Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


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)):
         _XOPEN_SOURCE >= 500
             || /* Since glibc 2.19: */ _DEFAULT_SOURCE
             || /* Glibc versions <= 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 & ~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(),
     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,  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().


     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)  path_reso-


     This  page  is  part of release 4.16 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 2017-09-15 MKNOD(2)

/data/webs/external/dokuwiki/data/pages/man/mknod.txt · Last modified: 2019/05/17 09:47 by

Was this page helpful?-10+1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki