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/.

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