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MKNOD(3P)                  POSIX Programmer's Manual                 MKNOD(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       mknod - make a directory, a special file, or a regular file
SYNOPSIS
       #include <sys/stat.h>
       int mknod(const char *path, mode_t mode, dev_t dev);

DESCRIPTION
       The mknod() function shall create a new file named by the  pathname  to
       which the argument path points.
       The  file type for path is OR'ed into the mode argument, and the appli-
       cation shall select one of the following symbolic constants:
                     Name      Description
                     S_IFIFO   FIFO-special
                     S_IFCHR   Character-special (non-portable)
                     S_IFDIR   Directory (non-portable)
                     S_IFBLK   Block-special (non-portable)
                     S_IFREG   Regular (non-portable)
       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 unspec-
       ified.
       The permissions for the new file are OR'ed into the mode argument,  and
       may  be  selected  from  any combination of the following symbolic con-
       stants:
                Name     Description
                S_ISUID  Set user ID on execution.
                S_ISGID  Set group ID on execution.
                S_IRWXU  Read, write, or execute (search) by owner.
                S_IRUSR  Read by owner.
                S_IWUSR  Write by owner.
                S_IXUSR  Execute (search) by owner.
                S_IRWXG  Read, write, or execute (search) by group.
                S_IRGRP  Read by group.
                S_IWGRP  Write by group.
                S_IXGRP  Execute (search) by group.
                S_IRWXO  Read, write, or execute (search) by others.
                S_IROTH  Read by others.
                S_IWOTH  Write by others.
                S_IXOTH  Execute (search) by others.
                S_ISVTX  On directories, restricted deletion flag.
       The user ID of the file shall be initialized to the effective  user  ID
       of the process. The group ID of the file shall be initialized to either
       the effective group ID of the process or the group  ID  of  the  parent
       directory. Implementations shall provide a way to initialize the file's
       group ID to the group ID of the parent directory. Implementations  may,
       but  need  not, provide an implementation-defined way to initialize the
       file's group ID to the effective group ID of the calling  process.  The
       owner,  group,  and  other permission bits of mode shall be modified by
       the file mode creation mask of the process. The mknod() function  shall
       clear  each  bit whose corresponding bit in the file mode creation mask
       of the process is set.
       If path names a symbolic link, mknod() shall  fail  and  set  errno  to
       [EEXIST].
       Upon successful completion, mknod() shall mark for update the st_atime,
       st_ctime, and st_mtime fields of  the  file.  Also,  the  st_ctime  and
       st_mtime  fields  of the directory that contains the new entry shall be
       marked for update.
       Only a process with appropriate privileges may invoke mknod() for  file
       types other than FIFO-special.
RETURN VALUE
       Upon successful completion, mknod() shall return 0. Otherwise, it shall
       return -1, the new file shall not be created, and errno shall be set to
       indicate the error.
ERRORS
       The mknod() function shall fail if:
       EACCES A  component  of  the  path  prefix denies search permission, or
              write permission is denied on the parent directory.
       EEXIST The named file exists.
       EINVAL An invalid argument exists.
       EIO    An I/O error occurred while accessing the file system.
       ELOOP  A loop exists in symbolic links encountered during resolution of
              the path argument.
       ENAMETOOLONG
              The length of a pathname exceeds {PATH_MAX} or a pathname compo-
              nent is longer than {NAME_MAX}.
       ENOENT A component of the path prefix specified by path does  not  name
              an existing directory or path is an empty string.
       ENOSPC The directory that would contain the new file cannot be extended
              or the file system is out of file allocation resources.
       ENOTDIR
              A component of the path prefix is not a directory.
       EPERM  The invoking process does not have  appropriate  privileges  and
              the file type is not FIFO-special.
       EROFS  The directory in which the file is to be created is located on a
              read-only file system.

       The mknod() function may fail if:
       ELOOP  More than {SYMLOOP_MAX} symbolic links were  encountered  during
              resolution of the path argument.
       ENAMETOOLONG
              Pathname  resolution of a symbolic link produced an intermediate
              result whose length exceeds {PATH_MAX}.

       The following sections are informative.
EXAMPLES
   Creating a FIFO Special File
       The following example shows how to create a  FIFO  special  file  named
       /home/cnd/mod_done,  with  read/write  permissions  for owner, and with
       read permissions for group and others.

              #include <sys/types.h>
              #include <sys/stat.h>

              dev_t dev;
              int   status;
              ...
              status  = mknod("/home/cnd/mod_done", S_IFIFO | S_IWUSR |
                  S_IRUSR | S_IRGRP | S_IROTH, dev);
APPLICATION USAGE
       The mkfifo() function is preferred over this function for  making  FIFO
       special files.
RATIONALE
       The POSIX.1-1990 standard required that the group ID of a newly created
       file be set to the group ID of its parent directory or to the effective
       group  ID of the creating process. FIPS 151-2 required that implementa-
       tions provide a way to have the group ID be set to the group ID of  the
       containing  directory,  but  did not prohibit implementations also sup-
       porting a way to set the group ID to the effective group ID of the cre-
       ating process. Conforming applications should not assume which group ID
       will be used. If it matters, an application can use chown() to set  the
       group  ID after the file is created, or determine under what conditions
       the implementation will set the desired group ID.
FUTURE DIRECTIONS
       None.
SEE ALSO
       chmod(), creat(), exec(), mkdir(), mkfifo() , open(), stat(),  umask(),
       the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                            MKNOD(3P)