MKNOD
Section: Linux Programmer's Manual (2)
Updated: 2010-09-20
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);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
mknod():
-
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
DESCRIPTION
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.
RETURN VALUE
mknod()
returns zero on success, or -1 if an error occurred (in which case,
errno
is set appropriately).
ERRORS
- EACCES
-
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).)
- EEXIST
-
pathname
already exists.
This includes the case where
pathname
is a symbolic link, dangling or not.
- EFAULT
-
pathname points outside your accessible address space.
- EINVAL
-
mode
requested creation of something other than a regular file, device
special file, FIFO or socket.
- ELOOP
-
Too many symbolic links were encountered in resolving
pathname.
- ENAMETOOLONG
-
pathname was too long.
- ENOENT
-
A directory component in
pathname
does not exist or is a dangling symbolic link.
- ENOMEM
-
Insufficient kernel memory was available.
- ENOSPC
-
The device containing
pathname
has no room for the new node.
- ENOTDIR
-
A component used as a directory in
pathname
is not, in fact, a directory.
- EPERM
-
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.
- EROFS
-
pathname
refers to a file on a read-only file system.
CONFORMING TO
SVr4, 4.4BSD, POSIX.1-2001 (but see below).
NOTES
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().
SEE ALSO
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)
COLOPHON
This page is part of release 3.27 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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Time: 07:34:56 GMT, March 26, 2013