Open System Services Programmer's Guide

• An XPG4 function, such as those provided in the fnmatch.h, nl_types.h, and wchar.h
header files.
• An XPG4 function that is an extension to standard header files, such as getw() in stdio.h.
• Any function related to OSS access control lists (ACLs)
• Any function designed to interact with OSS files that are larger than approximately 2 gigabytes.
These functions, often called 64-bit APIs or 64-bit functions, typically have the number 64 in
the name (for example the open64() function).
• Functions specified only in the ISO/IEC 9899:1999 standard, which is also referred to as
the C99 standard.
Extensions Based on Standards or Proposed Standards
The OSS API also includes functions that are HP extensions to the XPG4 specifications, but that
are also based on other approved or proposed standards:
• Functions designed to interact with OSS files larger than approximately 2 gigabytes in addition
to smaller OSS files. These functions, often called 64-bit APIs or 64-bit functions, typically have
the number 64 in the name (for example the open64() function). These 64-bit APIs are based
on the Adding Support for Arbitrary File Sizes to the Single Unix Specification, X/Open Large
File Summit (LFS) submission, version 1.5 (March 20, 1996), and are supported on systems
running J-series RVUs, H06.06 or later H-series RVUs, and G06.29 or later G-series RVUs.
• Functions that support OSS access control lists (ACLs). These functions are based on the HP-UX
implementation and Information Technology – Portable Operating System Interface (POSIX)
– Part 1: System Application Program Interface (API) Amendment #: Protection, Audit, and
Control Interfaces [C Language] (IEEE Draft P1003.1e), October 1997.
• Several functions that support wide-character formats. These functions conform to the
ISO/IEC 9899:1999 standard.
Two File Systems
The OSS environment enables you to access two file systems: the OSS file system and the Guardian
file system. The files in these file systems can exist as local files or remote files. A local file resides
on the local node. A remote file resides on a remote node.
The OSS File System
The OSS file system is a multilevel file system consisting of directories and subdirectories stemming
from a “root” directory denoted by /. A directory can contain files and more directories. A directory
that is in another directory is called a subdirectory. There are no theoretical limits to the number
of subdirectories and files in a directory. Figure 2 shows the structure of an OSS file system and
that there is no direct relationship between OSS filenames and disks.
28 Overview of the OSS Programming Environment