unlink(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON

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

NAME         top

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

SYNOPSIS         top

       #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         top

       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         top

       On success, zero is returned.  On error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

       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).

       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         top

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

CONFORMING TO         top

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

       unlinkat(): POSIX.1-2008.

NOTES         top

   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         top

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

SEE ALSO         top

       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         top

       This page is part of release 5.13 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/.

Linux                          2021-08-27                      UNLINK(2)

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