unlinkat(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);
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/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
