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

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.\"     @(#)mknod.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: April 1 2013 $
.Dt MKNOD 2
.Os
.Sh NAME
.Nm mknod ,
.Nm mknodat
.Nd make a special file node
.Sh SYNOPSIS
.Fd #include <sys/stat.h>
.Ft int
.Fn mknod "const char *path" "mode_t mode" "dev_t dev"
.Fd #include <sys/stat.h>
.Fd #include <fcntl.h>
.Ft int
.Fn mknodat "int fd" "const char *path" "mode_t mode" "dev_t dev"
.Sh DESCRIPTION
The device special file
.Fa path
is created with the major and minor
device numbers extracted from
.Fa mode .
The access permissions of
.Fa path
are descendant from the
.Xr umask 2
of the parent process.
.Pp
If
.Fa mode
indicates a block or character special file,
.Fa dev
is a configuration dependent specification of a character or block
I/O device and the superblock of the device.
If
.Fa mode
does not indicate a block special or character special device,
.Fa dev
is ignored.
.Pp
.Fn mknod
requires superuser privileges.
.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 .
.Sh RETURN VALUES
Upon successful completion a value of 0 is returned.
Otherwise, a value of \-1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn mknod
and
.Fn mknodat
will fail and the file will be not created 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 path name exceeded
.Dv {PATH_MAX}
characters.
.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
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 stat 2 ,
.Xr umask 2
.Sh STANDARDS
The
.Fn mknod
and
.Fn mknodat
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
A
.Fn mknod
function call appeared in
.At v6 .
The
.Fn mknodat
function appeared in
.Ox 5.0 .