.\"	$NetBSD: mknod.2,v 1.6 1995/02/27 12:34:33 cgd Exp $
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.\"     @(#)mknod.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt MKNOD 2
.Os BSD 4
.Sh NAME
.Nm mknod ,
.Nm mknodat
.Nd make a special file node
.Sh SYNOPSIS
.Fd #include <sys/stat.h>
.Ft int
.Fo mknod
.Fa "const char *path"
.Fa "mode_t mode"
.Fa "dev_t dev"
.Fc
.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 constrained by 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 super-user privileges.
.Pp
The
.Fn mknodat
system call is equivalent to
.Fn mknod
except in the case where
.Fa path
specifies a relative path.
In this case the newly created fifo file is created relative to the
directory associated with the file descriptor
.Fa fd
instead of the current working directory.
If
.Fn mknodat
is passed the special value
.Dv AT_FDCWD
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
will fail and the file will be not created if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ==========
.It Bq Er EACCES
Write permission is denied for the parent directory.
.\" ==========
.It Bq Er EDQUOT
The directory in which the entry for the new node
is being placed cannot be extended;
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 for the file system
on which the node is being created has been exhausted.
.\" ==========
.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
One or more of the arguments is invalid.
.\" ==========
.It Bq Er EIO
An I/O error occurs while making the directory entry
or allocating the inode.
.\" ==========
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
.\" ==========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeds 
.Dv {NAME_MAX}
characters or an entire path name exceeds 
.Dv {PATH_MAX}
characters.
.\" ==========
.It Bq Er ENOENT
A component of the path prefix does not exist
or path is an empty string.
.\" ==========
.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 ENOTDIR
A component of the path prefix is not a directory.
.\" ==========
.It Bq Er EPERM
The process's effective user ID is not super-user.
.\" ==========
.It Bq Er EROFS
The created node would reside on a read-only file system.
.El
.Pp
In addition to the errors returned by the
.Fn mknod ,
the
.Fn mknodat
function may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.El
.Sh LEGACY SYNOPSIS
.Fd #include <unistd.h>
.Pp
The include file has changed.
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr stat 2 ,
.Xr umask 2 ,
.Xr compat 5
.Sh HISTORY
A
.Fn mknod
function call appeared in 
.At v6 .
The
.Fn mknodat
system call appeared in macOS 13.0.