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Name

mknod - make a directory, or a special or ordinary file

Synopsis


#include <sys/types.h>
#include <sys/stat.h>

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

Description

mknod() 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_IFIFOfifo special
S_IFCHRcharacter special
S_IFDIRdirectory
S_IFBLKblock special
S_IFREGordinary file

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

S_ISUID04000Set user ID on execution.
S_ISGID020#0Set group ID on execution if # is 7, 5, 3, or 1.
Enable mandatory file/record locking if # is 6, 4, 2, or 0.
S_ISVTX01000Save text image after execution.
S_IRWXU00700Read, write, execute by owner.
S_IRUSR00400Read by owner.
S_IWUSR00200Write by owner.
S_IXUSR00100Execute (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_IRWXO00007Read, 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 ID s, 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) .

mknod() may be invoked only by a privileged user for file types other than FIFO special.

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

Return Values

0 is returned upon successful completion; otherwise, -1 is returned and errno is set to indicate the error.

Errors

mknod() fails and creates no new file if one or more of the following are true:

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.
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
path points to an illegal address.
EINTR
A signal was caught during the mknod() function.
EINVAL
dev is invalid.
ELOOP
Too many symbolic links were encountered in translating path.
EMULTIHOP
Components of path require hopping to multiple remote machines and the file system type does not allow it.
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 does not exist or is a null pathname.
ENOLINK
path points to a remote machine and the link to that machine is no longer active.
ENOSPC
No space is available.
ENOTDIR
A component of the path prefix is not a directory.
EPERM
The effective user of the calling process is not super-user.
EROFS
The directory in which the file is to be created is located on a read-only file system.

See Also

chmod(2) , exec(2) , mkdir(2) , umask(2) , makedev(3C) , mkfifo(3C) , stat(5)

Notes

Normally, applications should use the mkdir(2) routine to make a directory, since the function mknod() may not establish directory entries for . (the directory itself)
and .. (the parent directory), and appropriate permissions are not required. Similarly, mkfifo(3C) should be used in preference to mknod() in order to create FIFO s.

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