Linux manual pages Section 2  

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);
 
[Note] Note
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(2) 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), 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 4.07 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/.


  This manpage is Copyright (C) 1992 Drew Eckhardt;
            and Copyright (C) 1993 Ian Jackson
            and Copyright (C) 2006, 2014 Michael Kerrisk.

%%%LICENSE_START(VERBATIM)
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.
%%%LICENSE_END

Modified 1993-07-24 by Rik Faith <faithcs.unc.edu>
Modified 1996-09-08 by Arnt Gulbrandsen <agulbratroll.no>
Modified 1997-01-31 by Eric S. Raymond <esrthyrsus.com>
Modified 2001-05-17 by aeb
Modified 2004-06-23 by Michael Kerrisk <mtk.manpagesgmail.com>