unlinkat

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

       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.

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 5.10 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/.




Linux                              2017-09-15                          UNLINK(2)