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

       mknod, mknodat - create a special or ordinary file

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <fcntl.h>
       #include <unistd.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)):

           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||

       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 stat(2).

       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), 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.

       The mknodat() system call operates in exactly the same way as mknod(2),
       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(2) 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(2)).

       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,  or  -1  if  an  error
       occurred (in which case, errno is set appropriately).

       EACCES The  parent  directory  does  not  allow write permission to the
              process, or one of the directories in the path prefix  of  path-
              name  did  not  allow search permission.  (See also path_resolu-

       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 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
              a file other than a directory.

       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  behav-
       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), acl(5) path_resolution(7)

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Linux                             2015-05-07                          MKNOD(2)
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