mknod, mknodat - create a special or ordinary file
Standard C library (libc, -lc)
#include <sys/stat.h>
int mknod(const char *path, mode_t mode, dev_t dev);
#include <fcntl.h> /* Definition of AT_* constants */
#include <sys/stat.h>
int mknodat(int dirfd, const char *path, 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_SOURCEThe system call mknod() creates a filesystem node
(file, device special file, or named pipe) named path, 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).
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 path 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.
The mknodat() system call operates in exactly the same way as mknod(), except for the differences described here.
If path 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 path is relative and dirfd is the special value
AT_FDCWD, then path is interpreted relative to
the current working directory of the calling process (like
mknod()).
If path is absolute, then dirfd is ignored.
The parent directory does not allow write permission to the process,
or one of the directories in the path prefix of path did not
allow search permission. (See also
path_resolution(7).)
(mknodat()) path is relative but
dirfd is neither AT_FDCWD nor a valid file
descriptor.
The user's quota of disk blocks or inodes on the filesystem has been exhausted.
path already exists. This includes the case where
path is a symbolic link, dangling or not.
path 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
path.
path was too long.
A directory component in path does not exist or is a
dangling symbolic link.
Insufficient kernel memory was available.
The device containing path has no room for the new node.
A component used as a directory in path is not, in fact, a
directory.
(mknodat()) path is relative and
dirfd is a file descriptor referring to a file other than 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 filesystem containing path
does not support the type of node requested.
path refers to a file on a read-only filesystem.
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).
POSIX.1-2024 XSI.