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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) 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().  Cur-
     rently, 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_reso-
            lution(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  path-
            name.

     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  speci-
            fied 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 sym-
     bolic 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.