unlinkat(2) — Linux manual page


UNLINK(2)                 Linux Programmer's Manual                UNLINK(2)

NAME         top

       unlink, unlinkat - delete a name and possibly the file it refers to

SYNOPSIS         top

       #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)):

           Since glibc 2.10:
               _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:

DESCRIPTION         top

       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

       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

       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

       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:

              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         top

       On success, zero is returned.  On error, -1 is returned, and errno is
       set appropriately.

ERRORS         top

       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 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.

              A component used as a directory in pathname is not, in fact, a

       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

       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.

              pathname is relative and dirfd is a file descriptor referring
              to a file other than a directory.

VERSIONS         top

       unlinkat() was added to Linux in kernel 2.6.16; library support was
       added to glibc in version 2.4.

CONFORMING TO         top

       unlink(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.

       unlinkat(): POSIX.1-2008.

NOTES         top

   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

BUGS         top

       Infelicities in the protocol underlying NFS can cause the unexpected
       disappearance of files which are still being used.

SEE ALSO         top

       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         top

       This page is part of release 5.09 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

Linux                            2017-09-15                        UNLINK(2)

Pages that refer to this page: creat(2)open(2)openat(2)rmdir(2)syscalls(2)signal-safety(7)