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



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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       mknod(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       The  system  call  mknod() creates a file system 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  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 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 (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 file system 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.

RETURN VALUE
       mknod() returns zero on success, or -1 if an error occurred (in which case, errno is set appropriately).

ERRORS
       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).)

       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.

       ENAMETOOLONG
              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.

       ENOTDIR
              A component used as a directory in pathname is not, in fact, 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 file system containing pathname does not support the type of node requested.

       EROFS  pathname refers to a file on a read-only file system.

CONFORMING TO
       SVr4, 4.4BSD, POSIX.1-2001 (but see below).

NOTES
       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, this call 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().

SEE ALSO
       chmod(2),  chown(2),  fcntl(2),  mkdir(2),  mknodat(2),  mount(2),  socket(2),  stat(2),  umask(2),  unlink(2),
       makedev(3), mkfifo(3), path_resolution(7)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-12-01                          MKNOD(2)