MKNOD(2) System Calls Manual MKNOD(2)

mknod, mknodat — make a special file node

#include <sys/stat.h>

int
mknod(const char *path, mode_t mode, dev_t dev);

int
mknodat(int fd, const char *path, mode_t mode, dev_t dev);

The device special file path is created with the major and minor device numbers extracted from mode. The access permissions of path are constrained by the umask(2) of the parent process.

If mode indicates a block or character special file, dev is a configuration-dependent specification of a character or block I/O device and the superblock of the device. If mode does not indicate a block special or character special device, dev is ignored.

() requires super-user privileges.

The () system call is equivalent to mknod() except in the case where path specifies a relative path. In this case the newly created fifo file is created relative to the directory associated with the file descriptor fd instead of the current working directory. If mknodat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the behavior is identical to a call to mknod().

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

mknod() will fail and the file will be not created if:

[]
Search permission is denied for a component of the path prefix.
[]
Write permission is denied for the parent directory.
[]
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.
[]
The user's quota of inodes for the file system on which the node is being created has been exhausted.
[]
The named file exists.
[]
Path points outside the process's allocated address space.
[]
One or more of the arguments is invalid.
[]
An I/O error occurs while making the directory entry or allocating the inode.
[]
Too many symbolic links were encountered in translating the pathname. This is taken to be indicative of a looping symbolic link.
[]
A component of a pathname exceeds {NAME_MAX} characters or an entire path name exceeds {PATH_MAX} characters.
[]
A component of the path prefix does not exist or path is an empty string.
[]
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.
[]
There are no free inodes on the file system on which the node is being created.
[]
A component of the path prefix is not a directory.
[]
The process's effective user ID is not super-user.
[]
The created node would reside on a read-only file system.

In addition to the errors returned by the mknod(), the mknodat() function may fail if:

[]
The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
[]
The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

#include <unistd.h>

The include file has changed.

chmod(2), stat(2), umask(2), compat(5)

A mknod() function call appeared in Version 6 AT&T UNIX. The mknodat() system call appeared in macOS 13.0.

June 4, 1993 BSD 4