path: root/lib/libc/sys/mknod.2

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.\"     @(#)mknod.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: September 10 2015 $
.Dt MKNOD 2
.Os
.Sh NAME
.Nm mknod ,
.Nm mknodat
.Nd make a special file node
.Sh SYNOPSIS
.In sys/stat.h
.Ft int
.Fn mknod "const char *path" "mode_t mode" "dev_t dev"
.In sys/stat.h
.In fcntl.h
.Ft int
.Fn mknodat "int fd" "const char *path" "mode_t mode" "dev_t dev"
.Sh DESCRIPTION
The
.Fn mknod
function creates
.Fa path
with a file type and mode of
.Fa mode ,
as modified by
.Xr umask 2 .
Only FIFO and device special files are supported by this implementation.
.Pp
If
.Fa mode
is the bitwise OR of
.Dv S_IFIFO
and zero or more file permissions, and
.Fa dev
is zero, then a FIFO is created.
If
.Fa mode
is the bitwise OR of
.Dv S_IFCHR
or
.Dv S_IFBLK
and zero or more file permissions, then a character or block device
special (respectively) is created with major and minor device numbers
extracted from
.Fa dev .
.Pp
The
.Fn mknodat
function is equivalent to
.Fn mknod
except that where
.Fa path
specifies a relative path,
the newly created device special file is created relative to
the directory associated with file descriptor
.Fa fd
instead of the current working directory.
.Pp
If
.Fn mknodat
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 mknod .
.Pp
Creating a device special file with
.Fn mknod
or
.Fn mknodat
requires superuser privileges.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Fn mknod
and
.Fn mknodat
will fail and the file will be not created if:
.Bl -tag -width Er
.It Bq Er EINVAL
.Fa mode
is an invalid file type or
.Fa dev
is an invalid value for that file type.
.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
A component of the path prefix does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EPERM
.Fa mode
is a device special and the process's effective user ID is not superuser.
.It Bq Er EIO
An I/O error occurred while making the directory entry or allocating the inode.
.It Bq Er ENOSPC
The directory in which the entry for the new node is being placed
cannot be extended because there is no space left on the file
system containing the directory.
.It Bq Er ENOSPC
There are no free inodes on the file system on which the
node is being created.
.It Bq Er EDQUOT
The directory in which the entry for the new node
is being placed cannot be extended because the
user's quota of disk blocks on the file system
containing the directory has been exhausted.
.It Bq Er EDQUOT
The user's quota of inodes on the file system on
which the node is being created has been exhausted.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EEXIST
The named file exists.
.It Bq Er EFAULT
.Fa path
points outside the process's allocated address space.
.It Bq Er EINVAL
The process is running within an alternate root directory, as
created by
.Xr chroot 2 .
.El
.Pp
Additionally,
.Fn mknodat
will fail if:
.Bl -tag -width Er
.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 chmod 2 ,
.Xr chroot 2 ,
.Xr mkfifo 2 ,
.Xr stat 2 ,
.Xr umask 2
.Sh STANDARDS
The
.Fn mknod
and
.Fn mknodat
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn mknod
system call first appeared in
.At v4 ,
and
.Fn mknodat
has been available since
.Ox 5.0 .