mknodat(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():
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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 file mode 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 zero or more of the file mode bits listed in stat(2). The file mode is modified by the process's umask in the usual way: in the absence of a default ACL, 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 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. mknodat() The mknodat() system call operates in exactly the same way as mknod(), 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() 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()). 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 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).)
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
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 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 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, 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
mknod(1), chmod(2), chown(2), fcntl(2), mkdir(2), mount(2), socket(2), stat(2), umask(2), unlink(2), makedev(3), mkfifo(3), acl(5) path_resolution(7)
COLOPHON
This page is part of release 4.09 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 https://www.kernel.org/doc/man-pages/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
