MKNOD(2) Linux Programmer's Manual MKNOD(2)
NAME
mknod(1,2) - create a special or ordinary file(1,n)
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int mknod(1,2)(const char *pathname, mode_t mode, dev_t dev);
DESCRIPTION
The system call mknod(1,2) creates a filesystem node (file(1,n), device special
file(1,n) or named(5,8) pipe(2,8)) named(5,8) pathname, with attributes specified by mode
and dev.
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(1,n) types listed below and the permissions for the new
node.
The permissions are modified by the process's umask in(1,8) the usual way:
the permissions of the created node are (mode & ~umask).
The file(1,n) type must be one of S_IFREG, S_IFCHR, S_IFBLK, S_IFIFO or
S_IFSOCK to specify a normal file(1,n) (which will be created empty), char-
acter special file(1,n), block special file(1,n), FIFO (named(5,8) pipe(2,8)), or Unix
domain socket(2,7,n), respectively. (Zero file(1,n) type is equivalent to type
S_IFREG.)
If the file(1,n) type is S_IFCHR or S_IFBLK then dev specifies the major and
minor numbers of the newly created device special file(1,n); otherwise it is
ignored.
If pathname already exists, or is a symbolic link(1,2), 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(7,n,1 builtins) group ID bit
set(7,n,1 builtins), or if(3,n) 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.
RETURN VALUE
mknod(1,2) returns zero on success, or -1 if(3,n) an error(8,n) occurred (in(1,8) which
case, errno is set(7,n,1 builtins) appropriately).
ERRORS
EACCES The parent directory does not allow write(1,2) permission to the
process, or one of the directories in(1,8) the path prefix of path-
name did not allow search permission. (See also path_resolu-
tion(2).)
EEXIST pathname already exists.
EFAULT pathname points outside your accessible address space.
EINVAL mode requested creation of something other than a normal file(1,n),
device special file(1,n), FIFO or socket.
ELOOP Too many symbolic links were encountered in(1,8) resolving pathname.
ENAMETOOLONG
pathname was too long.
ENOENT A directory component in(1,8) 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.
ENOTDIR
A component used as a directory in(1,8) pathname is not, in(1,8) fact, a
directory.
EPERM mode requested creation of something other than a regular file(1,n),
FIFO (named(5,8) pipe(2,8)), or Unix domain socket(2,7,n), and the caller is not
privileged (Linux: does not have the CAP_MKNOD capability); also
returned if(3,n) the filesystem containing pathname does not support
the type of node requested.
EROFS pathname refers to a file(1,n) on a read-only filesystem.
CONFORMING TO
SVr4 (but the call requires privilege and is thus not in(1,8) POSIX),
4.4BSD. The Linux version(1,3,5) differs from the SVr4 version(1,3,5) in(1,8) that it
does not require root permission to create pipes, also in(1,8) that no EMUL-
TIHOP, ENOLINK, or EINTR error(8,n) is documented.
NOTES
POSIX 1003.1-2001 says: "The only portable use of mknod(1,2)() is to create
a FIFO-special file. If mode is not S_IFIFO or dev is not 0, the behav-
ior of mknod(1,2)() is unspecified."
Under Linux, this call cannot be used to create directories. One
should make directories with mkdir(1,2), and FIFOs with mkfifo(1,3).
There are many infelicities in(1,8) the protocol underlying NFS. Some of
these affect mknod(1,2).
SEE ALSO
fcntl(2), mkdir(1,2)(2), mount(2,8)(2), path_resolution(2), socket(2,7,n)(2), stat(1,2)(2),
umask(2), unlink(1,2)(2), mkfifo(1,3)(3)
Linux 2.6.7 2004-06-23 MKNOD(2)