NAME
mknod, mknodat
— make a special file
node
LIBRARY
library “libc”
SYNOPSIS
#include
<sys/stat.h>
int
mknod(const
char *path, mode_t
mode, dev_t
dev);
#include
<sys/stat.h>
#include <fcntl.h>
int
mknodat(int
fd, const char
*path, mode_t mode,
dev_t dev);
DESCRIPTION
mknod with S_IFIFO specified in
mode and 0 in dev makes a FIFO
file. This call is respectively a portable alias for
mkfifo(2) and
mkfifoat(2).
mknod with S_IFCHR
or S_IFBLK in mode makes a
device special file. The file path is created with the
major and minor device numbers specified by dev. The
access permissions of path are extracted from
mode, modified by the
umask(2) of the parent process.
mknodat()
works the same way as mknod() except if
path is relative. In that case, it is looked up from a
directory whose file descriptor was passed as fd.
Search permission is required on this directory. fd
can be set to AT_FDCWD in order to specify the
current directory.
mknod()
requires super-user privileges for creating device special files.
RETURN VALUES
The mknod() and
mknodat() functions return the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
ERRORS
mknod() and
mknodat() will fail and the file will be not created
if:
- [
EACCES] - Search permission is denied for a component of the path prefix.
- [
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; or the user's quota of inodes on the file system on which the node is being created has been exhausted.
- [
EEXIST] - The named file exists.
- [
EFAULT] - path points outside the process's allocated address space.
- [
EINVAL] - The supplied mode or dev is invalid.
- [
EIO] - An I/O error occurred while making the directory entry or allocating the inode.
- [
ELOOP] - Too many symbolic links were encountered in translating the pathname.
- [
ENAMETOOLONG] - A component of a pathname exceeded {
NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters. - [
ENOENT] - A component of the path prefix does not exist.
- [
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; or there are no free inodes on the file system on which the node is being created.
- [
ENOTDIR] - A component of the path prefix is not a directory.
- [
EOPNOTSUPP] - The kernel has not been configured to support FIFOs.
- [
EPERM] - The process's effective user ID is not super-user.
- [
EROFS] - The named file resides on a read-only file system.
In addition, mknodat() will fail if:
- [
EBADF] - path does not specify an absolute path and
fd is neither
AT_FDCWDnor a valid file descriptor open for reading or searching. - [
ENOTDIR] - path is not an absolute path and fd is a file descriptor associated with a non-directory file.
SEE ALSO
STANDARDS
The mknod() function conforms to
IEEE Std 1003.1-1990 (“POSIX.1”).
mknodat() conforms to IEEE Std
1003.1-2008 (“POSIX.1”).
HISTORY
A mknod() function call appeared in
Version 6 AT&T UNIX.
The alias mode for mkfifo(2) and mkfifoat(2) first appeared in NetBSD 9.