Content-type: text/html Man page of mknod


Section: System Calls (2)
Updated: 19 Feb 2004
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mknod - 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);  


The mknod() 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 fifo special

S_IFCHR character special

S_IFDIR directory

S_IFBLK block special

S_IFREG ordinary file

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_ISUID04000Set user ID on execution.
S_ISGID020#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_ISVTX01000 On directories, restricted deletion flag; on regular files on a UFS file system, do not cache flag.
S_IRWXU00700Read, write, execute by owner.
S_IRUSR00400Read by owner.
S_IWUSR00200Write by owner.
S_IXUSR00100 Execute (search if a directory) by owner.
S_IRWXG00070Read, write, execute by group.
S_IRGRP00040Read by group.
S_IWGRP00020Write by group.
S_IXGRP00010Execute by group.
S_IRWXO00007 Read, write, execute (search) by others.
S_IROTH00004Read by others.
S_IWOTH00002Write by others
S_IXOTH00001Execute 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.  


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


The mknod() function will fail if:

EACCES A component of the path prefix denies search permission, or write permission is denied on the parent directory.

EDQUOT The directory where the new file entry is being placed cannot be extended because the user's quota of disk blocks on that file system has been exhausted, or the user's quota of inodes on the file system where the file is being created has been exhausted.

EEXIST The named file exists.

EFAULT The path argument points to an illegal address.

EINTR A signal was caught during the execution of the mknod() function.

EINVAL An invalid argument exists.

EIO An I/O error occurred while accessing the file system.

ELOOP Too many symbolic links were encountered in translating path.

ENAMETOOLONG The length of the path argument exceeds {PATH_MAX}, or the length of a path component exceeds {NAME_MAX} while _POSIX_NO_TRUNC is in effect.

ENOENT A component of the path prefix specified by path does not name an existing directory or path is an empty string.

ENOLINK The path argument points to a remote machine and the link to that machine is no longer active.

ENOSPC The directory that would contain the new file cannot be extended or the file system is out of file allocation resources.

ENOTDIR A component of the path prefix is not a directory.

EPERM Not all privileges are asserted in the effective set of the calling process.

EROFS The directory in which the file is to be created is located on a read-only file system.

The mknod() function may fail if:

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



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(3DOOR) 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:

Interface StabilityStandard



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




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Time: 02:37:16 GMT, October 02, 2010