mknod() - Unix, Linux System Call
mknod - create a special or ordinary file
int mknod(const char *pathname, mode_t mode, dev_t dev);
The system call
mknod() creates a filesystem node (file, device special file or
named pipe) named
pathname, with attributes specified by
mode argument specifies both the permissions to use and the type of node
to be created.
It should be a combination (using bitwise OR) of one of the file types
listed below and the permissions for the new node.
The permissions are modified by the processs
umask in the usual way: the permissions of the created node are
(mode & ~umask).
The file type must be one of
S_IFREG, S_IFCHR, S_IFBLK, S_IFIFO or
S_IFSOCK to specify a normal file (which will be created empty), character
special file, block special file, FIFO (named pipe), or Unix domain socket,
(Zero file type is equivalent to type S_IFREG.)
If the file type is
S_IFCHR or S_IFBLK then
dev specifies the major and minor numbers of the newly created device
special file; otherwise it is ignored.
pathname already exists, or is a symbolic link, this call fails with an EEXIST error.
The newly created node will be owned by the effective user ID of the
process. If the directory containing the node has the set-group-ID
bit set, or if the filesystem is mounted with BSD group semantics, the
new node will inherit the group ownership from its parent directory;
otherwise it will be owned by the effective group ID of the process.
mknod() returns zero on success, or -1 if an error occurred (in which case,
errno is set appropriately).
The parent directory does not allow write permission to the process,
or one of the directories in the path prefix of
pathname did not allow search permission.
pathname already exists.
pathname points outside your accessible address space. |
mode requested creation of something other than a normal file, device
special file, FIFO or socket.
Too many symbolic links were encountered in resolving
pathname was too long. |
A directory component in
pathname does not exist or is a dangling symbolic link.
Insufficient kernel memory was available.
The device containing
pathname has no room for the new node.
A component used as a directory in
pathname is not, in fact, a directory.
mode requested creation of something other than a regular file,
FIFO (named pipe), or Unix domain socket, and the caller
is not privileged (Linux: does not have the
also returned if the filesystem containing
pathname does not support the type of node requested.
pathname refers to a file on a read-only filesystem.
SVr4, 4.4BSD, POSIX.1-2001 (but see below).
POSIX.1-2001 says: "The only portable use of
mknod() is to create a FIFO-special file. If
mode is not S_IFIFO or
dev is not 0, the behavior of
mknod() is unspecified."
Under Linux, this call cannot be used to create directories.
One should make directories with
and FIFOs with
There are many infelicities in the protocol underlying NFS. Some
of these affect