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int mknod(const char *pathname, mode_t mode, dev_t dev);
#include <fcntl.h> /* Definition of AT_* constants */
int mknodat(int dirfd, const char *pathname, mode_t mode, dev_t dev);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
The system call mknod() creates a filesystem node (file, device special
file, or named pipe) named pathname, with attributes specified by mode
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
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
domain socket, respectively. (Zero file type is equivalent to type
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.
See openat(2) for an explanation of the need for mknodat().
mknod() and mknodat() return zero on success, or -1 if an error
occurred (in which case, errno is set appropriately).
EACCES The parent directory does not allow write permission to the pro-
cess, 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
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.
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.
A component used as a directory in pathname is not, in fact, a
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.
pathname is relative and dirfd is a file descriptor referring to
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).
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)
Linux 2014-02-21 MKNOD(2)