libc/sys/mknod.2

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.\"     @(#)mknod.2	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/sys/mknod.2,v 1.18 2008/04/16 13:03:12 kib Exp $
.\"
.Dd July 7, 2021
.Dt MKNOD 2
.Os
.Sh NAME
.Nm mknod ,
.Nm mknodat
.Nd make a special file node
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/stat.h
.Ft int
.Fn mknod "const char *path" "mode_t mode" "dev_t dev"
.Ft int
.Fn mknodat "int fd" "const char *path" "mode_t mode" "dev_t dev"
.Sh DESCRIPTION
The file system node
.Fa path
is created with the file type and access permissions specified in
.Fa mode .
The access permissions are modified by the process's umask value.
.Pp
If
.Fa mode
is
.Dv S_IFIFO ,
.Fn mknod
and
.Fn mknodat
are equivalent to
.Fn mkfifo
and
.Fn mkfifoat .
If
.Fa mode
indicates a block or character special file,
.Fa dev
is a configuration dependent specification denoting a particular device
on the system.
Otherwise,
.Fa dev
is ignored.
.Pp
The
.Fn mknod
system call
requires super-user privileges except when creating a new fifo.
See
.Xr mkfifo 2
for more information.
.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 device node 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
.Rv -std mknod
.Sh ERRORS
The
.Fn mknod
system call
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 255 characters,
or an entire path name exceeded 1023 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 super-user.
.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
The
.Fa path
argument
points outside the process's allocated address space.
.It Bq Er EINVAL
Creating anything else than a block or character special
file (or a
.Em whiteout )
is not supported.
.El
.Pp
In addition to the errors returned by the
.Fn mknod ,
the
.Fn mknodat
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 SEE ALSO
.Xr chmod 2 ,
.Xr mkfifo 2 ,
.Xr stat 2 ,
.Xr umask 2
.Sh STANDARDS
The
.Fn mknodat
system call follows The Open Group Extended API Set 2 specification.
.Sh HISTORY
The
.Fn mknod
function appeared in
.At v4 .
The
.Fn mknodat
system call appeared in
.Dx 2.7 .