mknod — create a special or ordinary file
#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); |
![]() |
Note | ||
|---|---|---|---|
|
The system call mknod()
creates a file system 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 regular 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
(makedev(3) may be useful to
build the value for dev); 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 user ID of the process. If the directory containing the node has the set-group-ID bit set, or if the file system 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. (See also path_resolution(7).)
pathname
already exists. This includes the case where pathname is a symbolic
link, dangling or not.
pathname
points outside your accessible address space.
mode
requested creation of something other than a regular
file, device special file, FIFO or socket.
Too many symbolic links were encountered in
resolving pathname.
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
CAP_MKNOD capability);
also returned if the file system containing pathname does not support
the type of node requested.
pathname
refers to a file on a read-only file system.
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."
However, nowadays one should never use mknod() for this purpose; one should use
mkfifo(3), a function
especially defined for this purpose.
Under Linux, this call cannot be used to create directories. One should make directories with mkdir(2).
There are many infelicities in the protocol underlying
NFS. Some of these affect mknod().
chmod(2), chown(2), fcntl(2), mkdir(2), mknodat(2), mount(2), socket(2), stat(2), umask(2), unlink(2), makedev(3), mkfifo(3), path_resolution(7)
This page is part of release 3.29 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
This manpage is Copyright (C) 1992 Drew Eckhardt; 1993 Michael Haardt 1993,1994 Ian Jackson. You may distribute it under the terms of the GNU General Public License. It comes with NO WARRANTY. Modified 1996-08-18 by urs Modified 2003-04-23 by Michael Kerrisk Modified 2004-06-23 by Michael Kerrisk <mtk.manpagesgmail.com> |