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Manual page for mknod(2)

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_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 an OR 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   Save text image  after execution.
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

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.

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 FIFOs.