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

       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  pro‐
       cesses which have the object open may continue to use it.

       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  differ‐
       ences 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 rela‐
       tive 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  path‐

       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  permis‐
              sion.  (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  cre‐
              ated 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.

              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 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 pre‐
              scribed 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 ver‐
       sion 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 argu‐

       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)

       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.

Linux                                       2014-08-19                                  UNLINK(2)

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