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mknod, mknodat - make a directory, a special file, or a regular file

#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 mknod() and mknodat() function creates a new file named by the path name pointed to by path. The file type and permissions of the new file are initialized from mode.

The file type is specified in mode by the S_IFMT bits, which must be set to one of the following values: S_IFIFO

S_IFCHR S_IFDIR S_IFBLK S_IFREG

The file access permissions are specified in mode by the 0007777 bits, and may be constructed by a bitwise OR operation of the following values:

S_ISUID 04000 Set user ID on execution.

S_ISGID 020#0

Set group ID on execution if # is 7, 5, 3, or 1. Enable mandatory file/record locking if # is 6, 4, 2, or 0

S_ISVTX 01000

On directories, restricted deletion flag; on regular files on a UFS file system, do not cache flag.

S_IRWXU 00700 Read, write, execute by owner.

S_IRUSR 00400 Read by owner.

S_IWUSR 00200 Write by owner.

S_IXUSR 00100

Execute (search if a directory) by owner.

S_IRWXG 00070 Read, write, execute by group.

S_IRGRP 00040 Read by group.

S_IWGRP 00020 Write by group.

S_IXGRP 00010 Execute by group.

S_IRWXO 00007 Read, write, execute (search) by others.

S_IROTH 00004 Read by others.

S_IWOTH 00002 Write by others

S_IXOTH 00001 Execute by others.

The owner ID of the file is set to the effective user ID of the process. The group ID of the file is set to the effective group ID of the process. However, if the S_ISGID bit is set in the parent directory, then the group ID of the file is inherited from the parent. If the group ID of the new file does not match the effective group ID or one of the supplementary group IDs, the S_ISGID bit is cleared.

The access permission bits of mode are modified by the process's file mode creation mask: all bits set in the process's file mode creation mask are cleared (see umask(2)). If mode indicates a block or character special file, dev is a configuration-dependent specification of a character or block I/O device. If mode does not indicate a block special or character special device, dev is ignored. See makedev(3C).

If path is a symbolic link, it is not followed.

The mknodat() function is similar to mknod(); however, when path is a relative path, it is resolved starting at the directory represented by the file descriptor fd. To start at the current working directory, fd may be set to the special value AT_FDCWD.

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

The mknod() and mknodat() functions will fail if: EACCES

EDQUOT EEXIST EFAULT EINTR EINVAL EIO ELOOP ENAMETOOLONG ENOENT ENOLINK ENOSPC ENOTDIR EPERM EROFS

The mknodat() function will fail if: EBADF

The mknod() function may fail if: ENAMETOOLONG

Applications should use the mkdir(2) function to create a directory because appropriate permissions are not required and because mknod() might not establish directory entries for the directory itself (.) and the parent directory (.\|.). The mknod() function can be invoked only by a privileged user for file types other than FIFO special. The mkfifo(3C) function should be used to create FIFOs.

Doors are created using door_create(3C) and can be attached to the file system using fattach(3C). Symbolic links can be created using symlink(2). An endpoint for communication can be created using socket(3SOCKET).

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE

Interface Stability Standard

MT-Level Async-Signal-Safe

chmod(2), creat(2), exec(2), mkdir(2), open(2), stat(2), symlink(2), umask(2), door_create(3C), fattach(3C), makedev(3C), mkfifo(3C), socket(3SOCKET), stat.h(3HEAD), attributes(5), privileges(5), standards(5)