remain in existence until the last file descriptor
referring to it is closed.
If the name referred to a symbolic link, the link is removed.
If the name referred to a socket, FIFO, or device, the name for it is removed
but processes which have the object open may continue to use it.
The
unlinkat() system call operates in exactly the same way as either
unlink() or
rmdir(2) (depending on whether or not
flags
includes the
AT_REMOVEDIR flag) except for the differences described
here.
If the pathname given in
pathname is relative, then it is interpreted
relative to the directory referred to by the file descriptor
dirfd
(rather than relative to the current working directory of the calling process,
as is done by
unlink() and
rmdir(2) for a relative pathname).
If the pathname given in
pathname is relative and
dirfd is the
special value
AT_FDCWD, then
pathname is interpreted relative to
the current working directory of the calling process (like
unlink() and
rmdir(2)).
If the pathname given in
pathname is absolute, then
dirfd is
ignored.
flags is a bit mask that can either be specified as 0, or by ORing
together flag values that control the operation of
unlinkat().
Currently, only one such flag is defined:
- AT_REMOVEDIR
- By default, unlinkat() performs the equivalent of unlink()
on pathname. If the AT_REMOVEDIR flag is specified, then
performs the equivalent of rmdir(2) on pathname.
See
openat(2) for an explanation of the need for
unlinkat().
On success, zero is returned. On error, -1 is returned, and
errno is set
appropriately.
- EACCES
- Write access to the directory containing pathname is not allowed
for the process's effective UID, or one of the directories in
pathname did not allow search permission. (See also
path_resolution(7).)
- EBUSY
- The file pathname cannot be unlinked because it is being used by
the system or another process; for example, it is a mount point or the NFS
client software created it to represent an active but otherwise nameless
inode ("NFS silly renamed").
- EFAULT
- pathname points outside your accessible address space.
- EIO
- An I/O error occurred.
- EISDIR
- pathname refers to a directory. (This is the non-POSIX value
returned by Linux since 2.1.132.)
- ELOOP
- Too many symbolic links were encountered in translating
pathname.
- ENAMETOOLONG
- pathname was too long.
- ENOENT
- A component in pathname does not exist or is a dangling symbolic
link, or pathname is empty.
- ENOMEM
- Insufficient kernel memory was available.
- ENOTDIR
- A component used as a directory in pathname is not, in fact, a
directory.
- EPERM
- The system does not allow unlinking of directories, or unlinking of
directories requires privileges that the calling process doesn't have.
(This is the POSIX prescribed error return; as noted above, Linux returns
EISDIR for this case.)
- EPERM (Linux only)
- The filesystem does not allow unlinking of files.
- EPERM or EACCES
- The directory containing pathname has the sticky bit
(S_ISVTX) set and the process's effective UID is neither the UID of
the file to be deleted nor that of the directory containing it, and the
process is not privileged (Linux: does not have the CAP_FOWNER
capability).
- EPERM
- The file to be unlinked is marked immutable or append-only. (See
ioctl_iflags(2).)
- EROFS
- pathname refers to a file on a read-only filesystem.
The same errors that occur for
unlink() and
rmdir(2) can also
occur for
unlinkat(). The following additional errors can occur for
unlinkat():
- EBADF
- dirfd is not a valid file descriptor.
- EINVAL
- An invalid flag value was specified in flags.
- EISDIR
- pathname refers to a directory, and AT_REMOVEDIR was not
specified in flags.
- ENOTDIR
- pathname is relative and dirfd is a file descriptor
referring to a file other than a directory.
unlinkat() was added to Linux in kernel 2.6.16; library support was added
to glibc in version 2.4.
unlink(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
unlinkat(): POSIX.1-2008.
On older kernels where
unlinkat() is unavailable, the glibc wrapper
function falls back to the use of
unlink() or
rmdir(2). When
pathname is a relative pathname, glibc constructs a pathname based on
the symbolic link in
/proc/self/fd that corresponds to the
dirfd
argument.
Infelicities in the protocol underlying NFS can cause the unexpected
disappearance of files which are still being used.
rm(1),
unlink(1),
chmod(2),
link(2),
mknod(2),
open(2),
rename(2),
rmdir(2),
mkfifo(3),
remove(3),
path_resolution(7),
symlink(7)