mknod(2) -- Linux man page
NAME
mknod - create a special or ordinary file
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int mknod(const char *pathname, mode_t mode, dev_t dev);
DESCRIPTION
The system call
mknod
creates a filesystem node (file, device special file or
named pipe) named
pathname,
with attributes specified by
mode
and
dev.
The
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 process's
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,
respectively.
(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.
If
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 uid 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 gid of the process.
RETURN VALUE
mknod
returns zero on success, or -1 if an error occurred (in which case,
errno
is set appropriately).
ERRORS
- EPERM
-
mode
requested creation of something other than a regular file,
FIFO (named pipe), or Unix domain socket, and the caller
is not the superuser; also returned if the filesystem
containing
pathname
does not support the type of node requested.
- EINVAL
-
mode
requested creation of something other than a normal file, device
special file, FIFO or socket.
- EEXIST
-
pathname
already exists.
- EFAULT
-
pathname points outside your accessible address space.
- EACCES
-
The parent directory does not allow write permission to the process,
or one of the directories in
pathname
did not allow search (execute) permission.
- ENAMETOOLONG
-
pathname was too long.
- ENOENT
-
A directory component in
pathname
does not exist or is a dangling symbolic link.
- ENOTDIR
-
A component used as a directory in
pathname
is not, in fact, a directory.
- ENOMEM
-
Insufficient kernel memory was available.
- EROFS
-
pathname
refers to a file on a read-only filesystem.
- ELOOP
-
Too many symbolic links were encountered in resolving
pathname.
- ENOSPC
-
The device containing
pathname
has no room for the new node.
CONFORMING TO
SVr4 (but the call requires privilege and is thus not in POSIX),
4.4BSD. The Linux version differs from the SVr4 version in that it
does not require root permission to create pipes, also in that no
EMULTIHOP, ENOLINK, or EINTR error is documented.
NOTES
POSIX 1003.1-2001 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
mkdir,
and FIFOs with
mkfifo.
There are many infelicities in the protocol underlying NFS. Some
of these affect
mknod.
SEE ALSO
fcntl(2),
mkdir(2),
mount(2),
socket(2),
stat(2),
umask(2),
unlink(2),
mkfifo(3)
|
