mknod(2) - Linux manual page (original) (raw)
mknod(2) System Calls Manual mknod(2)
NAME top
mknod, mknodat - create a special or ordinary fileLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <sys/stat.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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEDESCRIPTION top
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 [inode(7)](../man7/inode.7.html).
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)](../man3/makedev.3.html) 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)](../man2/openat.2.html) for an explanation of the need for **mknodat**().RETURN VALUE top
**mknod**() and **mknodat**() return zero on success. On error, -1 is
returned and _[errno](../man3/errno.3.html)_ is set to indicate the error.ERRORS top
**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)](../man7/path%5Fresolution.7.html).)
**EBADF** (**mknodat**()) _pathname_ is relative but _dirfd_ is neither
**AT_FDCWD** nor a valid file descriptor.
**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.
**ENOTDIR**
(**mknodat**()) _pathname_ is relative and _dirfd_ is a file
descriptor referring to a file other than 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.VERSIONS top
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)](../man3/mkfifo.3.html), a
function especially defined for this purpose.
Under Linux, **mknod**() cannot be used to create directories. One
should make directories with [mkdir(2)](../man2/mkdir.2.html).STANDARDS top
POSIX.1-2008.HISTORY top
**mknod**()
SVr4, 4.4BSD, POSIX.1-2001 (but see VERSIONS).
**mknodat**()
Linux 2.6.16, glibc 2.4. POSIX.1-2008.NOTES top
There are many infelicities in the protocol underlying NFS. Some
of these affect **mknod**() and **mknodat**().SEE ALSO top
[mknod(1)](../man1/mknod.1.html), [chmod(2)](../man2/chmod.2.html), [chown(2)](../man2/chown.2.html), [fcntl(2)](../man2/fcntl.2.html), [mkdir(2)](../man2/mkdir.2.html), [mount(2)](../man2/mount.2.html),
[socket(2)](../man2/socket.2.html), [stat(2)](../man2/stat.2.html), [umask(2)](../man2/umask.2.html), [unlink(2)](../man2/unlink.2.html), [makedev(3)](../man3/makedev.3.html), [mkfifo(3)](../man3/mkfifo.3.html),
[acl(5)](../man5/acl.5.html), [path_resolution(7)](../man7/path%5Fresolution.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 mknod(2)
Pages that refer to this page:mknod(1), fcntl(2), mkdir(2), open(2), syscalls(2), unlink(2), dev_t(3type), makedev(3), mkfifo(3), remove(3), intro(4), fstab(5), proc_pid_attr(5), capabilities(7), inode(7), signal-safety(7), mount(8), xfs_db(8)