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Man page of UNLINK
UNLINK
Section: Linux Programmer's Manual (2)
Updated: 2016-10-08
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NAME
unlink, unlinkat - delete a name and possibly the file it refers to
SYNOPSIS
#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
DESCRIPTION
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.
unlinkat()
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().
RETURN VALUE
On success, zero is returned.
On error, -1 is returned, and
errno
is set appropriately.
ERRORS
- 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).
- 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.
VERSIONS
unlinkat()
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.
CONFORMING TO
unlink():
SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
unlinkat():
POSIX.1-2008.
NOTES
Glibc notes
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.
BUGS
Infelicities in the protocol underlying NFS can cause the unexpected
disappearance of files which are still being used.
SEE ALSO
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)
COLOPHON
This page is part of release 4.09 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- unlinkat()
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- CONFORMING TO
-
- NOTES
-
- Glibc notes
-
- BUGS
-
- SEE ALSO
-
- COLOPHON
-
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