Section: Linux Programmer's Manual (2)
mknod, mknodat - create a special or ordinary file
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
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
The system call
creates a filesystem node (file, device special file, or
named pipe) named
with attributes specified by
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
The file mode is modified by the process's
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
to specify a regular file (which will be created empty), character
special file, block special file, FIFO (named pipe), or UNIX domain socket,
(Zero file type is equivalent to type
If the file type is
specifies the major and minor numbers of the newly created device
may be useful to build the value for
otherwise it is ignored.
already exists, or is a symbolic link, this call fails with an
The newly created node will be owned by the effective user ID of the
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.
system call operates in exactly the same way as
except for the differences described here.
If the pathname given in
is relative, then it is interpreted relative to the directory
referred to by the file descriptor
(rather than relative to the current working directory of
the calling process, as is done by
for a relative pathname).
is relative and
is the special value
is interpreted relative to the current working
directory of the calling process (like
is absolute, then
for an explanation of the need for
return zero on success, or -1 if an error occurred (in which case,
is set appropriately).
The parent directory does not allow write permission to the process,
or one of the directories in the path prefix of
did not allow search permission.
The user's quota of disk blocks or inodes on the filesystem has been
This includes the case where
is a symbolic link, dangling or not.
pathname points outside your accessible address space.
requested creation of something other than a regular file, device
special file, FIFO or socket.
Too many symbolic links were encountered in resolving
pathname was too long.
A directory component in
does not exist or is a dangling symbolic link.
Insufficient kernel memory was available.
The device containing
has no room for the new node.
A component used as a directory in
is not, in fact, a directory.
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
also returned if the filesystem containing
does not support the type of node requested.
refers to a file on a read-only filesystem.
The following additional errors can occur for
is not a valid file descriptor.
is relative and
is a file descriptor referring to a file other than a directory.
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.
SVr4, 4.4BSD, POSIX.1-2001 (but see below), POSIX.1-2008.
POSIX.1-2001 says: "The only portable use of
is to create a FIFO-special file.
is not 0, the behavior of
However, nowadays one should never use
for this purpose; one should use
a function especially defined for this purpose.
cannot be used to create directories.
One should make directories with
There are many infelicities in the protocol underlying NFS.
Some of these affect
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