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MKNOD(2)		   Linux Programmer's Manual		      MKNOD(2)

NAME
       mknod, mknodat -	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);

       #include	<fcntl.h>	    /* Definition of AT_* constants */
       #include	<sys/stat.h>

       int mknodat(int dirfd, 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 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 regular file (which will be created empty), char-
       acter special file, block special file, FIFO (named pipe), or UNIX  do-
       main  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 filesystem is mounted with BSD group semantics, the new
       node will inherit the group ownership from its parent directory;	other-
       wise it will be owned by	the effective group ID of the process.

   mknodat()
       The mknodat() system call operates in exactly the same way as mknod(2),
       except for the differences described here.

       If the pathname given in	pathname is relative, then it  is  interpreted
       relative	 to  the  directory  referred  to by the file descriptor dirfd
       (rather than relative to	the current working directory of  the  calling
       process,	as is done by mknod(2) for a relative pathname).

       If  pathname  is	relative and dirfd is the special value	AT_FDCWD, then
       pathname	is interpreted relative	to the current	working	 directory  of
       the calling process (like mknod(2)).

       If pathname is absolute,	then dirfd is ignored.

       See openat(2) for an explanation	of the need for	mknodat().

RETURN VALUE
       mknod()	and  mknodat()	return	zero on	success, or -1 if an error oc-
       curred (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 path-
	      name did not allow search	permission.   (See  also  path_resolu-
	      tion(7).)

       EDQUOT The  user's quota	of disk	blocks or inodes on the	filesystem has
	      been exhausted.

       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  dan-
	      gling 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 filesystem containing pathname does not support
	      the type of node requested.

       EROFS  pathname refers to a file	on a read-only filesystem.

       The following additional	errors can occur for mknodat():

       EBADF  dirfd is not a valid file	descriptor.

       ENOTDIR
	      pathname is relative and dirfd is	a file descriptor referring to
	      a	file other than	a directory.

VERSIONS
       mknodat()  was  added  to  Linux	 in kernel 2.6.16; library support was
       added to	glibc in version 2.4.

CONFORMING TO
       mknod():	SVr4, 4.4BSD, POSIX.1-2001 (but	see below), POSIX.1-2008.

       mknodat(): POSIX.1-2008.

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	behav-
       ior of mknod() is unspecified."	However, nowadays one should never use
       mknod()	for  this  purpose; one	should use mkfifo(3), a	function espe-
       cially defined for this purpose.

       Under Linux, mknod() 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() and	mknodat(2).

SEE ALSO
       chmod(2), chown(2), fcntl(2), mkdir(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 3.74 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2014-02-21			      MKNOD(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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