MKNOD(2) | System Calls Manual | MKNOD(2)

# NAME

`mknod`, `mknodat` — make a special file node

# 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

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 created 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 behavior is identical to a call to `mknod`().

Creating a device special file with `mknod`() or `mknodat`() requires superuser privileges.

# RETURN VALUES

Upon successful completion, the value 0 is returned; 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:

[`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` characters, 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 path prefix.
[`ELOOP`]
  Too many symbolic links were encountered in translating 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 directory.
[`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 space.
[`EINVAL`]
  The process is running within an alternate root directory, 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 descriptor.
[`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.

# SEE ALSO

chmod(2), chroot(2), mkfifo(2), stat(2), umask(2)

# STANDARDS

The `mknod`() and `mknodat`() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

# HISTORY

The `mknod`() system call first appeared in Version 4 AT&T UNIX, and `mknodat`() has been available since OpenBSD 5.0.

September 10, 2015 | Debian