mknod()

NAME

mknod() - create a regular file, special file, or directory

SYNOPSIS

#include <sys/stat.h>


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

DESCRIPTION

The mknod(2) function creates a new file named by the path name to which the argument path points.

The file type for path is OR-ed into the mode argument, and must be selected from one of the following symbolic constants:

Name	Description
S_IFIFO	FIFO-special
S_IFCHR	Character-special
S_IFDIR	Directory
S_IFBLK	Block-special
S_IFREG	Regular

The permissions for the new file are OR-ed into the mode argument, and may be selected from any combination of the following symbolic constants:

Name	Description
S_ISUID	Set user ID on execution.
S_ISGID	Set group ID on execution.
S_IRWXU	Read, write or execute (search) by owner.
S_IRUSR	Read by owner.
S_IWUSR	Write by owner.
S_IXUSR	Execute (search) by owner.
S_IRWXG	Read, write or execute (search) by group.
S_IRGRP	Read by group.
S_IWGRP	Write by group.
S_IXGRP	Execute (search) by group.
S_IRWXO	Read, write or execute (search) by others.
S_IROTH	Read by others.
S_IWOTH	Write by others.
S_IXOTH	Execute (search) by others.
S_ISVTX	On directories, restricted deletion flag.

The dev argument is a 32-bit integer that identifies the device. It is constructed using the mkdev() macro using the following syntax:

mkdev(major, minor)

The minor argument is the ordinal number of the device, if more than one device of the specified type is present. The major argument specifies the device type, and must be one of the following values:

Device Type	Value	Path
tty-type devices
S_DEV_TTY	1	/dev/ttyn[00-63]
S_DEV_CONSOLE	2	/dev/console
S_DEV_CTRL_TTY	3	/dev/tty
S_DEV_PTM	4	/dev/ptynn [p0-Ef]
S_DEV_PTS	5	/dev/ttynn [p0-Ef]
S_DEV_PTMX	6	/dev/ptmx
S_DEV_SERIAL	7	/dev/ttynn [00-1f]
Stream-type devices
S_DEV_TAPE	17	/dev/tapen
S_DEV_PIPE	18	User created FIFO
S_DEV_SOCKET	19	User created socket
S_DEV_XTI	20	User created
Char/block special file types
S_DEV_NULL	48	/dev/null
S_DEV_ZERO	49	/dev/zero
S_DEV_RANDOM	50	/dev/random
S_DEV_FULL	51	/dev/full

In the case of tape drives, a bit (0x100) is set to indicate that the device does not rewind when it is closed and is cleared to indicate that the drive rewinds when closed. To set this bit, use the bitwise-OR operation when calling mkdev(), as shown:

mkdev(S_DEV_TAPE, 0x100 | minor)

The dev argument is used only when S_IFCHR or S_IFBLK is set in mode; otherwise, it should be set to 0.

The user ID of the file is initialized to the effective user ID of the process. The group ID of the file is initialized to either the effective group ID of the process or the group ID of the parent directory.

The owner, group, and other permission bits of mode are modified by the file mode creation mask of the process. The mknod(2) function clears each bit whose corresponding bit in the file mode creation mask of the process is set.

Upon successful completion, mknod(2) marks for update the st_atime, st_ctime and st_mtime fields of the file. Also, the st_ctime and st_mtime fields of the directory that contains the new entry are marked for update.

Upon successful completion, mknod(2) returns 0. Otherwise, it returns -1, the new file is not created, and errno is set to indicate the error.

You must be logged on as a member of the Administrators group to call mknod(2), otherwise the utility returns -1 and sets errno to [EPERM].

Interix recognizes the files created by mknod(2) as unique. Superficially identical files created through means other than mknod(1), mknod(2), and makedev(1) (for example, through backup and restore) will not be treated as device files by Interix, and attempts to open devices through such files with fail with the error code ENXIO.

RETURN VALUES

ERRORS

The mknod(2) function will fail if:

[EPERM]: The invoking process does not have appropriate privileges and the file type is not FIFO-special.
[ENOTDIR]: A component of the path prefix is not a directory.
[ENOENT]: A component of the path prefix specified by path does not name an existing directory or path is an empty string.
[EACCES]: A component of the path prefix denies search permission, or write permission is denied on the parent directory.
[EROFS]: The directory in which the file is to be created is located on a read-only file system.
[EEXIST]: The named file exists.
[EIO]: An I/O error occurred while accessing the file system.
[EINVAL]: An invalid argument exists.
[ENOSPC]: The directory that would contain the new file cannot be extended or the file system is out of file allocation resources.
[ELOOP]: Too many symbolic links were encountered in resolving path.
[ENAMETOOLONG]: The length of a pathname exceeds {PATH_MAX}, or pathname component is longer than {NAME_MAX}.
[EFTYPE]: The target file system cannot securely contain a device special file.

The mknod(2) function may fail if:

[ENAMETOOLONG]: Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.

APPLICATION USAGE

For portability to implementations conforming to earlier versions of this specification, mkfifo(2) is preferred over this function for making FIFO special files.

NOTE

Although it is possible to create device special files on a FAT file system, the Interix subsystem honors these files only if they are located in the /dev directory, which will only happen when Windows Services for UNIX is installed on a FAT partition. The open(2) function will generate an ENXIO error if it tries to open a device special file that is on a FAT partition but not in /dev.