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.\"     @(#)unlink.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: June 30 2021 $
.Dt UNLINK 2
.Os
.Sh NAME
.Nm unlink ,
.Nm unlinkat
.Nd remove directory entry
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn unlink "const char *path"
.In fcntl.h
.In unistd.h
.Ft int
.Fn unlinkat "int fd" "const char *path" "int flag"
.Sh DESCRIPTION
The
.Fn unlink
function removes the link named by
.Fa path
from its directory and decrements the link count of the
file which was referenced by the link.
If that decrement reduces the link count of the file
to zero,
and no process has the file open, then
all resources associated with the file are reclaimed.
If one or more processes have the file open when the last link is removed,
the link is removed, but the removal of the file is delayed until
all references to it have been closed.
.Pp
The
.Fn unlinkat
function is equivalent to either the
.Fn unlink
or
.Xr rmdir 2
function depending on the value of
.Fa flag
(see below), except that where
.Fa path
specifies a relative path,
the directory entry to be removed is determined relative to
the directory associated with file descriptor
.Fa fd
instead of the current working directory.
.Pp
If
.Fn unlinkat
is passed the special value
.Dv AT_FDCWD
(defined in
.In fcntl.h )
in the
.Fa fd
parameter, the current working directory is used
and the behavior is identical to a call to
.Fn unlink
or
.Xr rmdir 2 ,
depending on whether or not the
.Dv AT_REMOVEDIR
bit is set in
.Fa flag .
.Pp
The
.Fa flag
argument is the bitwise OR of zero or more of the following values:
.Pp
.Bl -tag -width AT_REMOVEDIR -offset indent -compact
.It Dv AT_REMOVEDIR
Remove the directory entry specified by
.Fa path
as a directory, not a normal file.
.El
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn unlink
and
.Fn unlinkat
functions will fail if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded
.Dv NAME_MAX
characters, or an entire pathname (including the terminating NUL)
exceeded
.Dv PATH_MAX
bytes.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er EACCES
Write permission is denied on the directory containing the link
to be removed.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EPERM
The named file is a directory and the effective user ID
of the process is not the superuser, or the file system
containing the file does not permit the use of
.Fn unlink
on a directory.
.It Bq Er EPERM
The directory containing the file is marked sticky,
and neither the containing directory nor the file to be removed
are owned by the effective user ID.
.It Bq Er EPERM
The named file or the directory containing it has its immutable or
append-only flag set (see
.Xr chflags 2 ) .
.It Bq Er EBUSY
The entry to be unlinked is the mount point for a
mounted file system.
.It Bq Er EIO
An I/O error occurred while deleting the directory entry
or deallocating the inode.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EFAULT
.Fa path
points outside the process's allocated address space.
.El
.Pp
Additionally,
.Fn unlinkat
will fail if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
The
.Dv AT_REMOVEDIR
flag bit is set and
.Fa path
does not name a directory.
.It Bq Er ENOTEMPTY
The
.Dv AT_REMOVEDIR
flag bit is set and the named directory contains files other than
.Ql \&.
and
.Ql \&..
in it.
.It Bq Er EINVAL
The value of the
.Fa flag
argument was neither zero nor
.Dv AT_REMOVEDIR .
.It Bq Er EINVAL
The value of the
.Fa flag
argument was
.Dv AT_REMOVEDIR
and the last element of
.Fa path
consists of
.Ql \&. .
.It Bq Er EBADF
The
.Fa path
argument specifies a relative path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor.
.It Bq Er ENOTDIR
The
.Fa path
argument specifies a relative path and the
.Fa fd
argument is a valid file descriptor but it does not reference a directory.
.It Bq Er EACCES
The
.Fa path
argument specifies a relative path but search permission is denied
for the directory which the
.Fa fd
file descriptor references.
.El
.Sh SEE ALSO
.Xr rm 1 ,
.Xr chflags 2 ,
.Xr close 2 ,
.Xr link 2 ,
.Xr rmdir 2 ,
.Xr symlink 7
.Sh STANDARDS
The
.Fn unlink
and
.Fn unlinkat
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn unlink
system call first appeared in
.At v1 .
The
.Fn unlinkat
function appeared in
.Ox 5.0 .