MKNOD(2)                    Linux Programmer's Manual                   MKNOD(2)

       mknod, mknodat - create a special or ordinary file

       #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)):

           _XOPEN_SOURCE >= 500
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       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).

       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 &

       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

       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;
       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 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) for an explanation of the need for mknodat().

       mknod() and mknodat() return zero on success.  On error, -1 is returned
       and errno is set to indicate the error.

       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).)

       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.

              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.

              A component used as a directory in pathname is not, in fact, a

              (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.

       mknodat() was added to Linux in kernel 2.6.16; library support was added
       to glibc in version 2.4.

       mknod(): SVr4, 4.4BSD, POSIX.1-2001 (but see below), POSIX.1-2008.

       mknodat(): POSIX.1-2008.

       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).

       There are many infelicities in the protocol underlying NFS.  Some of
       these affect mknod() and mknodat().

       mknod(1), chmod(2), chown(2), fcntl(2), mkdir(2), mount(2), socket(2),
       stat(2), umask(2), unlink(2), makedev(3), mkfifo(3), acl(5),

       This page is part of release 5.13 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                              2021-08-27                           MKNOD(2)