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MKNOD   (2) manpage
MKNOD
2
2003-04-23
Linux 2.4
Linux Programmer's Manual
  • NAME
      mknod - create a special or ordinary file
  • SYNOPSIS 
      
 #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 );
  • DESCRIPTION
      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 permissions 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 the permissions for the new node.

      The permissions are modified by the process's
      umask
       in the usual way: 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 normal 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 S_IFREG.)

      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; 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 uid 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 gid of the process.
  • RETURN VALUE
      mknod
       returns zero on success, or -1 if an error occurred (in which case,
      errno
       is set appropriately).
  • ERRORS
      EPERM
      mode
       requested creation of something other than a regular file,
      FIFO (named pipe), or Unix domain socket, and the caller
      is not the superuser; also returned if the filesystem
      containing
      pathname
       does not support the type of node requested.
      EINVAL
      mode
       requested creation of something other than a normal file, device
      special file, FIFO or socket.
      EEXIST
      pathname
       already exists.
      EFAULT
      pathname " points outside your accessible address space."
      EACCES
      The parent directory does not allow write permission to the process,
      or one of the directories in
      pathname
       did not allow search (execute) permission.
      ENAMETOOLONG
      pathname " was too long."
      ENOENT
      A directory component in
      pathname
       does not exist or is a dangling symbolic link.
      ENOTDIR
      A component used as a directory in
      pathname
       is not, in fact, a directory.
      ENOMEM
      Insufficient kernel memory was available.
      EROFS
      pathname
       refers to a file on a read-only filesystem.
      ELOOP
      Too many symbolic links were encountered in resolving
      pathname .
      ENOSPC
      The device containing
      pathname
       has no room for the new node.
  • CONFORMING TO
      SVr4 (but the call requires privilege and is thus not in POSIX),
      4.4BSD.  The Linux version differs from the SVr4 version in that it
      does not require root permission to create pipes, also in that no
      EMULTIHOP, ENOLINK, or EINTR error is documented.
  • NOTES
      POSIX 1003.1-2001 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."

      Under Linux, this call cannot be used to create directories.
      One should make directories with
      mkdir ,
       and FIFOs with
      mkfifo .

      There are many infelicities in the protocol underlying NFS.  Some
      of these affect
      mknod .
  • SEE ALSO
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