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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) ex‐
       cept 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 to indicate the error.

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 soft‐
              ware 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  pathname is relative but dirfd is neither AT_FDCWD nor 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  path‐
       name, 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)

Linux                                                                          2021-08-27                                                                      UNLINK(2)