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


       #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:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:


       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 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:

              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().


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


       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

       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).

       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.

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


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


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

       unlinkat(): POSIX.1-2008.


   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.


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


       rm(1),  chmod(2),  link(2),  mknod(2),  open(2),  rename(2),  rmdir(2),
       mkfifo(3), remove(3), path_resolution(7), symlink(7)


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