MKNOD(2) BSD System Calls Manual MKNOD(2)
mknod, mknodat -- make a special file node
mknod(const char *path, mode_t mode, dev_t dev);
mknodat(int fd, const char *path, mode_t mode, dev_t dev);
The mknod() function creates path with a file type and mode of mode, as
modified by umask(2). Only FIFO and device special files are supported
by this implementation.
If mode is the bitwise OR of S_IFIFO and zero or more file permissions,
and dev is zero, then a FIFO is created. If mode is the bitwise OR of
S_IFCHR or 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 dev.
The mknodat() function is equivalent to mknod() except that where path
specifies a relative path, the newly created device special file is cre-
ated relative to the directory associated with file descriptor fd instead
of the current working directory.
If mknodat() is passed the special value AT_FDCWD (defined in <fcntl.h>)
in the fd parameter, the current working directory is used and the behav-
ior is identical to a call to mknod().
Creating a device special file with mknod() or mknodat() requires supe-
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
mknod() and mknodat() will fail and the file will be not created if:
[EINVAL] mode is an invalid file type or dev is an invalid
value for that file type.
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded NAME_MAX charac-
ters, or an entire pathname (including the terminating
NUL) exceeded PATH_MAX bytes.
[ENOENT] A component of the path prefix does not exist.
[EACCES] Search permission is denied for a component of the
[ELOOP] Too many symbolic links were encountered in translat-
ing the pathname.
[EPERM] mode is a device special and the process's effective
user ID is not superuser.
[EIO] An I/O error occurred while making the directory entry
or allocating the inode.
[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 direc-
[ENOSPC] There are no free inodes on the file system on which
the node is being created.
[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.
[EDQUOT] The user's quota of inodes on the file system on which
the node is being created has been exhausted.
[EROFS] The named file resides on a read-only file system.
[EEXIST] The named file exists.
[EFAULT] path points outside the process's allocated address
[EINVAL] The process is running within an alternate root direc-
tory, as created by chroot(2).
Additionally, mknodat() will fail if:
[EBADF] The path argument specifies a relative path and the fd
argument is neither AT_FDCWD nor a valid file descrip-
[ENOTDIR] The path argument specifies a relative path and the fd
argument is a valid file descriptor but it does not
reference a directory.
[EACCES] The path argument specifies a relative path but search
permission is denied for the directory which the fd
file descriptor references.
chmod(2), chroot(2), mkfifo(2), stat(2), umask(2)
The mknod() and mknodat() functions conform to IEEE Std 1003.1-2008
The mknod() system call first appeared in Version 4 AT&T UNIX, and
mknodat() has been available since OpenBSD 5.0.
BSD April 28, 2017 BSD